Importantly, the histologically-confirmed hydrocephalus phenotype has remained 100% concordant with homozygosity for the mutations in Dnaaf1 (N = 12) and Lrrc48 (N = 16), and we have never observed hydrocephalus in mice that are not homozygous at these loci (N > 100 for both lines). This evidence concerns the gene DRC3 and Hydrocephalus.