RARE DISEASE
Pelizaeus-Merzbacher disease
Pelizaeus-Merzbacher disease
Pelizaeus-Merzbacher disease
Synonyms: Diffuse familial brain sclerosis, PMD, Pelizaeus-Merzbacher brain sclerosis, Sudanophilic leukodystrophy, Paelizeus-Merzbacher type
Synonyms: Diffuse familial brain sclerosis, PMD, Pelizaeus-Merzbacher brain sclerosis, Sudanophilic leukodystrophy, Paelizeus-Merzbacher type
Synonyms: Diffuse familial brain sclerosis, PMD, Pelizaeus-Merzbacher brain sclerosis, Sudanophilic leukodystrophy, Paelizeus-Merzbacher type
Drug discovery
2
drugs
With orphan designations
Overview
Pelizaeus-Merzbacher disease (PMD) is an X-linked leukodystrophy caused by PLP1 gene mutations, disrupting myelin formation in the central nervous system. It primarily affects males, presenting with nystagmus, hypotonia, ataxia, and progressive spasticity. PMD manifests as classic (developmental delay with partial myelination) or severe connatal forms (neonatal onset, minimal myelination). Hypomyelination leads to motor and cognitive impairment, with lifespan ranging from childhood to adulthood depending on severity [1][4][16].
Therapies
Supportive care: Physical therapy, antispasticity agents (baclofen), gastrostomy for dysphagia, and seizure management [4][7][9].
Emerging therapies: Antisense oligonucleotides to reduce toxic PLP1 protein [3][11], ketogenic diets to support oligodendrocyte function [4], and neural stem cell transplantation trials [5][19].
Categories: rare genetic diseases, rare neurological diseases, rare ophthalmic disorders
Research Papers
133 drug discovery papers about Pelizaeus-Merzbacher disease, with 5 first-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
133 drug discovery papers about Pelizaeus-Merzbacher disease, with 5 first-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
categories:
Small molecules
gene therapies
2026-08-11 | Pelizaeus-Merzbacher disease in a manifesting female carrier with a PLP1 frameshift variant: neuroimaging and neurophysiological findings
The Annals of Clinical Neurophysiology (ACN), the joint official journal of The Korean Society of Clinical Neurophysiology and The Korean Society of Pain & Autonomic Disorders, publishes twice a year on April 30 and October 31 in English.
2026-08-03 | Gap junction protein gamma 2 (GJC2) gene frameshift deletion in Toy Poodles with hypomyelinating leukodystrophy resembling human Pelizaeus-Merzbacher-like disease 1.
Pelizaeus-Merzbacher-like disease type 1 (PMLD1), also known as hypomyelinating dystrophy 2, is a typical slowly progressive hypomyelinating leukodystrophy (HLD) that manifests in the neonatal period or early infancy. In humans, PMLD1 is inherited as an autosomal recessive trait, with genetic variants identified in the gap junction protein gamma 2 (GJC2) gene. Six juvenile-age Toy Poodle dogs exhibited coarse, vertical head and trunk tremors from immediately after birth. Conventional magnetic resonance imaging revealed uniform signal hyperintensities throughout the subcortical white matter in all dogs. All dogs were euthanized. Subsequent histopathological examination revealed vacuolar changes and demyelination in the cerebral and cerebellar white matter, leading to a diagnosis of HLD. Genetic analysis of five affected dogs identified a shared homozygous 14-base pair deletion in the GJC2 gene, XM_038556433.1:c.920_933del. To the best of our knowledge, this is the first report of a pathogenic GJC2 variant in dogs or any other domestic animal species. The results will enable genetic testing and provide a spontaneous large animal model for the homologous human disease.
2026-02-25 | Spatially concentrated adenine base editors efficiently correct PLP1 mutations in oligodendrocytes.
Oligodendrocytes (OLs), the myelinating cells of the central nervous system, are particularly prone to pathogenic G-to-A mutations, such as PLP1A243V, which causes Pelizaeus-Merzbacher disease (PMD), a lethal hypomyelinating disorder lacking effective therapy. Although adenine base editors (ABEs) can in principle correct such mutations, their application in OLs is limited by inefficient on-target editing. Here, we develop a spatially concentrated ABE (cABE) strategy that enhances editing by promoting nuclear translocation of tRNA adenosine deaminase (TadA*) from the cytoplasm. Using a SunTag-based multivalent recruitment system, TadA* is locally enriched at genomic targets (cABE-1.0), achieving robust editing in vitro. To enable in vivo delivery while preserving high efficiency and fidelity, SpCas9 is replaced with compact eNme2-C Cas9, generating an AAV-compatible variant (cABE-2.0). Notably, cABE-2.0 forms dynamic nuclear puncta with properties of liquid-liquid phase separation, enhancing on-target editing while substantially reducing transcriptome-wide RNA off-target effects. Functionally, cABE-2.0 efficiently corrects the PLP1A243V mutation in OLs, restores Plp subcellular localization, and rescues myelination-related phenotypes. These findings demonstrate that spatial reorganization, rather than increasing intrinsic catalytic activity of TadA*, provides a distinct principle for improving base editing in difficult-to-edit cell types, such as OLs, offering a mechanistic and technical framework for gene therapy of PMD and related myelin disorders.
2025-06-10 | Molecular dynamics simulation of GJC2 mutants reveal pathogenic mechanisms of PMLD1 and SPG44.
GJC2 encodes connexin 47 (Cx47), a gap junction protein expressed by oligodendrocytes that forms gap junction channels (GJCs) between adjacent oligodendrocytes (or astrocytes, via heterotypic Cx47-Cx43 GJCs). Autosomal recessive mutations of GJC2 lead to at least three central nervous system phenotypes: Pelizaeus-Merzbacher-like disease 1 (PMLD1), spastic paraparesis 44 (SPG44), and a minimal leukodystrophy. Here, we describe the clinical, functional, and molecular effects of two mutations in GJC2, p.G40S, and p.R244P, identified in two different families with GJC2-related disorders. Expressed exogenously, p.G40S forms GJC plaques like WT but does not functionally couple with WT nor with Cx43. p.R244P also fails to demonstrate functional coupling. Moreover, plaque formation is absent, concomitant with intracellular connexin accumulation. When the two mutants are co-expressed in a compound heterozygous state, plaques form, but no GJC coupling is detected in any configuration. MD simulations demonstrate that p.G40S modifies secondary structure of the pore-lining α-helix, disrupting supersecondary interactions with the N-terminal helix and predicting channel closure. p.R244P simulations are characterized by partial loss of the extracellular β-sheet domains and a marked reduction of electrostatic interactions between the connexin and lipid headgroups of the plasma membrane, suggesting pathways by which p.R244P mutation impairs GJC formation. This combination of in vitro assays and molecular simulations provides mechanistic insight into the pathogenesis of GJC2-related disease.
2024-09-26 | Inherited white matter disorders: Hypomyelination (myelin disorders).
Hypomyelinating leukodystrophies are a subset of genetic white matter diseases characterized by insufficient myelin deposition during development. MRI patterns are used to identify hypomyelinating disorders, and genetic testing is used to determine the causal genes implicated in individual disease forms. Clinical course can range from severe, with patients manifesting neurologic symptoms in infancy or early childhood, to mild, with onset in adolescence or adulthood. This chapter discusses the most common hypomyelinating leukodystrophies, including X-linked Pelizaeus-Merzbacher disease and other PLP1-related disorders, autosomal recessive Pelizaeus-Merzbacher-like disease, and POLR3-related leukodystrophy. PLP1-related disorders are caused by hemizygous pathogenic variants in the proteolipid protein 1 (PLP1) gene, and encompass classic Pelizaeus-Merzbacher disease, the severe connatal form, PLP1-null syndrome, spastic paraplegia type 2, and hypomyelination of early myelinating structures. Pelizaeus-Merzbacher-like disease presents a similar clinical picture to Pelizaeus-Merzbacher disease, however, it is caused by biallelic pathogenic variants in the GJC2 gene, which encodes for the gap junction protein Connexin-47. POLR3-related leukodystrophy, or 4H leukodystrophy (hypomyelination, hypodontia, and hypogonadotropic hypogonadism), is caused by biallelic pathogenic variants in genes encoding specific subunits of the transcription enzyme RNA polymerase III. In this chapter, the clinical features, disease pathophysiology and genetics, imaging patterns, as well as supportive and future therapies are discussed for each disorder.
small molecules
2026-02-27 | Mutant PLP1 impairs COPII vesicle formation via ER calcium depletion in Pelizaeus-Merzbacher disease.
Pelizaeus-Merzbacher disease (PMD) is a devastating, X-linked hypomyelinating leukodystrophy caused by mutations in a myelin gene, PLP1. While overwhelming endoplasmic reticulum (ER) stress caused by the accumulation of mutant PLP1 is widely recognized, blockade of the apoptotic arm of the unfolded protein response (UPR) failed to rescue the phenotypes in murine disease models, suggesting the involvement of additional, critical cellular mechanisms in oligodendrocyte dysfunction. Herein, we identified ER Ca2+ depletion and disrupted ER-Golgi trafficking as key cellular pathologies in PMD. Mutant PLP1 impairs COPII vesicle formation by destabilizing its key components, including Sec31A at ER exit sites due to the Ca2+ transport dysregulation and deconstruction of the ALG-2/Sec31A/AnxA11 interaction. Pharmacological restoration of ER Ca2+ levels rescued COPII formation. These findings highlight how PLP1 mutations affect the intracellular trafficking of membrane and secretory proteins through the ER Ca2+ depletion, which may be associated with the clinical consequences of PMD and other inherited myelin disorders.
2025-12-27 | Integrated stress response inhibition prolongs the lifespan of a Pelizaeus-Merzbacher disease mouse model by increasing oligodendrocyte survival.
The leukodystrophy Pelizaeus-Merzbacher disease (PMD) is caused by myelin protein proteolipid protein gene (PLP1) mutations. PMD is characterized by oligodendrocyte death and CNS hypomyelination; thus, increasing oligodendrocyte survival and enhancing myelination could provide therapeutic benefit. Here, we use the PMD mouse model Jimpy to determine the impact of the integrated stress response (ISR) on the oligodendrocyte response to mutant PLP expression. Male Jimpy animals in which the ISR-triggering eukaryotic initiation factor (eIF) 2α kinase, protein kinase-like endoplasmic reticulum kinase (PERK), is inactivated have an extended lifespan that correlates with increased oligodendrocyte survival and enhanced CNS myelination. Inactivation of downstream components of the ISR pathway, in contrast, does not rescue oligodendrocytes or myelin. Phosphorylated eIF2α inhibits the exchange factor eIF2B, resulting in diminished protein synthesis. Treatment with small molecule eIF2B activators 2BAct and ISRIB increases oligodendrocyte survival, CNS myelination, and doubled the Jimpy lifespan. These results suggest that ISR modulation could provide therapeutic benefit to PMD patients.
2025-05-16 | Pelizaeus-Merzbacher Disease as a Cause of Early-Onset Developmental Delay: A Case Report.
Pelizaeus-Merzbacher disease (PMD) is a rare X-linked hypomyelinating leukodystrophy disorder caused by a mutation in the proteolipid protein 1 (PLP1) gene which is responsible for myelin formation in the central nervous system. We report a case of PMD in a male patient who initially presented with developmental delay at three months and was ultimately diagnosed at 10 years and 7 months of age. We aim to describe the initial presentation, clinical course of PMD and the investigations that aid in diagnosis so that future cases may be identified earlier. During the investigative workup of our patient, a deletion of exon 16 - an extremely rare heterozygous nucleotide variation, c.330C>T (p.D110D) - was identified, the pathogenicity of which has not been previously documented in the literature. In our report, we also aim to highlight the potential use of biotin in improving symptoms in such patients as there is currently no curative treatment available.
2024-11-29 | Efficacy of combined treatment with a wearable cyborg hybrid assistive limb and intrathecal baclofen therapy in a pediatric patient with spastic paraplegia
Hybrid Assistive Limb (HAL) is a movement support robot that assists the walking function of patients with diseases causing muscle weakness in the lower limbs. Intrathecal baclofen (ITB) therapy exerts positive effects on muscle tone in children with severe spasticity who have difficulty walking. The present case report describes a child with spastic paraplegia who underwent intensive robotic rehabilitation with HAL and combined ITB therapy. A 14-year-old boy with spastic paraplegia from Pelizaeus-Merzbacher disease was undergoing treatment with oral muscle relaxants and botulinum toxin A. However, the medications were ineffective and his spasticity was progressing. A baclofen infusion pump was implanted with the catheter tip at the T10 level and ITB therapy was started. A regimen of 12.5 μg/day dose of baclofen was administered and his spasticity of limbs and trunk were attenuated. Walking practice using HAL was performed under spasticity relief by ITB therapy and gait function and patterns, excluding endurance, were improved. The attenuation of spasticity by ITB therapy made “Lying, Rolling and Sitting” easier for the patient, but may have affected “Standing”, which was supported using spasticity, and also affected the Caregiver Assistance Scale of the Mobility domain of the Pediatric Evaluation of Disability Inventory (PEDI). While, the amount of assistance required for the Activities of Daily Living (ADLs) related to self-care and the overall caregiver burden both decreased. This is the first case report to demonstrate the efficacy and safety of combined ITB therapy and HAL rehabilitation in an ambulatory pediatric patient.
2024-07-31 | Alleviating Neurodegenerative Diseases Associated with Mitochondrial Defects by Therapeutic Biomolecules.
Neurodegenerative diseases are emerging as a global health concern in the current scenario, and their association with mitochondrial defects has been a potential area of research. Mitochondria, one of the essential organelles of the cell, serve as the cell's powerhouse, producing energy and ensuring cellular health. Neurodegenerative diseases such as Alzheimer's, Parkinson's, Huntington's, amyotrophic lateral sclerosis, and Pelizaeus-Merzbacher disease have been found to be primarily triggered by mitochondrial malfunction. One of the key byproducts of mitochondrial respiration, reactive oxygen species, also contributes significantly to mitochondrial DNA mutations that eventually cause mitochondrial breakdown. This review paper comprehensively examines the potential of therapeutic biomolecules, specifically mitochondria-specific antioxidants, in mitigating the impact of mitochondrial defects on neurodegenerative diseases. It provides a detailed analysis of the mechanisms involved in mitochondrial dysfunction, the potential therapeutic targets of these biomolecules, and their structureactivity relationship information are also discussed in this review. Various research articles and publications were used extensively in compiling the data, and the structures of biomolecules were prepared using software such as ChemDraw and ChemSketch. Crucial elements triggering mitochondrial abnormalities were identified and a tabular compilation of bioactive antioxidant compounds along with their therapeutic targets, was presented. Mitochondria-specific antioxidant therapy is an innovative and promising strategy for the management of neurodegenerative diseases associated with mitochondrial defects. This review provides a thorough summary of the current state of research and promising avenues of research and development in this field, emphasizing the importance of further investigations and clinical trials to elucidate their therapeutic benefits.
cell therapies
2024-10-03 | A rare case of radiologically diagnosed Pelizaeus-Merzbacher\'s disease (PMD) in a female infant
Pelizaeus-Merzbacher disease (PMD) is a rare X-linked dysmyelinating disorder caused by mutations in the PLP1 gene. Typically affecting males, PMD can also manifest in females due to skewed X-inactivation. Early diagnosis is crucial for managing the disease, with MRI serving as a potential alternative to genetic testing in resource-limited settings. We report the case of an 11-month-old female infant presenting with regression of developmental milestones. Initially, the infant achieved appropriate milestones but later exhibited impaired motor functions and reduced interest in toys. Routine laboratory tests were normal. MRI revealed bilaterally symmetrical T2/FLAIR hyperintense and T1 hypointense signal alterations in the cerebral white matter and brainstem, suggestive of PMD. Genetic testing was unavailable due to financial constraints. The patient’s two elder sisters, aged 9 and 10, also exhibited neuroregression and were bedridden, hinting at a genetic link. Diagnosis was based on characteristic MRI findings, as genetic testing was inaccessible. Differential diagnoses, including Salla disease and other leukodystrophies, were ruled out via imaging. Management involved a multidisciplinary approach, incorporating play therapy, speech therapy, physiotherapy for spasticity, and behavioral therapy. Parents were counseled on seizure management and potential antiepileptic use. Emerging treatments like stem cell therapy are under investigation. This case underscores the importance of MRI in diagnosing PMD, especially in settings where genetic testing is impractical. We advocate for the use of brain imaging in early diagnosis to improve patient outcomes through timely supportive therapy. Recognizing PMD in females, though rare, is essential for comprehensive care.
2023-08-04 | Human iPSC-derived neural stem cells display a radial glia-like signaturein vitroand favorable long-term safety in transplanted mice
ABSTRACT Human induced pluripotent stem cell-derived neural stem/progenitor cells (hiPSC-NSCs) are a promising source for cell therapy approaches to treat neurodegenerative and demyelinating disorders. Despite ongoing efforts to characterize hiPSC-derived cells in vitro and in vivo , we lack comprehensive genome- and transcriptome-wide studies addressing hiPSC-NSC identity and safety, which are critical for establishing accepted criteria for prospective clinical applications. Here, we evaluated the transcriptional and epigenetic signatures of hiPSCs and differentiated hiPSC-NSC progeny, finding that the hiPSC-to-NSC transition results in a complete loss of pluripotency and the acquisition of a radial glia-associated transcriptional signature. Importantly, hiPSC-NSCs share with somatic human fetal NSCs (hfNSCs) the main transcriptional and epigenetic patterns associated with NSC-specific biology. In vivo , long-term observation (up to 10 months) of mice intracerebrally transplanted as neonates with hiPSC-NSCs showed robust engraftment and widespread distribution of human cells in the host brain parenchyma. Engrafted hiPSC-NSCs displayed multilineage potential and preferentially generated glial cells. No hyperproliferation, tumor formation, or expression of pluripotency markers was observed. Finally, we identified a novel role of the Sterol Regulatory Element Binding Transcription Factor 1 (SREBF1) in the regulation of astroglial commitment of hiPSC-NSCs. Overall, these comprehensive in vitro and in vivo analyses provide transcriptional and epigenetic reference datasets to define the maturation stage of NSCs derived from different hiPSC sources, and to clarify the safety profile of hiPSC-NSCs, supporting their continuing development as an alternative to somatic hfNSCs in treating neurodegenerative and demyelinating disorders.
2023-02-07 | Cell reprogramming for oligodendrocytes: A review of protocols and their applications to disease modeling and cell‐based remyelination therapies
Abstract Oligodendrocytes are a type of glial cells that produce a lipid‐rich membrane called myelin. Myelin assembles into a sheath and lines neuronal axons in the brain and spinal cord to insulate them. This not only increases the speed and efficiency of nerve signal transduction but also protects the axons from damage and degradation, which could trigger neuronal cell death. Demyelination, which is caused by a loss of myelin and oligodendrocytes, is a prominent feature of many neurological conditions, including Multiple sclerosis (MS), spinal cord injuries (SCI), and leukodystrophies. Demyelination is followed by a time of remyelination mediated by the recruitment of endogenous oligodendrocyte precursor cells, their migration to the injury site, and differentiation into myelin‐producing oligodendrocytes. Unfortunately, endogenous remyelination is not sufficient to overcome demyelination, which explains why there are to date no regenerative‐based treatments for MS, SCI, or leukodystrophies. To better understand the role of oligodendrocytes and develop cell‐based remyelination therapies, human oligodendrocytes have been derived from somatic cells using cell reprogramming. This review will detail the different cell reprogramming methods that have been developed to generate human oligodendrocytes and their applications to disease modeling and cell‐based remyelination therapies. Recent developments in the field have seen the derivation of brain organoids from pluripotent stem cells, and protocols have been devised to incorporate oligodendrocytes within the organoids, which will also be reviewed.
2023-01-19 | Oligodendrogenesis and myelination tracing in a CRISPR/Cas9-engineered brain microphysiological system
Introduction Oligodendrocytes (OLs) are the myelin-forming cells of the central nervous system (CNS). Although OLs can be differentiated from human-induced pluripotent stem cells (hiPSCs), the in vitro modeling of axon myelination in human cells remains challenging. Brain microphysiological systems (bMPS, e.g. organoids) are complex three-dimensional (3D) cultures that offer an ideal system to study this process as OLs differentiate in a more in vivo -like environment; surrounded by neurons and astrocytes, which support the myelination of axons. Methods Here, we take advantage of CRISPR/Cas9 technology to generate a hiPSC line in which proteolipid protein 1 (PLP1), an OLs marker, is tagged with super-fold GFP (sfGFP). While generating the PLP1-sfGFP reporter, we used reverse transfection and obtained higher Knock-In (KI) efficiency compared to forward transfection (61–72 vs. 46%). Results After validation of the KI and quality control of the PLP1-sfGFP line, selected clones were differentiated into bMPS, and the fidelity, specificity, and function of the tagged PLP protein were verified in this model. We tracked different stages of oligodendrogenesis in the verified lines based on PLP1-sfGFP + cells’ morphology, and the presence of PLP1-sfGFP surrounding axons during bMPS’ differentiation. Finally, we challenged the bMPS with cuprizone and quantified changes in both the percentage of PLP1-sfGFP expressing cells and the intensity of GFP expression. Discussion This work demonstrates an efficient method for generating hiPSC KI lines and the description of a new 3D model to study OL differentiation, migration, and maturation both during in vitro neurodevelopment as well as in response to environmental chemicals or disease-associated stressors.
2022-06-27 | Generation of functional human oligodendrocytes from dermal fibroblasts by direct lineage conversion.
Oligodendrocytes, the myelinating cells of the central nervous system, possess great potential for disease modeling and cell transplantation-based therapies for leukodystrophies. However, caveats to oligodendrocyte differentiation protocols ( Ehrlich et al., 2017; Wang et al., 2013; Douvaras and Fossati, 2015) from human embryonic stem and induced pluripotent stem cells (iPSCs), which include slow and inefficient differentiation, and tumorigenic potential of contaminating undifferentiated pluripotent cells, are major bottlenecks towards their translational utility. Here, we report the rapid generation of human oligodendrocytes by direct lineage conversion of human dermal fibroblasts (HDFs). We show that the combination of the four transcription factors OLIG2, SOX10, ASCL1 and NKX2.2 is sufficient to convert HDFs to induced oligodendrocyte precursor cells (iOPCs). iOPCs resemble human primary and iPSC-derived OPCs based on morphology and transcriptomic analysis. Importantly, iOPCs can differentiate into mature myelinating oligodendrocytes in vitro and in vivo. Finally, iOPCs derived from patients with Pelizaeus Merzbacher disease, a hypomyelinating leukodystrophy caused by mutations in the proteolipid protein 1 (PLP1) gene, showed increased cell death compared with iOPCs from healthy donors. Thus, human iOPCs generated by direct lineage conversion represent an attractive new source for human cell-based disease models and potentially myelinating cell grafts.
oligonucleotides
2025-06-23 | Molecular pathologies and therapies for Pelizaeus-Merzbacher disease.
Pelizaeus-Merzbacher disease (PMD) is the most common and representative disorder among hypomyelinating leukodystrophies, affecting myelin in the central nervous system. PMD is caused by various mutations in the PLP1 gene, including the most common duplications, point mutations (which often lead to severe forms), deletions/null mutations (resulting in milder forms), and deep intron mutations associated with hypomyelination of early myelinated structures (HEMS), a mild variant with characteristic MRI findings. Each mutation type is known to trigger distinct cellular and molecular mechanisms. Understanding these mutation-specific pathologies provides crucial insights for developing targeted therapies. For instance, duplication mutations lead to overexpression of the wild-type PLP1 protein, which disrupts myelination by oligodendrocytes, suggesting that gene suppression could be a potential treatment strategy. Therapeutic approaches under investigation include antisense oligonucleotides and artificial miRNA gene therapy. On the other hand, point mutations in mutant PLP1 proteins often confer cytotoxicity, which has been linked to endoplasmic reticulum stress responses, ferroptosis, and intracellular transport dysfunction within the secretory pathway. As a result, therapies targeting these molecular mechanisms are being explored, including antisense oligonucleotides and iron chelators. Given these advancements, it is not overly optimistic to anticipate that PMD could become a treatable disease in the near future.
2024-05-21 | Investigating myelination in humanbioengineered neuronal organoids (BENOs)
Myelination is a critical process for the optimal functioning of both the central and peripheral nervous systems. It involves wrapping nerve fibers with a myelin sheath to ensure the swift transmission of electrical signals, thereby facilitating rapid neuron-neuron communication. While in vivo models have significantly advanced our understanding of myelination, there remains a gap in our ability to observe human oligodendrocyte lineage cells' responses to various stimuli or genetic alterations that lead to dysmyelination or demyelination. Demyelination is the damaging loss of myelin in nerves, while dysmyelination is the faulty myelin formation. This study aimed to investigate myelination using a human brain organoid model, bioengineered neuronal organoids (BENOs), and to model Pelizaeus-Merzbacher disease (PMD), a disorder characterized by dysmyelination. We employed genome engineering and human induced pluripotent stem cell (iPSC) technologies in combination with machine learning-based analysis to trace oligodendrocytes in living tissues. Through temporal bulk RNA sequencing analysis of BENOs between days 60 and 150, we delineated gene expression patterns, shedding light on neurogenesis and gliogenesis. Further gene expression analysis revealed the cell-line-independent presence of oligodendrocytes start ing from day 90. To better understand and model diseases like PMD, we introduced two novel reporter systems, bioluminescent (lumi-PLP1) and fluorescent (f -PLP1), to monitor PLP1 expression and myelination in real-time. These systems effectively identified oligodendrocytes and their myelination activity. Furthermore, we developed a new 3D Oligodendrocyte Morphometrics (3DOM) analysis tool designed to quantify morphological alterations in oligo dendrocytes resulting from mutations or therapeutic interventions. 3DOM measures soma size, the extent of cellular processes, and signs of apoptosis. Leveraging our previously published BENO model, we refined myelination protocols, incorporated detailed 3D analysis tools and reporter systems for evaluating oligodendrocyte characteristics, and effectively modeled the dysmyelinating disorder PMD. In conclusion, this study developed a comprehensive human brain organoid model for examining myelination processes and the potential for dysmyelination and remyelination studies. The outcomes of this study highlight the critical need for ongoing research in this domain and showcase the potential of BENOs as a versatile platform for advancing future therapies.
2024-05-09 | Pelizaeus-Merzbacher disease: on the cusp of myelin medicine.
Pelizaeus-Merzbacher disease (PMD) is caused by mutations in the proteolipid protein 1 (PLP1) gene encoding proteolipid protein (PLP). As a major component of myelin, mutated PLP causes progressive neurodegeneration and eventually death due to severe white matter deficits. Medical care has long been limited to symptomatic treatments, but first-in-class PMD therapies with novel mechanisms now stand poised to enter clinical trials. Here, we review PMD disease mechanisms and outline rationale for therapeutic interventions, including PLP1 suppression, cell transplantation, iron chelation, and intracellular stress modulation. We discuss available preclinical data and their implications on clinical development. With several novel treatments on the horizon, PMD is on the precipice of a new era in the diagnosis and treatment of patients suffering from this debilitating disease.
2023-01-23 | Knockdown of Rab7B, but not of Rab7A, which antagonistically regulates oligodendroglial cell morphological differentiation, recovers tunicamycin-induced defective differentiation in FBD-102b cells
Abstract In the central nervous system (CNS), insulative myelin sheaths are generated from the differentiated plasma membranes of oligodendrocytes (oligodendroglial cells) and surround neuronal axons to achieve saltatory conduction. Despite the functional involvement of myelin sheaths in the CNS, the molecular mechanism by which oligodendroglial cells themselves undergo differentiation of plasma membranes remains unclear. It also remains to be explored whether their signaling mechanisms can be applied to treating diseases of the oligodendroglial cells. Here we describe that Rab7B of Rab7 subfamily small GTPases negatively regulates oligodendroglial cell morphological differentiation using FBD-102b cells, which are model cells undergoing differentiation of oligodendroglial precursors. Knockdown of Rab7B or Rab7A by the respective specific siRNAs in cells positively or negatively regulated morphological differentiation, respectively. Consistently, these changes were supported by changes on differentiation- and myelination-related structural protein and protein kinase markers. We also found that knockdown of Rab7B has the ability to recover inhibition of morphological differentiation following tunicamycin-induced endoplasmic reticulum (ER) stress, which mimics one of the major molecular pathological causes of hereditary hypomyelinating disorders in oligodendroglial cells, such as Pelizaeus-Merzbacher disease (PMD). These results suggest that the respective molecules among very close Rab7 homologues exhibit differential roles in morphological differentiation and that knocking down Rab7B can recover defective differentiating phenotypes under ER stress, thereby adding Rab7B to the list of molecular therapeutic cues taking advantage of signaling mechanisms for oligodendroglial diseases like PMD.
2021-12-10 | Recent Advancements in the Diagnosis and Treatment of Leukodystrophies.
Leukodystrophies and genetic leukoencephalopathies comprise a growing group of inherited white matter disorders. Diagnostic rates have improved with increased utilization of next generation sequencing. As treatment options continue to advance for leukodystrophies, so will candidacy for inclusion in the United States' newborn Recommended Universal Screening Panel as was achieved for X-linked adrenoleukodystrophy. Stem cell therapies have become standard of care for selected leukodystrophies. However, transplantation-related risks remain high and outcomes are not fully satisfactory. Transduction of autologous hematopoietic stem cells with lentiviral vectors, referred to as ex vivo gene therapy, circumvents some, but not all, of the risks of traditional transplantation and has recently been demonstrated to be safe and efficective in clinical studies of X-linked adrenoleukodystrophy and metachromatic leukodystrophy. Gene therapy, through direct infusion of adeno-associated virus vectors, has emerged as a safer alternative for many monogenetic pediatric neurological disorders. Numerous preclinical studies have shown safety and efficacy of adeno-associated virus gene therapy in leukodystrophies allowing expanded access treatment for Canavan disease prior to initiation of a clinical trial. For inherited white matter disorders resulting from overexpression of a protein, such as Pelizaeus-Merzbacher disease, emerging RNA therapies have shown success in preclinical studies and promise for rapid translation to the clinic. Lastly, small molecule and protein therapies remain a long-term treatment option for a number of leukodystrophies, including intrathecal enzyme replacement therapy for metachromatic leukodystrophy. Herein we review recent advances in diagnosis and treatment of inherited white matter disorders.
gene therapies
2026-08-11 | Pelizaeus-Merzbacher disease in a manifesting female carrier with a PLP1 frameshift variant: neuroimaging and neurophysiological findings
The Annals of Clinical Neurophysiology (ACN), the joint official journal of The Korean Society of Clinical Neurophysiology and The Korean Society of Pain & Autonomic Disorders, publishes twice a year on April 30 and October 31 in English.
2026-08-03 | Gap junction protein gamma 2 (GJC2) gene frameshift deletion in Toy Poodles with hypomyelinating leukodystrophy resembling human Pelizaeus-Merzbacher-like disease 1.
Pelizaeus-Merzbacher-like disease type 1 (PMLD1), also known as hypomyelinating dystrophy 2, is a typical slowly progressive hypomyelinating leukodystrophy (HLD) that manifests in the neonatal period or early infancy. In humans, PMLD1 is inherited as an autosomal recessive trait, with genetic variants identified in the gap junction protein gamma 2 (GJC2) gene. Six juvenile-age Toy Poodle dogs exhibited coarse, vertical head and trunk tremors from immediately after birth. Conventional magnetic resonance imaging revealed uniform signal hyperintensities throughout the subcortical white matter in all dogs. All dogs were euthanized. Subsequent histopathological examination revealed vacuolar changes and demyelination in the cerebral and cerebellar white matter, leading to a diagnosis of HLD. Genetic analysis of five affected dogs identified a shared homozygous 14-base pair deletion in the GJC2 gene, XM_038556433.1:c.920_933del. To the best of our knowledge, this is the first report of a pathogenic GJC2 variant in dogs or any other domestic animal species. The results will enable genetic testing and provide a spontaneous large animal model for the homologous human disease.
2026-02-25 | Spatially concentrated adenine base editors efficiently correct PLP1 mutations in oligodendrocytes.
Oligodendrocytes (OLs), the myelinating cells of the central nervous system, are particularly prone to pathogenic G-to-A mutations, such as PLP1A243V, which causes Pelizaeus-Merzbacher disease (PMD), a lethal hypomyelinating disorder lacking effective therapy. Although adenine base editors (ABEs) can in principle correct such mutations, their application in OLs is limited by inefficient on-target editing. Here, we develop a spatially concentrated ABE (cABE) strategy that enhances editing by promoting nuclear translocation of tRNA adenosine deaminase (TadA*) from the cytoplasm. Using a SunTag-based multivalent recruitment system, TadA* is locally enriched at genomic targets (cABE-1.0), achieving robust editing in vitro. To enable in vivo delivery while preserving high efficiency and fidelity, SpCas9 is replaced with compact eNme2-C Cas9, generating an AAV-compatible variant (cABE-2.0). Notably, cABE-2.0 forms dynamic nuclear puncta with properties of liquid-liquid phase separation, enhancing on-target editing while substantially reducing transcriptome-wide RNA off-target effects. Functionally, cABE-2.0 efficiently corrects the PLP1A243V mutation in OLs, restores Plp subcellular localization, and rescues myelination-related phenotypes. These findings demonstrate that spatial reorganization, rather than increasing intrinsic catalytic activity of TadA*, provides a distinct principle for improving base editing in difficult-to-edit cell types, such as OLs, offering a mechanistic and technical framework for gene therapy of PMD and related myelin disorders.
2025-06-10 | Molecular dynamics simulation of GJC2 mutants reveal pathogenic mechanisms of PMLD1 and SPG44.
GJC2 encodes connexin 47 (Cx47), a gap junction protein expressed by oligodendrocytes that forms gap junction channels (GJCs) between adjacent oligodendrocytes (or astrocytes, via heterotypic Cx47-Cx43 GJCs). Autosomal recessive mutations of GJC2 lead to at least three central nervous system phenotypes: Pelizaeus-Merzbacher-like disease 1 (PMLD1), spastic paraparesis 44 (SPG44), and a minimal leukodystrophy. Here, we describe the clinical, functional, and molecular effects of two mutations in GJC2, p.G40S, and p.R244P, identified in two different families with GJC2-related disorders. Expressed exogenously, p.G40S forms GJC plaques like WT but does not functionally couple with WT nor with Cx43. p.R244P also fails to demonstrate functional coupling. Moreover, plaque formation is absent, concomitant with intracellular connexin accumulation. When the two mutants are co-expressed in a compound heterozygous state, plaques form, but no GJC coupling is detected in any configuration. MD simulations demonstrate that p.G40S modifies secondary structure of the pore-lining α-helix, disrupting supersecondary interactions with the N-terminal helix and predicting channel closure. p.R244P simulations are characterized by partial loss of the extracellular β-sheet domains and a marked reduction of electrostatic interactions between the connexin and lipid headgroups of the plasma membrane, suggesting pathways by which p.R244P mutation impairs GJC formation. This combination of in vitro assays and molecular simulations provides mechanistic insight into the pathogenesis of GJC2-related disease.
2024-09-26 | Inherited white matter disorders: Hypomyelination (myelin disorders).
Hypomyelinating leukodystrophies are a subset of genetic white matter diseases characterized by insufficient myelin deposition during development. MRI patterns are used to identify hypomyelinating disorders, and genetic testing is used to determine the causal genes implicated in individual disease forms. Clinical course can range from severe, with patients manifesting neurologic symptoms in infancy or early childhood, to mild, with onset in adolescence or adulthood. This chapter discusses the most common hypomyelinating leukodystrophies, including X-linked Pelizaeus-Merzbacher disease and other PLP1-related disorders, autosomal recessive Pelizaeus-Merzbacher-like disease, and POLR3-related leukodystrophy. PLP1-related disorders are caused by hemizygous pathogenic variants in the proteolipid protein 1 (PLP1) gene, and encompass classic Pelizaeus-Merzbacher disease, the severe connatal form, PLP1-null syndrome, spastic paraplegia type 2, and hypomyelination of early myelinating structures. Pelizaeus-Merzbacher-like disease presents a similar clinical picture to Pelizaeus-Merzbacher disease, however, it is caused by biallelic pathogenic variants in the GJC2 gene, which encodes for the gap junction protein Connexin-47. POLR3-related leukodystrophy, or 4H leukodystrophy (hypomyelination, hypodontia, and hypogonadotropic hypogonadism), is caused by biallelic pathogenic variants in genes encoding specific subunits of the transcription enzyme RNA polymerase III. In this chapter, the clinical features, disease pathophysiology and genetics, imaging patterns, as well as supportive and future therapies are discussed for each disorder.
small molecules
2026-02-27 | Mutant PLP1 impairs COPII vesicle formation via ER calcium depletion in Pelizaeus-Merzbacher disease.
Pelizaeus-Merzbacher disease (PMD) is a devastating, X-linked hypomyelinating leukodystrophy caused by mutations in a myelin gene, PLP1. While overwhelming endoplasmic reticulum (ER) stress caused by the accumulation of mutant PLP1 is widely recognized, blockade of the apoptotic arm of the unfolded protein response (UPR) failed to rescue the phenotypes in murine disease models, suggesting the involvement of additional, critical cellular mechanisms in oligodendrocyte dysfunction. Herein, we identified ER Ca2+ depletion and disrupted ER-Golgi trafficking as key cellular pathologies in PMD. Mutant PLP1 impairs COPII vesicle formation by destabilizing its key components, including Sec31A at ER exit sites due to the Ca2+ transport dysregulation and deconstruction of the ALG-2/Sec31A/AnxA11 interaction. Pharmacological restoration of ER Ca2+ levels rescued COPII formation. These findings highlight how PLP1 mutations affect the intracellular trafficking of membrane and secretory proteins through the ER Ca2+ depletion, which may be associated with the clinical consequences of PMD and other inherited myelin disorders.
2025-12-27 | Integrated stress response inhibition prolongs the lifespan of a Pelizaeus-Merzbacher disease mouse model by increasing oligodendrocyte survival.
The leukodystrophy Pelizaeus-Merzbacher disease (PMD) is caused by myelin protein proteolipid protein gene (PLP1) mutations. PMD is characterized by oligodendrocyte death and CNS hypomyelination; thus, increasing oligodendrocyte survival and enhancing myelination could provide therapeutic benefit. Here, we use the PMD mouse model Jimpy to determine the impact of the integrated stress response (ISR) on the oligodendrocyte response to mutant PLP expression. Male Jimpy animals in which the ISR-triggering eukaryotic initiation factor (eIF) 2α kinase, protein kinase-like endoplasmic reticulum kinase (PERK), is inactivated have an extended lifespan that correlates with increased oligodendrocyte survival and enhanced CNS myelination. Inactivation of downstream components of the ISR pathway, in contrast, does not rescue oligodendrocytes or myelin. Phosphorylated eIF2α inhibits the exchange factor eIF2B, resulting in diminished protein synthesis. Treatment with small molecule eIF2B activators 2BAct and ISRIB increases oligodendrocyte survival, CNS myelination, and doubled the Jimpy lifespan. These results suggest that ISR modulation could provide therapeutic benefit to PMD patients.
2025-05-16 | Pelizaeus-Merzbacher Disease as a Cause of Early-Onset Developmental Delay: A Case Report.
Pelizaeus-Merzbacher disease (PMD) is a rare X-linked hypomyelinating leukodystrophy disorder caused by a mutation in the proteolipid protein 1 (PLP1) gene which is responsible for myelin formation in the central nervous system. We report a case of PMD in a male patient who initially presented with developmental delay at three months and was ultimately diagnosed at 10 years and 7 months of age. We aim to describe the initial presentation, clinical course of PMD and the investigations that aid in diagnosis so that future cases may be identified earlier. During the investigative workup of our patient, a deletion of exon 16 - an extremely rare heterozygous nucleotide variation, c.330C>T (p.D110D) - was identified, the pathogenicity of which has not been previously documented in the literature. In our report, we also aim to highlight the potential use of biotin in improving symptoms in such patients as there is currently no curative treatment available.
2024-11-29 | Efficacy of combined treatment with a wearable cyborg hybrid assistive limb and intrathecal baclofen therapy in a pediatric patient with spastic paraplegia
Hybrid Assistive Limb (HAL) is a movement support robot that assists the walking function of patients with diseases causing muscle weakness in the lower limbs. Intrathecal baclofen (ITB) therapy exerts positive effects on muscle tone in children with severe spasticity who have difficulty walking. The present case report describes a child with spastic paraplegia who underwent intensive robotic rehabilitation with HAL and combined ITB therapy. A 14-year-old boy with spastic paraplegia from Pelizaeus-Merzbacher disease was undergoing treatment with oral muscle relaxants and botulinum toxin A. However, the medications were ineffective and his spasticity was progressing. A baclofen infusion pump was implanted with the catheter tip at the T10 level and ITB therapy was started. A regimen of 12.5 μg/day dose of baclofen was administered and his spasticity of limbs and trunk were attenuated. Walking practice using HAL was performed under spasticity relief by ITB therapy and gait function and patterns, excluding endurance, were improved. The attenuation of spasticity by ITB therapy made “Lying, Rolling and Sitting” easier for the patient, but may have affected “Standing”, which was supported using spasticity, and also affected the Caregiver Assistance Scale of the Mobility domain of the Pediatric Evaluation of Disability Inventory (PEDI). While, the amount of assistance required for the Activities of Daily Living (ADLs) related to self-care and the overall caregiver burden both decreased. This is the first case report to demonstrate the efficacy and safety of combined ITB therapy and HAL rehabilitation in an ambulatory pediatric patient.
2024-07-31 | Alleviating Neurodegenerative Diseases Associated with Mitochondrial Defects by Therapeutic Biomolecules.
Neurodegenerative diseases are emerging as a global health concern in the current scenario, and their association with mitochondrial defects has been a potential area of research. Mitochondria, one of the essential organelles of the cell, serve as the cell's powerhouse, producing energy and ensuring cellular health. Neurodegenerative diseases such as Alzheimer's, Parkinson's, Huntington's, amyotrophic lateral sclerosis, and Pelizaeus-Merzbacher disease have been found to be primarily triggered by mitochondrial malfunction. One of the key byproducts of mitochondrial respiration, reactive oxygen species, also contributes significantly to mitochondrial DNA mutations that eventually cause mitochondrial breakdown. This review paper comprehensively examines the potential of therapeutic biomolecules, specifically mitochondria-specific antioxidants, in mitigating the impact of mitochondrial defects on neurodegenerative diseases. It provides a detailed analysis of the mechanisms involved in mitochondrial dysfunction, the potential therapeutic targets of these biomolecules, and their structureactivity relationship information are also discussed in this review. Various research articles and publications were used extensively in compiling the data, and the structures of biomolecules were prepared using software such as ChemDraw and ChemSketch. Crucial elements triggering mitochondrial abnormalities were identified and a tabular compilation of bioactive antioxidant compounds along with their therapeutic targets, was presented. Mitochondria-specific antioxidant therapy is an innovative and promising strategy for the management of neurodegenerative diseases associated with mitochondrial defects. This review provides a thorough summary of the current state of research and promising avenues of research and development in this field, emphasizing the importance of further investigations and clinical trials to elucidate their therapeutic benefits.
cell therapies
2024-10-03 | A rare case of radiologically diagnosed Pelizaeus-Merzbacher\'s disease (PMD) in a female infant
Pelizaeus-Merzbacher disease (PMD) is a rare X-linked dysmyelinating disorder caused by mutations in the PLP1 gene. Typically affecting males, PMD can also manifest in females due to skewed X-inactivation. Early diagnosis is crucial for managing the disease, with MRI serving as a potential alternative to genetic testing in resource-limited settings. We report the case of an 11-month-old female infant presenting with regression of developmental milestones. Initially, the infant achieved appropriate milestones but later exhibited impaired motor functions and reduced interest in toys. Routine laboratory tests were normal. MRI revealed bilaterally symmetrical T2/FLAIR hyperintense and T1 hypointense signal alterations in the cerebral white matter and brainstem, suggestive of PMD. Genetic testing was unavailable due to financial constraints. The patient’s two elder sisters, aged 9 and 10, also exhibited neuroregression and were bedridden, hinting at a genetic link. Diagnosis was based on characteristic MRI findings, as genetic testing was inaccessible. Differential diagnoses, including Salla disease and other leukodystrophies, were ruled out via imaging. Management involved a multidisciplinary approach, incorporating play therapy, speech therapy, physiotherapy for spasticity, and behavioral therapy. Parents were counseled on seizure management and potential antiepileptic use. Emerging treatments like stem cell therapy are under investigation. This case underscores the importance of MRI in diagnosing PMD, especially in settings where genetic testing is impractical. We advocate for the use of brain imaging in early diagnosis to improve patient outcomes through timely supportive therapy. Recognizing PMD in females, though rare, is essential for comprehensive care.
2023-08-04 | Human iPSC-derived neural stem cells display a radial glia-like signaturein vitroand favorable long-term safety in transplanted mice
ABSTRACT Human induced pluripotent stem cell-derived neural stem/progenitor cells (hiPSC-NSCs) are a promising source for cell therapy approaches to treat neurodegenerative and demyelinating disorders. Despite ongoing efforts to characterize hiPSC-derived cells in vitro and in vivo , we lack comprehensive genome- and transcriptome-wide studies addressing hiPSC-NSC identity and safety, which are critical for establishing accepted criteria for prospective clinical applications. Here, we evaluated the transcriptional and epigenetic signatures of hiPSCs and differentiated hiPSC-NSC progeny, finding that the hiPSC-to-NSC transition results in a complete loss of pluripotency and the acquisition of a radial glia-associated transcriptional signature. Importantly, hiPSC-NSCs share with somatic human fetal NSCs (hfNSCs) the main transcriptional and epigenetic patterns associated with NSC-specific biology. In vivo , long-term observation (up to 10 months) of mice intracerebrally transplanted as neonates with hiPSC-NSCs showed robust engraftment and widespread distribution of human cells in the host brain parenchyma. Engrafted hiPSC-NSCs displayed multilineage potential and preferentially generated glial cells. No hyperproliferation, tumor formation, or expression of pluripotency markers was observed. Finally, we identified a novel role of the Sterol Regulatory Element Binding Transcription Factor 1 (SREBF1) in the regulation of astroglial commitment of hiPSC-NSCs. Overall, these comprehensive in vitro and in vivo analyses provide transcriptional and epigenetic reference datasets to define the maturation stage of NSCs derived from different hiPSC sources, and to clarify the safety profile of hiPSC-NSCs, supporting their continuing development as an alternative to somatic hfNSCs in treating neurodegenerative and demyelinating disorders.
2023-02-07 | Cell reprogramming for oligodendrocytes: A review of protocols and their applications to disease modeling and cell‐based remyelination therapies
Abstract Oligodendrocytes are a type of glial cells that produce a lipid‐rich membrane called myelin. Myelin assembles into a sheath and lines neuronal axons in the brain and spinal cord to insulate them. This not only increases the speed and efficiency of nerve signal transduction but also protects the axons from damage and degradation, which could trigger neuronal cell death. Demyelination, which is caused by a loss of myelin and oligodendrocytes, is a prominent feature of many neurological conditions, including Multiple sclerosis (MS), spinal cord injuries (SCI), and leukodystrophies. Demyelination is followed by a time of remyelination mediated by the recruitment of endogenous oligodendrocyte precursor cells, their migration to the injury site, and differentiation into myelin‐producing oligodendrocytes. Unfortunately, endogenous remyelination is not sufficient to overcome demyelination, which explains why there are to date no regenerative‐based treatments for MS, SCI, or leukodystrophies. To better understand the role of oligodendrocytes and develop cell‐based remyelination therapies, human oligodendrocytes have been derived from somatic cells using cell reprogramming. This review will detail the different cell reprogramming methods that have been developed to generate human oligodendrocytes and their applications to disease modeling and cell‐based remyelination therapies. Recent developments in the field have seen the derivation of brain organoids from pluripotent stem cells, and protocols have been devised to incorporate oligodendrocytes within the organoids, which will also be reviewed.
2023-01-19 | Oligodendrogenesis and myelination tracing in a CRISPR/Cas9-engineered brain microphysiological system
Introduction Oligodendrocytes (OLs) are the myelin-forming cells of the central nervous system (CNS). Although OLs can be differentiated from human-induced pluripotent stem cells (hiPSCs), the in vitro modeling of axon myelination in human cells remains challenging. Brain microphysiological systems (bMPS, e.g. organoids) are complex three-dimensional (3D) cultures that offer an ideal system to study this process as OLs differentiate in a more in vivo -like environment; surrounded by neurons and astrocytes, which support the myelination of axons. Methods Here, we take advantage of CRISPR/Cas9 technology to generate a hiPSC line in which proteolipid protein 1 (PLP1), an OLs marker, is tagged with super-fold GFP (sfGFP). While generating the PLP1-sfGFP reporter, we used reverse transfection and obtained higher Knock-In (KI) efficiency compared to forward transfection (61–72 vs. 46%). Results After validation of the KI and quality control of the PLP1-sfGFP line, selected clones were differentiated into bMPS, and the fidelity, specificity, and function of the tagged PLP protein were verified in this model. We tracked different stages of oligodendrogenesis in the verified lines based on PLP1-sfGFP + cells’ morphology, and the presence of PLP1-sfGFP surrounding axons during bMPS’ differentiation. Finally, we challenged the bMPS with cuprizone and quantified changes in both the percentage of PLP1-sfGFP expressing cells and the intensity of GFP expression. Discussion This work demonstrates an efficient method for generating hiPSC KI lines and the description of a new 3D model to study OL differentiation, migration, and maturation both during in vitro neurodevelopment as well as in response to environmental chemicals or disease-associated stressors.
2022-06-27 | Generation of functional human oligodendrocytes from dermal fibroblasts by direct lineage conversion.
Oligodendrocytes, the myelinating cells of the central nervous system, possess great potential for disease modeling and cell transplantation-based therapies for leukodystrophies. However, caveats to oligodendrocyte differentiation protocols ( Ehrlich et al., 2017; Wang et al., 2013; Douvaras and Fossati, 2015) from human embryonic stem and induced pluripotent stem cells (iPSCs), which include slow and inefficient differentiation, and tumorigenic potential of contaminating undifferentiated pluripotent cells, are major bottlenecks towards their translational utility. Here, we report the rapid generation of human oligodendrocytes by direct lineage conversion of human dermal fibroblasts (HDFs). We show that the combination of the four transcription factors OLIG2, SOX10, ASCL1 and NKX2.2 is sufficient to convert HDFs to induced oligodendrocyte precursor cells (iOPCs). iOPCs resemble human primary and iPSC-derived OPCs based on morphology and transcriptomic analysis. Importantly, iOPCs can differentiate into mature myelinating oligodendrocytes in vitro and in vivo. Finally, iOPCs derived from patients with Pelizaeus Merzbacher disease, a hypomyelinating leukodystrophy caused by mutations in the proteolipid protein 1 (PLP1) gene, showed increased cell death compared with iOPCs from healthy donors. Thus, human iOPCs generated by direct lineage conversion represent an attractive new source for human cell-based disease models and potentially myelinating cell grafts.
oligonucleotides
2025-06-23 | Molecular pathologies and therapies for Pelizaeus-Merzbacher disease.
Pelizaeus-Merzbacher disease (PMD) is the most common and representative disorder among hypomyelinating leukodystrophies, affecting myelin in the central nervous system. PMD is caused by various mutations in the PLP1 gene, including the most common duplications, point mutations (which often lead to severe forms), deletions/null mutations (resulting in milder forms), and deep intron mutations associated with hypomyelination of early myelinated structures (HEMS), a mild variant with characteristic MRI findings. Each mutation type is known to trigger distinct cellular and molecular mechanisms. Understanding these mutation-specific pathologies provides crucial insights for developing targeted therapies. For instance, duplication mutations lead to overexpression of the wild-type PLP1 protein, which disrupts myelination by oligodendrocytes, suggesting that gene suppression could be a potential treatment strategy. Therapeutic approaches under investigation include antisense oligonucleotides and artificial miRNA gene therapy. On the other hand, point mutations in mutant PLP1 proteins often confer cytotoxicity, which has been linked to endoplasmic reticulum stress responses, ferroptosis, and intracellular transport dysfunction within the secretory pathway. As a result, therapies targeting these molecular mechanisms are being explored, including antisense oligonucleotides and iron chelators. Given these advancements, it is not overly optimistic to anticipate that PMD could become a treatable disease in the near future.
2024-05-21 | Investigating myelination in humanbioengineered neuronal organoids (BENOs)
Myelination is a critical process for the optimal functioning of both the central and peripheral nervous systems. It involves wrapping nerve fibers with a myelin sheath to ensure the swift transmission of electrical signals, thereby facilitating rapid neuron-neuron communication. While in vivo models have significantly advanced our understanding of myelination, there remains a gap in our ability to observe human oligodendrocyte lineage cells' responses to various stimuli or genetic alterations that lead to dysmyelination or demyelination. Demyelination is the damaging loss of myelin in nerves, while dysmyelination is the faulty myelin formation. This study aimed to investigate myelination using a human brain organoid model, bioengineered neuronal organoids (BENOs), and to model Pelizaeus-Merzbacher disease (PMD), a disorder characterized by dysmyelination. We employed genome engineering and human induced pluripotent stem cell (iPSC) technologies in combination with machine learning-based analysis to trace oligodendrocytes in living tissues. Through temporal bulk RNA sequencing analysis of BENOs between days 60 and 150, we delineated gene expression patterns, shedding light on neurogenesis and gliogenesis. Further gene expression analysis revealed the cell-line-independent presence of oligodendrocytes start ing from day 90. To better understand and model diseases like PMD, we introduced two novel reporter systems, bioluminescent (lumi-PLP1) and fluorescent (f -PLP1), to monitor PLP1 expression and myelination in real-time. These systems effectively identified oligodendrocytes and their myelination activity. Furthermore, we developed a new 3D Oligodendrocyte Morphometrics (3DOM) analysis tool designed to quantify morphological alterations in oligo dendrocytes resulting from mutations or therapeutic interventions. 3DOM measures soma size, the extent of cellular processes, and signs of apoptosis. Leveraging our previously published BENO model, we refined myelination protocols, incorporated detailed 3D analysis tools and reporter systems for evaluating oligodendrocyte characteristics, and effectively modeled the dysmyelinating disorder PMD. In conclusion, this study developed a comprehensive human brain organoid model for examining myelination processes and the potential for dysmyelination and remyelination studies. The outcomes of this study highlight the critical need for ongoing research in this domain and showcase the potential of BENOs as a versatile platform for advancing future therapies.
2024-05-09 | Pelizaeus-Merzbacher disease: on the cusp of myelin medicine.
Pelizaeus-Merzbacher disease (PMD) is caused by mutations in the proteolipid protein 1 (PLP1) gene encoding proteolipid protein (PLP). As a major component of myelin, mutated PLP causes progressive neurodegeneration and eventually death due to severe white matter deficits. Medical care has long been limited to symptomatic treatments, but first-in-class PMD therapies with novel mechanisms now stand poised to enter clinical trials. Here, we review PMD disease mechanisms and outline rationale for therapeutic interventions, including PLP1 suppression, cell transplantation, iron chelation, and intracellular stress modulation. We discuss available preclinical data and their implications on clinical development. With several novel treatments on the horizon, PMD is on the precipice of a new era in the diagnosis and treatment of patients suffering from this debilitating disease.
2023-01-23 | Knockdown of Rab7B, but not of Rab7A, which antagonistically regulates oligodendroglial cell morphological differentiation, recovers tunicamycin-induced defective differentiation in FBD-102b cells
Abstract In the central nervous system (CNS), insulative myelin sheaths are generated from the differentiated plasma membranes of oligodendrocytes (oligodendroglial cells) and surround neuronal axons to achieve saltatory conduction. Despite the functional involvement of myelin sheaths in the CNS, the molecular mechanism by which oligodendroglial cells themselves undergo differentiation of plasma membranes remains unclear. It also remains to be explored whether their signaling mechanisms can be applied to treating diseases of the oligodendroglial cells. Here we describe that Rab7B of Rab7 subfamily small GTPases negatively regulates oligodendroglial cell morphological differentiation using FBD-102b cells, which are model cells undergoing differentiation of oligodendroglial precursors. Knockdown of Rab7B or Rab7A by the respective specific siRNAs in cells positively or negatively regulated morphological differentiation, respectively. Consistently, these changes were supported by changes on differentiation- and myelination-related structural protein and protein kinase markers. We also found that knockdown of Rab7B has the ability to recover inhibition of morphological differentiation following tunicamycin-induced endoplasmic reticulum (ER) stress, which mimics one of the major molecular pathological causes of hereditary hypomyelinating disorders in oligodendroglial cells, such as Pelizaeus-Merzbacher disease (PMD). These results suggest that the respective molecules among very close Rab7 homologues exhibit differential roles in morphological differentiation and that knocking down Rab7B can recover defective differentiating phenotypes under ER stress, thereby adding Rab7B to the list of molecular therapeutic cues taking advantage of signaling mechanisms for oligodendroglial diseases like PMD.
2021-12-10 | Recent Advancements in the Diagnosis and Treatment of Leukodystrophies.
Leukodystrophies and genetic leukoencephalopathies comprise a growing group of inherited white matter disorders. Diagnostic rates have improved with increased utilization of next generation sequencing. As treatment options continue to advance for leukodystrophies, so will candidacy for inclusion in the United States' newborn Recommended Universal Screening Panel as was achieved for X-linked adrenoleukodystrophy. Stem cell therapies have become standard of care for selected leukodystrophies. However, transplantation-related risks remain high and outcomes are not fully satisfactory. Transduction of autologous hematopoietic stem cells with lentiviral vectors, referred to as ex vivo gene therapy, circumvents some, but not all, of the risks of traditional transplantation and has recently been demonstrated to be safe and efficective in clinical studies of X-linked adrenoleukodystrophy and metachromatic leukodystrophy. Gene therapy, through direct infusion of adeno-associated virus vectors, has emerged as a safer alternative for many monogenetic pediatric neurological disorders. Numerous preclinical studies have shown safety and efficacy of adeno-associated virus gene therapy in leukodystrophies allowing expanded access treatment for Canavan disease prior to initiation of a clinical trial. For inherited white matter disorders resulting from overexpression of a protein, such as Pelizaeus-Merzbacher disease, emerging RNA therapies have shown success in preclinical studies and promise for rapid translation to the clinic. Lastly, small molecule and protein therapies remain a long-term treatment option for a number of leukodystrophies, including intrathecal enzyme replacement therapy for metachromatic leukodystrophy. Herein we review recent advances in diagnosis and treatment of inherited white matter disorders.
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Drug Discovery Landscape
2 orphan drug designations for Pelizaeus-Merzbacher disease.
2 orphan drug designations for Pelizaeus-Merzbacher disease.
Drug | Therapy type | Orphan designation | Clinical trial status | Sponsor |
|---|---|---|---|---|
2'-O-(2-methoxyethyl) modified antisense oligonucleotide targeting PLP1 pre-mRNA | oligonucleotides | FDA | Ionis Pharmaceuticals, Inc. | |
2'-O-(2-methoxyethyl) modified antisense oligonucleotide targeting PLP1 pre-mRNA | oligonucleotides | EMA | Ionis Development (Ireland) Limited |
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