At Day 3 post-eclosion, although 45% of set1 KD testes have germline loss, 55% have an early germ cell overpopulation phenotype, where the germ cells surrounding the hub form a large, disorganized cluster with very few intercalating cyst cells and are often devoid of or have very few late-stage spermatocytes (Fig. 1D). This evidence concerns the gene SETD1A and cyst.