Early life functional advantage coupled with accelerated aging: The case for antagonistic pleiotropy in Huntington's...

Recent findings suggest that neurodevelopment plays a critical role in Huntington's Disease (HD) pathogenesis. This review integrates data from human studies of children and young adults at risk for HD (the Kids-HD study) with the theory of antagonistic pleiotropy (AP), which posits that genes promoting early-life advantages may confer late-life risks. Longitudinal imaging of gene-expanded (GE) children and adolescents shows that mHTT is associated with larger cortical volumes, enhanced surface morphology, and superior cognitive performance-decades before clinical onset. However, this early benefit is paired with accelerated striatal decline, suggesting that mHTT drives an early "ability" that transitions into a "liability." Vertex-wise analyses reveal cortical enlargement in regions with dense glutamatergic projections to the striatum, implicating excitotoxicity as a mechanism linking development to degeneration. This pleiotropic pattern parallels evolutionary models, where genes like HTT may have an evolutionary trade-off where genes supporting growth and reproduction are favored over those that serve long-term somatic maintenance, leaving cells with diminished repair capacity and resulting in an accelerated aging process. Altogether, these findings support a novel framework in which mHTT accelerates both brain maturation and neurodegeneration, offering new insights into HD biology and therapeutic targets.