Regarding sperm head malformation, while globozoospermia results in male infertility (e.g., Zpbp1 (24), Gopc (25), and Spaca1 (26) knockout mice), most of the knockout mice with only subtle head malformation can produce offspring, although at lower levels (e.g., Zpbp2 (24), Fam71f2 (22), and Garin2-Garin5 (47) knockout mice). This evidence concerns the gene ZPBP2 and male infertility.