Xenopus and chicken sperm contain a cytosolic soluble protein factor whichcan trigger calcium oscillations in mouse eggs

There is evidence showing that at fertilization the sperm introduces into e gg cytoplasm a protein-based cytosolic factor, which serves as the physiolo gical trigger for inducing Ca2+ oscillations in mammalian eggs. Here we sho w that sperm of nonmammalian vertebrates also contain a cytosolic protein f actor that can induce Ca2+ oscillations when introduced into mammalian eggs . We have observed that cytosolic extracts derived from Xenopus or chicken sperm could induce mouse eggs to undergo Ca2+ oscillations similar to those induced by bovine sperm extracts. The factor responsible for inducing Ca2 oscillations was of high molecular weight and heat- or proteinase K-labile . We show that 0.5 chicken sperm-equivalents or 1-2 Xenopus sperm-equivalen ts of the extracts had enough activity to trigger Ca2+ oscillations in mous e eggs. Our findings illustrate that although Xenopus, chicken, and mammals are evolutionarily divergent species, the function of the sperm protein fa ctor in triggering Ca2+ oscillations in mammalian eggs appears not to be sp ecies specific in vertebrates. (C) 2000 Academic Press.