Comprehensive behavioral and biochemical outcomes of novel murine models of GM1-gangliosidosis and Morquio syndrome type B

Deficiencies in the lysosomal hydrolase β-galactosidase (β-gal) lead to two distinct diseases: the skeletal disease Morquio syndrome type B, and the neurodegenerative disease GM1-gangliosidosis. Utilizing CRISPR-Cas9 genome editing, the mouse β-gal encoding gene, Glb1, was targeted to generate both models of β-gal deficiency in a single experiment. For Morquio syndrome type B, the common human missense mutation W273L (position 274 in mice) was introduced into the Glb1 gene (Glb1 ^W274L ), while for GM1-gangliosidosis, a 20 bp mutation was generated to remove the catalytic nucleophile of β-gal (β-gal ^−/− ). Glb1 ^W274L mice showed a significant reduction in β-gal enzyme activity (8.4–13.3% of wildtype), but displayed no marked phenotype after one year. In contrast, β-gal ^−/− mice were devoid of β-gal enzyme activity (≤1% of wildtype), resulting in ganglioside accumulation and severe cellular vacuolation throughout the central nervous system (CNS). β-gal ^−/− mice also displayed severe neuromotor and neurocognitive dysfunction, and as the disease progressed, the mice became emaciated and succumbed to the disease by 10 months of age. Overall, in addition to generating a novel murine model that phenotypically resembles GM1-gangliosidosis, the first model of β-galactosidase deficiency with residual enzyme activity has been developed.