(a) Schematic representation of KIF1A. The motor domain (aa 1–361) is detailed on the left with pathogenic mutations identified. Mutations highlighted in green are the early reported homozygous mutations. Those in blue are the recently reported de novo mutations. The mutations in purple are those of P1 and P2 reported here. Additionally, the microtubule binding domains (MT1, MT2, MT3) are labeled. The schematic also includes distal mutations, not in the motor domain, that have been reported to cause Hereditary Sensory and Autonomic Neuropathy IIC (HSAN2C). Other important functional domains are identified: forkhead-associated domain (FHA) and pleckstrin homology domain (PH). (b) Illustration of the amino acid conservation amongst KIF1A orthologs at the residues altered in the two cases reported (G199 and R307, highlighted in purple). The amino acid alignment was generated using HomoloGene (NCBI) and includes human (H. sapiens; NP_001230937), mouse (M. musculus; NP_032466.2), chicken (G. gallus; XP_003641781.1), Zebrafish (D. rerio; XP_005166002.1), Drosophila (D. melanogaster; NP_001246373.1), roundworm (C. elegans; NP_001022041.1), and frog (X. tropicalis; XP_002933380.2).