In mammals, SMAP2 is necessary for spermiogenesis (Han et al., 2020), where SMAP2-deficient mice have been shown display male infertility (Sumiyoshi et al., 2015), globozoospermia (Funaki et al., 2013), asthenozoospermia (Funaki et al., 2013), and abnormal acrosome formation (Funaki et al., 2013). Here, SMAP2 is linked to male infertility.