BRD2 and polycystic ovary syndrome: We observed the induction of constant darkness to a PCOS-like rat model with hallmarks including acyclic estrous cycles (Fig. 1b, c), increased numbers of cyst-like follicles and decreased corpora lutea in ovaries (Fig. 1d), elevated serum luteinizing hormone (LH)/ follicle-stimulating hormone (FSH) ratio (Fig. 1e) and testosterone concentration (Fig. 1f), and decreased serum sex hormone-binding globulin (SHBG) level (Fig. 1g), which were consistent with our previous research14.