Abstract
Although the conditional gene knockout (KO) is a better choice for observing its phenotype in a specific cell, tissue, and/or organ, the simple null gene KO could nevertheless be attempted initially to scan its overall phenotypes at the level of the whole-body system, especially for a new gene such as Crlz-1. Therefore, with a hope to glean phenotypic clues for Crlz-1 at the whole-body system, we attempted to generate its null KO mice. Contrary to our original desire, Crlz-1 homozygous null KO mice were not born. However, in the chasing of their homozygous KO embryos, they were found to be lethally impaired from early development, remaining in a state of small globular mass without ever leading to a body shape, indicating the critical role of Crlz-1 as a Wnt target gene for the proliferation and/or differentiation of cells during early mouse embryonic development.