TBXT and spina bifida: We speculate that the close links between TBXT-driven posterior axial identity programming in the NC and NMP ontogeny may explain some cases of spina bifida observed in individuals carrying mutations within the TBXT locus (Agopian et al., 2013; Carter et al., 2011; Fellous et al., 1982; Morrison et al., 1996; Shields et al., 2000), especially in light of the potential involvement of impaired NC specification and HOX gene dysregulation in neural tube defects (Anderson et al., 2016; Degenhardt et al., 2010; Poncet et al., 2020; Rochtus et al., 2015; Yu et al., 2019).