Identification of phospholipase C zeta in normospermic and teratospermic domestic cat sperm

Abstract

In mammalian species, oocyte activation is initiated by oscillations in the intracellular concentration of free calcium ([Ca(2+)]i), which are also essential to allow embryonic development. To date, evidence supporting the hypothesis that a sperm factor is responsible for initiating oocyte activation has been presented in various mammalian species. Among the possible candidates to be the active sperm factor is the novel sperm-specific phospholipase C ζ (PLCζ), which besides its testis-specific expression is capable of initiating [Ca(2+)]i oscillations. In this study, we investigated the presence of PLCζ in the sperm of the domestic cat and whether normospermic and teratospermic cats differ in their PLCζ expression. Immunoblotting with anti-PLCζ antibodies confirmed the presence of an immunoreactive band of ∼70 kDa in whole sperm lysates of domestic cat as well as in both soluble and "insoluble" fractions from this sperm. Additional immunoreactive bands, probably C- and N-terminal truncated versions of PLCζ, were also visualized in the soluble sperm fractions. Interestingly, immunoreactivity of PLCζ was detectable in teratospermic sperm, although with slightly less intensity than in normospermic sperm. In conclusion, domestic cat sperm express PLCζ in both cytosolic and high-pH fractions, which is consistent with data in other mammals. Sperm from teratospermic cats also express PLCζ, albeit at reduced concentrations, which may affect the fertility of these males.

Keywords: Fertilization; Immunoblotting; Oocyte activation; PLCζ; Two-dimensional PAGE.