TRIM28 and Testicular atrophy: Of note, Trim28 deletion using the Stra8-Cre deleter strain yielded an initially unexpected milder testicular degeneration phenotype, which could be explained by the activation of Stra8-cre in response to retinoic acid in late undifferentiated spermatogonia (Anderson et al., 2008), hence avoiding recombination in SSC.