PIKFYVE and Charcot-Marie-Tooth disease type 4J: In humans, mutations in the FIG4 and VAC14 encoding genes have been shown to lead to rare cases of genetic disorders, such as Charcot–Marie–Tooth syndrome type 4J (CMT4J), amyotrophic lateral sclerosis (ALS) and Yunis–Varón syndrome, confirming that the PIKfyve complex and formation of PI(3,5)P2 are crucial for the neuronal integrity and function in humans [4,6,8].