The cerberus-related gene, Cerr1, is not essential for mouse head formation

The Xenopus cerberus gene encodes a secreted factor expressed in the Speman n organizer that can cause ectopic head formation when its mRNA is injected into Xenopus embryos. In mouse, the cerberus-related gene, Cerr1, is expre ssed in the anterior mesendoderm that underlies the presumptive anterior ne ural plate and its expression is downregulated in Lim1 headless embryos. To determine whether Cerr1 is required for head formation we generated a null mutation in Cerr1 by gene targeting in mouse embryonic stem cells. We foun d that head formation is normal in Cerr1(-/-) embryos and we detected no ob vious phenotypic defects in adult Cerr1(-/-) mice. However, in embryonic ti ssue layer recombination assays, Cerr1(-/-) presomitic/somitic mesoderm, un like Cerr1-expressing wild-type presomitic/ semitic mesoderm, was unable to maintain expression of the anterior neural marker gene Otx2 in ectoderm ex plants, These findings suggest that establishment of anterior identity in t he mouse may involve the action of multiple functionally redundant factors, genesis 26: 253-258, 2000, (C) 2000 Wiley-Liss, Inc.