SIX1 and cancer: The 102 DEGs upregulated during the M-to-T1 transition included X-linked cancer-testis antigens belonging to the MAGE and PAGE gene families, including MAGEA4, MAGEB2, MAGEC2, PAGE1, PAGE2, and PAGE2B. Many genes previously recognized as markers for prospermatogonia (RHOXF1, NANOS2, DDX4) or adult spermatogonia (SIX1, DCAF4L1, PLPPR3, EGR4) were also upregulated during this transition11,25,28.