RARE DISEASE
Pelizaeus-Merzbacher-like disease
Pelizaeus-Merzbacher-like disease
Pelizaeus-Merzbacher-like disease
Synonyms: PMLD
Synonyms: PMLD
Synonyms: PMLD
Drug discovery
0
drugs
With orphan designations
Overview
Pelizaeus-Merzbacher-like disease (PMLD) is a rare autosomal recessive hypomyelinating leukodystrophy caused by GJC2 mutations, impairing oligodendrocyte gap junction communication critical for myelination. Clinical hallmarks include early-onset nystagmus, hypotonia progressing to spasticity, ataxia, motor delays, and dysarthria. Unlike X-linked Pelizaeus-Merzbacher disease (PMD), PMLD affects both sexes equally. Most patients retain normal cognition but develop progressive motor disability, often requiring wheelchair assistance by adolescence. Skeletal complications (e.g., scoliosis) and seizures may occur [1][5][9].
Therapies
Symptomatic management: Physical therapy, anti-spasticity medications (baclofen, botulinum toxin), seizure control, and scoliosis correction [3][10].
Investigational approaches: Ketogenic diet to support oligodendrocyte integrity, stem cell transplantation, and gene-targeted therapies in preclinical stages [3][7][15].
Categories: rare genetic diseases, rare neurological diseases
Research Papers
91 drug discovery papers about Pelizaeus-Merzbacher-like disease, with 1 first-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
91 drug discovery papers about Pelizaeus-Merzbacher-like disease, with 1 first-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
categories:
Small molecules
small molecules
2025-12-26 | 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. Pelizaeus-Merzbacher disease (PMD) is due to myelin proteolipid protein gene mutations. Here, the authors show that inhibiting the integrated stress response extends the lifespan of a mouse PMD model by increasing oligodendrocyte survival and myelination.
2022-06-24 | Enhancers of human and rodent oligodendrocyte formation predominantly induce cholesterol precursor accumulation
ABSTRACT Regeneration of myelin in the CNS is being pursued as a potential therapeutic approach for multiple sclerosis. Several labs have reported small molecules that promote oligodendrocyte formation and remyelination in vivo . Recently, we reported that many such molecules function by inhibiting a narrow window of enzymes in the cholesterol biosynthesis pathway. Here we describe a new high-throughput screen of 1,836 bioactive molecules and a thorough re-analysis of more than 60 molecules previously-identified as promoting oligodendrocyte formation from human, rat, or mouse oligodendrocyte progenitor cells (OPCs). These studies highlight that an overwhelming fraction of validated screening hits, including several molecules being evaluated clinically for remyelination, inhibit cholesterol pathway enzymes like EBP. To rationalize these findings, we suggest a model that relies on the high druggability of sterol-metabolizing enzymes and the ability of cationic amphiphiles to mimic the transition state of EBP. These studies further establish cholesterol pathway inhibition as a dominant mechanism among screening hits that enhance human, rat, or mouse oligodendrocyte formation.
2022-06-08 | Activation of the unfolded protein response by Connexin47 mutations associated with Pelizaeus-Merzbacher-like disease.
Pelizaeus-Merzbacher-like disease type 1 (PMLD1) is a hypomyelinating disorder arising in patients with mutations in GJC2, encoding Connexin47 (Cx47). PMLD1 causes nystagmus, cerebellar ataxia, spasticity and changes in CNS white matter detected by MRI. At least one mutation (p.I33M) yields a much milder phenotype, spastic paraplegia type 44 (SPG44). Cx47 contributes to gap junction communication channels between oligodendrocytes (OLs), the myelinating cells in the central nervous system (CNS), and between OLs and astrocytes. Prior studies in cell lines have shown that PMLD1 mutants such as p.P87S display defective protein trafficking, intracellular retention in the ER and loss-of-function. Here we show that when expressed in primary OLs, three PMLD1 associated mutants (p.P87S, p.Y269D and p.M283T) show ER retention of Cx47 and evidence of activation of the cellular stress (unfolded protein response, UPR) and apoptotic pathways. On the other hand, the milder SPG44 associated mutation p.I33M shows a wild-type-like subcellular distribution and no activation of the UPR or apoptotic pathways. These studies provide new insight into a potential element of toxic gain of function underlying the mechanism of PMLD1 that should help guide future therapeutic approaches.
2022-05-25 | An in vivo accelerated developmental myelination model for testing promyelinating therapeutics
Abstract Background Therapeutic agents stimulating the process of myelination could be beneficial for the treatment of demyelinating diseases, such as multiple sclerosis. The efficient translation of compounds promoting myelination in vitro to efficacy in vivo is inherently time-consuming and expensive. Thyroid hormones accelerate the differentiation and maturation of oligodendrocytes, thereby promoting myelination. Systemic administration of the thyroid hormone thyroxine (T4) accelerates brain maturation, including myelination, during early postnatal development. The objective of this study was to validate an animal model for rapid testing of promyelinating therapeutic candidates for their effects on early postnatal development by using T4 as a reference compound. Methods Daily subcutaneous injections of T4 were given to Sprague Dawley rat pups from postnatal day (PND) 2 to PND10. Changes in white matter were determined at PND10 using diffusion tensor magnetic resonance imaging (DTI). Temporal changes in myelination from PND3 to PND11 were also assessed by quantifying myelin basic protein (MBP) expression levels in the brain using the resonance Raman spectroscopy/enzyme-linked immunosorbent assay (RRS-ELISA) and quantitative immunohistochemistry. Results DTI of white matter tracts showed significantly higher fractional anisotropy in the internal capsule of T4-treated rat pups. The distribution of total FA values in the forebrain was significantly shifted towards higher values in the T4-treated group, suggesting increased myelination. In vivo imaging data were supported by in vitro observations, as T4 administration significantly potentiated the developmental increase in MBP levels in brain lysates starting from PND8. MBP levels in the brain of animals that received treatment for 9 days correlated with the FA metric determined in the same pups in vivo a day earlier. Furthermore, accelerated developmental myelination following T4 administration was confirmed by immunohistochemical staining for MBP in coronal brain sections of treated rat pups. Conclusions T4-treated rat pups had increased MBP expression levels and higher MRI fractional anisotropy values, both indications of accelerated myelination. This simple developmental myelination model affords a rapid test of promyelinating activity in vivo within several days, which could facilitate in vivo prescreening of candidate therapeutic compounds for developmental hypomyelinating diseases. Further research will be necessary to assess the utility of this platform for screening promyelination compounds in more complex demyelination disease models, such us multiple sclerosis.
2022-02-25 | Missense mutation of MAL causes a rare leukodystrophy similar to Pelizaeus-Merzbacher disease
Leukodystrophies are a heterogenous group of genetic disorders, characterised by abnormal development of cerebral white matter. Pelizaeus-Merzbacher disease is caused by mutations in PLP1, encoding major myelin-resident protein required for myelin sheath assembly. We report a missense variant p.(Ala109Asp) in MAL as causative for a rare, hypomyelinating leukodystrophy similar to Pelizaeus-Merzbacher disease. MAL encodes a membrane proteolipid that directly interacts with PLP1, ensuring correct distribution during myelin assembly. In contrast to wild-type MAL, mutant MAL was retained in the endoplasmic reticulum but was released following treatment with 4-phenylbutyrate. Proximity-dependent identification of wild-type MAL interactants implicated post-Golgi vesicle-mediated protein transport and protein localisation to membranes, whereas mutant MAL interactants suggested unfolded protein responses. Our results suggest that mislocalisation of MAL affects PLP1 distribution, consistent with known pathomechanisms for hypomyelinating leukodystrophies.
oligonucleotides
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.
2024-03-17 | A loss of function mutation in CLDN25 causing Pelizaeus-Merzbacher-like leukodystrophy.
Abstract Claudin-25 (CLDN-25), also known as Claudin containing domain 1, is an uncharacterized claudin family member. It has less conserved amino acid sequences when compared to other claudins. It also has a very broad tissue expression profile and there is currently a lack of functional information from murine knockout models. Here, we report a de novo missense heterozygous variant in CLDN25 (c. 745G>C, p. A249P) found in a patient diagnosed with Pelizaeus-Merzbacher-like leukodystrophy and presenting with symptoms such as delayed motor development, several episodes of tonic absent seizures and generalized dystonia. The variant protein does not localize to the cell-cell borders where it would normally be expected to be expressed. Amino acid position 249 is located 4 amino acids from the C-terminal end of the protein where most claudin family members have a conserved binding motif for the key scaffolding protein ZO-1. However, CLDN-25 does not contain this motif. Here, we show that the C-terminal end of CLDN-25 is required for its junctional localization in a ZO-1 independent manner. The A249P mutant protein as well as a deletion mutant lacking its last 5 C-terminal amino acids also failed to localize to the cell-cell border in vitro. Intriguingly, cellular knockout of CLDN25, in vitro, appeared to increase the integrity of the tight junction between 2 contacting cells, while driving highly unusual increased movement of solutes between cells. We propose that the barrier function of CLDN-25 is akin to a decoy claudin, whereby decreasing its expression in “leaky” epithelial cells and endothelial cells will drive dynamic changes in the adhesion and interaction capacity of cell-cell contact points. While it remains unclear how this de novo CLDN-25 mutant induces leukodystrophy, our findings strongly suggest that this mutation induces haploinsufficiency of CLDN-25. Elucidating the function of this uncharacterized claudin protein will lead to a better understanding of the role of claudin proteins in health and 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.
2018-07-05 | Morpholino Antisense Oligomers as a Potential Therapeutic Option for the Correction of Alternative Splicing in PMD, SPG2, and HEMS
DNA variants of the proteolipid protein 1 gene (PLP1) that shift PLP1/DM20 alternative splicing away from the PLP1 form toward DM20 cause the allelic X-linked leukodystrophies Pelizaeus-Merzbacher disease (PMD), spastic paraplegia 2 (SPG2), and hypomyelination of early myelinating structures (HEMS). We designed a morpholino oligomer (MO-PLP) to block use of the DM20 5′ splice donor site, thereby shifting alternative splicing toward the PLP1 5′ splice site. Treatment of an immature oligodendrocyte cell line with MO-PLP significantly shifted alternative splicing toward PLP1 expression from the endogenous gene and from transfected human minigene splicing constructs harboring patient variants known to reduce the amount of the PLP1 spliced product. Additionally, a single intracerebroventricular injection of MO-PLP into the brains of neonatal mice, carrying a deletion of an intronic splicing enhancer identified in a PMD patient that reduces the Plp1 spliced form, corrected alternative splicing at both RNA and protein levels in the CNS. The effect lasted to post-natal day 90, well beyond the early post-natal spike in myelination and PLP production. Further, the single injection produced a sustained reduction of inflammatory markers in the brains of the mice. Our results suggest that morpholino oligomers have therapeutic potential for the treatment of PMD, SPG2, and HEMS. DNA variants of the proteolipid protein 1 gene (PLP1) that shift PLP1/DM20 alternative splicing away from the PLP1 form toward DM20 cause the allelic X-linked leukodystrophies Pelizaeus-Merzbacher disease (PMD), spastic paraplegia 2 (SPG2), and hypomyelination of early myelinating structures (HEMS). We designed a morpholino oligomer (MO-PLP) to block use of the DM20 5′ splice donor site, thereby shifting alternative splicing toward the PLP1 5′ splice site. Treatment of an immature oligodendrocyte cell line with MO-PLP significantly shifted alternative splicing toward PLP1 expression from the endogenous gene and from transfected human minigene splicing constructs harboring patient variants known to reduce the amount of the PLP1 spliced product. Additionally, a single intracerebroventricular injection of MO-PLP into the brains of neonatal mice, carrying a deletion of an intronic splicing enhancer identified in a PMD patient that reduces the Plp1 spliced form, corrected alternative splicing at both RNA and protein levels in the CNS. The effect lasted to post-natal day 90, well beyond the early post-natal spike in myelination and PLP production. Further, the single injection produced a sustained reduction of inflammatory markers in the brains of the mice. Our results suggest that morpholino oligomers have therapeutic potential for the treatment of PMD, SPG2, and HEMS.
2010-07-13 | PLP/DM20 Expression and turnover in a transgenic mouse model of pelizaeus‐merzbacher disease
The most common cause of Pelizaeus-Merzbacher (PMD) is due to duplication of the PLP1 gene but it is unclear how increased gene dosage affects PLP turnover and causes dysmyelination. We have studied the dynamics of PLP/DM20 in a transgenic mouse model of PMD with increased gene dosage of the proteolipid protein gene (Plp1). The turnover of PLP/DM20 were investigated using an ex-vivo brain slice system and cultured oligodendrocytes. Homozygous mice have reduced PLP translation, markedly enhanced PLP degradation, and markedly reduced incorporation of PLP into myelin. Proteasome inhibition (MG132) prevented the enhanced degradation. Numerous autophagic vesicles are present in homozygous transgenic mice that may influence protein dynamics. Surprisingly, promoting autophagy with rapamycin decreases the degradation of nascent PLP suggesting autophagic vacuoles serve as a cellular storage compartment. We suggest that there are multiple subcellular fates of PLP/DM20 when overexpressed: the vast majority being degraded by the proteasome, a proportion sequestered into autophagic vacuoles, probably fused with endolysosomes, and only a small proportion entering the myelin sheath, where its association with lipid rafts is perturbed. Transgenic oligodendrocytes have fewer membrane sheets and this phenotype is improved with siRNA-mediated knockdown of PLP expression that promotes the formation of MBP+ myelin-like sheets. This finding suggests that RNAi technology is in principle applicable to improve CNS myelination when compromised by PLP/DM20 overexpression.
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.
2023-02-07 | 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.
2021-03-12 | Study on the Safety of Human Oligodendrocyte Precursor Cells Transplantation in Young Animals and Its Efficacy on Myelination
Abstract Oligodendrocyte precursor cells (OPCs), which can differentiate into myelinating oligodendrocytes during embryonic development, are an important potential source for myelin repair or regeneration. To date, OPCs from human sources (hOPCs) remain limited. In this study, we aimed to evaluate the safety and remyelination capacity of hOPCs developed in our laboratory by transplanting them into the lateral ventricles of Sprague–Dawley rats of different ages. The toxicity, biodistribution, and tumor formation abilities of the injected hOPCs were examined by evaluating rats’ vital signs, developmental indicators, neural reflexes, along with hematological, immunological, and pathological assessments. In addition, the hOPCs were transplanted into the corpus callosum of shiverer mice to verify cell myelination efficacy. Overall, our results showed that transplanted hOPCs into young mice showed no toxicity against their organ function or immune system, engrafted only in the brain, and caused no tissue proliferation or tumor formation. In terms of efficacy, the transplanted hOPCs formed myelin in the corpus callosum, alleviated the trembling phenotype of shiverer mice, and promoted normal development. The transplantation of hOPCs is safe and can effectively form myelin in the brain, thereby providing a theoretical basis for the future clinical transplantation of hOPCs.
2021-03-08 | Neuron-Oligodendrocyte Interactions in the Structure and Integrity of Axons
The myelination of axons by oligodendrocytes is a highly complex cell-to-cell interaction. Oligodendrocytes and axons have a reciprocal signaling relationship in which oligodendrocytes receive cues from axons that direct their myelination, and oligodendrocytes subsequently shape axonal structure and conduction. Oligodendrocytes are necessary for the maturation of excitatory domains on the axon including nodes of Ranvier, help buffer potassium, and support neuronal energy metabolism. Disruption of the oligodendrocyte-axon unit in traumatic injuries, Alzheimer’s disease and demyelinating diseases such as multiple sclerosis results in axonal dysfunction and can culminate in neurodegeneration. In this review, we discuss the mechanisms by which demyelination and loss of oligodendrocytes compromise axons. We highlight the intra-axonal cascades initiated by demyelination that can result in irreversible axonal damage. Both the restoration of oligodendrocyte myelination or neuroprotective therapies targeting these intra-axonal cascades are likely to have therapeutic potential in disorders in which oligodendrocyte support of axons is disrupted.
2020-07-24 | Beneficial contribution of iPSC-progeny to connexin 47 dynamics during demyelination-remyelination
Abstract Oligodendrocytes are extensively coupled to astrocytes, a phenomenon ensuring glial homeostasis and maintenance of CNS myelin. Molecular disruption of this communication occurs in demyelinating diseases such as multiple sclerosis. Less is known about the vulnerability and reconstruction of the panglial network during adult demyelination-remyelination. Here, we took advantage of LPC-induced demyelination to investigate the expression dynamics of the oligodendrocyte specific connexin 47 (Cx47) and whether this dynamic could be modulated by grafted iPSC-neural progeny. Our data show that deconstruction of the panglial network following demyelination is larger in size than demyelination. Loss of Cx47 expression is timely rescued during remyelination and accelerated by the grafted neural precursors. Moreover, mouse and human iPS-derived oligodendrocytes express Cx47, which co-labels with astrocyte Cx43, indicating their integration into the panglial network. These data suggest that full lesion repair following transplantation occurs by panglial reconstruction in addition to remyelination. Targeting panglial elements by cell therapy or pharmacological compounds may help accelerating or stabilizing re/myelination in myelin disorders.
gene therapies
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.
2017-05-29 | Gene therapy targeting oligodendrocytes provides therapeutic benefit in a leukodystrophy model.
Pelizaeus-Merzbacher-like disease or hypomyelinating leukodystrophy-2 is an autosomal recessively inherited leukodystrophy with childhood onset resulting from mutations in the gene encoding the gap junction protein connexin 47 (Cx47, encoded by GJC2). Cx47 is expressed specifically in oligodendrocytes and is crucial for gap junctional communication throughout the central nervous system. Previous studies confirmed that a cell autonomous loss-of-function mechanism underlies hypomyelinating leukodystrophy-2 and that transgenic oligodendrocyte-specific expression of another connexin, Cx32 (GJB1), can restore gap junctions in oligodendrocytes to achieve correction of the pathology in a disease model. To develop an oligodendrocyte-targeted gene therapy, we cloned the GJC2/Cx47 gene under the myelin basic protein promoter and used an adeno-associated viral vector (AAV.MBP.Cx47myc) to deliver the gene to postnatal Day 10 mice via a single intracerebral injection in the internal capsule area. Lasting Cx47 expression specifically in oligodendrocytes was detected in Cx47 single knockout and Cx32/Cx47 double knockout mice up to 12 weeks post-injection, including the corpus callosum and the internal capsule but also in more distant areas of the cerebrum and in the spinal cord. Application of this oligodendrocyte-targeted somatic gene therapy at postnatal Day 10 in groups of double knockout mice, a well characterized model of hypomyelinating leukodystrophy-2, resulted in significant improvement in motor performance and coordination at 1 month of age in treated compared to mock-treated mice, as well as prolonged survival. Furthermore, immunofluorescence and morphological analysis revealed improvement in demyelination, oligodendrocyte apoptosis, inflammation, and astrogliosis, all typical features of this leukodystrophy model in both brain and spinal cord. Functional dye transfer analysis confirmed the re-establishment of oligodendrocyte gap junctional connectivity in treated as opposed to untreated mice. These results provide a significant advance in the development of oligodendrocyte-cell specific gene therapy. Adeno-associated viral vectors can be used to target therapeutic expression of a myelin gene to oligodendrocytes. We show evidence for the first somatic gene therapy approach to treat hypomyelinating leukodystrophy-2 preclinically, providing a potential treatment for this and similar forms of leukodystrophies.
small molecules
2025-12-26 | 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. Pelizaeus-Merzbacher disease (PMD) is due to myelin proteolipid protein gene mutations. Here, the authors show that inhibiting the integrated stress response extends the lifespan of a mouse PMD model by increasing oligodendrocyte survival and myelination.
2022-06-24 | Enhancers of human and rodent oligodendrocyte formation predominantly induce cholesterol precursor accumulation
ABSTRACT Regeneration of myelin in the CNS is being pursued as a potential therapeutic approach for multiple sclerosis. Several labs have reported small molecules that promote oligodendrocyte formation and remyelination in vivo . Recently, we reported that many such molecules function by inhibiting a narrow window of enzymes in the cholesterol biosynthesis pathway. Here we describe a new high-throughput screen of 1,836 bioactive molecules and a thorough re-analysis of more than 60 molecules previously-identified as promoting oligodendrocyte formation from human, rat, or mouse oligodendrocyte progenitor cells (OPCs). These studies highlight that an overwhelming fraction of validated screening hits, including several molecules being evaluated clinically for remyelination, inhibit cholesterol pathway enzymes like EBP. To rationalize these findings, we suggest a model that relies on the high druggability of sterol-metabolizing enzymes and the ability of cationic amphiphiles to mimic the transition state of EBP. These studies further establish cholesterol pathway inhibition as a dominant mechanism among screening hits that enhance human, rat, or mouse oligodendrocyte formation.
2022-06-08 | Activation of the unfolded protein response by Connexin47 mutations associated with Pelizaeus-Merzbacher-like disease.
Pelizaeus-Merzbacher-like disease type 1 (PMLD1) is a hypomyelinating disorder arising in patients with mutations in GJC2, encoding Connexin47 (Cx47). PMLD1 causes nystagmus, cerebellar ataxia, spasticity and changes in CNS white matter detected by MRI. At least one mutation (p.I33M) yields a much milder phenotype, spastic paraplegia type 44 (SPG44). Cx47 contributes to gap junction communication channels between oligodendrocytes (OLs), the myelinating cells in the central nervous system (CNS), and between OLs and astrocytes. Prior studies in cell lines have shown that PMLD1 mutants such as p.P87S display defective protein trafficking, intracellular retention in the ER and loss-of-function. Here we show that when expressed in primary OLs, three PMLD1 associated mutants (p.P87S, p.Y269D and p.M283T) show ER retention of Cx47 and evidence of activation of the cellular stress (unfolded protein response, UPR) and apoptotic pathways. On the other hand, the milder SPG44 associated mutation p.I33M shows a wild-type-like subcellular distribution and no activation of the UPR or apoptotic pathways. These studies provide new insight into a potential element of toxic gain of function underlying the mechanism of PMLD1 that should help guide future therapeutic approaches.
2022-05-25 | An in vivo accelerated developmental myelination model for testing promyelinating therapeutics
Abstract Background Therapeutic agents stimulating the process of myelination could be beneficial for the treatment of demyelinating diseases, such as multiple sclerosis. The efficient translation of compounds promoting myelination in vitro to efficacy in vivo is inherently time-consuming and expensive. Thyroid hormones accelerate the differentiation and maturation of oligodendrocytes, thereby promoting myelination. Systemic administration of the thyroid hormone thyroxine (T4) accelerates brain maturation, including myelination, during early postnatal development. The objective of this study was to validate an animal model for rapid testing of promyelinating therapeutic candidates for their effects on early postnatal development by using T4 as a reference compound. Methods Daily subcutaneous injections of T4 were given to Sprague Dawley rat pups from postnatal day (PND) 2 to PND10. Changes in white matter were determined at PND10 using diffusion tensor magnetic resonance imaging (DTI). Temporal changes in myelination from PND3 to PND11 were also assessed by quantifying myelin basic protein (MBP) expression levels in the brain using the resonance Raman spectroscopy/enzyme-linked immunosorbent assay (RRS-ELISA) and quantitative immunohistochemistry. Results DTI of white matter tracts showed significantly higher fractional anisotropy in the internal capsule of T4-treated rat pups. The distribution of total FA values in the forebrain was significantly shifted towards higher values in the T4-treated group, suggesting increased myelination. In vivo imaging data were supported by in vitro observations, as T4 administration significantly potentiated the developmental increase in MBP levels in brain lysates starting from PND8. MBP levels in the brain of animals that received treatment for 9 days correlated with the FA metric determined in the same pups in vivo a day earlier. Furthermore, accelerated developmental myelination following T4 administration was confirmed by immunohistochemical staining for MBP in coronal brain sections of treated rat pups. Conclusions T4-treated rat pups had increased MBP expression levels and higher MRI fractional anisotropy values, both indications of accelerated myelination. This simple developmental myelination model affords a rapid test of promyelinating activity in vivo within several days, which could facilitate in vivo prescreening of candidate therapeutic compounds for developmental hypomyelinating diseases. Further research will be necessary to assess the utility of this platform for screening promyelination compounds in more complex demyelination disease models, such us multiple sclerosis.
2022-02-25 | Missense mutation of MAL causes a rare leukodystrophy similar to Pelizaeus-Merzbacher disease
Leukodystrophies are a heterogenous group of genetic disorders, characterised by abnormal development of cerebral white matter. Pelizaeus-Merzbacher disease is caused by mutations in PLP1, encoding major myelin-resident protein required for myelin sheath assembly. We report a missense variant p.(Ala109Asp) in MAL as causative for a rare, hypomyelinating leukodystrophy similar to Pelizaeus-Merzbacher disease. MAL encodes a membrane proteolipid that directly interacts with PLP1, ensuring correct distribution during myelin assembly. In contrast to wild-type MAL, mutant MAL was retained in the endoplasmic reticulum but was released following treatment with 4-phenylbutyrate. Proximity-dependent identification of wild-type MAL interactants implicated post-Golgi vesicle-mediated protein transport and protein localisation to membranes, whereas mutant MAL interactants suggested unfolded protein responses. Our results suggest that mislocalisation of MAL affects PLP1 distribution, consistent with known pathomechanisms for hypomyelinating leukodystrophies.
oligonucleotides
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.
2024-03-17 | A loss of function mutation in CLDN25 causing Pelizaeus-Merzbacher-like leukodystrophy.
Abstract Claudin-25 (CLDN-25), also known as Claudin containing domain 1, is an uncharacterized claudin family member. It has less conserved amino acid sequences when compared to other claudins. It also has a very broad tissue expression profile and there is currently a lack of functional information from murine knockout models. Here, we report a de novo missense heterozygous variant in CLDN25 (c. 745G>C, p. A249P) found in a patient diagnosed with Pelizaeus-Merzbacher-like leukodystrophy and presenting with symptoms such as delayed motor development, several episodes of tonic absent seizures and generalized dystonia. The variant protein does not localize to the cell-cell borders where it would normally be expected to be expressed. Amino acid position 249 is located 4 amino acids from the C-terminal end of the protein where most claudin family members have a conserved binding motif for the key scaffolding protein ZO-1. However, CLDN-25 does not contain this motif. Here, we show that the C-terminal end of CLDN-25 is required for its junctional localization in a ZO-1 independent manner. The A249P mutant protein as well as a deletion mutant lacking its last 5 C-terminal amino acids also failed to localize to the cell-cell border in vitro. Intriguingly, cellular knockout of CLDN25, in vitro, appeared to increase the integrity of the tight junction between 2 contacting cells, while driving highly unusual increased movement of solutes between cells. We propose that the barrier function of CLDN-25 is akin to a decoy claudin, whereby decreasing its expression in “leaky” epithelial cells and endothelial cells will drive dynamic changes in the adhesion and interaction capacity of cell-cell contact points. While it remains unclear how this de novo CLDN-25 mutant induces leukodystrophy, our findings strongly suggest that this mutation induces haploinsufficiency of CLDN-25. Elucidating the function of this uncharacterized claudin protein will lead to a better understanding of the role of claudin proteins in health and 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.
2018-07-05 | Morpholino Antisense Oligomers as a Potential Therapeutic Option for the Correction of Alternative Splicing in PMD, SPG2, and HEMS
DNA variants of the proteolipid protein 1 gene (PLP1) that shift PLP1/DM20 alternative splicing away from the PLP1 form toward DM20 cause the allelic X-linked leukodystrophies Pelizaeus-Merzbacher disease (PMD), spastic paraplegia 2 (SPG2), and hypomyelination of early myelinating structures (HEMS). We designed a morpholino oligomer (MO-PLP) to block use of the DM20 5′ splice donor site, thereby shifting alternative splicing toward the PLP1 5′ splice site. Treatment of an immature oligodendrocyte cell line with MO-PLP significantly shifted alternative splicing toward PLP1 expression from the endogenous gene and from transfected human minigene splicing constructs harboring patient variants known to reduce the amount of the PLP1 spliced product. Additionally, a single intracerebroventricular injection of MO-PLP into the brains of neonatal mice, carrying a deletion of an intronic splicing enhancer identified in a PMD patient that reduces the Plp1 spliced form, corrected alternative splicing at both RNA and protein levels in the CNS. The effect lasted to post-natal day 90, well beyond the early post-natal spike in myelination and PLP production. Further, the single injection produced a sustained reduction of inflammatory markers in the brains of the mice. Our results suggest that morpholino oligomers have therapeutic potential for the treatment of PMD, SPG2, and HEMS. DNA variants of the proteolipid protein 1 gene (PLP1) that shift PLP1/DM20 alternative splicing away from the PLP1 form toward DM20 cause the allelic X-linked leukodystrophies Pelizaeus-Merzbacher disease (PMD), spastic paraplegia 2 (SPG2), and hypomyelination of early myelinating structures (HEMS). We designed a morpholino oligomer (MO-PLP) to block use of the DM20 5′ splice donor site, thereby shifting alternative splicing toward the PLP1 5′ splice site. Treatment of an immature oligodendrocyte cell line with MO-PLP significantly shifted alternative splicing toward PLP1 expression from the endogenous gene and from transfected human minigene splicing constructs harboring patient variants known to reduce the amount of the PLP1 spliced product. Additionally, a single intracerebroventricular injection of MO-PLP into the brains of neonatal mice, carrying a deletion of an intronic splicing enhancer identified in a PMD patient that reduces the Plp1 spliced form, corrected alternative splicing at both RNA and protein levels in the CNS. The effect lasted to post-natal day 90, well beyond the early post-natal spike in myelination and PLP production. Further, the single injection produced a sustained reduction of inflammatory markers in the brains of the mice. Our results suggest that morpholino oligomers have therapeutic potential for the treatment of PMD, SPG2, and HEMS.
2010-07-13 | PLP/DM20 Expression and turnover in a transgenic mouse model of pelizaeus‐merzbacher disease
The most common cause of Pelizaeus-Merzbacher (PMD) is due to duplication of the PLP1 gene but it is unclear how increased gene dosage affects PLP turnover and causes dysmyelination. We have studied the dynamics of PLP/DM20 in a transgenic mouse model of PMD with increased gene dosage of the proteolipid protein gene (Plp1). The turnover of PLP/DM20 were investigated using an ex-vivo brain slice system and cultured oligodendrocytes. Homozygous mice have reduced PLP translation, markedly enhanced PLP degradation, and markedly reduced incorporation of PLP into myelin. Proteasome inhibition (MG132) prevented the enhanced degradation. Numerous autophagic vesicles are present in homozygous transgenic mice that may influence protein dynamics. Surprisingly, promoting autophagy with rapamycin decreases the degradation of nascent PLP suggesting autophagic vacuoles serve as a cellular storage compartment. We suggest that there are multiple subcellular fates of PLP/DM20 when overexpressed: the vast majority being degraded by the proteasome, a proportion sequestered into autophagic vacuoles, probably fused with endolysosomes, and only a small proportion entering the myelin sheath, where its association with lipid rafts is perturbed. Transgenic oligodendrocytes have fewer membrane sheets and this phenotype is improved with siRNA-mediated knockdown of PLP expression that promotes the formation of MBP+ myelin-like sheets. This finding suggests that RNAi technology is in principle applicable to improve CNS myelination when compromised by PLP/DM20 overexpression.
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.
2023-02-07 | 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.
2021-03-12 | Study on the Safety of Human Oligodendrocyte Precursor Cells Transplantation in Young Animals and Its Efficacy on Myelination
Abstract Oligodendrocyte precursor cells (OPCs), which can differentiate into myelinating oligodendrocytes during embryonic development, are an important potential source for myelin repair or regeneration. To date, OPCs from human sources (hOPCs) remain limited. In this study, we aimed to evaluate the safety and remyelination capacity of hOPCs developed in our laboratory by transplanting them into the lateral ventricles of Sprague–Dawley rats of different ages. The toxicity, biodistribution, and tumor formation abilities of the injected hOPCs were examined by evaluating rats’ vital signs, developmental indicators, neural reflexes, along with hematological, immunological, and pathological assessments. In addition, the hOPCs were transplanted into the corpus callosum of shiverer mice to verify cell myelination efficacy. Overall, our results showed that transplanted hOPCs into young mice showed no toxicity against their organ function or immune system, engrafted only in the brain, and caused no tissue proliferation or tumor formation. In terms of efficacy, the transplanted hOPCs formed myelin in the corpus callosum, alleviated the trembling phenotype of shiverer mice, and promoted normal development. The transplantation of hOPCs is safe and can effectively form myelin in the brain, thereby providing a theoretical basis for the future clinical transplantation of hOPCs.
2021-03-08 | Neuron-Oligodendrocyte Interactions in the Structure and Integrity of Axons
The myelination of axons by oligodendrocytes is a highly complex cell-to-cell interaction. Oligodendrocytes and axons have a reciprocal signaling relationship in which oligodendrocytes receive cues from axons that direct their myelination, and oligodendrocytes subsequently shape axonal structure and conduction. Oligodendrocytes are necessary for the maturation of excitatory domains on the axon including nodes of Ranvier, help buffer potassium, and support neuronal energy metabolism. Disruption of the oligodendrocyte-axon unit in traumatic injuries, Alzheimer’s disease and demyelinating diseases such as multiple sclerosis results in axonal dysfunction and can culminate in neurodegeneration. In this review, we discuss the mechanisms by which demyelination and loss of oligodendrocytes compromise axons. We highlight the intra-axonal cascades initiated by demyelination that can result in irreversible axonal damage. Both the restoration of oligodendrocyte myelination or neuroprotective therapies targeting these intra-axonal cascades are likely to have therapeutic potential in disorders in which oligodendrocyte support of axons is disrupted.
2020-07-24 | Beneficial contribution of iPSC-progeny to connexin 47 dynamics during demyelination-remyelination
Abstract Oligodendrocytes are extensively coupled to astrocytes, a phenomenon ensuring glial homeostasis and maintenance of CNS myelin. Molecular disruption of this communication occurs in demyelinating diseases such as multiple sclerosis. Less is known about the vulnerability and reconstruction of the panglial network during adult demyelination-remyelination. Here, we took advantage of LPC-induced demyelination to investigate the expression dynamics of the oligodendrocyte specific connexin 47 (Cx47) and whether this dynamic could be modulated by grafted iPSC-neural progeny. Our data show that deconstruction of the panglial network following demyelination is larger in size than demyelination. Loss of Cx47 expression is timely rescued during remyelination and accelerated by the grafted neural precursors. Moreover, mouse and human iPS-derived oligodendrocytes express Cx47, which co-labels with astrocyte Cx43, indicating their integration into the panglial network. These data suggest that full lesion repair following transplantation occurs by panglial reconstruction in addition to remyelination. Targeting panglial elements by cell therapy or pharmacological compounds may help accelerating or stabilizing re/myelination in myelin disorders.
gene therapies
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.
2017-05-29 | Gene therapy targeting oligodendrocytes provides therapeutic benefit in a leukodystrophy model.
Pelizaeus-Merzbacher-like disease or hypomyelinating leukodystrophy-2 is an autosomal recessively inherited leukodystrophy with childhood onset resulting from mutations in the gene encoding the gap junction protein connexin 47 (Cx47, encoded by GJC2). Cx47 is expressed specifically in oligodendrocytes and is crucial for gap junctional communication throughout the central nervous system. Previous studies confirmed that a cell autonomous loss-of-function mechanism underlies hypomyelinating leukodystrophy-2 and that transgenic oligodendrocyte-specific expression of another connexin, Cx32 (GJB1), can restore gap junctions in oligodendrocytes to achieve correction of the pathology in a disease model. To develop an oligodendrocyte-targeted gene therapy, we cloned the GJC2/Cx47 gene under the myelin basic protein promoter and used an adeno-associated viral vector (AAV.MBP.Cx47myc) to deliver the gene to postnatal Day 10 mice via a single intracerebral injection in the internal capsule area. Lasting Cx47 expression specifically in oligodendrocytes was detected in Cx47 single knockout and Cx32/Cx47 double knockout mice up to 12 weeks post-injection, including the corpus callosum and the internal capsule but also in more distant areas of the cerebrum and in the spinal cord. Application of this oligodendrocyte-targeted somatic gene therapy at postnatal Day 10 in groups of double knockout mice, a well characterized model of hypomyelinating leukodystrophy-2, resulted in significant improvement in motor performance and coordination at 1 month of age in treated compared to mock-treated mice, as well as prolonged survival. Furthermore, immunofluorescence and morphological analysis revealed improvement in demyelination, oligodendrocyte apoptosis, inflammation, and astrogliosis, all typical features of this leukodystrophy model in both brain and spinal cord. Functional dye transfer analysis confirmed the re-establishment of oligodendrocyte gap junctional connectivity in treated as opposed to untreated mice. These results provide a significant advance in the development of oligodendrocyte-cell specific gene therapy. Adeno-associated viral vectors can be used to target therapeutic expression of a myelin gene to oligodendrocytes. We show evidence for the first somatic gene therapy approach to treat hypomyelinating leukodystrophy-2 preclinically, providing a potential treatment for this and similar forms of leukodystrophies.
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