This finding is reminiscent of the situation in CathAS190A-neo mice (the Ctsa hypomorph mouse model of galactosialidosis; ref. 27), in which NEU1 activity in the brain tissues was reduced to below 10% of normal, whereas GALNS and GLB1 activities were decreased by only approximately 30% and approximately 20%, respectively (Figure 5F). The gene discussed is NEU1; the disease is galactosialidosis.