Navigating the Landscape of CMT1B: Understanding Genetic Pathways, Disease Models, and Potential Therapeutic Approaches.

Charcot-Marie-Tooth type 1B (CMT1B) is a peripheral neuropathy caused by mutations in the gene encoding myelin protein zero (MPZ), a key component of the myelin sheath in Schwann cells. Mutations in the MPZ gene can lead to protein misfolding, unfolded protein response (UPR), endoplasmic reticulum (ER) stress, or protein mistrafficking. Despite significant progress in understanding the disease mechanisms, there is currently no effective treatment for CMT1B, with therapeutic strategies primarily focused on supportive care. Gene therapy represents a promising therapeutic approach for treating CMT1B. To develop a treatment and better design preclinical studies, an in-depth understanding of the pathophysiological mechanisms and animal models is essential. In this review, we present a comprehensive overview of the disease mechanisms, preclinical models, and recent advancements in therapeutic research for CMT1B, while also addressing the existing challenges in the field. This review aims to deepen the understanding of CMT1B and to encourage further research towards the development of effective treatments for CMT1B patients.

The cytoplasmic tail of myelin protein zero induces morphological changes in lipid membranes.

The major myelin protein expressed by the peripheral nervous system Schwann cells is protein zero (P0), which represents 50% of the total protein content in myelin. This 30-kDa integral membrane protein consists of an immunoglobulin (Ig)-like domain, a transmembrane helix, and a 69-residue C-terminal cytoplasmic tail (P0ct). The basic residues in P0ct contribute to the tight packing of myelin lipid bilayers, and alterations in the tail affect how P0 functions as an adhesion molecule necessary for the stability of compact myelin. Several neurodegenerative neuropathies are related to P0, including the more common Charcot-Marie-Tooth disease (CMT) and Dejerine-Sottas syndrome (DSS) as well as rare cases of motor and sensory polyneuropathy. We found that high P0ct concentrations affected the membrane properties of bicelles and induced a lamellar-to-inverted hexagonal phase transition, which caused bicelles to fuse into long, protein-containing filament-like structures. These structures likely reflect the formation of semicrystalline lipid domains with potential relevance for myelination. Not only is P0ct important for stacking lipid membranes, but time-lapse fluorescence microscopy also shows that it might affect membrane properties during myelination. We further describe recombinant production and low-resolution structural characterization of full-length human P0. Our findings shed light on P0ct effects on membrane properties, and with the successful purification of full-length P0, we have new tools to study the role of P0 in myelin formation and maintenance in vitro.

Cilostazol Ameliorates Motor Dysfunction and Schwann Cell Impairment in Streptozotocin-Induced Diabetic Rats.

This study investigated the effects of cilostazol on motor dysfunction, spinal motor neuron abnormalities, and schwannopathy in rats with diabetes. Diabetes mellitus (DM) was induced in rats via femoral intravenous streptozotocin (STZ) injection (60 mg/kg). After successful DM induction, cilostazol was administered on day 15 via oral gavage (100 mg/kg/day) for 6 weeks until sacrifice. Behavioral assays, including motor function, were performed weekly. The sciatic nerve, L5 spinal cord, and spinal ventral root were collected to evaluate the expression of the glial fibrillary acidic protein (GFAP), myelin protein zero (P0), and choline acetyltransferase (ChAT) by immunofluorescence and Western blotting. DM rats displayed decreased running speeds, running distances, and toe spread but increased foot pressure. In addition, loss of non-myelinating Schwann cells and myelin sheaths was observed in the sciatic nerve and L5 spinal ventral root. Reduced numbers of motor neurons were also found in the L5 spinal ventral horn. Cilostazol administration significantly potentiated running speed and distance; increased hind paw toe spread; and decreased foot pressure. In the sciatic nerve and L5 spinal ventral root, cilostazol treatment significantly improved non-myelinated Schwann cells and increased myelin mass. ChAT expression in motor neurons in the spinal ventral horn was improved, but not significantly. Cilostazol administration may protect sensorimotor function in diabetic rats.

Charcot-Marie-Tooth Disease with Myelin Protein Zero Mutation Presenting as Painful, Predominant Small-Fiber Neuropathy.

Charcot-Marie-Tooth disease (CMT) rarely presents with painful symptoms, which mainly occur in association with myelin protein zero (MPZ) gene mutations. We aimed to further characterize the features of painful neuropathic phenotypes in MPZ-related CMT. We report on a 58-year-old woman with a longstanding history of intermittent migrant pain and dysesthesias. Examination showed minimal clinical signs of neuropathy along with mild changes upon electroneurographic examination, consistent with an intermediate pattern, and small-fiber loss upon skin biopsy. Genetic testing identified the heterozygous variant p.Trp101Ter in MPZ. We identified another 20 CMT patients in the literature who presented with neuropathic pain as a main feature in association with MPZ mutations, mostly in the extracellular MPZ domain; the majority of these patients showed late onset (14/20), with motor-nerve-conduction velocities predominantly in the intermediate range (12/20). It is hypothesized that some MPZ mutations could manifest with, or predispose to, neuropathic pain. However, the mechanisms linking MPZ mutations and pain-generating nerve changes are unclear, as are the possible role of modifier factors. This peculiar CMT presentation may be diagnostically misleading, as it is suggestive of an acquired pain syndrome rather than of an inherited neuropathy.

Myelin protein zero mutation-related hereditary neuropathies: Neuropathological insight from a new nerve biopsy cohort.

Myelin protein zero (MPZ/P0) is a major structural protein of peripheral nerve myelin. Disease-associated variants in the MPZ gene cause a wide phenotypic spectrum of inherited peripheral neuropathies. Previous nerve biopsy studies showed evidence for subtype-specific morphological features. Here, we aimed at enhancing the understanding of these subtype-specific features and pathophysiological aspects of MPZ neuropathies. We examined archival material from two Central European centers and systematically determined genetic, clinical, and neuropathological features of 21 patients with MPZ mutations compared to 16 controls. Cases were grouped based on nerve conduction data into congenital hypomyelinating neuropathy (CHN; n = 2), demyelinating Charcot-Marie-Tooth (CMT type 1; n = 11), intermediate (CMTi; n = 3), and axonal CMT (type 2; n = 5). Six cases had combined muscle and nerve biopsies and one underwent autopsy. We detected four MPZ gene variants not previously described in patients with neuropathy. Light and electron microscopy of nerve biopsies confirmed fewer myelinated fibers, more onion bulbs and reduced regeneration in demyelinating CMT1 compared to CMT2/CMTi. In addition, we observed significantly more denervated Schwann cells, more collagen pockets, fewer unmyelinated axons per Schwann cell unit and a higher density of Schwann cell nuclei in CMT1 compared to CMT2/CMTi. CHN was characterized by basal lamina onion bulb formation, a further increase in Schwann cell density and hypomyelination. Most late onset axonal neuropathy patients showed microangiopathy. In the autopsy case, we observed prominent neuromatous hyperinnervation of the spinal meninges. In four of the six muscle biopsies, we found marked structural mitochondrial abnormalities. These results show that MPZ alterations not only affect myelinated nerve fibers, leading to either primarily demyelinating or axonal changes, but also affect non-myelinated nerve fibers. The autopsy case offers insight into spinal nerve root pathology in MPZ neuropathy. Finally, our data suggest a peculiar association of MPZ mutations with mitochondrial alterations in muscle.

Structural bases for the Charcot-Marie-Tooth disease induced by single amino acid substitutions of myelin protein zero.

Myelin protein zero (MPZ or P0) is a transmembrane protein which functions to glue membranes in peripheral myelin. Inter-membrane adhesion is mediated by homophilic interactions between the extracellular domains (ECDs) of MPZ. Single amino acid substitutions in an ECD cause demyelinating neuropathy, Charcot-Marie-Tooth disease (CMT), with unknown mechanisms. In this study, by using a novel assay system "nanomyelin," we revealed that a stacked-rings-like ECD-8-mer is responsible for membrane adhesion. Two inter-ECD interactions, cis and head-to-head, are essential to constituting the 8-mer and to gluing the membranes. This result was reinforced by the observation that the CMT-related N87H substitution at the cis interface abolished membrane-adhesion activity. In contrast, the CMT-related D32G and E68V variants retained membrane-stacking activity, whereas their thermal stability was lower than that of the WT. Reduced thermal stability may lead to impairment of the long-term stability of ECD and the layered membranes of myelin.

Homomeric interactions of the MPZ Ig domain and their relation to Charcot-Marie-Tooth disease.

Mutations in MPZ (myelin protein zero) can cause demyelinating early-onset Charcot-Marie-Tooth type 1B disease or later onset type 2I/J disease characterized by axonal degeneration, reflecting the diverse roles of MPZ in Schwann cells. MPZ holds apposing membranes of the myelin sheath together, with the adhesion role fulfilled by its extracellular immunoglobulin-like domain (IgMPZ), which oligomerizes. Models for how the IgMPZ might form oligomeric assemblies has been extrapolated from a protein crystal structure in which individual rat IgMPZ subunits are packed together under artificial conditions, forming three weak interfaces. One interface organizes the IgMPZ into tetramers, a second 'dimer' interface links tetramers together across the intraperiod line, and a third hydrophobic interface that mediates binding to lipid bilayers or the same hydrophobic surface on another IgMPZ domain. Presently, there are no data confirming whether the proposed IgMPZ interfaces actually mediate oligomerization in solution, whether they are required for the adhesion activity of MPZ, whether they are important for myelination, or whether their loss results in disease. We performed nuclear magnetic resonance spectroscopy and small angle X-ray scattering analysis of wild-type IgMPZ as well as mutant forms with amino acid substitutions designed to interrupt its presumptive oligomerization interfaces. Here, we confirm the interface that mediates IgMPZ tetramerization, but find that dimerization is mediated by a distinct interface that has yet to be identified. We next correlated different types of Charcot-Marie-Tooth disease symptoms to subregions within IgMPZ tetramers. Variants causing axonal late-onset disease (CMT2I/J) map to surface residues of IgMPZ proximal to the transmembrane domain. Variants causing early-onset demyelinating disease (CMT1B) segregate into two groups: one is described by variants that disrupt the stability of the Ig-fold itself and are largely located within the core of the IgMPZ domain; whereas another describes a region on the surface of IgMPZ tetramers, accessible to protein interactions. Computational docking studies predict that this latter disease-relevant subregion may potentially mediate dimerization of IgMPZ tetramers.

Canine models of Charcot-Marie-Tooth: MTMR2, MPZ, and SH3TC2 variants in golden retrievers with congenital hypomyelinating polyneuropathy.

Congenital hypomyelinating polyneuropathy (HPN) restricted to the peripheral nervous system was reported in 1989 in two Golden Retriever (GR) littermates. Recently, four additional cases of congenital HPN in young, unrelated GRs were diagnosed via neurological examination, electrodiagnostic evaluation, and peripheral nerve pathology. Whole-genome sequencing was performed on all four GRs, and variants from each dog were compared to variants found across >1,000 other dogs, all presumably unaffected with HPN. Likely causative variants were identified for each HPN-affected GR. Two cases shared a homozygous splice donor site variant in MTMR2, with a stop codon introduced within six codons following the inclusion of the intron. One case had a heterozygous MPZ isoleucine to threonine substitution. The last case had a homozygous SH3TC2 nonsense variant predicted to truncate approximately one-half of the protein. Haplotype analysis using 524 GR established the novelty of the identified variants. Each variant occurs within genes that are associated with the human Charcot-Marie-Tooth (CMT) group of heterogeneous diseases, affecting the peripheral nervous system. Testing a large GR population (n = >200) did not identify any dogs with these variants. Although these variants are rare within the general GR population, breeders should be cautious to avoid propagating these alleles.

A Truncated 14-Amino-Acid Myelin Protein-Zero-Targeting Peptide for Fluorescence-Guided Nerve-Preserving Surgery.

BACKGROUND: The occurrence of accidental nerve damage during surgery and the increasing application of image guidance during head-and-neck surgery have highlighted the need for molecular targeted nerve-sparing interventions. The implementation of such interventions relies on the availability of nerve-specific tracers. In this paper, we describe the development of a truncated peptide that has an optimized affinity for protein zero (P0), the most abundant protein in myelin. METHODS AND MATERIALS: Further C- and N-terminal truncation was performed on the lead peptide Cy5-P0101-125. The resulting nine Cy5-labelled peptides were characterized based on their photophysical properties, P0 affinity, and in vitro staining. These characterizations were combined with evaluation of the crystal structure of P0, which resulted in the selection of the optimized tracer Cy5-P0112-125. A near-infrared Cy7-functionalized derivative (Cy7-P0112-125) was used to perform an initial evaluation of fluorescence-guided surgery in a porcine model. RESULTS: Methodological truncation of the 26-amino-acid lead compound Cy5-P0101-125 resulted in a size reduction of 53.8% for the optimized peptide Cy5-P0112-125. The peptide design and the 1.5-fold affinity gain obtained after truncation could be linked to interactions observed in the crystal structure of the extracellular portion of P0. The near-infrared analogue Cy7-P0112-125 supported nerve illumination during fluorescence-guided surgery in the head-and-neck region in a porcine model. CONCLUSIONS: Methodological truncation yielded a second-generation P0-specific peptide. Initial surgical evaluation suggests that the peptide can support molecular targeted nerve imaging.

Evaluation of Pathogenicity and Causativity of Variants in the MPZ and SH3TC2 Genes in a Family Case of Hereditary Peripheral Neuropathy.

The implementation of NGS methods into clinical practice allowed researchers effectively to establish the molecular cause of a disorder in cases of a genetically heterogeneous pathology. In cases of several potentially causative variants, we need additional analysis that can help in choosing a proper causative variant. In the current study, we described a family case of hereditary motor and sensory neuropathy (HMSN) type 1 (Charcot-Marie-Tooth disease). DNA analysis revealed two variants in the SH3TC2 gene (c.279G>A and c.1177+5G>A), as well as a previously described variant c.449-9C>T in the MPZ gene, in a heterozygous state. This family segregation study was incomplete because of the proband's father's unavailability. To evaluate the variants' pathogenicity, minigene splicing assay was carried out. This study showed no effect of the MPZ variant on splicing, but the c.1177+5G>A variant in the SH3TC2 gene leads to the retention of 122 nucleotides from intron 10 in the RNA sequence, causing a frameshift and an occurrence of a premature stop codon (NP_078853.2:p.Ala393GlyfsTer2).

Effects of Curcumin on Axon Growth and Myelin Sheath Formation in an In Vitro Model.

Although the beneficial effects of curcumin, extracted from rhizomes of the ginger family genus Curcuma, on the repair and regeneration of nerves have been evaluated in vitro, there are few studies concerning its effects on axon myelination. Here, we used pheochromocytoma cells as an in vitro model of peripheral nerves. Pheochromocytoma cells were cultured alone or cocultured with Schwann cells and treated with increasing concentrations of curcumin. Cell growth was observed, and the expression levels of growth-associated protein 43 (GAP-43), microtubule-associated protein 2 (MAP-2), myelin basic protein (MBP), myelin protein zero (MPZ), Krox-20, and octamer binding factor 6 (Oct-6) were quantified. We found a significant increase in expression of all six proteins following curcumin treatment, with a corresponding increase in the levels of MBP, MPZ, Krox-20, and Oct-6 mRNA. Upregulation was greater with increasing curcumin concentration, showing a concentration-dependent effect. The results suggested that curcumin can promote the growth of axons by upregulating the expression of GAP-43 and MAP-2, stimulate synthesis and secretion of myelin-related proteins, and facilitate formation of the myelin sheath in axons by upregulating the expression of Krox-20 and Oct-6. Therefore, curcumin could be widely applied in future strategies for the treatment of nerve injuries.

Complete Loss of Myelin protein zero (MPZ) in a patient with a late onset Charcot-Marie-Tooth (CMT).

Charcot-Marie-Tooth (CMT) comprises a group of hereditary neuropathies with clinical, epidemiological, and molecular heterogeneity in which variants in more than 80 different genes have been reported. One of the important genes which cause 5% of all CMT cases is Myelin protein zero (P0, MPZ). Variants in this gene have been reported in association with different forms of CMT including classical CMT1, severe DSS (CMT3B), DI-CMT, CMT2I and CMT2J with autosomal dominant (AD) inheritance. To our knowledge, MPZ variants have not been described in autosomal recessive (AR) form of CMT in previous studies. Moreover, its complete deletion has not been reported in human. Here, we described clinical characteristics of a patient with CMT symptoms who demonstrated manifestations of the disease late in his life. We performed exome sequencing for identifying CMT subtype and its associated gene, and follow that co-segregation analysis has been done to characterize inheritance pattern of the disorder. Through using exome sequencing, we identified a novel 4074 bp homozygote deletion which encompasses all 6 exons of the MPZ gene in this patient. After identifying the alteration, variant confirmation and co-segregation analysis have been performed by using specific primers. Our result revealed that the patient's parents were heterozygous for the alteration and they did not show any symptoms of CMT. Although most MPZ variants have been described with early onset CMT with AD pattern of inheritance, the reported patient in our study had late onset form and his parents did not show any symptoms. Considering substantial role of MPZ protein in the biogenesis of peripheral nervous system (PNS) myelin, we proposed that there should be another protein in PNS that compensates for lack of MPZ protein. Taken together, our finding is the first report of MPZ association with AR form of CMT with late onset features. Moreover, our results propose the presence of another protein in PNS myelin biogenesis and its assembly. However, functional studies alongside with other molecular studies are needed to confirm our results and identify the proposed protein.

[The role of CD4+ CD25+ Treg in the mechanism of autoimmune auditory neuropathy in SD rats].

Objective: To investigate the role of CD4+CD25+regulatory cell (CD4+CD25+Treg) in auditory neuropathy (AN) using a rat model of autoimmune auditory neuropathy. Methods: The SD rats were immunized with P0 protein emulsified in complete Freunds adjuvant for 8 weeks. The number of CD4+CD25+Treg in peripheral blood and cochlea and the expression of Foxp3 gene in cochlea were detected respectively 2, 4, 6 and 8 weeks after the immunization with P0 protein in rats. Then CD4+CD25+Treg were transferred intravenously to the AN rats at 2, 4, 6 and 8 weeks of the immunization, respectively. The change of auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) were detected, and the morphological changes in the inner ear were investigated. Results: The number of CD4+CD25+Treg in the peripheral blood of AN rats decreased gradually after 2, 4, 6 and 8 weeks of P0 protein immunization. The number of CD4+CD25+Treg in cochlea gradually increased with the prolongation of immunization time, but the expression of Foxp3 gene in cochlea gradually decreased over time. After intravenous transplantation of CD4+CD25+Treg in AN rats, the threshold of ABR response decreased, and DPOAE had no significant change. The number of spiral ganglion neurons in cochlea increased, and hair cells had no significant change under electron microscope. Conclusions: The decrease in the number and function of CD4+CD25+Treg reduces its inhibitory effect on autoimmune response and promotes the occurrence of autoimmune auditory neuropathy in AN rats. Adoptive transfer of CD4+CD25+Treg can reduce the autoimmune response and promote the recovery of autoimmune auditory neuropathy.

Intravenous immunoglobulin preparations attenuate lysolecithin-induced peripheral demyelination in mice and comprise anti-large myelin protein zero antibody.

Intravenous immunoglobulin (IVIg) has been used to treat inflammatory demyelinating diseases such as chronic inflammatory demyelinating polyneuropathy, Guillain-Barré syndrome, and multifocal motor neuropathy. Despite studies demonstrating the clinical effectiveness of IVIg, the mechanisms underlying its effects remain to be elucidated in detail. Herein, we examined the effects of IVIg on lysolecithin-induced demyelination of the sciatic nerve in a mouse model. Mice -administered with IVIg 1 and 3 days post-injection (dpi) of lysolecithin -exhibited a significantly decreased demyelination area at 7 dpi. Immunoblotting analysis using two different preparations revealed that IVIg reacted with a 36-kDa membrane glycoprotein in the sciatic nerve. Subsequent analyses of peptide absorption identified the protein as a myelin protein in the peripheral nervous system (PNS) known as large myelin protein zero (L-MPZ). Moreover, injected IVIg penetrated the demyelinating lesion, leading to deposition on L-MPZ in the myelin debris. These results indicate that IVIg may modulate PNS demyelination, possibly by binding to L-MPZ on myelin debris.

Exercise induced myelin protein zero improvement in neuropathic pain rats.

PURPOSE: Aerobic exercise including swimming plays a suitable role in improving somatosensory injuries. Neuropathic pain is a debilitating condition that occurs following injury or diseases of somatosensory system. In the present study, we tried to investigate the effect of exercise on myelin protein zero of sciatic nerve injured rats. MATERIALS AND METHODS: Forty male rats (180-220 g) were divided into five groups (intact, sham, sham + exercise, neuropathy, and neuropathy + exercise). Right Sciatic nerve of anesthetized rats was exposed and loosely ligated (four ligations with 1 mm apart) using catgut chromic sutures to induce neuropathy. After 3 days of recovery, swimming exercise began (20 min/day/5 days a week/4 weeks). Mechanical allodynia and thermal hyperalgesia were detected using Von Frey filaments and plantar test, respectively. Sciatic nerve at the place of injury was dissected out to measure the myelin protein zero by western blot analysis. In the intact and sham groups, sciatic nerve removed at the place similar to injured group. RESULTS: We found that neuropathy significantly (p < 0.05) reduced paw withdrawal mechanical and thermal thresholds and swimming exercise significantly (p < 0.05) increased paw withdrawal mechanical and thermal thresholds compared to the neuropathy group. Moreover, we found that MPZ level significantly (p < 0.01) decreased in neuropathy group against that in sham group, and exercise prominently (p < 0.05) reversed MPZ level towards control level. CONCLUSIONS: Swimming exercise improves myelin protein zero level in neuropathic rats along with attenuating neuropathic pain. This is a promising approach in improving neuropathological disorders including Charcot-Marie-Tooth and Dejerine-Sottas disease.

Genotype-phenotype characteristics and baseline natural history of Chinese myelin protein zero gene related neuropathy patients.

BACKGROUND AND PURPOSE: The aim was to characterize the phenotypic and genotypic features of myelin protein zero (MPZ) related neuropathy and provide baseline data for longitudinal natural history studies or drug clinical trials. METHOD: Clinical, neurophysiological and genetic data of 37 neuropathy patients with MPZ mutations were retrospectively collected. RESULTS: Nineteen different MPZ mutations in 23 unrelated neuropathy families were detected, and the frequency of MPZ mutations was 5.84% in total. Mutations c.103_104InsTGGTTTACACCG, c.513dupG, c.521_557del and c.696_699delCAGT had not been reported previously. Hot spot mutation p.Thr124Met was detected in four unrelated families, and seven patients carried de novo mutations. The onset age indicated a bimodal distribution: prominent clustering in the first and fourth decades. The infantile-onset group included 12 families, the childhood-onset group consisted of two families and the adult-onset group included nine families. The Charcot-Marie-Tooth Disease Neuropathy Score ranged from 3 to 25 with a mean value of 15.85 ± 5.88. Mutations that changed the cysteine residue (p.Arg98Cys, p.Cys127Trp, p.Ser140Cys and p.Cys127Arg) in the extracellular region were more likely to cause severe early-onset Charcot-Marie-Tooth disease type 1B (CMT1B) or Dejerine-Sottas syndrome. Nonsense-mediated mRNA decay mutations p.Asp35delInsVVYTD, p.Leu174Argfs*66 and p.Leu172Alafs*63 were related to severe infantile-onset CMT1B or Dejerine-Sottas syndrome; however, mutation p.Val232Valfs*19 was associated with a relatively milder childhood-onset CMT1 phenotype. CONCLUSION: Four novel MPZ mutations are reported that expand the genetic spectrum. De novo mutations accounted for 30.4% and were most related to a severe infantile-onset phenotype. Genetic and clinical data from this cohort will provide the baseline data necessary for clinical trials and natural history studies.

Disease Progression in Charcot-Marie-Tooth Disease Related to MPZ Mutations: A Longitudinal Study.

OBJECTIVE: The paucity of longitudinal natural history studies in MPZ neuropathy remains a barrier to clinical trials. We have completed a longitudinal natural history study in patients with MPZ neuropathies across 13 sites of the Inherited Neuropathies Consortium. METHODS: Change in Charcot-Marie-Tooth Examination Score (CMTES) and Rasch modified CMTES (CMTES-R) were evaluated using longitudinal regression over a 5-year period in subjects with MPZ neuropathy. Data from 139 patients with MPZ neuropathy were examined. RESULTS: The average baseline CMTES and CMTES-R were 10.84 (standard deviation [SD] = 6.0, range = 0-28) and 14.60 (SD = 7.56, range = 0-32), respectively. A mixed regression model showed significant change in CMTES at years 2-5 (mean change from baseline of 0.87 points at 2 years, p = 0.008). Subgroup analysis revealed greater change in CMTES at 2 years in subjects with axonal as compared to demyelinating neuropathy (mean change of 1.30 points [p = 0.016] vs 0.06 points [p = 0.889]). Patients with a moderate baseline neuropathy severity also showed more notable change, by estimate, than those with mild or severe neuropathy (mean 2-year change of 1.14 for baseline CMTES 8-14 [p = 0.025] vs -0.03 for baseline CMTES 0-7 [p = 0.958] and 0.25 for baseline CMTES ≥ 15 [p = 0.6897]). The progression in patients harboring specific MPZ mutations was highly variable. INTERPRETATION: CMTES is sensitive to change over time in adult patients with axonal but not demyelinating forms of MPZ neuropathy. Change in CMTES was greatest in patients with moderate baseline disease severity. These findings will inform future clinical trials of MPZ neuropathies. ANN NEUROL 2023;93:563-576.

The role of CD4+ CD25+ Treg in the mechanism of autoimmune auditory neuropathy in SD rats / 中华耳鼻咽喉头颈外科杂志

Objective: To investigate the role of CD4+CD25+regulatory cell (CD4+CD25+Treg) in auditory neuropathy (AN) using a rat model of autoimmune auditory neuropathy. Methods: The SD rats were immunized with P0 protein emulsified in complete Freunds adjuvant for 8 weeks. The number of CD4+CD25+Treg in peripheral blood and cochlea and the expression of Foxp3 gene in cochlea were detected respectively 2, 4, 6 and 8 weeks after the immunization with P0 protein in rats. Then CD4+CD25+Treg were transferred intravenously to the AN rats at 2, 4, 6 and 8 weeks of the immunization, respectively. The change of auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) were detected, and the morphological changes in the inner ear were investigated. Results: The number of CD4+CD25+Treg in the peripheral blood of AN rats decreased gradually after 2, 4, 6 and 8 weeks of P0 protein immunization. The number of CD4+CD25+Treg in cochlea gradually increased with the prolongation of immunization time, but the expression of Foxp3 gene in cochlea gradually decreased over time. After intravenous transplantation of CD4+CD25+Treg in AN rats, the threshold of ABR response decreased, and DPOAE had no significant change. The number of spiral ganglion neurons in cochlea increased, and hair cells had no significant change under electron microscope. Conclusions: The decrease in the number and function of CD4+CD25+Treg reduces its inhibitory effect on autoimmune response and promotes the occurrence of autoimmune auditory neuropathy in AN rats. Adoptive transfer of CD4+CD25+Treg can reduce the autoimmune response and promote the recovery of autoimmune auditory neuropathy.

Novel mutation in the MPZ gene causes early-onset but slow-progressive Charcot-Marie-Tooth disease in a Russian family: a case report.

Charcot-Marie-Tooth disease (CMT) is a genetically heterogeneous group of peripheral neuropathies most of which are associated with mutations in four genes including peripheral myelin protein-22 (PMP22), myelin protein zero (MPZ), gap junction protein beta1 (GJB1) and mitofusin2 (MFN2). This current case report describes the clinical and genetic characteristics of a 6-year-old male proband. A physical examination revealed muscular hypotonia. He started walking on his own at 18 months. A nerve conduction study with needle electromyography revealed conduction block. A novel MPZ mutation (c.398C > T, p.Pro133Leu) was revealed in the proband. This mutation was also found in the 32-year-old father of the proband. The father had had deformity of the feet and distal muscle weakness since childhood. The novel p.Pro133Leu pathogenic mutation was responsible for early onset but slowly progressive CMT1B. We assume that this site is an intolerant to change region in the MPZ gene. This variant in the MPZ gene is an important contributor to hereditary neuropathy with reduced nerve conduction velocity in the Russian population. This case highlights the importance of whole exome sequencing for a proper clinical diagnosis of CMT associated with a mutation in the MPZ gene.