De novo disease-associated mutations in KIF1A dominant negatively inhibit axonal transport of synaptic vesicle precursors

Abstract

AbstractKIF1A is a kinesin superfamily molecular motor that transports synaptic vesicle precursors in axons. Mutations in Kif1a lead to a group of neuronal diseases called KIF1A-associated neuronal disorder (KAND). KIF1A forms a homodimer and KAND mutations are mostly de novo and autosomal dominant; however, it is not known whether the function of wild-type KIF1A is inhibited by disease-associated KIF1A. No reliable in vivo model systems to analyze the molecular and cellular biology of KAND have been developed; therefore, here, we established Caenorhabditis elegans models for KAND using CRISPR/cas9 technology and analyzed defects in axonal transport. In the C. elegans models, heterozygotes and homozygotes exhibited reduced axonal transport phenotypes. In addition, we developed in vitro assays to analyze the motility of single heterodimers composed of wild-type KIF1A and disease-associated KIF1A. Disease-associated KIF1A significantly inhibited the motility of wild-type KIF1A when heterodimers were formed. These data indicate the molecular mechanism underlying the dominant nature of de novo KAND mutations.Significance StatementKIF1A is a molecular motor that transports synaptic vesicle precursors in axons. Recent studies have identified many KIF1A mutations in congenital neuropathy patients; however, the molecular mechanism of pathogenesis remains elusive. This study established a model for KIF1A-associated neuronal disorder (KAND) in Caenorhabditis elegans to analyze the molecular and cell biology of the disease in vivo. This study also established in vitro single-molecule assays to quantitatively analyze the effect of KAND mutations when mutant KIF1A forms heterodimers with wild-type KIF1A. Our findings provide a foundation for future genetic screening and for drug screening to search for KAND treatments.