The testis-specific bromodomain and extra-terminal domain (BET) protein BRDT is a key regulator of spermatogenesis and a compelling target for non-hormonal male contraceptive development. Despite significant interest in the regulatory function and contraceptive potential of BRDT, fundamental questions remain about how BRDT governs critical processes during meiosis and spermiogenesis. These gaps largely stem from the historical absence of genetic models and molecular tools necessary to dissect the stage-specific roles of BRDT in the germline.

A primary focus of this dissertation is to explore the effects of transient BRDT inhibition using the small-molecule inhibitor (+)-JQ1. Single-cell transcriptomic and cytological analyses reveal that BRDT inhibition leads to post-meiotic germ cell loss, followed by full recovery upon drug withdrawal. These findings demonstrate that meiosis is a reversible point of intervention and that BRDT disruption selectively affects direct transcriptional targets, highlighting its essential role in orchestrating meiotic gene expression and chromosomal events during prophase I.

To further characterize BRDT function, this dissertation introduces two novel mouse models – a knockout line and an epitope-tagged line. The Brdt^-/- line exhibits dual-stage defects in meiosis and spermiogenesis, underscoring the stage-specific regulatory roles of BRDT. In parallel, the BRDT epitope-tagged line enables reliable detection of the endogenous protein, overcoming longstanding technical barriers due to limited antibody availability.

To address the broad regulatory influence of BRDT, this work identifies a refined list of germline-restricted, testis-specific target genes with greater potential for selective contraceptive intervention. It also establishes proof-of-concept for gene manipulation in enriched spermatocytes and spermatids via lentiviral transduction, enabling future CRISPR-based screens. Finally, novel in vitro platforms for meiotic initiation and progression provide a foundational framework for functional studies in defined germ cell stages.

Collectively, this dissertation positions BRDT as a central coordinator of male germ cell development and a gateway to identifying downstream targets with high contraceptive potential. Through genetic modeling, transcriptomic analysis, and foundational work in germ cell manipulation, this research offers new tools and insights to support the development of safe, reversible, and testis-specific strategies for male contraception.