Exome Sequence Analysis Suggests that Genetic Burden Contributes to Phenotypic Variability and Complex Neuropathy

Area of Science:

• Genetics
• Neurology
• Molecular Biology

Background:

• Charcot-Marie-Tooth (CMT) disease is a complex peripheral neuropathy with diverse genetic causes.
• Identifying the genetic underpinnings of CMT remains challenging, particularly in cases refractory to standard molecular diagnosis.

Purpose of the Study:

• To identify novel genetic causes of Charcot-Marie-Tooth (CMT) disease using whole-exome sequencing.
• To investigate the role of rare variant burden and gene interactions in CMT phenotypic variability.

Main Methods:

• Whole-exome sequencing (WES) was performed on 40 individuals from 37 unrelated families with CMT-like neuropathy.
• Candidate gene validation involved genetic analysis and in vivo studies.
• Aggregate mutation data analysis and zebrafish genetic interaction assays were employed.

Main Results:

• Apparent causal mutations were identified in approximately 45% (17/37) of families.
• Three novel candidate disease genes were proposed.
• A significant increase in rare variants across 58 neuropathy-associated genes was observed in subjects compared to controls, suggesting a contribution to phenotypic variability.
• Genetic interaction assays in zebrafish demonstrated that combined mutations in neuropathy genes exacerbate disease phenotypes.

Conclusions:

• Whole-exome sequencing is effective in identifying genetic causes for a subset of Charcot-Marie-Tooth disease cases.
• A cumulative burden of rare variants in multiple neuropathy-associated genes may contribute to the complex inheritance and variable expressivity observed in CMT.
• Genetic interactions between neuropathy genes play a role in disease pathogenesis.