Novel FIG4 mutations in Yunis-Varon syndrome.

Yunis-Varon syndrome (YVS, MIM 216340) is a rare autosomal recessive disorder characterized by skeletal abnormalities and severe neurological impairment with vacuolation of the central nervous system, skeletal muscles and cartilages. Very recently, mutations of the FIG4 (FIG4 homolog, SAC1 lipid phosphatase domain containing (Saccharomyces cerevisiae)) gene, which encodes a 5'-phosphoinositide phosphatase essential for endosome/lysosome function have been identified as the cause for YVS. Interestingly, FIG4 mutations were previously reported to be responsible for other neurodegenerative diseases such as autosomal recessive Charcot-Marie-Tooth disease type 4J and autosomal dominant amyotrophic lateral sclerosis/primary lateral sclerosis. We analyzed a YVS patient using whole-exome sequencing, and identified novel biallelic FIG4 mutations: c.1750+1delG and c.2284_2285delCT (p.S762Wfs*3). These two mutations were mutations supposed to have null function. To our knowledge, this is the second report of FIG4 mutations in YVS and our result supports the idea that biallelic null mutations of FIG4 cause YVS in human.