Hexosaminidase subunits alpha and beta (HEXA and HEXB) form a glycosyl hydrolase in lysosomes and catalyze the degradation of the ganglioside GM2, and loss-of-function mutations in these genes lead to Tay–Sachs disease (GM2-gangliosidosis type I) and Sandhoff disease (GM2-gangliosidosis type II) [50, 51]. The gene discussed is HEXA; the disease is Sandhoff disease.