HPRT1 and nervous system disorder: Perhaps the best example for this is the generation of hESCs for the modeling of Lesch–Nyhan syndrome, a disease caused by a mutation in the HPRT1 (hypoxanthine-guanine phosphoribosyltransferase) gene that triggers an overproduction of uric acid, causing gout-like symptoms, and urinary stones, in addition to neurological disorders.