We further backcrossed to B6 (Fig. 1b) and found an increased ratio of mice exhibiting abnormal development (e.g., developmental delay and hydrocephalus) (Fisher’s exact test, P = 0.145) (Fig. 1c) and significantly decreased lifespan in the adult St8sia2 homozygous null mutant mice (one-way ANOVA, P < 0.001; Fig. 1d,e). The gene discussed is ST8SIA2; the disease is Hydrocephalus.