GM2A, encoding the GM2 activator protein, is crucial for the hydrolysis of GM2 gangliosides into GM3 form within the cell's lysosomes. Mutations in GM2A lead to AB-variant GM2 gangliosidosis, a rare lysosomal storage disorder. GM2 gangliosidoses are a group of recessive disorders characterized by GM2 ganglioside accumulation in neuronal cells [1,2,3].

Gm2a-/-mice, a model of ABGM2, have a mild phenotype with moderate GM2 accumulation and mild neurological defects, which is attributed to compensation by the sialidase, neuraminidase 3 (NEU3)-mediated alternative GM2 degradation pathway. Double knock-out (Gm2a-/-Neu3-/-) mice present a more severe ABGM2-like phenotype, including ataxia, reduced mobility, weight loss, and lethality, along with increased GM2 accumulation in the CNS. This shows that NEU3 contributes to GM2 degradation and double knockout mice can be used as a relevant model for pre-clinical drug studies in severe ABGM2 [3].

In conclusion, GM2A is essential for GM2 ganglioside degradation. The study of Gm2a-/-and Gm2a-/-Neu3-/-mouse models has provided insights into the role of GM2A in AB-variant GM2 gangliosidosis, helping to understand the disease mechanism and potentially guiding the development of treatment strategies for this rare disorder.