Research Institute for Microbial Diseases, Osaka University, Yamadaoka 3-1, Suita, Osaka 565-0871, Japan.
J Cell Sci. 2010 May 1;123(Pt 9):1531-6. doi: 10.1242/jcs.067363. Epub 2010 Apr 7.
Mammalian fertilization is a multistep process that culminates in the fusion of the sperm and egg plasma membrane. It is widely accepted that the equatorial segment of the acrosome-reacted sperm is important in initiating fusion with the egg plasma membrane during fertilization. There are various proteins known to be distributed only in the equatorial segment of sperm. The role of these proteins must be clarified to understand the membrane fusion process. We produced a mouse line that lacked SPESP1 (sperm equatorial segment protein 1) and analyzed the fertilizing ability of the sperm. The average number of pups that were fathered by Spesp1(+/-) and Spesp1(-/-) males was significantly lower than that of wild-type fathers. In these mouse lines, fewer sperm were found to migrate into oviducts and fewer eggs were fertilized. The Spesp1(+/-) and Spesp1(-/-) sperm showed a lower fusing ability compared with the wild-type sperm. The disruption of Spesp1 was shown to cause an aberrant distribution of various sperm proteins. Moreover, scanning electron microscopy revealed that the membrane in the equatorial segment area, which usually forms an acrosomal sheath, disappears after acrosome reaction in Spesp1-deficient mice. It was demonstrated that SPESP1 is necessary to produce the fully 'fusion competent' sperm.
哺乳动物的受精是一个多步骤的过程，最终导致精子和卵子的质膜融合。人们普遍认为，顶体反应后的精子赤道段在受精过程中与卵子质膜融合的起始中起着重要作用。有许多已知的蛋白质仅分布在精子的赤道段。为了理解膜融合过程，必须阐明这些蛋白质的作用。我们产生了缺乏 SPESP1（精子赤道段蛋白 1）的小鼠品系，并分析了精子的受精能力。Spesp1(+/-)和 Spesp1(-/-)雄性产生的幼仔数量明显低于野生型父本。在这些小鼠品系中，发现进入输卵管的精子数量减少，受精的卵子数量减少。Spesp1(+/-)和 Spesp1(-/-)精子与野生型精子相比融合能力较低。Spesp1 的缺失导致各种精子蛋白的异常分布。此外，扫描电子显微镜显示，在 Spesp1 缺陷小鼠中，顶体反应后，通常形成顶体鞘的赤道段区域的膜消失。证明 SPESP1 是产生完全“融合能力”精子所必需的。
