HEXB and Sandhoff disease: For example, mutations in the human HEXB gene, which encodes a subunit of the lysosomal enzyme β-hexosaminidase, cause Sandhoff disease, which is neurodegenerative (O’Dowd et al., 1986; O’Dowd et al., 1985), and Hexb mRNA is a microglial marker in the mouse (Masuda et al., 2020).