“…On the male side, several surface-expressed molecules are required for mouse gamete fusion in addition to IZUMO1. These include sperm acrosome membrane-associated protein 6 (SPACA6) (Barbaux et al, 2020; Lamas-Toranzo et al, 2020; Lorenzetti et al, 2014; Noda et al, 2020) and transmembrane protein 95 (TMEM95) (Lamas-Toranzo et al, 2020) , both of which are type I-transmembrane proteins with an IZUMO1-like ectodomain structure (Lamas-Toranzo et al, 2020; Nishimura et al, 2016; Vance et al, 2022) . Sperm dendrocyte expressed seven transmembrane protein domain-containing proteins 1 and 2 (DCST1/2), which interact with each other (Noda et al, 2022) and are orthologues of molecules essential for fusion in worm (SPE-49/42) (Kroft et al, 2005; Wilson et al, 2018) and fly (SNEAKY/DCST-2) (Wilson et al, 2006) , are required for fertility not only in the mouse but also in fish (Inoue et al, 2021 ; Noda et al, 2022) .…”