From my previous work, I had some experience relevant to their interests as they had recently described a monoclonal antibody that recognized a mouse preimplantation stage‐specific antigen (SSEA1), also expressed on the immunizing F9 EC cells.[5] Moreover, with the developing use of mouse teratocarcinomas as models for early mouse embryos, as described by Papaioannou in this issue,[6] Barbara and Davor had been exploring the possibility of using cell lines from human germ cell tumors, which include teratocarcinomas, as tools for studying human embryogenesis. Here, FUT4 is linked to germ cell tumor.