NTDs are the second human disease to be linked to mutations of FZD genes after familial exudative vitreoretinopathy (FEVR; MIM# 133780) that arise from loss of function mutations of FZD4, a FZD gene that has not far been implicated in neural tube closure [Robitaille et al., 2002]. This evidence concerns the gene FZD4 and exudative vitreoretinopathy.