The R15L variant of CHCHD10 challenges prevailing assumptions about how familial ALS develops, suggesting that motor neuron death can occur through pathways independent of the mitochondrial dysfunction typically associated with this disease. This finding has immediate relevance for families carrying this mutation and broader implications for understanding ALS heterogeneity.
Genetically engineered mice carrying the human R15L mutation in CHCHD10 developed measurable motor neuron loss and elevated neurofilament light—a biomarker of neurodegeneration—by advanced age. The neurological damage manifested as reduced compound muscle action potential amplitude and actual motor neuron loss in spinal cord tissue. However, the mutation produced these effects without causing protein aggregation, altered mitochondrial respiration, or hydrogen peroxide emission abnormalities that characterize other CHCHD10 variants. Human fibroblasts from R15L carriers similarly showed normal mitochondrial function.
This mouse model reveals that R15L represents a distinct ALS mechanism compared to more aggressive CHCHD10 mutations. The absence of obvious mitochondrial pathology suggests alternative cellular stress pathways may drive the gradual motor neuron degeneration seen in affected families. Enhanced PGC-1α expression in muscle tissue indicates compensatory mitochondrial biogenesis responses, possibly representing the cell's attempt to maintain function despite subtle underlying damage. The late-onset, mild progression mirrors the human clinical presentation, validating this model for therapeutic development. For ALS research, these findings underscore that familial forms may require mutation-specific treatment approaches rather than universal mitochondrial-targeted interventions.