PAX7 and spina bifida: However, the removal of one Pax7 allele was sufficient to significantly increase the frequency of neural tube defects (from 66% Pax3neo/∆5/Pax7+/+ having spina bifida and/or exencephaly to 95% (n = 47/49) of Pax3neo/∆5/Pax7Δ2/+ having spina bifida and/or exencephaly).