Stephanie Tanis, Leah E. Simon, Adriana K. Alexander, Tegan S. Horan, María de las Mercedes Carro, Samantha Jane Bonnett, An Xie, Roni Ben-Shlomo, Connor Owens, Charles G. Danko, Jelena Lujić, Paula E. Cohen
Developing safe, reversible, and nonhormonal male contraceptives has been hindered by the lack of defined biological windows that can be transiently interrupted without compromising long-term fertility. Here, we tested whether meiotic prophase I can serve as such a window by pharmacologically inhibiting the testis-specific chromatin reader BRDT using the small-molecule bromodomain inhibitor (+)-JQ1 as proof-of-principle. Short-term JQ1 administration (3 wk) selectively disrupted the pachytene transcriptional program, depleted postmeiotic germ cells, and induced a reversible arrest in spermatogenesis. Upon drug withdrawal, prophase I cytological markers normalized within 6 wk, accompanied by restoration of testis architecture and germ-cell composition. Crossover metrics and transcriptional programs recovered more gradually, reaching full normalization by 30 wk alongside complete restoration of fertility and fecundity. These results demonstrate that meiotic prophase I can be transiently inhibited to suppress spermatogenesis reversibly without inducing lasting genomic or reproductive defects, defining a stage-specific framework for the rational design of nonhormonal male contraceptives.