RARE DISEASE
PGM1-CDG
PGM1-CDG
PGM1-CDG
Synonyms: CDG syndrome type It, CDG-It, CDG1T, Congenital disorder of glycosylation type 1t, Congenital disorder of glycosylation type It, PGM1-related congenital disorder of glycosylation, Phosphoglucomutase-1 deficiency
Synonyms: CDG syndrome type It, CDG-It, CDG1T, Congenital disorder of glycosylation type 1t, Congenital disorder of glycosylation type It, PGM1-related congenital disorder of glycosylation, Phosphoglucomutase-1 deficiency
Synonyms: CDG syndrome type It, CDG-It, CDG1T, Congenital disorder of glycosylation type 1t, Congenital disorder of glycosylation type It, PGM1-related congenital disorder of glycosylation, Phosphoglucomutase-1 deficiency
Drug discovery
1
drug
With orphan designation
Overview
PGM1-CDG is a rare autosomal recessive disorder disrupting glycosylation and glycogen metabolism due to PGM1 mutations. Clinically, it manifests with cleft palate, hypoglycemia, hepatopathy, myopathy, and cardiomyopathy. Diagnosis combines transferrin glycosylation analysis and genetic testing. D-galactose supplementation (0.3–3 g/kg/day) improves hypoglycemia, coagulation, and glycoprotein profiles but does not resolve cardiac complications [1][2][10][17].
Categories: rare cardiac diseases, rare genetic diseases, rare hepatic diseases, rare inborn errors of metabolism, rare transplant-related disorders
Research Papers
110 drug discovery papers about PGM1-CDG, with 1 first-in-class and 1 next-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
110 drug discovery papers about PGM1-CDG, with 1 first-in-class and 1 next-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
categories:
Small molecules
gene therapies
2026-07-07 | Structural insights into mutated human phosphoglucomutase 1 (PGM1) using computational approaches
The phosphoglucomutase 1 (PGM1) enzyme plays a critical role in metabolism and glycosylation in the human body. PGM1 has been linked to multiple disease phenotypes, including the inherited metabolic disorder known as congenital disorders of glycosylation (CDGs). Numerous clinical studies have shown that mutations in key regions of the PGM1 gene affect catalytic activity and induce folding defects of the enzyme. To delve into molecular changes at the supramolecular level, the structural, stability, and other features of PGM1 variants (T19A, N38Y, and D62H) were studied in the present work. To this end, molecular dynamics (MD) simulation at a long timescale (500 ns) was carried out. Parameters such as root-mean-square deviation (RMSD), root-mean-square fluctuations (RMSF), radius of gyration (Rg), solvent-accessible surface area (SASA), hydrogen bonds, and free energy landscape (FEL) were studied and compared with those of the wild-type PGM1. It was noted that mutations 19 A, N38Y, and D62H significantly alter the protein’s structural behavior, causing increased flexibility, reduced stability, and compactness.
2025-08-14 | Are viral vector-mediated therapies compatible with aberrant glycosylation?
The ability of adeno-associated viruses (AAVs) to transduce host cells relies on interactions with glycan moieties on the cellular surface. Consequently, disrupted protein glycosylation, which is seen in a range of neurodevelopmental and neurodegenerative diseases, could impair transduction efficiency. Understanding how altered glycosylation impacts AAV binding is essential to optimize AAV-mediated therapeutic strategies. We used glycoproteomics data from cortical brain organoids and iCardiomyocytes of individuals with congenital disorders of glycosylation (CDG) (ALG13-, PMM2-, and PGM1-CDG) to examine the abundance of AAV-binding glycan species. Additionally, we assessed the abundance of coreceptors in proteomics data. We found that the abundance of AAV-binding glycan species was downregulated for all CDG subtypes, but this was significant only for AAV5-, AAV8-, and AAV9-binding glycan motifs in PGM1-CDG. The proteomics data showed significantly decreased abundance of the coreceptor PDGFRβ in ALG13-CDG. The downregulation of glycan species and AAV coreceptors in models of aberrant protein glycosylation underscores the need to optimize AAV selection for conditions with altered protein glycosylation, including CDG and neurodegenerative diseases such as Parkinson's and Alzheimer's disease.
2023-05-17 | AAV-based gene therapy prevents and halts the progression of dilated cardiomyopathy in a mouse model of phosphoglucomutase 1 deficiency (PGM1-CDG).
Phosphoglucomutase 1 (PGM1) deficiency is recognized as the third most common N-linked congenital disorders of glycosylation (CDG) in humans. Affected individuals present with liver, musculoskeletal, endocrine, and coagulation symptoms; however, the most life-threatening complication is the early onset of dilated cardiomyopathy (DCM). Recently, we discovered that oral D-galactose supplementation improved liver disease, endocrine, and coagulation abnormalities, but does not alleviate the fatal cardiomyopathy and the associated myopathy. Here we report on left ventricular ejection fraction (LVEF) in 6 individuals with PGM1-CDG. LVEF was pathologically low in most of these individuals and varied between 10% and 65%. To study the pathobiology of the cardiac disease observed in PGM1-CDG, we constructed a novel cardiomyocyte-specific conditional Pgm2 gene (mouse ortholog of human PGM1) knockout (Pgm2 cKO) mouse model. Echocardiography studies corroborated a DCM phenotype with significantly reduced ejection fraction and left ventricular dilation similar to those seen in individuals with PGM1-CDG. Histological studies demonstrated excess glycogen accumulation and fibrosis, while ultrastructural analysis revealed Z-disk disarray and swollen/fragmented mitochondria, which was similar to the ultrastructural pathology in the cardiac explant of an individual with PGM1-CDG. In addition, we found decreased mitochondrial function in the heart of KO mice. Transcriptomic analysis of hearts from mutant mice demonstrated a gene signature of DCM. Although proteomics revealed only mild changes in global protein expression in left ventricular tissue of mutant mice, a glycoproteomic analysis unveiled broad glycosylation changes with significant alterations in sarcolemmal proteins including different subunits of laminin-211, which was confirmed by immunoblot analyses. Finally, augmentation of PGM1 in KO mice via AAV9-PGM1 gene replacement therapy prevented and halted the progression of the DCM phenotype.
2005-07-07 | Glycosylation defects in muscular dystrophies.
Congenital disorders of glycosylation are caused by defects in the synthesis of the glycan moiety of glycoproteins or other glycoconjugates. There has been a great explosion in the number of neuromuscular diseases caused by mutations in genes that affect carbohydrate metabolism or protein glycosylation. A common defect in these disorders is the defective processing of alpha-dystroglycan. Recent advances demonstrating mutations in glycosyltransferases and dysfunction of the alpha-beta dystroglycan axis causing different forms of muscular dystrophy, especially with brain involvement, shows clearly that muscle integrity is dependent on glycosylation. We first review the newly identified muscular dystrophies, with a focus on the hypoglycosylation of alpha-dystroglycan, from a clinical, biochemical and genetic standpoint, and second hereditary inclusion body myopathies caused by mutations in the gene that encodes an enzyme responsible for the protein's posttranslational modification that cause sialidation defects. It is shown very recently that molecular recognition of dystroglycan by LARGE is a key determinant in the biosynthetic pathway to produce mature and functional dystroglycan. Gene transfer of LARGE into the cells of individuals with congenital muscular dystrophies restores alpha-dystroglycan function. The clinical spectrum of congenital disorders of glycosylation is becoming increasingly broad. A demonstration of mutations in glycosyltransferases will further help to design diagnostic tools and therapeutic approaches. Recent findings which show that molecular recognition by LARGE is essential for expression of functional dystroglycan and LARGE can functionally bypass alpha-dystroglycan glycosylation defects in distinct congenital muscular dystrophies, indicate a new therapeutic strategy.
2003-07-01 | Highly Efficient Lentiviral Gene Transfer in CD34 + and CD34 + /38 − /lin − Cells from Mobilized Peripheral Blood after Cytokine Prestimulation
Because mobilized peripheral blood (mPB) represents an attractive source of cells for gene therapy, we investigated lentiviral gene transfer in CD34+ cells and the stem/progenitor-cell-enriched CD34+/38−/lin− cell subset isolated from mPB. In this study, we used an optimized third-generation self-inactivating lentiviral vector containing both the central polypurine tract and the woodchuck hepatitis posttranscriptional regulatory element sequences and encoding enhanced green fluorescent protein (EGFP) under the control of the elongation factor lα promoter. This lentivector was first used to compare multiplicity of infection (MOI)-dependent gene transfer efficiency in cord blood (CB) versus mPB CD34+-derived cells, colony-forming cells (CFCs), and long-term culture-initiating cells (LTC-ICs). Results showed a difference in the percentage of transduced cells particularly significant at low MOIs. A plateau was reached where 15% and 25% of CB and mPB cells, respectively, remained refractory to lentiviral trans-duction. Effects of a cytokine prestimulation period (18 hours) with interleukin-3, stem cell factor, Flt-3 ligand, and thrombopoietin were then analyzed in total cells, CFCs, and LTC-ICs derived from mPB CD34+ cells. Transduction levels in those conditions demonstrated a two- and fourfold increase in CFCs and LTC-ICs, respectively, compared with unstimulated (<3 hours) control cells. Moreover, using the same transduction protocol, we were able to efficiently transduce CD34+/38−/lin− cells isolated from mPB, with up to >85% of colonies derived from LTC-ICs expressing EGFP and gene transfer levels remaining stable for 10 weeks in liquid culture. We therefore demonstrate a highly efficient gene transfer in this therapeutically relevant target cell population.
small molecules
2026-08-07 | Hypoglycosylation lowers the mechanical activation threshold of Piezo1 and enhances cortical neuronal mechanotransduction: implications for PMM2-CDG
Abstract Piezo1 is a mechanically activated cation channel whose N-linked glycans support protein maturation and plasma membrane trafficking, but their contribution to mechanical gating is unknown. We asked whether hypoglycosylation alters Piezo1 mechanosensitivity and cortical neuronal mechanotransduction, with potential relevance to neurological manifestations of congenital disorders of glycosylation (CDG). Human Piezo1 was studied in HEK293 cells after mutation of two conserved cap-domain N-glycosylation sites or inhibition of N-glycan maturation with swainsonine or kifunensine. Mechanically activated currents were recorded by cell-attached patch-clamp during incremental negative-pressure pulses, whereas Ca 2+ responses were measured during uniaxial stretch. Piezo1 abundance, synaptic localisation and stretch-evoked Ca 2+ signals were also examined in primary mouse cortical neurons. On poly-L-lysine, N2293Q or N2330Q shifted the pressure-response relationship towards lower activating pressures without changing maximal current or inactivation kinetics. This effect was absent on collagen. Swainsonine and kifunensine reduced mature Piezo1 glycosylation and lowered the mechanical activation threshold. Hypoglycosylation enhanced Ca 2+ entry during submaximal stretch in HEK293 cells. In cortical neurons, inhibition of glycan maturation increased somatic Piezo1 immunoreactivity without changing its association with synaptic markers, and potentiated Ca 2+ responses to both the Piezo1 activator Yoda1 and submaximal stretch. Thus, mature N-glycans and the extracellular adhesive environment jointly set Piezo1’s mechanical activation threshold rather than merely regulating biosynthesis and trafficking. These findings establish glycosylation-mechanics coupling as a determinant of neuronal force sensing and suggest that, by facilitating Piezo1 recruitment, defective glycosylation may increase cortical vulnerability to mechanical stress, potentially contributing to head trauma-triggered neurological episodes in phosphomannomutase 2 deficiency (PMM2-CDG). Key points Piezo1 channels convert mechanical forces into electrical and calcium signals. N-linked glycans support channel trafficking to the plasma membrane, but whether they tune the force needed for Piezo1 activation was unknown. Mutating either of two conserved N-glycosylation sites in Piezo1 cap domain, or pharmacologically restricting N-glycan maturation, lowered channel’s mechanical activation threshold without changing maximal current or inactivation. This sensitisation depended on the adhesive substrate (occurred on poly-L-lysine but not collagen), and was most evident during submaximal stretch, showing that glycosylation and the extracellular mechanical environment jointly determine Piezo1 force sensing. In mouse cortical neurons, impaired N-glycan maturation increased somatic Piezo1 abundance and enhanced Ca 2+ responses to its chemical activator Yoda1 and stretch, without changing synaptic localisation. By allowing weak mechanical inputs to recruit Piezo1 more effectively, defective glycosylation may increase cortical responses to mechanical stress and help explain susceptibility to head trauma-triggered neurological episodes in phosphomannomutase 2 deficiency (PMM2-CDG).
2026-02-21 | PGM1 deficiency is linked to sarcomeric and mitochondrial dysfunction in patient-derived iPSC-cardiomyocytes
Abstract Background PGM1-congenital disorder of glycosylation (PGM1-CDG) is frequently associated with cardiomyopathy. Although galactose therapy corrects glycosylation defects, cardiac dysfunction typically persists, suggesting a glycosylation-independent mechanism. Recent evidence of mitochondrial abnormalities in PGM1-deficient human and murine heart, together with the association of PGM1 with the Z-disk protein LDB3 (ZASP/Cypher), suggests a critical role for PGM1 in cardiomyocyte structural and energetic homeostasis. We hypothesized that PGM1-related cardiomyopathy arises from a glycosylation-independent disruption of Z-disk–mitochondrial coupling driven by loss of PGM1–LDB3 interactions, resulting in mitochondrial energy failure and impaired contractile function. Methods Induced pluripotent stem cell–derived cardiomyocytes (iCMs) were generated from PGM1-deficient patient fibroblasts. Multielectrode array (MEA) recordings, untargeted (glyco)proteomics, and pathway analysis were performed to assess functional and molecular changes. Key findings were validated using tracer metabolomics and mitochondrial respiration assays. Results PGM1-deficient iCMs exhibited reduced beating frequency, impaired contractility, and prolonged contraction kinetics. Proteomic analyses revealed depletion of Z-disk components, including LDB3. AlphaFold3 structural modeling predicted a direct interaction between PGM1 and LDB3, implicating PGM1 in Z-disk integrity, which was confirmed in vitro. In addition, mitochondrial proteins were severely depleted, prompting us to investigate mitochondrial function. Functional validation confirmed extensive metabolic rewiring, energy depletion, and severely impaired mitochondrial respiration. Finally, the in silico drug repurposing identified possible therapeutic options that could target PGM1-deficient cardiomyopathy. Conclusion Our data suggests PGM1 is key regulator of cardiomyocyte function, linking sarcomeric Z-disk integrity with mitochondrial metabolism. These mechanistic insights offer a foundation for developing targeted therapies for PGM1-CDG and potentially other cardiomyopathies involving Z-disk dysfunction. Graphical Abstract
2025-11-28 | SLC35A2-Related Brain Disorders: Genetics, Pathophysiology, and Therapeutic Insights
SLC35A2 encodes the Golgi uridine diphosphate galactose transporter, which is essential for glycosylation of glycoproteins and glycolipids. Variants in this gene, either germline or somatic, have emerged as causes of diverse neurological disorders ranging from congenital disorders of glycosylation (SLC35A2-CDG) to focal cortical malformations such as mild malformation of cortical development with oligodendroglial hyperplasia in epilepsy (MOGHE). This review summarizes the molecular function of SLC35A2, clinical phenotypes of congenital and somatic variants, insights from functional assays and animal models, and therapeutic perspectives including galactose supplementation and precision medicine. We aim to provide an integrative synthesis of human genetics, neuropathology, glycomics, and translational approaches.
2025-11-03 | Novel PGM1 Mutation in Congenital Disorder of Glycosylation Type 1T: A Case Report of Liver Failure and Myopathy.
BACKGROUND Congenital disorders of glycosylation (CDG) are rare, inherited metabolic conditions caused by defects in glycoprotein synthesis. CDG Type 1T, associated with mutations in the phosphoglucomutase 1 (PGM1) gene, often presents with hepatic dysfunction, developmental delay, and multisystem involvement. Due to clinical overlap with other metabolic disorders, misdiagnosis is common, leading to delayed treatment. CASE REPORT We report a 20-month-old boy, born to consanguineous parents, who initially received a misdiagnosis of galactosemia following abnormal newborn screening. Despite dietary modifications, he developed persistent transaminitis, coagulopathy, hypotonia, and delayed motor milestones. Further evaluation revealed abnormal carbohydrate-deficient transferrin analysis, and whole exome sequencing identified a homozygous PGM1 variant of uncertain significance, supporting CDG Type 1T diagnosis. Liver biopsy demonstrated steatosis with bridging portal fibrosis. The patient was started on oral D-galactose supplementation (1.5 g/kg/day). Over a 51-day follow-up period, liver enzymes improved markedly, with AST declining from 1980 to 385 U/L and ALT from 695 to 210 U/L, alongside normalization of coagulation profiles. Muscle enzyme response was partial, with creatine kinase levels remaining mildly elevated, reflecting differential therapeutic effects across tissues. CONCLUSIONS This case underscores the diagnostic challenges of CDG Type 1T and emphasizes the importance of combining biochemical markers and genetic sequencing to achieve timely diagnosis. The identified PGM1 variant, although classified as a variant of uncertain significance, was strongly supported by clinical and biochemical findings. Significant hepatic improvement with D-galactose highlights the therapeutic potential of early targeted supplementation, although incomplete muscular response indicates the need for ongoing follow-up and exploration of adjunctive therapies.
2025-10-06 | Exploring Secondary Biotinidase Deficiency and Biotin Supplementation in PMM2-CDG
The congenital disorders of glycosylation (CDG) encompass >190 multiorgan disorders with predominantly neurodevelopmental phenotypes with no causative treatment available. The glycoprotein biotinidase (BTD) provides biotin, an essential cofactor for carboxylases in ubiquitous metabolic pathways. Individuals with (partial) BTD deficiency (BTDD) and CDG patients show overlapping phenotypes like movement disorders, seizures, and neurodevelopmental issues. Biotin is a water-soluble, inexpensive, and safe food supplement. Patients with primary BTDD respond well to oral biotin supplement. We here explore secondary BTDD and the effect of biotin supplementation in PMM2-CDG in an initial open-label study.BTD activity in dried blood spots from 29 individuals with PMM2-CDG indicated a mean reduction to 27% (range: 23.0-40.5%) at group level. Patients (mean: 19.6 ± 11.9 years) were supplemented with 10 mg biotin daily for 12 months. The parents/caretaker reported positive responses in 62 to 69% of patients across seven (performance, social, at home, self-control, self-care, leisure, health) of the nine categories covered by the Adaptive Behavior Assessment System-II (ABAS-II) questionnaires. The reported positive effect of biotin supplementation differed between age groups, ranging from 54% (16-43 years) via 62% (2-5 years) to 80% (6-13 years). Its effect was reported to be the highest in the moderate to severely affected patient subgroups, with significant improvements in home functioning, health, performance, leisure, self-control. No adverse effects were reported.Given the absence of other treatments, the supportive effect of Biotin in PMM2-CDG deserves further exploration.
proteins
2025-10-16 | Phosphoglucomutase 1 deficiency misdiagnosed as Laron syndrome.
Protein glycosylation is a crucial process involving the addition of oligosaccharides to proteins, which plays a significant role in stabilizing proteins and mediating protein-protein interactions. Mutations in genes associated with glycosylation can lead to congenital disorders of glycosylation (CDG), resulting in multisystem disorders. One such example is phosphoglucomutase 1 (PGM1) -CDG, caused by a deficiency of the PGM1 enzyme. In this report, we describe a patient with PGM1-CDG who was initially misdiagnosed with growth hormone insensitivity and benefited from recombinant human insulin-like growth factor-1 (rhIGF-1) therapy. A 2-year-11-month-old female patient, born to first-degree cousin parents, presented with hypoglycemia and short stature. Her physical examination revealed frontal bossing, infantile facial appearance, and short stature. Laboratory investigations revealed that basal and stimulated growth hormone levels were very high, IGF-1 was low, and the inadequate response to the IGF generation test was consistent with growth hormone insensitivity (GHI). The patient was started on rhIGF-1 therapy, resulting in significant height gain. Subsequently, the patient showed improvement in height with rhIGF-1 therapy. The patient, who had additional findings such as elevated creatine kinase (CK) and transaminase levels and cardiomyopathy, was diagnosed with PGM1-CDG. This case highlights that PGM1-CDG can mimic clinical and laboratory findings of GHI. CDG diagnosis should be considered in cases with clinical and laboratory findings of GHI accompanied by multisystem disorders such as hepatopathy, elevated CK, and cardiomyopathy. This patient's successful response to rhIGF-1 therapy highlights the potential benefits of targeted therapies in treating growth hormone-related disorders in patients.
2024-09-18 | Genetics of glycosylation in mammalian development and disease.
Glycosylation of proteins and lipids in mammals is essential for embryogenesis and the development of all tissues. Analyses of glycosylation mutants in cultured mammalian cells and model organisms have been key to defining glycosylation pathways and the biological functions of glycans. More recently, applications of genome sequencing have revealed the breadth of rare congenital disorders of glycosylation in humans and the influence of genetics on the synthesis of glycans relevant to infectious diseases, cancer progression and diseases of the immune system. This improved understanding of glycan synthesis and functions is paving the way for advances in the diagnosis and treatment of glycosylation-related diseases, including the development of glycoprotein therapeutics through glycosylation engineering.
2022-03-08 | A novel fission yeast platform to model N-glycosylation and the bases of congenital disorders of glycosylation type I.
Congenital disorders of glycosylation type I (CDG-I) are inherited human diseases caused by deficiencies in lipid-linked oligosaccharide (LLO) synthesis or the glycan transfer to proteins during N-glycosylation. We constructed a platform of 16 Schizosaccharomyces pombe strains that synthesize all possible theoretical combinations of LLOs containing three to zero glucose (Glc) residues and nine to five mannose (Man) residues. The occurrence of unexpected LLOs suggested the requirement of specific Man residues for glucosyltransferase activities. We then quantified protein hypoglycosylation in each strain and found that in S. pombe the presence of Glc in the LLO is more relevant to the transfer efficiency than the number of Man residues. Surprisingly, a decrease in the number of Man residues in glycans somehow improved the glycan transfer. The most severe hypoglycosylation was produced in cells that synthesized LLOs completely lacking Glc and having a high number of Man residues. This deficiency could be reverted by expressing a single-subunit oligosaccharyltransferase with a broad range of substrate specificity. Our work shows the usefulness of this new S. pombe set of mutants as a platform to model the molecular bases of human CDG-I diseases. This article has an associated First Person interview with the first authors of the paper.
2018-11-02 | Abrogation of glucosidase I–mediated glycoprotein deglucosylation results in a sick phenotype in fission yeasts: Model for the human MOGS-CDG disorder
Glucosidase I (GI) removes the outermost glucose from protein-linked Glc3Man9GlcNAc2 (G3M9) in the endoplasmic reticulum (ER). Individuals with congenital disorders of glycosylation MOGS-CDG bear mutations in the GI-encoding gene (gls1). Although GI absence has been reported to produce lethality in Schizosaccharomyces pombe yeasts, here we obtained two viable Δgls1 mutants, one with a very sick but not lethal phenotype (Δgls1-S) and the other with a healthier one (Δgls1-H). The sick strain displayed only G3M9 as an ER protein–linked oligosaccharide, whereas the healthier strain had both G3M9 and Man9GlcNAc2. The lipid-linked oligosaccharide patterns of the two strains revealed that the most abundantly formed glycans were G3M9 in Δgls1-S and Glc2Man9GlcNAc2 in Δgls1-H, suggesting reduced Alg10p glucosyltransferase activity in the Δgls1-H strain. A mutation in the alg10+ gene was indeed observed in this strain. Our results indicated that abrogated G3M9 deglucosylation was responsible for the severe defects observed in Δgls1-S cells. Further studies disclosed that the defects could not be ascribed to disruption of glycoprotein entrance into calnexin-folding cycles, inhibition of the oligosaccharyltransferase by transfer reaction products, or reduced proteasomal degradation of misfolded glycoproteins. Lack of triglucosylated glycoprotein deglucosylation neither significantly prevented glycan elongation in the Golgi nor modified the overall cell wall monosaccharide composition. Nevertheless, it resulted in a distorted cell wall and in the absence of underlying ER membranes. Furthermore, Golgi expression of human endomannosidase partially restored normal growth in Δgls1-S cells. We propose that accumulation of G3M9-bearing glycoproteins is toxic and at least partially responsible for defects observed in MOGS-CDG. Glucosidase I (GI) removes the outermost glucose from protein-linked Glc3Man9GlcNAc2 (G3M9) in the endoplasmic reticulum (ER). Individuals with congenital disorders of glycosylation MOGS-CDG bear mutations in the GI-encoding gene (gls1). Although GI absence has been reported to produce lethality in Schizosaccharomyces pombe yeasts, here we obtained two viable Δgls1 mutants, one with a very sick but not lethal phenotype (Δgls1-S) and the other with a healthier one (Δgls1-H). The sick strain displayed only G3M9 as an ER protein–linked oligosaccharide, whereas the healthier strain had both G3M9 and Man9GlcNAc2. The lipid-linked oligosaccharide patterns of the two strains revealed that the most abundantly formed glycans were G3M9 in Δgls1-S and Glc2Man9GlcNAc2 in Δgls1-H, suggesting reduced Alg10p glucosyltransferase activity in the Δgls1-H strain. A mutation in the alg10+ gene was indeed observed in this strain. Our results indicated that abrogated G3M9 deglucosylation was responsible for the severe defects observed in Δgls1-S cells. Further studies disclosed that the defects could not be ascribed to disruption of glycoprotein entrance into calnexin-folding cycles, inhibition of the oligosaccharyltransferase by transfer reaction products, or reduced proteasomal degradation of misfolded glycoproteins. Lack of triglucosylated glycoprotein deglucosylation neither significantly prevented glycan elongation in the Golgi nor modified the overall cell wall monosaccharide composition. Nevertheless, it resulted in a distorted cell wall and in the absence of underlying ER membranes. Furthermore, Golgi expression of human endomannosidase partially restored normal growth in Δgls1-S cells. We propose that accumulation of G3M9-bearing glycoproteins is toxic and at least partially responsible for defects observed in MOGS-CDG.
2012-06-12 | A sensitive green fluorescent protein biomarker of N-glycosylation site occupancy.
N-glycosylation mediates many biological functions. Genetic defects in the N-glycosylation pathway cause >35 inherited human disorders called congenital disorders of glycosylation (CDGs). As a result, some N-glycosylation sites are unoccupied. Serum transferrin is a diagnostic marker for these patients, but there are no corresponding cellular markers to assess glycosylation competence. Therefore, we engineered a green fluorescent protein (GFP) construct to measure N-glycosylation site occupancy. We designed an endoplasmic reticulum-retained GFP biomarker whose fluorescence is lost when it is N-glycosylated due to steric hindrance by the glycan. This marker is a highly sensitive indicator of N-glycosylation site occupancy. In CDG cells carrying the GFP construct, a 25% decrease of glycosylation efficiency induces a 5-fold increase in fluorescence, while cDNA complementation of the genetic defect results in a 5-fold decrease in fluorescence. This engineered GFP detects impaired N-glycosylation in multiple cell lines, including CHO cells, HeLa cells, normal and patient fibroblasts, induced pluripotent stem cells (iPSCs), and human embryonic stem cells (hESCs). This marker is a highly sensitive tool to study N-glycosylation site occupancy. It can be used to screen for compounds that reverse poor N-glycosylation site occupancy.
vaccines
2023-06-02 | A liposomal carbohydrate vaccine, adjuvanted with an NKT cell agonist, induces rapid and enhanced immune responses and antibody class switching
Congenital disorders of glycosylation (CDGs) are genetic diseases caused by gene defects in glycan biosynthesis pathways, and there is an increasing number of patients diagnosed with CDGs. Because CDGs show many different clinical symptoms, their accurate clinical diagnosis is challenging. Recently, we have shown that liposome nanoparticles bearing the ALG1-CDG and PMM2-CDG biomarkers (a tetrasaccharide: Neu5Ac-α2,6-Gal-β1,4-GlcNAc-β1,4-GlcNAc) stimulate a moderate immune response, while the generated antibodies show relatively weak affinity maturation. Thus, mature antibodies with class switching to IgG are desired to develop high-affinity antibodies that may be applied in medical applications.In the present study, a liposome-based vaccine platform carrying a chemoenzymatic synthesized phytanyl-linked tetrasaccharide biomarker was optimized. The liposome nanoparticles were constructed by dioleoylphosphatidylcholine (DOPC) to improve the stability and immunogenicity of the vaccine, and adjuvanted with the NKT cell agonist PBS57 to generate high level of IgG antibodies. The results indicated that the reformulated liposomal vaccine stimulated a stronger immune response, and PBS57 successfully induce an antibody class switch to IgG. Further analyses of IgG antibodies elicited by liposome vaccines suggested their specific binding to tetrasaccharide biomarkers, which were mainly IgG2b isotypes.Immunization with a liposome vaccine carrying a carbohydrate antigen and PBS57 stimulates high titers of CDG biomarker-specific IgG antibodies, thereby showing great potential as a platform to develop rapid diagnostic methods for ALG1-CDG and PMM2-CDG.
other
2025-09-18 | Table 3_Immunopathology in PMM2-CDG: Defective glycosylation impact in the TNFα -TNFR1 signalling pathway.xlsx
Introduction Glycosylation is a post-translational modification that plays a crucial role in immune system activity. Phosphomannomutase 2-Congenital Disorder of Glycosylation (PMM2-CDG) is a rare genetic disease affecting glycosylation with a multi-systemic impact. PMM2-CDG patients commonly show immune disfunction and elevated pro-inflammatory cytokine levels that may link to other symptoms. However, the underlying immune mechanisms remain unclear. Given Tumour Necrosis Factor (TNF)’s key role in inflammation, this study proposes that defective glycosylation of its receptors disrupts intracellular signalling, leading to changes in the immune response of PMM2-CDG patients. Methods To address this, we applied an integrative approach, combining transcriptomics, glycomics, and immune-related assays to investigate the impact of TNF-a stimulation via TNF receptor 1 (TNFR1) in a cohort of PMM2-CDG patients’ skin fibroblasts. Results Our results reveal a multifaceted disruption of TNF-a signalling in PMM2-CDG fibroblasts. We observed structural abnormalities in TNFR1, including altered receptor shedding. PMM2-CDG cells also showed an altered N-glycosylation profile, affecting particularly, high mannose N-glycans. At transcriptional level, PMM2-CDG cells, especially those bearing the R141H heterozygous variant, exhibited a distinct gene expression profile, after stimulation, characterized by dysregulation of immune and signalling pathways. Functionally, these molecular alterations translated into a diminished secretion of key inflammation and infection mediators, such as interleukin-6 (IL-6) and C-C Motif chemokine ligand 5 (CCL5) upon TNF-a stimulation. Similarly, essential signalling kinases including extracellular-signal-regulated kinase (ERK) 1/2, p38 and c-Jun N- terminal kinase (JNK) 2 showed reduced expression in PMM2-CDG cells, and their expression did not alter following TNF-a stimulation, unlike control cells. Conslusion Our findings point to TNFR1 signalling dysregulation as a key contributor to immune dysfunction in PMM2-CDG. Importantly, our study identifies TNFR1 as a promising therapeutic target, suggesting that strategies aimed at modulating TNFR1 activity or restoring glycosylation homeostasis could provide new approaches for treatment development. This work advances our understanding of PMM2 -CDG immunopathology and opens opportunities for targeted therapeutics.
gene therapies
2026-07-07 | Structural insights into mutated human phosphoglucomutase 1 (PGM1) using computational approaches
The phosphoglucomutase 1 (PGM1) enzyme plays a critical role in metabolism and glycosylation in the human body. PGM1 has been linked to multiple disease phenotypes, including the inherited metabolic disorder known as congenital disorders of glycosylation (CDGs). Numerous clinical studies have shown that mutations in key regions of the PGM1 gene affect catalytic activity and induce folding defects of the enzyme. To delve into molecular changes at the supramolecular level, the structural, stability, and other features of PGM1 variants (T19A, N38Y, and D62H) were studied in the present work. To this end, molecular dynamics (MD) simulation at a long timescale (500 ns) was carried out. Parameters such as root-mean-square deviation (RMSD), root-mean-square fluctuations (RMSF), radius of gyration (Rg), solvent-accessible surface area (SASA), hydrogen bonds, and free energy landscape (FEL) were studied and compared with those of the wild-type PGM1. It was noted that mutations 19 A, N38Y, and D62H significantly alter the protein’s structural behavior, causing increased flexibility, reduced stability, and compactness.
2025-08-14 | Are viral vector-mediated therapies compatible with aberrant glycosylation?
The ability of adeno-associated viruses (AAVs) to transduce host cells relies on interactions with glycan moieties on the cellular surface. Consequently, disrupted protein glycosylation, which is seen in a range of neurodevelopmental and neurodegenerative diseases, could impair transduction efficiency. Understanding how altered glycosylation impacts AAV binding is essential to optimize AAV-mediated therapeutic strategies. We used glycoproteomics data from cortical brain organoids and iCardiomyocytes of individuals with congenital disorders of glycosylation (CDG) (ALG13-, PMM2-, and PGM1-CDG) to examine the abundance of AAV-binding glycan species. Additionally, we assessed the abundance of coreceptors in proteomics data. We found that the abundance of AAV-binding glycan species was downregulated for all CDG subtypes, but this was significant only for AAV5-, AAV8-, and AAV9-binding glycan motifs in PGM1-CDG. The proteomics data showed significantly decreased abundance of the coreceptor PDGFRβ in ALG13-CDG. The downregulation of glycan species and AAV coreceptors in models of aberrant protein glycosylation underscores the need to optimize AAV selection for conditions with altered protein glycosylation, including CDG and neurodegenerative diseases such as Parkinson's and Alzheimer's disease.
2023-05-17 | AAV-based gene therapy prevents and halts the progression of dilated cardiomyopathy in a mouse model of phosphoglucomutase 1 deficiency (PGM1-CDG).
Phosphoglucomutase 1 (PGM1) deficiency is recognized as the third most common N-linked congenital disorders of glycosylation (CDG) in humans. Affected individuals present with liver, musculoskeletal, endocrine, and coagulation symptoms; however, the most life-threatening complication is the early onset of dilated cardiomyopathy (DCM). Recently, we discovered that oral D-galactose supplementation improved liver disease, endocrine, and coagulation abnormalities, but does not alleviate the fatal cardiomyopathy and the associated myopathy. Here we report on left ventricular ejection fraction (LVEF) in 6 individuals with PGM1-CDG. LVEF was pathologically low in most of these individuals and varied between 10% and 65%. To study the pathobiology of the cardiac disease observed in PGM1-CDG, we constructed a novel cardiomyocyte-specific conditional Pgm2 gene (mouse ortholog of human PGM1) knockout (Pgm2 cKO) mouse model. Echocardiography studies corroborated a DCM phenotype with significantly reduced ejection fraction and left ventricular dilation similar to those seen in individuals with PGM1-CDG. Histological studies demonstrated excess glycogen accumulation and fibrosis, while ultrastructural analysis revealed Z-disk disarray and swollen/fragmented mitochondria, which was similar to the ultrastructural pathology in the cardiac explant of an individual with PGM1-CDG. In addition, we found decreased mitochondrial function in the heart of KO mice. Transcriptomic analysis of hearts from mutant mice demonstrated a gene signature of DCM. Although proteomics revealed only mild changes in global protein expression in left ventricular tissue of mutant mice, a glycoproteomic analysis unveiled broad glycosylation changes with significant alterations in sarcolemmal proteins including different subunits of laminin-211, which was confirmed by immunoblot analyses. Finally, augmentation of PGM1 in KO mice via AAV9-PGM1 gene replacement therapy prevented and halted the progression of the DCM phenotype.
2005-07-07 | Glycosylation defects in muscular dystrophies.
Congenital disorders of glycosylation are caused by defects in the synthesis of the glycan moiety of glycoproteins or other glycoconjugates. There has been a great explosion in the number of neuromuscular diseases caused by mutations in genes that affect carbohydrate metabolism or protein glycosylation. A common defect in these disorders is the defective processing of alpha-dystroglycan. Recent advances demonstrating mutations in glycosyltransferases and dysfunction of the alpha-beta dystroglycan axis causing different forms of muscular dystrophy, especially with brain involvement, shows clearly that muscle integrity is dependent on glycosylation. We first review the newly identified muscular dystrophies, with a focus on the hypoglycosylation of alpha-dystroglycan, from a clinical, biochemical and genetic standpoint, and second hereditary inclusion body myopathies caused by mutations in the gene that encodes an enzyme responsible for the protein's posttranslational modification that cause sialidation defects. It is shown very recently that molecular recognition of dystroglycan by LARGE is a key determinant in the biosynthetic pathway to produce mature and functional dystroglycan. Gene transfer of LARGE into the cells of individuals with congenital muscular dystrophies restores alpha-dystroglycan function. The clinical spectrum of congenital disorders of glycosylation is becoming increasingly broad. A demonstration of mutations in glycosyltransferases will further help to design diagnostic tools and therapeutic approaches. Recent findings which show that molecular recognition by LARGE is essential for expression of functional dystroglycan and LARGE can functionally bypass alpha-dystroglycan glycosylation defects in distinct congenital muscular dystrophies, indicate a new therapeutic strategy.
2003-07-01 | Highly Efficient Lentiviral Gene Transfer in CD34 + and CD34 + /38 − /lin − Cells from Mobilized Peripheral Blood after Cytokine Prestimulation
Because mobilized peripheral blood (mPB) represents an attractive source of cells for gene therapy, we investigated lentiviral gene transfer in CD34+ cells and the stem/progenitor-cell-enriched CD34+/38−/lin− cell subset isolated from mPB. In this study, we used an optimized third-generation self-inactivating lentiviral vector containing both the central polypurine tract and the woodchuck hepatitis posttranscriptional regulatory element sequences and encoding enhanced green fluorescent protein (EGFP) under the control of the elongation factor lα promoter. This lentivector was first used to compare multiplicity of infection (MOI)-dependent gene transfer efficiency in cord blood (CB) versus mPB CD34+-derived cells, colony-forming cells (CFCs), and long-term culture-initiating cells (LTC-ICs). Results showed a difference in the percentage of transduced cells particularly significant at low MOIs. A plateau was reached where 15% and 25% of CB and mPB cells, respectively, remained refractory to lentiviral trans-duction. Effects of a cytokine prestimulation period (18 hours) with interleukin-3, stem cell factor, Flt-3 ligand, and thrombopoietin were then analyzed in total cells, CFCs, and LTC-ICs derived from mPB CD34+ cells. Transduction levels in those conditions demonstrated a two- and fourfold increase in CFCs and LTC-ICs, respectively, compared with unstimulated (<3 hours) control cells. Moreover, using the same transduction protocol, we were able to efficiently transduce CD34+/38−/lin− cells isolated from mPB, with up to >85% of colonies derived from LTC-ICs expressing EGFP and gene transfer levels remaining stable for 10 weeks in liquid culture. We therefore demonstrate a highly efficient gene transfer in this therapeutically relevant target cell population.
small molecules
2026-08-07 | Hypoglycosylation lowers the mechanical activation threshold of Piezo1 and enhances cortical neuronal mechanotransduction: implications for PMM2-CDG
Abstract Piezo1 is a mechanically activated cation channel whose N-linked glycans support protein maturation and plasma membrane trafficking, but their contribution to mechanical gating is unknown. We asked whether hypoglycosylation alters Piezo1 mechanosensitivity and cortical neuronal mechanotransduction, with potential relevance to neurological manifestations of congenital disorders of glycosylation (CDG). Human Piezo1 was studied in HEK293 cells after mutation of two conserved cap-domain N-glycosylation sites or inhibition of N-glycan maturation with swainsonine or kifunensine. Mechanically activated currents were recorded by cell-attached patch-clamp during incremental negative-pressure pulses, whereas Ca 2+ responses were measured during uniaxial stretch. Piezo1 abundance, synaptic localisation and stretch-evoked Ca 2+ signals were also examined in primary mouse cortical neurons. On poly-L-lysine, N2293Q or N2330Q shifted the pressure-response relationship towards lower activating pressures without changing maximal current or inactivation kinetics. This effect was absent on collagen. Swainsonine and kifunensine reduced mature Piezo1 glycosylation and lowered the mechanical activation threshold. Hypoglycosylation enhanced Ca 2+ entry during submaximal stretch in HEK293 cells. In cortical neurons, inhibition of glycan maturation increased somatic Piezo1 immunoreactivity without changing its association with synaptic markers, and potentiated Ca 2+ responses to both the Piezo1 activator Yoda1 and submaximal stretch. Thus, mature N-glycans and the extracellular adhesive environment jointly set Piezo1’s mechanical activation threshold rather than merely regulating biosynthesis and trafficking. These findings establish glycosylation-mechanics coupling as a determinant of neuronal force sensing and suggest that, by facilitating Piezo1 recruitment, defective glycosylation may increase cortical vulnerability to mechanical stress, potentially contributing to head trauma-triggered neurological episodes in phosphomannomutase 2 deficiency (PMM2-CDG). Key points Piezo1 channels convert mechanical forces into electrical and calcium signals. N-linked glycans support channel trafficking to the plasma membrane, but whether they tune the force needed for Piezo1 activation was unknown. Mutating either of two conserved N-glycosylation sites in Piezo1 cap domain, or pharmacologically restricting N-glycan maturation, lowered channel’s mechanical activation threshold without changing maximal current or inactivation. This sensitisation depended on the adhesive substrate (occurred on poly-L-lysine but not collagen), and was most evident during submaximal stretch, showing that glycosylation and the extracellular mechanical environment jointly determine Piezo1 force sensing. In mouse cortical neurons, impaired N-glycan maturation increased somatic Piezo1 abundance and enhanced Ca 2+ responses to its chemical activator Yoda1 and stretch, without changing synaptic localisation. By allowing weak mechanical inputs to recruit Piezo1 more effectively, defective glycosylation may increase cortical responses to mechanical stress and help explain susceptibility to head trauma-triggered neurological episodes in phosphomannomutase 2 deficiency (PMM2-CDG).
2026-02-21 | PGM1 deficiency is linked to sarcomeric and mitochondrial dysfunction in patient-derived iPSC-cardiomyocytes
Abstract Background PGM1-congenital disorder of glycosylation (PGM1-CDG) is frequently associated with cardiomyopathy. Although galactose therapy corrects glycosylation defects, cardiac dysfunction typically persists, suggesting a glycosylation-independent mechanism. Recent evidence of mitochondrial abnormalities in PGM1-deficient human and murine heart, together with the association of PGM1 with the Z-disk protein LDB3 (ZASP/Cypher), suggests a critical role for PGM1 in cardiomyocyte structural and energetic homeostasis. We hypothesized that PGM1-related cardiomyopathy arises from a glycosylation-independent disruption of Z-disk–mitochondrial coupling driven by loss of PGM1–LDB3 interactions, resulting in mitochondrial energy failure and impaired contractile function. Methods Induced pluripotent stem cell–derived cardiomyocytes (iCMs) were generated from PGM1-deficient patient fibroblasts. Multielectrode array (MEA) recordings, untargeted (glyco)proteomics, and pathway analysis were performed to assess functional and molecular changes. Key findings were validated using tracer metabolomics and mitochondrial respiration assays. Results PGM1-deficient iCMs exhibited reduced beating frequency, impaired contractility, and prolonged contraction kinetics. Proteomic analyses revealed depletion of Z-disk components, including LDB3. AlphaFold3 structural modeling predicted a direct interaction between PGM1 and LDB3, implicating PGM1 in Z-disk integrity, which was confirmed in vitro. In addition, mitochondrial proteins were severely depleted, prompting us to investigate mitochondrial function. Functional validation confirmed extensive metabolic rewiring, energy depletion, and severely impaired mitochondrial respiration. Finally, the in silico drug repurposing identified possible therapeutic options that could target PGM1-deficient cardiomyopathy. Conclusion Our data suggests PGM1 is key regulator of cardiomyocyte function, linking sarcomeric Z-disk integrity with mitochondrial metabolism. These mechanistic insights offer a foundation for developing targeted therapies for PGM1-CDG and potentially other cardiomyopathies involving Z-disk dysfunction. Graphical Abstract
2025-11-28 | SLC35A2-Related Brain Disorders: Genetics, Pathophysiology, and Therapeutic Insights
SLC35A2 encodes the Golgi uridine diphosphate galactose transporter, which is essential for glycosylation of glycoproteins and glycolipids. Variants in this gene, either germline or somatic, have emerged as causes of diverse neurological disorders ranging from congenital disorders of glycosylation (SLC35A2-CDG) to focal cortical malformations such as mild malformation of cortical development with oligodendroglial hyperplasia in epilepsy (MOGHE). This review summarizes the molecular function of SLC35A2, clinical phenotypes of congenital and somatic variants, insights from functional assays and animal models, and therapeutic perspectives including galactose supplementation and precision medicine. We aim to provide an integrative synthesis of human genetics, neuropathology, glycomics, and translational approaches.
2025-11-03 | Novel PGM1 Mutation in Congenital Disorder of Glycosylation Type 1T: A Case Report of Liver Failure and Myopathy.
BACKGROUND Congenital disorders of glycosylation (CDG) are rare, inherited metabolic conditions caused by defects in glycoprotein synthesis. CDG Type 1T, associated with mutations in the phosphoglucomutase 1 (PGM1) gene, often presents with hepatic dysfunction, developmental delay, and multisystem involvement. Due to clinical overlap with other metabolic disorders, misdiagnosis is common, leading to delayed treatment. CASE REPORT We report a 20-month-old boy, born to consanguineous parents, who initially received a misdiagnosis of galactosemia following abnormal newborn screening. Despite dietary modifications, he developed persistent transaminitis, coagulopathy, hypotonia, and delayed motor milestones. Further evaluation revealed abnormal carbohydrate-deficient transferrin analysis, and whole exome sequencing identified a homozygous PGM1 variant of uncertain significance, supporting CDG Type 1T diagnosis. Liver biopsy demonstrated steatosis with bridging portal fibrosis. The patient was started on oral D-galactose supplementation (1.5 g/kg/day). Over a 51-day follow-up period, liver enzymes improved markedly, with AST declining from 1980 to 385 U/L and ALT from 695 to 210 U/L, alongside normalization of coagulation profiles. Muscle enzyme response was partial, with creatine kinase levels remaining mildly elevated, reflecting differential therapeutic effects across tissues. CONCLUSIONS This case underscores the diagnostic challenges of CDG Type 1T and emphasizes the importance of combining biochemical markers and genetic sequencing to achieve timely diagnosis. The identified PGM1 variant, although classified as a variant of uncertain significance, was strongly supported by clinical and biochemical findings. Significant hepatic improvement with D-galactose highlights the therapeutic potential of early targeted supplementation, although incomplete muscular response indicates the need for ongoing follow-up and exploration of adjunctive therapies.
2025-10-06 | Exploring Secondary Biotinidase Deficiency and Biotin Supplementation in PMM2-CDG
The congenital disorders of glycosylation (CDG) encompass >190 multiorgan disorders with predominantly neurodevelopmental phenotypes with no causative treatment available. The glycoprotein biotinidase (BTD) provides biotin, an essential cofactor for carboxylases in ubiquitous metabolic pathways. Individuals with (partial) BTD deficiency (BTDD) and CDG patients show overlapping phenotypes like movement disorders, seizures, and neurodevelopmental issues. Biotin is a water-soluble, inexpensive, and safe food supplement. Patients with primary BTDD respond well to oral biotin supplement. We here explore secondary BTDD and the effect of biotin supplementation in PMM2-CDG in an initial open-label study.BTD activity in dried blood spots from 29 individuals with PMM2-CDG indicated a mean reduction to 27% (range: 23.0-40.5%) at group level. Patients (mean: 19.6 ± 11.9 years) were supplemented with 10 mg biotin daily for 12 months. The parents/caretaker reported positive responses in 62 to 69% of patients across seven (performance, social, at home, self-control, self-care, leisure, health) of the nine categories covered by the Adaptive Behavior Assessment System-II (ABAS-II) questionnaires. The reported positive effect of biotin supplementation differed between age groups, ranging from 54% (16-43 years) via 62% (2-5 years) to 80% (6-13 years). Its effect was reported to be the highest in the moderate to severely affected patient subgroups, with significant improvements in home functioning, health, performance, leisure, self-control. No adverse effects were reported.Given the absence of other treatments, the supportive effect of Biotin in PMM2-CDG deserves further exploration.
proteins
2025-10-16 | Phosphoglucomutase 1 deficiency misdiagnosed as Laron syndrome.
Protein glycosylation is a crucial process involving the addition of oligosaccharides to proteins, which plays a significant role in stabilizing proteins and mediating protein-protein interactions. Mutations in genes associated with glycosylation can lead to congenital disorders of glycosylation (CDG), resulting in multisystem disorders. One such example is phosphoglucomutase 1 (PGM1) -CDG, caused by a deficiency of the PGM1 enzyme. In this report, we describe a patient with PGM1-CDG who was initially misdiagnosed with growth hormone insensitivity and benefited from recombinant human insulin-like growth factor-1 (rhIGF-1) therapy. A 2-year-11-month-old female patient, born to first-degree cousin parents, presented with hypoglycemia and short stature. Her physical examination revealed frontal bossing, infantile facial appearance, and short stature. Laboratory investigations revealed that basal and stimulated growth hormone levels were very high, IGF-1 was low, and the inadequate response to the IGF generation test was consistent with growth hormone insensitivity (GHI). The patient was started on rhIGF-1 therapy, resulting in significant height gain. Subsequently, the patient showed improvement in height with rhIGF-1 therapy. The patient, who had additional findings such as elevated creatine kinase (CK) and transaminase levels and cardiomyopathy, was diagnosed with PGM1-CDG. This case highlights that PGM1-CDG can mimic clinical and laboratory findings of GHI. CDG diagnosis should be considered in cases with clinical and laboratory findings of GHI accompanied by multisystem disorders such as hepatopathy, elevated CK, and cardiomyopathy. This patient's successful response to rhIGF-1 therapy highlights the potential benefits of targeted therapies in treating growth hormone-related disorders in patients.
2024-09-18 | Genetics of glycosylation in mammalian development and disease.
Glycosylation of proteins and lipids in mammals is essential for embryogenesis and the development of all tissues. Analyses of glycosylation mutants in cultured mammalian cells and model organisms have been key to defining glycosylation pathways and the biological functions of glycans. More recently, applications of genome sequencing have revealed the breadth of rare congenital disorders of glycosylation in humans and the influence of genetics on the synthesis of glycans relevant to infectious diseases, cancer progression and diseases of the immune system. This improved understanding of glycan synthesis and functions is paving the way for advances in the diagnosis and treatment of glycosylation-related diseases, including the development of glycoprotein therapeutics through glycosylation engineering.
2022-03-08 | A novel fission yeast platform to model N-glycosylation and the bases of congenital disorders of glycosylation type I.
Congenital disorders of glycosylation type I (CDG-I) are inherited human diseases caused by deficiencies in lipid-linked oligosaccharide (LLO) synthesis or the glycan transfer to proteins during N-glycosylation. We constructed a platform of 16 Schizosaccharomyces pombe strains that synthesize all possible theoretical combinations of LLOs containing three to zero glucose (Glc) residues and nine to five mannose (Man) residues. The occurrence of unexpected LLOs suggested the requirement of specific Man residues for glucosyltransferase activities. We then quantified protein hypoglycosylation in each strain and found that in S. pombe the presence of Glc in the LLO is more relevant to the transfer efficiency than the number of Man residues. Surprisingly, a decrease in the number of Man residues in glycans somehow improved the glycan transfer. The most severe hypoglycosylation was produced in cells that synthesized LLOs completely lacking Glc and having a high number of Man residues. This deficiency could be reverted by expressing a single-subunit oligosaccharyltransferase with a broad range of substrate specificity. Our work shows the usefulness of this new S. pombe set of mutants as a platform to model the molecular bases of human CDG-I diseases. This article has an associated First Person interview with the first authors of the paper.
2018-11-02 | Abrogation of glucosidase I–mediated glycoprotein deglucosylation results in a sick phenotype in fission yeasts: Model for the human MOGS-CDG disorder
Glucosidase I (GI) removes the outermost glucose from protein-linked Glc3Man9GlcNAc2 (G3M9) in the endoplasmic reticulum (ER). Individuals with congenital disorders of glycosylation MOGS-CDG bear mutations in the GI-encoding gene (gls1). Although GI absence has been reported to produce lethality in Schizosaccharomyces pombe yeasts, here we obtained two viable Δgls1 mutants, one with a very sick but not lethal phenotype (Δgls1-S) and the other with a healthier one (Δgls1-H). The sick strain displayed only G3M9 as an ER protein–linked oligosaccharide, whereas the healthier strain had both G3M9 and Man9GlcNAc2. The lipid-linked oligosaccharide patterns of the two strains revealed that the most abundantly formed glycans were G3M9 in Δgls1-S and Glc2Man9GlcNAc2 in Δgls1-H, suggesting reduced Alg10p glucosyltransferase activity in the Δgls1-H strain. A mutation in the alg10+ gene was indeed observed in this strain. Our results indicated that abrogated G3M9 deglucosylation was responsible for the severe defects observed in Δgls1-S cells. Further studies disclosed that the defects could not be ascribed to disruption of glycoprotein entrance into calnexin-folding cycles, inhibition of the oligosaccharyltransferase by transfer reaction products, or reduced proteasomal degradation of misfolded glycoproteins. Lack of triglucosylated glycoprotein deglucosylation neither significantly prevented glycan elongation in the Golgi nor modified the overall cell wall monosaccharide composition. Nevertheless, it resulted in a distorted cell wall and in the absence of underlying ER membranes. Furthermore, Golgi expression of human endomannosidase partially restored normal growth in Δgls1-S cells. We propose that accumulation of G3M9-bearing glycoproteins is toxic and at least partially responsible for defects observed in MOGS-CDG. Glucosidase I (GI) removes the outermost glucose from protein-linked Glc3Man9GlcNAc2 (G3M9) in the endoplasmic reticulum (ER). Individuals with congenital disorders of glycosylation MOGS-CDG bear mutations in the GI-encoding gene (gls1). Although GI absence has been reported to produce lethality in Schizosaccharomyces pombe yeasts, here we obtained two viable Δgls1 mutants, one with a very sick but not lethal phenotype (Δgls1-S) and the other with a healthier one (Δgls1-H). The sick strain displayed only G3M9 as an ER protein–linked oligosaccharide, whereas the healthier strain had both G3M9 and Man9GlcNAc2. The lipid-linked oligosaccharide patterns of the two strains revealed that the most abundantly formed glycans were G3M9 in Δgls1-S and Glc2Man9GlcNAc2 in Δgls1-H, suggesting reduced Alg10p glucosyltransferase activity in the Δgls1-H strain. A mutation in the alg10+ gene was indeed observed in this strain. Our results indicated that abrogated G3M9 deglucosylation was responsible for the severe defects observed in Δgls1-S cells. Further studies disclosed that the defects could not be ascribed to disruption of glycoprotein entrance into calnexin-folding cycles, inhibition of the oligosaccharyltransferase by transfer reaction products, or reduced proteasomal degradation of misfolded glycoproteins. Lack of triglucosylated glycoprotein deglucosylation neither significantly prevented glycan elongation in the Golgi nor modified the overall cell wall monosaccharide composition. Nevertheless, it resulted in a distorted cell wall and in the absence of underlying ER membranes. Furthermore, Golgi expression of human endomannosidase partially restored normal growth in Δgls1-S cells. We propose that accumulation of G3M9-bearing glycoproteins is toxic and at least partially responsible for defects observed in MOGS-CDG.
2012-06-12 | A sensitive green fluorescent protein biomarker of N-glycosylation site occupancy.
N-glycosylation mediates many biological functions. Genetic defects in the N-glycosylation pathway cause >35 inherited human disorders called congenital disorders of glycosylation (CDGs). As a result, some N-glycosylation sites are unoccupied. Serum transferrin is a diagnostic marker for these patients, but there are no corresponding cellular markers to assess glycosylation competence. Therefore, we engineered a green fluorescent protein (GFP) construct to measure N-glycosylation site occupancy. We designed an endoplasmic reticulum-retained GFP biomarker whose fluorescence is lost when it is N-glycosylated due to steric hindrance by the glycan. This marker is a highly sensitive indicator of N-glycosylation site occupancy. In CDG cells carrying the GFP construct, a 25% decrease of glycosylation efficiency induces a 5-fold increase in fluorescence, while cDNA complementation of the genetic defect results in a 5-fold decrease in fluorescence. This engineered GFP detects impaired N-glycosylation in multiple cell lines, including CHO cells, HeLa cells, normal and patient fibroblasts, induced pluripotent stem cells (iPSCs), and human embryonic stem cells (hESCs). This marker is a highly sensitive tool to study N-glycosylation site occupancy. It can be used to screen for compounds that reverse poor N-glycosylation site occupancy.
vaccines
2023-06-02 | A liposomal carbohydrate vaccine, adjuvanted with an NKT cell agonist, induces rapid and enhanced immune responses and antibody class switching
Congenital disorders of glycosylation (CDGs) are genetic diseases caused by gene defects in glycan biosynthesis pathways, and there is an increasing number of patients diagnosed with CDGs. Because CDGs show many different clinical symptoms, their accurate clinical diagnosis is challenging. Recently, we have shown that liposome nanoparticles bearing the ALG1-CDG and PMM2-CDG biomarkers (a tetrasaccharide: Neu5Ac-α2,6-Gal-β1,4-GlcNAc-β1,4-GlcNAc) stimulate a moderate immune response, while the generated antibodies show relatively weak affinity maturation. Thus, mature antibodies with class switching to IgG are desired to develop high-affinity antibodies that may be applied in medical applications.In the present study, a liposome-based vaccine platform carrying a chemoenzymatic synthesized phytanyl-linked tetrasaccharide biomarker was optimized. The liposome nanoparticles were constructed by dioleoylphosphatidylcholine (DOPC) to improve the stability and immunogenicity of the vaccine, and adjuvanted with the NKT cell agonist PBS57 to generate high level of IgG antibodies. The results indicated that the reformulated liposomal vaccine stimulated a stronger immune response, and PBS57 successfully induce an antibody class switch to IgG. Further analyses of IgG antibodies elicited by liposome vaccines suggested their specific binding to tetrasaccharide biomarkers, which were mainly IgG2b isotypes.Immunization with a liposome vaccine carrying a carbohydrate antigen and PBS57 stimulates high titers of CDG biomarker-specific IgG antibodies, thereby showing great potential as a platform to develop rapid diagnostic methods for ALG1-CDG and PMM2-CDG.
other
2025-09-18 | Table 3_Immunopathology in PMM2-CDG: Defective glycosylation impact in the TNFα -TNFR1 signalling pathway.xlsx
Introduction Glycosylation is a post-translational modification that plays a crucial role in immune system activity. Phosphomannomutase 2-Congenital Disorder of Glycosylation (PMM2-CDG) is a rare genetic disease affecting glycosylation with a multi-systemic impact. PMM2-CDG patients commonly show immune disfunction and elevated pro-inflammatory cytokine levels that may link to other symptoms. However, the underlying immune mechanisms remain unclear. Given Tumour Necrosis Factor (TNF)’s key role in inflammation, this study proposes that defective glycosylation of its receptors disrupts intracellular signalling, leading to changes in the immune response of PMM2-CDG patients. Methods To address this, we applied an integrative approach, combining transcriptomics, glycomics, and immune-related assays to investigate the impact of TNF-a stimulation via TNF receptor 1 (TNFR1) in a cohort of PMM2-CDG patients’ skin fibroblasts. Results Our results reveal a multifaceted disruption of TNF-a signalling in PMM2-CDG fibroblasts. We observed structural abnormalities in TNFR1, including altered receptor shedding. PMM2-CDG cells also showed an altered N-glycosylation profile, affecting particularly, high mannose N-glycans. At transcriptional level, PMM2-CDG cells, especially those bearing the R141H heterozygous variant, exhibited a distinct gene expression profile, after stimulation, characterized by dysregulation of immune and signalling pathways. Functionally, these molecular alterations translated into a diminished secretion of key inflammation and infection mediators, such as interleukin-6 (IL-6) and C-C Motif chemokine ligand 5 (CCL5) upon TNF-a stimulation. Similarly, essential signalling kinases including extracellular-signal-regulated kinase (ERK) 1/2, p38 and c-Jun N- terminal kinase (JNK) 2 showed reduced expression in PMM2-CDG cells, and their expression did not alter following TNF-a stimulation, unlike control cells. Conslusion Our findings point to TNFR1 signalling dysregulation as a key contributor to immune dysfunction in PMM2-CDG. Importantly, our study identifies TNFR1 as a promising therapeutic target, suggesting that strategies aimed at modulating TNFR1 activity or restoring glycosylation homeostasis could provide new approaches for treatment development. This work advances our understanding of PMM2 -CDG immunopathology and opens opportunities for targeted therapeutics.
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Drug Discovery Landscape
1 orphan drug designation for PGM1-CDG.
1 orphan drug designation for PGM1-CDG.
Drug | Therapy type | Regulator | Orphan designation | Approval | Sponsor |
|---|---|---|---|---|---|
D-Galactose | small molecules | FDA | 2019-01-14 | — | AUG Therapeutics, LLC |
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