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

Proteins with intrinsically disordered regions (IDRs) perform essential cellular functions despite lacking stable structures, challenging the traditional structure-function paradigm. Neurofilament-light (NFL) proteins self-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 compact the hydrogel, disrupt filament nematic order by generating microdomains, and alter water retention dynamics by shifting sequence-dependent conformational ensembles, leading to macroscopic network rearrangements. These findings demonstrate how subtle sequence changes in IDRs modulate protein network organization and function, offering structural insights into IDR-related pathologies.