SPACA1 and male infertility: Regarding sperm head malformation, while globozoospermia results in male infertility (e.g., Zpbp1 [Lin et al., 2007], Gopc [Yao et al., 2002], and Spaca1 [Fujihara et al., 2012] knockout mice), most of the knockout mice with only subtle head malformation can produce offspring, although at lower levels (e.g., Zpbp2 [Lin et al., 2007], Fam71f2 [Morohoshi et al., 2021], and Garin2-Garin5 [Wang et al., 2024] knockout mice).