A deletion encompassing Zic3 in Bent tail, a mouse model for X-linked neural tube defects

Abstract

Bent tail is a mouse model for human neural tube defects. Bent tail mice are characterized by a shortened, kinked tail. We have observed numerous aberrations in Bent tail embryos including exencephaly, rotation defects and occasionally omphalocele, orofacial schisis and situs abnormalities. Exencephaly was seen in >10% of all embryos and resulted from a closure defect of the hindbrain. Bent tail maps to the proximal part of the X chromosome. By haplotype analysis we have appointed the Bent tail locus to a 1.1 cM interval between markers DXMit159 and DXMit143. Subsequent analysis has revealed the presence of a deletion in all affected animals. The deletion is ∼1 Mb in size and encompasses the gene for Zic3, a zinc finger transcription factor expressed in murine neuroectoderm and dorsal axial mesoderm during neurulation. Zic3 is a homolog of the Drosophila segmentation gene odd-paired. Although the Bent tail phenotype probably is the result of the deletion of several genes, combining data on Zic3 expression and function of Zic genes in the mouse shows that deletion of Zic3 alone is compatible with a major role of this gene in the congenital malformations of the Bent tail mouse. In man, mutations in ZIC3 are associated with situs abnormalities. These patients occasionally also show spina bifida, indicating that genetic variation in human ZIC3 may contribute to other congenital malformations, including neural tube defects.