A previous study reported that Ccnd1 expression was undetectable in embryonic germ cells, but was aberrantly expressed in E15.5 testicular germ cells in the teratoma-susceptible M19 mouse strain, and Ccnd1 knock-out M19 mice showed a decreased incidence of teratoma (Lanza et al., 2016). Here, CCND1 is linked to teratoma.