ATP10D and Infertility: Therefore, ATP10A deficiency alone is sufficient to cause the male-specific infertility phenotypes in mice and this suggests that the specific ATP10A substrate critical for male fertility might be PC and not GlcCer; because ATP10A flips both PC and GlcCer (Naito et al., 2015; Roland et al., 2019) and ATP10D only flips GlcCer (Roland et al., 2019).