The Wls gene encodes a chaperon protein with a role in regulation of Wnt protein sorting and secretion, anterior-posterior body axis development, proper formation of the skin, skeletal development and disease, tooth morphogenesis, craniofacial development and deformity, mammary gland morphogenesis and Wnt-induced tumorigenesis. These mice carry a gene trap mutation in which the beta-geo reporter has been inserted into intron 9. Mice that are heterozygous for the mutation are viable and fertile. Homozygous mice are not viable, and fail to develop past embryonic day 10.5. Immunohistochemical staining and immunoblot analysis do not detect the gene protein product in homozygous E7.5 embryos. Homozygous embryos, E6.5 to E8.5 in age, exhibit impaired embryogenesis, with only 2 layers of tissue, ectoderm and endoderm, but lacking mesoderm, as well as impaired anterior-posterior body axis development. Wnt signaling is also disrupted in mutant animals. During backcrossing, the Y chromosome may not have been fixed to the C57BL/6J genetic background.
