The goal of this study is to better understand the progression of CMT1A and identify risk factors influencing disease course. CMT1A, the most common hereditary peripheral neuropathy, shows high variability in individual phenotypes despite genetic similarity. Key objectives include analyzing determinants of phenotypic expression and documenting symptom variability over five years to capture disease dynamics.

Although incurable, novel CMT therapies are in development. Proving efficacy is challenging due to slow progression and limited sensitive outcome measures. This study aims to validate biomarkers (DNA/epigenetics and RNA/RT-PCR) and sensitive outcome measures from blood and skin of CMT patients over five years to support clinical therapy trials. Approximately 25 healthy volunteers will serve as controls, providing blood and skin samples for biomarker validation.

Additionally, the project will build a tissue collection (skin, blood, and cultured fibroblasts) from CMT patients of various subtypes for unrestricted scientific research, especially for the German CMT-NET network (NCT03386266). Scientific partners have free access to samples and data for research (commercial use is excluded). Currently, this collection includes over 100 standardized skin biopsies from CMT1A patients and is Germany's only repository for hereditary neuropathy tissue samples.

Until now, only physical and electrophysiological examinations have been used to determine disease severity in patients with CMT. The CMT Neuropathy Score (CMTNS) is a valid and reliable nine-point composite scale that considers sensory and motor symptoms. However, its function as a severity or progression marker is controversial due to the slow deterioration over years. Surrogate biomarkers for disease severity and progression would serve as powerful tools for monitoring therapeutic effects in clinical studies. Currently, no practical biomarkers for CMT1A are available. A non-invasive MRI study showed changes in muscle and intramuscular fat accumulation in the lower limbs that correlated with clinical impairment. This method shows promising results as a surrogate outcome measure for clinical trials, but it is technically demanding and has so far only been tested in a small group of CMT patients and those with various other neuromuscular disorders.

Molecular analysis of body fluids or tissue samples is a promising strategy for developing clinically practical surrogate biomarkers for disease severity in CMT1A. In preliminary work by our research group, gene expression analyses of CMT rats were correlated with skin biopsies in CMT1A patients. This analysis identified several individual genes (STT2, CTSA, PPARG, CDA, ENPP1, and NRG1) that correlated with disease severity. Additional experiments using gene expression analyses of skin and the sciatic nerve (N. ischiadicus) enabled a distinction between mildly and severely affected CMT rats.

Due to the high variability in disease expression, we postulated that a large portion of disease manifestation occurs at the epigenetic level. Building on this, our initial approach revealed significant overlap between differentially methylated DNA regions and transcriptional changes in CMT rats. This finding suggested that changes in DNA methylation could contribute to altered gene expression and thus to the pathogenesis of CMT1A. Notably, two clusters contained highly upregulated transcripts enriched with genes associated with cell cycle regulation. Cell cycle regulation is linked to pmp22/gas315, the gene that causes CMT1A. Analysis of transcription factors indicated significant involvement of the important cell cycle regulator from the E2F family, along with its known downstream effector EZH2, a methylase essential for transcriptional repression in Schwann cells through methylation of histone H3.

Based on this, a recruitment of a total of 150 patients took place from 2016 to 2019, who were assessed over three visits for phenotypic variability, disease severity, and clinical scores (NCT03386266). In this translational study, rats overexpressing the Pmp22 gene and patient material were used. From 150 animals, 4 or 5 with mild and severe disease expressions, respectively, were selected. Patients were recruited through the CMT-NET network, where the CMTNSv2 was used as a disease score. RNAseq analyses identified several candidate genes that overlapped in both CMT1A patients and the rat models, indicating potential markers for disease severity.

These preliminary data provide evidence that epigenetic and other OMICs data from both CMT1A animal models and human patients can be used for bidirectional, informative translation in both forward and backward directions. Based on these bidirectional data, RNA sequencing was conducted from the blood of patients in CMT-NET, where initial potential biomarkers, disease modifiers, and surrogate markers were identified. The rt-PCR data provide insights into predictive statements about patients' clinical development over time.

Based on these findings, we plan to further investigate the identified biomarkers in a 4th visit, following our latest ethics application to CMT-NET, and confirm their presence in skin biopsies. The focus is particularly on markers associated with newly observed symptoms, such as autonomic dysfunction and tremors. This expanded approach aims to improve the diagnosis and monitoring of the disease, enabling more precise and individualized therapeutic approaches.

The aim of this project is to better understand the natural progression of CMT1A disease and to identify potential risk factors that may influence the course of the disease. CMT1A, a subtype of CMT, is the most common hereditary peripheral neuropathy. Its slow, progressive disease course shows a high variability of individual phenotypes despite genetic homogeneity. The primary goal of the project is to analyze potential determinants of phenotypic expression, including severity levels, and to document symptom variability over a total period of five years as an indicator of disease dynamics.

CMT is a rare, incurable disease, though novel pharmacotherapies are currently being developed. Demonstrating efficacy in clinical trials is challenging due to the slow progression and lack of sensitive outcome measures. The main goal of this subproject is to validate identified biomarkers (DNA/epigenetics and RNA/RT-PCR) and selected sensitive outcome measures in the blood and skin of CMT patients over an observation period of at least 5 years to improve the assessment of efficacy in future clinical therapy trials, including diagnostic monitoring of disease progression in CMT patients. Approximately 25 healthy volunteers will also be included as controls. For the volunteers, a brief medical history will be recorded, and blood and skin samples will be collected to validate the biomarkers.

The goal of this subproject is to collect tissue samples (skin, blood, and cultured fibroblasts) from CMT patients with various subtypes for unrestricted scientific and medical research purposes, for example, for research projects within the German CMT-NET network. Scientific partners will receive free access to the samples and data. Commercial use outside of research purposes is not intended. With the help of the CMT tissue collection, CMT-NET partners can conduct morphological and molecular biological analyses of patient material, as well as utilize fibroblast cultures. Genotype-phenotype studies can also be conducted. To date, a collection of over 100 standardized skin biopsies from clinically well-characterized CMT1A patients already exists. This collection is the only tissue repository for tissue samples from patients with hereditary neuropathies in Germany.

The aim of this project is to better understand the natural progression of CMT1A disease and to identify potential risk factors that may influence the course of the disease. CMT1A, a subtype of CMT, is the most common hereditary peripheral neuropathy. Its slow, progressive disease course shows a high variability of individual phenotypes despite genetic homogeneity. The primary goal of the project is to analyze potential determinants of phenotypic expression, including severity levels, and to document symptom variability over a total period of five years as an indicator of disease dynamics.

CMT is a rare, incurable disease, though novel pharmacotherapies are currently being developed. Demonstrating efficacy in clinical trials is challenging due to the slow progression and lack of sensitive outcome measures. The main goal of this subproject is to validate identified biomarkers (DNA/epigenetics and RNA/RT-PCR) and selected sensitive outcome measures in the blood and skin of CMT patients over an observation period of at least 5 years to improve the assessment of efficacy in future clinical therapy trials, including diagnostic monitoring of disease progression in CMT patients. Approximately 25 healthy volunteers will also be included as controls. For the volunteers, a brief medical history will be recorded, and blood and skin samples will be collected to validate the biomarkers.

The goal of this subproject is to collect tissue samples (skin, blood, and cultured fibroblasts) from CMT patients with various subtypes for unrestricted scientific and medical research purposes, for example, for research projects within the German CMT-NET network. Scientific partners will receive free access to the samples and data. Commercial use outside of research purposes is not intended. With the help of the CMT tissue collection, CMT-NET partners can conduct morphological and molecular biological analyses of patient material, as well as utilize fibroblast cultures. Genotype-phenotype studies can also be conducted. To date, a collection of over 100 standardized skin biopsies from clinically well-characterized CMT1A patients already exists. This collection is the only tissue repository for tissue samples from patients with hereditary neuropathies in Germany.

The aim of this project is to better understand the natural progression of CMT1A disease and to identify potential risk factors that may influence the course of the disease. CMT1A, a subtype of CMT, is the most common hereditary peripheral neuropathy. Its slow, progressive disease course shows a high variability of individual phenotypes despite genetic homogeneity. The primary goal of the project is to analyze potential determinants of phenotypic expression, including severity levels, and to document symptom variability over a total period of five years as an indicator of disease dynamics.

CMT is a rare, incurable disease, though novel pharmacotherapies are currently being developed. Demonstrating efficacy in clinical trials is challenging due to the slow progression and lack of sensitive outcome measures. The main goal of this subproject is to validate identified biomarkers (DNA/epigenetics and RNA/RT-PCR) and selected sensitive outcome measures in the blood and skin of CMT patients over an observation period of at least 5 years to improve the assessment of efficacy in future clinical therapy trials, including diagnostic monitoring of disease progression in CMT patients. Approximately 25 healthy volunteers will also be included as controls. For the volunteers, a brief medical history will be recorded, and blood and skin samples will be collected to validate the biomarkers.

Inclusion Criteria:

• Clinical CMT Diagnosis / Anamnestically Healthy Control Group
• Genetic confirmation of CMT in adult patients
• Ability to achieve the outcome measure at baseline
• Age between 18 and 65 years
• Capacity of all study participants to consent and signed informed consent, including patient or participant information and consent form

Exclusion Criteria:

• Pregnancy or breastfeeding period
• Other relevant neurological or psychiatric disorders, acute or in the past history
• Presence of a serious previous internal disease

Participants from the Biomarkers and Validation of Selected Outcome Measures (CMTNSmod) study (ClinicalTrials.gov ID NCT03386266)