Targeted insertion of a lacZ reporter gene into the mouse Cer1 locus reveals complex and dynamic expression during embryogenesis.

The mouse Cer1 (mCer1, Cer-l, Cerr1) gene encodes one member of a family of cytokines structurally and functionally related to the Xenopus head-inducing factor, Cerberus (xCer). We generated a mouse line in which the Cer1 gene was inactivated by replacing the first coding exon with a lacZ reporter gene. Mice homozygous for this allele (Cer1(lacZ)) showed no apparent perturbation of embryogenesis or later development. However, the lacZ reporter revealed a number of hitherto uncharacterised sites of Cer1 expression in late fetal and adult tissues. Preliminary analysis suggests that Cer1 is not essential for their morphogenesis, differentiation, or homeostasis.