GM2A, a lysosomal activator protein required for ganglioside GM2 degradation, is deficient or functionally compromised in the AB variant of GM2 gangliosidosis, which leads to neurodegeneration [Renaud and Brodsky, 2015, Conzelmann and Sandhoff, 1978]. The gene discussed is GM2A; the disease is GM2 gangliosidosis.