Elucidation of the molecular network controlling sperm acrosome formation in mammals

哺乳动物的精子具有帽状的胞外囊泡，顶体位于细胞核的前部。ACRBP/sp32是一种顶体蛋白，最初被鉴定为精子丝氨酸蛋白酶ACR前体（proACR）的结合蛋白。与其他哺乳动物的Acrbp不同，在小鼠中，通过Acrbp的选择性剪接产生了两种形式的Acrbp mRNA，即野生型Acrbp- w和变体Acrbp- v5 mRNA。在这项研究中，我们制造了缺乏ACRBP的敲除小鼠，以揭示ACRBP在精子发生和受精中的作用。这些结果表明，在精子发生过程中，ACRBP-V5在顶体蛋白的凝聚和随后的扩散中起着关键作用。这也提示ACRBP-W可能在顶体保留proACR直至精子顶体胞吐过程中起作用。

Mammalian sperm possess a cap-shaped, exocytotic vesicle, acrosome that is located at the anterior part of the nucleus. ACRBP/sp32, is an acrosomal protein, initially identified as a binding protein for the precursor (proACR) of sperm serine protease ACR. Unlike other mammalian ACRBPs, two forms of Acrbp mRNA, wild-type ACRBP-W and variant Acrbp-V5 mRNAs, were generated by alternative splicing of Acrbp in the mouse. In this study, we produced knockout mice lacking ACRBP to uncover the role of ACRBP in spermatogenesis and fertilization. These results demonstrate that ACRBP-V5 palys key role in condensation and subsequent spread of acrosomal proteins in the acrosome during spermiogenesis. It is also suggested that ACRBP-W may function in the retention of proACR in the acrosome until after sperm undergo acrosomal exocytosis.