Pathogenesis of Pax3+/Δ5/Pax7+/Δ2 mutant hydrocephalus (Figure 7A–I) is grossly and anatomically indistinguishable from that observed in Pax3flox/flox; Wnt1-Cre (Figure 1 and Figure 2) and Pax3flox/flox/Pax7−Cre mutants (Figure 6). The gene discussed is PAX3; the disease is Hydrocephalus.