PKD2 Cation Channel Is Required for Directional Sperm Movement and Male Fertility

Abstract

Sperm of both mammals and invertebrates move toward specific sites in the female reproductive tract. However, molecular mechanisms for sperm to follow directional cues are unknown. Here, we report genetic analysis of Drosophila Pkd2 at 33E3 (Pkd2, CG6504), which encodes a Ca(2+)-activated, nonselective cation channel homologous to the human Pkd2 autosomal dominant polycystic kidney disease (ADPKD) gene. The PKD2 family of genes has been implicated in sensory responses through protein localization on primary cilia of epithelia and neurons. In renal tubules, cilium-associated PKD2 appears to mediate Ca(2+) influx in response to fluid flow, and the loss of fluid sensation probably contributes to cyst growth and ADPKD. Sperm tails or flagella are specialized cilia essential for movement. Drosophila Pkd2 is abundantly associated with the tail and the acrosome-containing head region of mature sperm. Targeted disruption of Pkd2 results in male sterility without affecting spermatogenesis. The mutant sperm are motile but fail to swim into the storage organs in the female. Rare mutant sperm that reach the storage organs are able to fertilize the egg and produce viable progeny. Our data demonstrate that the Drosophila PKD2 cation channel operates in sperm for directional movement inside the female reproductive tract.

Drosophila Pkd2 Is Haploid-insufficient for Mediating Optimal Smooth Muscle Contractility

“…3A). Western blotting showed that neither wild type size nor truncated Met 1 -Gln 729 PKD2 protein is produced by Pkd2 ko67 homozygote (10). This could be explained by possible instability of the truncated Met 1 -Gln 729 peptide or that the truncated peptide is never made due to the additional changes introduced into the Pkd2 ko67 allele during the targeted knock-out procedure.…”

“…The allele used in this study is Pkd2 ko67 that was derived from the integration of a mutated Pkd2 donor into the endogenous Pkd2 locus (10). Pkd2 ko67 contains a tandem duplication of Pkd2 with one copy carrying the BamHI and the other copy carrying the MunI frameshift mutations (see Fig.…”

“…Similar to these, the fly Pkd2 is abundantly present on sperm flagella, a type of motile cilia (10,11). Pkd2 mutant sperm are motile but fail to congregate at the anterior uterus (10) and the storage organs in the female (10,11), which results in a severe reduction of male fertility. Thus, it appears that the fly PKD2 functions on sperm flagella to sense directional cues in the female reproductive tract.…”

“…CG6504, also known as Pkd2 (10) or almost there (11), was analyzed in this study. The protein encoded by CG6504 is most closely related to the human PKD2 family of proteins (ϳ40% amino acid identity to PKD2 and 39% identity to PKD2L).…”

“…For example, ciliaassociated PKD2 of mouse kidney epithelia has been shown to mediate calcium influx in response to fluid flow (17). Similar to these, the fly Pkd2 is abundantly present on sperm flagella, a type of motile cilia (10,11). Pkd2 mutant sperm are motile but fail to congregate at the anterior uterus (10) and the storage organs in the female (10,11), which results in a severe reduction of male fertility.…”