All of these mutants have spina bifida, which denotes incomplete closure of the spinal neural tube. A large majority (4 out 6 of these mutants which have only spina bifida) have a second phenotype that is a second neural tube. Vacuolated lens mutant embryos develop spina bifida and, in addition, an ectopic neural tube is observed, ventral to the open neural tube . In Shp2, FGFR1α, and vacuolated lens mutants, an ectopic neural tube is observed during the period of neurulation between E8.5 and E9.5 [94, 96]. In contrast, an ectopic neural tube has only been observed at E12.5 and later stages in Gcm1 mutant embryos .