Expression and phosphorylation of mitogen-activated protein kinases duringspermatogenesis and epididymal sperm maturation in mice

The expression and phosphorylation/dephosphorylation of mitogen-activated p rotein (MAP) kinases during mouse spermatogenesis and epididymal sperm matu ration have been investigated by immunoblotting and immunohistochemical sta ining with commercially available anti-ERK2 and anti-Active MAPK antibodies . Two forms of MAP kinases, p42ERK2 and p44ERK1, were expressed in a simila r amount in spermatogenic cells at different stages. ERK1 and ERK2 were pho sphorylated (activated) in early spermatogenic cells from primitive spermat ogonia to zygotene primary spermatocytes, while only a small quantity of ph osphorylated MAP kinases could be detected in pachytene primary spermatocyt es and spermatids. MAP kinase activity in primative spermatogonia and prele ptotene primary spermatocytes was the highest among spermatogenic cells. ER K1 and ERK2 were also present in epididymal spermatozoa, and their phosphor ylation was increased while spermatozoa pass through epididymis and vas def erens for maturation. It would appear that MAP kinase activation may contri bute to the mitotic proliferation of primative spermatogonia, an early phas e of spermatogenic meiosis, and, later, sperm motility acquirement.