TFF2 and spina bifida: Lack of replication of the reported NTD prevention in Pax3Sp/Sp; Trp53−/− embryos (Pani et al., 2002) could potentially reflect an allele-specific difference between Sp, which primarily causes spinal NTDs, and Sp2H, which causes both cranial NTDs (∼60% of homozygotes) and almost fully penetrant spina bifida (Burren et al., 2008; Greene et al., 2009).