Objective
To determine the role of Dkkl1 on mouse development, viability, and fertility. Design: Prospective experimental study. Setting: Government research institution. Animal(s): Mice of C57BL/6 and 129X1/SvJ strains, as well as transgenic mice of mixed C57BL/6 and 129X1/SvJ strains were used for the studies. Intervention(s): Mice were constructed that lacked a functional Dkkl1 gene. Main outcome measure(s): Deletion of the gene was confirmed by DNA, RNA, and protein analyses; in vivo fertility was examined by continuous mating scheme. Result(s): Previous studies have shown that Dkkl1, a gene unique to mammals, is expressed predominantly, if not exclusively, in developing spermatocytes, and the DKKL1 protein accumulates in the acrosome of mature sperm. Subsequent studies (reported in the accompanying article) demonstrate that Dkkl1 also is expressed in the trophectoderm/placental lineage. Taken together, these