Lavitrano M, Maione B, Forte E, Francolini M, Sperandio S, Testi R, Spadafora C
Department of Experimental Medicine, University La Sapienza, Rome, Italy.
Exp Cell Res. 1997 May 25;233(1):56-62. doi: 10.1006/excr.1997.3534.
Mouse epidydimal sperm cells have the spontaneous ability to take up exogenous DNA, a part of which is further internalized into nuclei. We report here that sperm cells from MHC class II knockout mice have a reduced ability to bind DNA compared to sperm cells from wild-type animals. Spermatozoa from CD4 knockout mice are instead fully capable of binding exogenous DNA, yet lose the ability to further internalize it. MHC class II expression was not detected on sperm heads using monoclonal antibodies. In contrast, CD4 molecules were found on sperm heads by both immunofluorescence and Western blot analysis. Moreover, we show that nuclear internalization of exogenous DNA was prevented in wild-type sperm cells preincubated with anti-CD4 mAbs. These results support the conclusion that CD4 and MHC class II molecules play distinct roles in the process of sperm/DNA interaction: though not present in mature sperm cells, MHC class II expression appears to be required during spermatogenesis to produce sperm cells capable of taking up foreign DNA, while CD4 molecules present on sperm cells mediate the nuclear internalization of sperm-bound DNA.
小鼠附睾精子细胞具有摄取外源DNA的自发能力，其中一部分会进一步内化到细胞核中。我们在此报告，与野生型动物的精子细胞相比，MHC II类基因敲除小鼠的精子细胞结合DNA的能力降低。相反，CD4基因敲除小鼠的精子能够完全结合外源DNA，但失去了进一步内化它的能力。使用单克隆抗体未在精子头部检测到MHC II类分子的表达。相比之下，通过免疫荧光和蛋白质印迹分析在精子头部发现了CD4分子。此外，我们发现，用抗CD4单克隆抗体预孵育的野生型精子细胞中，外源DNA的细胞核内化受到了抑制。这些结果支持以下结论：CD4和MHC II类分子在精子/DNA相互作用过程中发挥不同作用：尽管成熟精子细胞中不存在MHC II类分子，但在精子发生过程中似乎需要MHC II类分子的表达才能产生能够摄取外源DNA的精子细胞，而精子细胞上存在的CD4分子则介导结合在精子上的DNA的细胞核内化。
