Recently de novo VPS4A variants were identified to cause a multi-systemic neurodevelopmental disorder including sensorineural hearing loss due to the abnormal accumulation of IST1 protein in the limiting membrane of proband-derived fibroblasts and also in neuronal endosomes [76], suggesting that proper localization of IST1 is required for neuronal function. This evidence concerns the gene IST1 and neurodevelopmental disorder.