The finding that both Csf1a and Il34 ligands contribute to ovary-to-testis transformation associated with ovarian failure is exciting because it provides a mechanism for differential macrophage activation that could allow macrophages within the ovary to distinguish between normal homeostatic turnover or “quality control” and catastrophic events within the germline/follicle, such as loss of Bmp15. The gene discussed is IL34; the disease is ovarian dysfunction.