PMP22 Research Articles

Genetically confirmed Charcot–Marie–Tooth disease type 2A manifesting with postural tremor: a case report

BackgroundCharcot–Marie–Tooth disease is a spectrum of inherited disorders characterized by both motor and sensory manifestations, which include prominent distal muscle weakness, foot deformities (pes cavus and hammer toes), and sensory deficits. Postural tremor as a manifestation of Charcot–Marie–Tooth is seldom present, except in a variant of Charcot–Marie–Tooth subtype 1 (Roussy–Levy syndrome), and its presence often results in a diagnostic dilemma.Case presentationWe present a 34-year-old Eritrean man who came to our hospital with a complaint of tremors of the hands of 6 months duration. Associated with this, he had difficulty walking and weakness of the distal extremities bilaterally, prominently involving the lower limbs. The patient denied a family history of such illness. Physical examination revealed distal muscle weakness (4+/5 on upper limbs, while 3/5 on lower limbs bilaterally), pes cavus deformity, absent ankle reflexes, and mild vibratory sensory loss. We noted a postural tremor that attenuated when the patient assumed an anatomic position. The tremor was limited to the hands. Nerve conduction study of upper and lower limbs showed moderate to severe motor axonal and demyelinating polyneuropathy (axonal > demyelinating), suggestive of mixed axonal and demyelinating hereditary polyneuropathy. Subsequently, genetic testing revealed copy number changes (heterozygous deletion) on the MPZ and MFN2, while the PMP22 gene showed ambiguous copy number changes (decrease) on exons 2 and 3. Tying the clinical, electrophysiologic, and genetic findings, consideration of Charcot–Marie–Tooth subtype 2A with postural tremor was made. Subsequently, the patient was managed with regular physiotherapy and an anxiolytic resulting in minimal symptom improvement.ConclusionThe present case describes a 34-year-old male patient with Charcot–Marie–Tooth subtype 2A presenting with neuropathic postural tremor, which is a rare presentation of a common hereditary polyneuropathy. This case highlights the fact that tremors can be associated with peripheral neuropathy syndromes, and a high index of suspicion is needed to rightly diagnose our patients.

Loss of YAP in Schwann cells improves HNPP pathophysiology.

Rapid nerve conduction in the peripheral nervous system (PNS) is facilitated by the multilamellar myelin sheath encasing many axons of peripheral nerves. Charcot-Marie-Tooth type 1A (CMT1A), and hereditary neuropathy with liability to pressure palsy (HNPP) are common demyelinating inherited peripheral neuropathies and are caused by mutations in the peripheral myelin protein 22 (PMP22) gene. Duplication of PMP22 leads to its overexpression and causes CMT1A, while its deletion results in PMP22 under expression and causes HNPP. Here, we investigated novel targets for modulating the protein level of PMP22 in HNPP. We found that genetic attenuation of the transcriptional coactivator Yap in Schwann cells reduces p-TAZ levels, increased TAZ activity, and increases PMP22 in peripheral nerves. Based on these findings, we ablated Yap alleles in Schwann cells of the Pmp22-haploinsufficient mouse model of HNPP and identified fewer tomacula on morphological assessment and improved nerve conduction in peripheral nerves. These findings suggest YAP modulation may be a new avenue for treatment of HNPP.

Clinical markers of Charcot-Marie-Tooth disease (own experience)

Charcot-Marie-Tooth disease is also called hereditary motor and sensory neuropathy. It is a genetically determined disease that has different variants of inheritance whose substratum is neuromuscular disorders. It may begin during childhood or later in life. Scientists have identified and described more than thirty genetic mutations that form an individual unique passport of violations of the sequence of a group of organic compounds or nucleotides in nucleic acid molecules. There are autosomal dominant, autosomal recessive and X-linked types of genetic inheritance of Charcot-Marie-Tooth disease. This pathology was first described in 1886 and affects about 10 to 40 per 100,000 population. More than 15,000 cases of Charcot-Marie-Tooth disease have been registered in Ukraine. It should be noted that peripheral myelin protein 22 became the first described gene causing Charcot-Marie-Tooth disease. Autosomal dominant Charcot-Marie-Tooth type 1 is the most common form of the disease. When observing patients, a neurologist pays attention to gait disturbances (steppage gait), foot distortion (pes cavus), distal hypotrophy, decrease or absence of tendon and periosteal reflexes, weakness and loss of sensitivity in the distal parts of the limbs. Hypotrophic changes in the limbs are continuously progressive. As a result of muscle atrophy and foot deformity, high-arched feet and extension of the big toe (Friedreich’s foot) are formed. To date, no pathogenetically substantiated treatment exists for Charcot-Marie-Tooth disease, but a multi-vector approach to comprehensive rehabilitation measures creates the necessary conditions to effectively control the manifestations of the inevitable progression of this pathology.

EMP3: A promising biomarker for tumor prognosis and targeted cancer therapy.

Epithelial membrane protein 3 (EMP3) belongs to the peripheral myelin protein 22 kDa (PMP22) gene family, characterized by four transmembrane domains and widespread expression across various human tissues and organs. Other members of the PMP22 family, including EMP1, EMP2, and PMP22, have been linked to various cancers, such as glioblastoma, laryngeal cancer, nasopharyngeal cancer, gastric cancer, breast cancer, and endometrial cancer. However, few studies report on the function and relevance of EMP3 in tumorigenicity. Given the significant structural similarities among members of the PMP22 family, there are likely potential functional similarities as well. Previous studies have established the regulatory role of EMP3 in immune cells like T cells and macrophages. Additionally, EMP3 is found to be involved in critical signaling pathways, including HER-2/PI3K/Akt, MAPK/ERK, and TGF-beta/Smad. Furthermore, EMP3 is associated with cell cycle regulation, cellular proliferation, and apoptosis. Hence, it is likely that EMP3 participates in cancer development through these aforementioned pathways and mechanisms. This review aims to systematically examine and summarize the structure and function of EMP3 and its association to various cancers. EMP3 is expected to emerge as a significant biological marker for tumor prognosis and a potential target in cancer therapeutics.

Quantitative proteomics unveils known and previously unrecognized alterations in neuropathic nerves.

Charcot-Marie-Tooth disease type 1E (CMT1E) is an inherited autosomal dominant peripheral neuropathy caused by mutations in the peripheral myelin protein 22 (PMP22) gene. The identical leucine-to-proline (L16P) amino acid substitution in PMP22 is carried by the Trembler J (TrJ) mouse and is found in CMT1E patients presenting with early-onset disease. Peripheral nerves of patients diagnosed with CMT1E display a complex and varied histopathology, including Schwann cell hyperproliferation, abnormally thin myelin, axonal degeneration, and subaxonal morphological changes. Here, we have taken an unbiased data-independent analysis (DIA) mass spectrometry (MS) approach to quantify proteins from nerves of 3-week-old, age and genetic strain-matched wild-type (Wt) and heterozygous TrJ mice. Nerve proteins were dissolved in lysis buffer and digested into peptide fragments, and protein groups were quantified by liquid chromatography-mass spectrometry (LC-MS). A linear model determined statistically significant differences between the study groups, and proteins with an adjusted p-value of less than 0.05 were deemed significant. This untargeted proteomics approach identified 3759 quality-controlled protein groups, of which 884 demonstrated differential expression between the two genotypes. Gene ontology (GO) terms related to myelin and myelin maintenance confirm published data while revealing a previously undetected prominent decrease in peripheral myelin protein 2. The dataset corroborates the described pathophysiology of TrJ nerves, including elevated activity in the proteasome-lysosomal pathways, alterations in protein trafficking, and an increase in three macrophage-associated proteins. Previously unrecognized perturbations in RNA processing pathways and GO terms were also discovered. Proteomic abnormalities that overlap with other human neurological disorders besides CMT include Lafora Disease and Amyotrophic Lateral Sclerosis. Overall, this study confirms and extends current knowledge on the cellular pathophysiology in TrJ neuropathic nerves and provides novel insights for future examinations. Recognition of shared pathomechanisms across discrete neurological disorders offers opportunities for innovative disease-modifying therapeutics that could be effective for distinct neuropathies.

Roles for PMP22 in Schwann cell cholesterol homeostasis in health and disease.

Underexpression, overexpression, and point mutations in peripheral myelin protein 22 (PMP22) cause most cases of Charcot-Marie-Tooth disease (CMTD). While its exact functions remain unclear, PMP22 is clearly essential for formation and maintenance of healthy myelin in the peripheral nervous system. This review explores emerging evidence for roles of PMP22 in cholesterol homeostasis. First, we highlight dysregulation of lipid metabolism in PMP22-based forms of CMTD and recently-discovered interactions between PMP22 and cholesterol biosynthesis machinery. We then examine data that demonstrates PMP22 and cholesterol co-traffic in cells and co-localize in lipid rafts, including how disease-causing PMP22 mutations result in aberrations in cholesterol localization. Finally, we examine roles for interactions between PMP22 and ABCA1 in cholesterol efflux. Together, this emerging body of evidence suggests that PMP22 plays a role in facilitating enhanced cholesterol synthesis and trafficking necessary for production and maintenance of healthy myelin.

Potential analgesic effect of a novel cannabidiol nanocrystals powder for the treatment of neuropathic pain.

The current analgesics often prevent patients from getting effective treatment due to their adverse effects. Cannabidiol (CBD) is well tolerated, has few side effects and has been extensively investigated in analgesia. However, its oral bioavailability is extremely low. In order to solve this problem, we developed the cannabidiol nanocrystals (CBD-NC) in the earlier stage. In this study, we evaluated the nociceptive behaviours associated with neuropathic pain (NP) induced by the spared nerve injury (SNI) model. Assessment of pain threshold was evaluated by paw withdraw threshold (PWT) and paw withdrawal latency (PWL). The improving effect on the motor dysfunction was determined by rota-rod testing. To assess the neuroprotective effect, nerve demyelination and expression of peripheral myelin protein PMP22 were measured with myelin sheath staining and western blotting. Protein expressions in microglia of spinal cord were tested by western blot to explore the underlying mechanism. Compared with the CBD oil solution, CBD-NC significantly reduced mechanical allodynia and thermal hyperalgesia in rats. CBD-NC could improve motor dysfunction induced by SNI in rats, significantly reverse the demyelination and increase the expression of the marker protein of peripheral myelin. Underlying spinal analgesic mechanism of microglia and related factors were preliminarily confirmed. CBD-NC administration is an effective treatment for NP associated with SNI, and the analgesic effect of CBD-NC was significantly better than that of CBD oil sol. By contrast, CBD-NC has a fast-acting and long-term effect in the treatment of NP. Our study further supports the potential therapeutic effect of CBD-NC on NP. The absolute bioavailability of the CBD-NC intramuscular injection formulation can reach 203.31%, which can solve the problem of low oral bioavailability. This research evaluated the therapeutic effect of CBD-NC on NP associated with the SNI model for the first time. All available date showed that whatever the analgesic or neuroprotective effect of CBD-NC, it was significantly better than that of CBD oil sol., which was consistent with the results of the pharmacokinetic. This research supports the initiation of more trials testing the efficacy of CBD-NC for treating NP.

Spatial selectivity of ATase inhibition in mouse models of Charcot-Marie-Tooth disease.

The endoplasmic reticulum acetylation machinery has emerged as a new branch of the larger endoplasmic reticulum quality control system. It regulates the selection of correctly folded polypeptides as well as reticulophagy-mediated removal of toxic protein aggregates with the former being a particularly important aspect of the proteostatic functions of endoplasmic reticulum acetylation. Essential to this function is the Nε-lysine acetyltransferase activity of acetyltransferase 1 and acetyltransferase 2, which regulates the induction of endoplasmic reticulum-specific autophagy through the acetylation of the autophagy-related protein 9A. Here, we used three mouse models of Charcot-Marie-Tooth disease, peripheral myelin protein 22/Tr-J, C3-peripheral myelin protein 22 and myelin protein zero/ttrr, to study spatial and translational selectivity of endoplasmic reticulum acetyltransferase inhibitors. The results show that inhibition of the endoplasmic reticulum acetyltransferases selectively targets misfolding/pro-aggregating events occurring in the lumen of the organelle. Therefore, they establish acetyltransferase 1 and acetyltransferase 2 as the first proven targets for disease-causing proteotoxic states that initiate within the lumen of the endoplasmic reticulum/secretory pathway.

A recurrent missense variant in ITPR3 causes demyelinating Charcot-Marie-Tooth with variable severity

Abstract Charcot-Marie-Tooth (CMT) disease is a neuromuscular disorder affecting the peripheral nervous system. The diagnostic yield in demyelinating CMT (CMT1) is typically ∼80-95%, of which at least 60% is due to the PMP22 gene duplication. The remainder of CMT1 is more genetically heterogeneous. We used whole exome and whole genome sequencing data included in the GENESIS database to investigate novel causal genes and mutations in a cohort of ∼2,670 individuals with CMT neuropathy. A recurrent heterozygous missense variant p.Thr1424Met in the recently described CMT gene ITPR3, encoding IP3R3 (inositol 1,4,5-trisphosphate receptor 3) was identified. This previously reported p.Thr1424Met change was present in 33 affected individuals from nine unrelated families from multiple populations, representing an unusual recurrence rate at a mutational hotspot, strengthening the gene-disease relationship (GnomADv4 allele frequency 1.76e-6). Sanger sequencing confirmed the co-segregation of the CMT phenotype with the presence of the mutation in autosomal dominant and de novo inheritance patterns, including a four-generation family with multiple affected second-degree cousins. Probands from all families presented with slow nerve conduction velocities, matching the diagnostic category of CMT1. Remarkably, we observed a uniquely variable clinical phenotype for age at onset and phenotype severity in p.Thr1424Met carrying patients, even within families. Finally, we present data supportive of a dominant-negative effect of the p.Thr1424Met mutation with associated changes in protein expression in patient-derived cells.

Optimizing NMR fragment-based drug screening for membrane protein targets

NMR spectroscopy has played a pivotal role in fragment-based drug discovery by coupling detection of weak ligand-target binding with structural mapping of the binding site. Fragment-based screening by NMR has been successfully applied to many soluble protein targets, but only to a limited number of membrane proteins, despite the fact that many drug targets are membrane proteins. This is partly because of difficulties preparing membrane proteins for NMR—especially human membrane proteins—and because of the inherent complexity associated with solution NMR spectroscopy on membrane protein samples, which require the inclusion of membrane-mimetic agents such as micelles, nanodiscs, or bicelles. Here, we developed a generalizable protocol for fragment-based screening of membrane proteins using NMR. We employed two human membrane protein targets, both in fully protonated detergent micelles: the single-pass C-terminal domain of the amyloid precursor protein, C99, and the tetraspan peripheral myelin protein 22 (PMP22). For both we determined the optimal NMR acquisition parameters, protein concentration, protein-to-micelle ratio, and upper limit to the concentration of D6-DMSO in screening samples. Furthermore, we conducted preliminary screens of a plate-format molecular fragment mixture library using our optimized conditions and were able to identify hit compounds that selectively bound to the respective target proteins. It is hoped that the approaches presented here will be useful in complementing existing methods for discovering lead compounds that target membrane proteins.

P.062 Normal NCS in 42-year-old man with PMP22 duplication

Background: Charcot Marie Tooth disease is a polygenic disorder with cannonical features of distal amyotrophy, acrohypesthesia, and tight tendoachilles of either axonal (type 2) or demeylinating (type 1) varieties. Type 1 CMT patients are required to possess conduction slowing of a sufficient degree to qualify as demyelinating. Presented is a middle-aged man with an unremarkable neurologic exam and normal electrophysiology. Methods: Standard electrophysiological techniques were employed to obtain the nerve conduction data (Natus Nicolet EDX AT2; Middleton, WI, USA). Repeated next generation sequencing and deletion/duplication analyses were performed. Results: The nerve conduction studies showed no evidence of demyelination in the upper or lower extremeties. The duplication error was confirmed with repeat testing. The heterozygous PMP22 gene duplication encompassed the entire coding sequence involving exons 1-5. Conclusions: CMT1A accounts for the vast majority of dysmyelinating hereditary neuropathies. Phenotypic variability is well described. Presentations include (a) classic conduction slowing, (b) intermediate slowing, (c) conduction block, (d) HNPP-like, (e) absent CMAPs, and (f) normal NCSs in young infants. This is the first case of a neurologically intact adult with CMT1A. Cryptogenic genetic modifier-effect(s) are posited as a possible explanation of the lack of penetrance. Identifying the nature of this modification may prove instructive for future therapies.

PMP22 duplication dysregulates lipid homeostasis and plasma membrane organization in developing human Schwann cells.

Charcot-Marie-Tooth disease type 1A (CMT1A) is the most common inherited peripheral neuropathy caused by a 1.5 Mb tandem duplication of chromosome 17 harbouring the PMP22 gene. This dose-dependent overexpression of PMP22 results in disrupted Schwann cell myelination of peripheral nerves. To obtain better insights into the underlying pathogenic mechanisms in CMT1A, we investigated the role of PMP22 duplication in cellular homeostasis in CMT1A mouse models and in patient-derived induced pluripotent stem cells differentiated into Schwann cell precursors (iPSC-SCPs). We performed lipidomic profiling and bulk RNA sequencing (RNA-seq) on sciatic nerves of two developing CMT1A mouse models and on CMT1A patient-derived iPSC-SCPs. For the sciatic nerves of the CMT1A mice, cholesterol and lipid metabolism was downregulated in a dose-dependent manner throughout development. For the CMT1A iPSC-SCPs, transcriptional analysis unveiled a strong suppression of genes related to autophagy and lipid metabolism. Gene ontology enrichment analysis identified disturbances in pathways related to plasma membrane components and cell receptor signalling. Lipidomic analysis confirmed the severe dysregulation in plasma membrane lipids, particularly sphingolipids, in CMT1A iPSC-SCPs. Furthermore, we identified reduced lipid raft dynamics, disturbed plasma membrane fluidity and impaired cholesterol incorporation and storage, all of which could result from altered lipid storage homeostasis in the patient-derived CMT1A iPSC-SCPs. Importantly, this phenotype could be rescued by stimulating autophagy and lipolysis. We conclude that PMP22 duplication disturbs intracellular lipid storage and leads to a more disordered plasma membrane owing to an alteration in the lipid composition, which might ultimately lead to impaired axo-glial interactions. Moreover, targeting lipid handling and metabolism could hold promise for the treatment of patients with CMT1A.

A study concept of expeditious clinical enrollment for genetic modifier studies in Charcot-Marie-Tooth neuropathy 1A.

Caused by duplications of the gene encoding peripheral myelin protein 22 (PMP22), Charcot-Marie-Tooth disease type 1A (CMT1A) is the most common hereditary neuropathy. Despite this shared genetic origin, there is considerable variability in clinical severity. It is hypothesized that genetic modifiers contribute to this heterogeneity, the identification of which may reveal novel therapeutic targets. In this study, we present a comprehensive analysis of clinical examination results from 1564 CMT1A patients sourced from a prospective natural history study conducted by the RDCRN-INC (Inherited Neuropathy Consortium). Our primary objective is to delineate extreme phenotype profiles (mild and severe) within this patient cohort, thereby enhancing our ability to detect genetic modifiers with large effects. We have conducted large-scale statistical analyses of the RDCRN-INC database to characterize CMT1A severity across multiple metrics. We defined patients below the 10th (mild) and above the 90th (severe) percentiles of age-normalized disease severity based on the CMT Examination Score V2 and foot dorsiflexion strength (MRC scale). Based on extreme phenotype categories, we defined a statistically justified recruitment strategy, which we propose to use in future modifier studies. Leveraging whole genome sequencing with base pair resolution, a future genetic modifier evaluation will include single nucleotide association, gene burden tests, and structural variant analysis. The present work not only provides insight into the severity and course of CMT1A, but also elucidates the statistical foundation and practical considerations for a cost-efficient and straightforward patient enrollment strategy that we intend to conduct on additional patients recruited globally.

Testing SIPA1L2 as a modifier of CMT1A using mouse models.

Charcot-Marie-Tooth disease type 1A (CMT1A) is a demyelinating peripheral neuropathy caused by the duplication of peripheral myelin protein 22 (PMP22), leading to muscle weakness and loss of sensation in the hands and feet. A recent case-only genome-wide association study of CMT1A patients conducted by the Inherited Neuropathy Consortium identified a strong association between strength of foot dorsiflexion and variants in signal induced proliferation associated 1 like 2 (SIPA1L2), indicating that it may be a genetic modifier of disease. To validate SIPA1L2 as a candidate modifier and to assess its potential as a therapeutic target, we engineered mice with deletion of exon 1 (including the start codon) of the Sipa1l2 gene and crossed them to the C3-PMP22 mouse model of CMT1A. Neuromuscular phenotyping showed that Sipa1l2 deletion in C3-PMP22 mice preserved muscular endurance assayed by inverted wire hang duration and changed femoral nerve axon morphometrics such as myelin thickness. Gene expression changes suggest involvement of Sipa1l2 in cholesterol biosynthesis, a pathway that is also implicated in C3-PMP22 mice. Although Sipa1l2 deletion did impact CMT1A-associated phenotypes, thereby validating a genetic interaction, the overall effect on neuropathy was mild.

PERP May Affect the Prognosis of Lung Adenocarcinoma by Inhibiting Apoptosis.

PERP, a member of the peripheral myelin protein gene family, is a new therapeutic target in cancer. The relationships between PERP and immune cell infiltration in lung cancer have not been studied. Therefore, the role of PERP in the tumour microenvironment (TME) of lung cancer needs to be further explored. In this study, we explored the association between PERP expression and clinical characteristics by analysing data from the TCGA database. Cox regression and Kaplan‒Meier methods were used to investigate the relationship between the expression of PERP and overall survival in patients with lung adenocarcinoma (LUAD). The relationship between PERP expression and the degree of infiltration of specific immune cell subsets in LUAD was evaluated using the TIMER database and GEPIA. We also performed GO enrichment analysis and KEGG enrichment analysis to reveal genes coexpressed with PERP using the Coexpedia database. Finally, we verified the expression and function of PERP in LUAD tissues and the A549 cell line by RT‒PCR, Western blot, CCK-8, IHC, and wound healing assays. The mouse model was used to study the in vivo effects of PERP. According to our results, PERP expression was significantly higher in LUAD tissues and associated with the clinical characteristics of the disease. Survival was independently associated with PERP in LUAD patients. We further verified that PERP might regulate B-cell infiltration in LUAD to affect the prognosis of LUAD. To identify PERP-related signalling pathways in LUAD, we performed a genome-aggregation analysis (GSEA) between low and high PERP expression datasets. LUAD cells express higher levels of PERP than paracarcinoma cells, and PERP inhibits the proliferation and metastasis of A549 cells through apoptosis. PERP may affect the prognosis of lung adenocarcinoma by inhibiting apoptosis and is associated with immune cell infiltration.

Adult-onset Krabbe disease manifesting as Charcot- Marie-Tooth disease

Krabbe disease (KD) is a progressive lysosomal storage disorder characterized by the deficiency of β-galactocerebrosidase (GALC). It mainly manifests as central nervous system involvement, but peripheral nervous system damage is also found. Although it can appear as a widespread neuropathy, it is very rare to manifest in a form similar to Charcot-Marie-Tooth disease (CMT). A 34-year-old woman presented with progressive gait disturbance and foot deformity. There were no other medical or family history of abnormalities. Nerve conduction studies showed demyelinating neuropathy, and brain MRI showed white matter hyperintensities. Sequencing of PMP22 gene was normal, followed by next-generation sequencing (NGS). Potential compound heterozygous variants in the GALC gene were found; additionally a decrease in GALC enzymatic activity was confirmed, and KD was diagnosed. Although CMT has been previously diagnosed through a single genetic test, since the introduction of NGS, various genetic mutations have been identified in patients suspected of having CMT. In addition to the phenotypes mainly found in KD, other unusual phenotypes have also been found. In this case, we identified a unique clinical phenotype similar to CMT in a KD patient. We also confirmed the clinical usefulness of NGS by demonstrating in a KD patient diagnosed through NGS, who was not identified by conventional genetic mutation testing.

Aberrant miR-29 is a predictive feature of severe phenotypes in pediatric Crohn's disease.

Crohn's disease (CD) is a chronic inflammatory gut disorder. Molecular mechanisms underlying the clinical heterogeneity of CD remain poorly understood. MicroRNAs (miRNAs) are important regulators of gut physiology, and several have been implicated in the pathogenesis of adult CD. However, there is a dearth of large-scale miRNA studies for pediatric CD. We hypothesized that specific miRNAs uniquely mark pediatric CD. We performed small RNA-Seq of patient-matched colon and ileum biopsies from treatment-naive pediatric patients with CD (n = 169) and a control cohort (n = 108). Comprehensive miRNA analysis revealed 58 miRNAs altered in pediatric CD. Notably, multinomial logistic regression analysis revealed that index levels of ileal miR-29 are strongly predictive of severe inflammation and stricturing. Transcriptomic analyses of transgenic mice overexpressing miR-29 show a significant reduction of the tight junction protein gene Pmp22 and classic Paneth cell markers. The dramatic loss of Paneth cells was confirmed by histologic assays. Moreover, we found that pediatric patients with CD with elevated miR-29 exhibit significantly lower Paneth cell counts, increased inflammation scores, and reduced levels of PMP22. These findings strongly indicate that miR-29 upregulation is a distinguishing feature of pediatric CD, highly predictive of severe phenotypes, and associated with inflammation and Paneth cell loss.

Demyelination and Na+ Channel Redistribution Underlie Auditory and Vestibular Dysfunction in PMP22-Null Mice.

Altered expression of peripheral myelin protein 22 (PMP22) results in demyelinating peripheral neuropathy. PMP22 exhibits a highly restricted tissue distribution with marked expression in the myelinating Schwann cells of peripheral nerves. Auditory and vestibular Schwann cells and the afferent neurons also express PMP22, suggesting a unique role in hearing and balancing. Indeed, neuropathic patients diagnosed with PMP22-linked hereditary neuropathies often present with auditory and balance deficits, an understudied clinical complication. To investigate the mechanism by which abnormal expression of PMP22 may cause auditory and vestibular deficits, we studied gene-targeted PMP22-null mice. PMP22-null mice exhibit an unsteady gait, have difficulty maintaining balance, and live for only ∼3-5 weeks relative to unaffected littermates. Histological analysis of the inner ear revealed reduced auditory and vestibular afferent nerve myelination and profound Na+ channel redistribution without PMP22. Yet, Na+ current density was unaltered, in stark contrast to increased K+ current density. Atypical postsynaptic densities and a range of neuronal abnormalities in the organ of Corti were also identified. Analyses of auditory brainstem responses (ABRs) and vestibular sensory-evoked potential (VsEP) revealed that PMP22-null mice had auditory and vestibular hypofunction. These results demonstrate that PMP22 is required for hearing and balance, and the protein is indispensable for the formation and maintenance of myelin in the peripheral arm of the eighth nerve. Our findings indicate that myelin abnormalities and altered signal propagation in the peripheral arm of the auditory nerve are likely causes of auditory deficits in patients with PMP22-linked neuropathies.

Gene Distribution in Pediatric-Onset Inherited Peripheral Neuropathy: A Single Tertiary Center in Thailand.

Inherited peripheral neuropathy presents a diagnostic and therapeutic challenge due to its association with mutations in over 100 genes. This condition leads to long-term disability and poses a substantial healthcare burden on society. This study aimed to investigate the distribution of genes and establish the genotype-phenotype correlations, focusing on pediatric-onset cases. Exome sequencing and other analytical techniques were employed to identify pathogenic variants, including duplication analysis of the PMP22 gene. Each patient underwent physical examination and electrophysiological studies. Genotypes were correlated with phenotypic features, such as age at disease onset and ulnar motor nerve conduction velocity. We identified 35 patients with pediatric-onset inherited peripheral neuropathy. Pathogenic or likely pathogenic variants were confirmed in 24 out of 35 (68.6%) patients, with 4 of these variants being novel. A confirmed molecular diagnosis was achieved in 90.9% (10/11) of patients with demyelinating Charcot-Marie-Tooth disease (CMT) and 56.3% (9/16) of patients with axonal CMT. Among patients with infantile-onset CMT (≤2 years), the most common causative genes were MFN2 and NEFL, while GDAP1 and MFN2 were frequent causes among patients with childhood- or adolescent-onset CMT (3-9 years). The MFN2 gene was the most commonly implicated gene, and the axonal type was predominant in this cohort of Thai patients with pediatric-onset inherited peripheral neuropathy.

IMPAIRMENT OF AUDITORY FUNCTION IN PERSONS WITH TYPE 2 DIABETES MELLITUS DEPENDING ON THE LEVEL OF PERIPHERAL MYELIN PROTEIN

Introduction: One of the priority tasks of modern medicine is early diagnosis and treatment of micro- and macrovascular complications of diabetes mellitus (DM). Variability of carbohydrate metabolism indicators, metabolic dysfunction are leading factors in the development and progression of complications of type 2 DM with hearing loss due to degenerative changes in nerve fibers. An important aspect of diagnostic and treatment algorithms of SNHL in patients with type 2 DM is early detection of demyelinating processes to prevent neuronal structures damage. The purpose of the study is to determine the relationship between the level of peripheral myelin protein 22 (PMP 22) and the condition of the auditory analyzer according to the data of examination in patients with type 2 DM combined with hearing impairment. Material and methods: There were examined 30 patients with type 2 DM (15 men and 15 women aged 56,28±4,54 years) associated with degree I–II sensorineural disorders; 15 persons with signs of sensorineural hearing loss (SNHL) (8 men, 7 women aged 59,33±2,65 years) without diabetes and 15 controls. During the examination the studied patients were divided into groups: the 1st group (n=15) without or with isolated microvascular complications of type 2 DM, the 2nd group (n = 15) with neuro-, nephro- and retinopathy. All patients underwent a set of laboratory tests, clinical and instrumental diagnostics of auditory function. The obtained data subjected to statistical processing and correlations identified. Results: The analysis revealed that in patients both groups with type 2 DM and SNHL the level of PMP22 significantly increased compared to controls and the comparison group and more significantly in those with microangiopathies. Conclusions: A significant increase was revealed in the content of PMP 22 and manifestations of SNHL in patients with type 2 DM associated with microangiopathies that indicate demyelinating processes in the neural structures of the auditory analyzer.