Expression and localization of two-pore domain K+ channels in bovine germ cells

Abstract

Two-pore domain K C (K 2P ) channels that help set the resting membrane potential of excitable and nonexcitable cells are expressed in many kinds of cells and tissues. However, the expression of K 2P channels has not yet been reported in bovine germ cells. In this study, we demonstrate for the first time that K 2P channels are expressed in the reproductive organs and germ cells of Korean cattle. RT-PCR data showed that members of the K 2P channel family, specifically KCNK3, KCNK9, KCNK2, KCNK10, and KCNK4, were expressed in the ovary, testis, oocytes, embryo, and sperm. Out of these channels, KCNK2 and KCNK4 mRNAs were abundantly expressed in the mature oocytes, eight-cell stage embryos, and blastocysts compared with immature oocytes. KCNK4 and KCNK3 were significantly increased in eight-cell stage embryos. Immunocytochemical data showed that KCNK2, KCNK10, KCNK4, KCNK3, and KCNK9 channel proteins were expressed at the membrane of oocytes and blastocysts. KCNK10 and KCNK4 were strongly expressed and distributed in oocyte membranes. These channel proteins were also localized to the acrosome sperm cap. In particular, KCNK3 and KCNK4 were strongly localized to the post-acrosomal region of the sperm head and the equatorial band within the sperm head respectively. These results suggest that K 2P channels might contribute to the background K C conductance of germ cells and regulate various physiological processes, such as maturation, fertilization, and development.

K+ efflux through two-pore domain K+ channels is required for mouse embryonic development

“…The expression of the K 2P channel member transcripts identified by RT-PCR was subsequently studied at the protein level. The specificity and sensitivity of the antibodies used in these experiments were confirmed in previous studies (Kang et al 2007, Hur et al 2009). Each antibody was specific for its own antigen (Supplementary Figure 1, see section on supplementary data given at the end of this article).…”

“…Recent studies have found that K 2P channels are expressed in the mammalian reproductive organ and cells, such as in human cytotrophoblast cells, placental villous tissue and trophoblast cells, myometrium, the placental vascular system, and uterine smooth muscle cells (Bai et al 2005a, 2005b, Tichenor et al 2005, Wareing et al 2006, Chow et al 2007. In addition, a previous study from our laboratory also found these channels to be expressed in bovine ovaries, testis, and germ cells (Hur et al 2009). Furthermore, they were also present in monkeys, where their expression was restricted to sperm (Chow et al 2007).…”

Male fertility status is associated with DNA methylation signatures in sperm and transcriptomic profiles of bovine preimplantation embryos

“…For instance, a study by Ferrer et al [67] found that MMP2 co-localizes with acrosin on the inner acrosomal membrane of bull spermatozoa, where the authors suggest the protease may mediate sperm penetration at the zona pellucida as matrix metalloproteases function to cleave extracellular matrix components. Another DMR was identified in the KCK4 gene, a member a two-pore domain potassium (K 2P ) channel family [68], where potassium channels have important physiological roles in the acrosome reaction and fertilization [69]. In bull spermatozoa, a study by Hur et al [68] reported that the protein of KCK4 localizes to the equatorial region of acrosome reacted sperm, and that inhibitor of the K 2P channels reduces not only fertilization but also development of bovine and mouse embryos in vitro.…”

Genome-wide association study for semen volume and total number of sperm in Holstein-Friesian bulls

“…The specific function of transmembrane protein TMEM110 is unknown. Among two additional candidate genes RBFOX1 and KCNK10, the latter one is expressed in germ lines and can have indirect link with semen quantity (Hur et al, 2009).…”