The distal hereditary motor neuropathies

Area of Science:

• Neuroscience
• Genetics
• Neurology

Background:

• Distal hereditary motor neuropathies (dHMN) represent a heterogeneous group of disorders characterized by length-dependent, predominantly motor neuropathy.
• dHMN often shows overlap with Charcot-Marie-Tooth disease (CMT2) and juvenile forms of amyotrophic lateral sclerosis and hereditary spastic paraplegia.
• While eleven causative genes and four loci are known, mutations in undiscovered genes account for 80% of dHMN cases.

Purpose of the Study:

• To summarize clinical features of dHMN subtypes to guide genetic testing.
• To review the underlying neuroscience of how mutations cause motor-specific neuropathy.
• To highlight potential therapeutic strategies for dHMN.

Main Methods:

• Literature review of clinical features, genetic causes, and neuroscience of dHMN.
• Analysis of known causative genes and their implicated protein functions (misfolding, RNA metabolism, axonal transport, cation channels).
• Discussion of the role of next-generation sequencing in identifying pathogenic mutations.

Main Results:

• Identified eleven causative genes and four loci for dHMN with various inheritance patterns.
• Highlighted diverse protein functions implicated in dHMN pathogenesis, including HSPB1, HSPB8, BSCL2, IGHMBP2, SETX, GARS, DYNC1H1, DCTN1, ATP7A, and TRPV4.
• Emphasized that 80% of dHMN cases are linked to currently undiscovered genes.

Conclusions:

• Understanding dHMN subtypes and genetic causes is crucial for accurate diagnosis and genetic testing.
• Elucidating the functional consequences of gene mutations is vital for developing targeted therapies.
• Advances in genetic sequencing technologies will accelerate the discovery of novel dHMN-causing genes and inform therapeutic development.