Neurofilament Light Disordered Tail Mutations Reshape Its Self-Assembled Network Structure

Abstract

Proteins with intrinsically disordered regions (IDRs) perform essential cellular functions despite lacking stable structures, challenging the traditional structure-function paradigm. Neurofilament-light (NFL) proteins assemble into bottlebrush filaments, whose disordered tail domains mediate nematic hydrogel formation critical for neuronal integrity. Mutations in NFL are linked to Charcot-Marie-Tooth (CMT) disease, yet their molecular effects remain unclear. Here, aiming to gain insight into these molecular mechanisms, we combine small-angle X-ray scattering, microscopy, and deep-learning conformational analysis to investigate CMT-associated NFL tail mutations. We find that these mutations induce pathological hydrogel compaction, disrupt filament nematic order by generating microdomains, and alter water retention dynamics by reshaping of sequence-dependent conformational ensembles, leading to macroscopic network rearrangements. These findings provide mechanistic insight into how subtle sequence changes in IDRs modulate protein network organization and function, informing an understanding of IDR-related pathologies and mutation-based disease characterization.