Dickkopf-like 1 (DKKL1) or soggy 1, is a glycoprotein unique to mammals that is expressed primarily in developing spermatocytes and localized in the acrosome of mature sperm. It is also expressed in the trophectoderm / placental lineage. This glycoprotein is secreted by postmeiotic male germ cells. DKKL1 is a member of the Dickkopf (DKK) family, a group of proteins that are characterized as secreted antagonists of Wnt signal transduction proteins. In mammals, embryos lacking DKKL1 protein developed into viable, fertile adults. DKKL1, either directly or indirectly, facilitates the ability of sperm to penetrate the zona pellucid. DKKL1 is related to the sperm apoptotic procession. Molecular analyses identified the Fas death ligand (FasL) as a target for DkkL1 pro-apoptotic activity in adult mice. DKKL1 is considered as a negative regulator of adult testic homeostasis and identifies a novel, DKKL1 / FasL- dependent, regulation that specifically controls the number of postpubertal spermatocytes.