👤 Megan E Gilmore

Testosterone production by testicular Leydig cells (steroidogenesis) is vital to male fertility and overall male health. Information about how nutrition influences Leydig cell steroidogenesis is lacking. Branched chain amino acids (BCAAs - leucine, isoleucine, and valine) are essential amino acids and important regulators of protein synthesis and energy production. Circulating and tissue BCAA levels are tightly regulated by the enzyme branched chain a-keto acid dehydrogenase kinase (BCKDK), which inhibits their catabolism. This work explored how BCAAs, and especially leucine, modulate male fertility and testosterone production. In a mutant mouse model of Bckdk, breeding analysis showed reduced male fertility and circulating testosterone. Further, morphological evaluation demonstrated testicular and epididymal abnormalities consistent with abnormal testicular androgen signaling. Fertility was partially rescued by feeding a high protein diet while circulating testosterone was not. In wild type testes, Leydig cells were the primary cell type to express BCKDK. Leveraging a primary interstitial cell culture, cell survival and apoptosis analyses demonstrated Leydig cells are highly sensitive to leucine deprivation and this sensitivity is enhanced under steroidogenesis stimulating conditions. Lastly, using the same primary cell culture system, testosterone production was shown to be lost under leucine deprivation. In total, this work demonstrates Leydig cells are uniquely sensitive to BCAA status under steroidogenesis stimulation and that regulated BCAA catabolism may be important for optimal male fertility. Show less

Proteins that respond to DNA damage play critical roles in normal and diseased states in human biology. Studies have suggested that the S. cerevisiae protein CMR1/YDL156w is associated with histones and is possibly associated with DNA repair and replication processes. Through a quantitative proteomic analysis of affinity purifications here we show that the human homologue of this protein, WDR76, shares multiple protein associations with the histones H2A, H2B, and H4. Furthermore, our quantitative proteomic analysis of WDR76 associated proteins demonstrated links to proteins in the DNA damage response like PARP1 and XRCC5 and heterochromatin related proteins like CBX1, CBX3, and CBX5. Co-immunoprecipitation studies validated these interactions. Next, quantitative imaging studies demonstrated that WDR76 was recruited to laser induced DNA damage immediately after induction, and we compared the recruitment of WDR76 to laser induced DNA damage to known DNA damage proteins like PARP1, XRCC5, and RPA1. In addition, WDR76 co-localizes to puncta with the heterochromatin proteins CBX1 and CBX5, which are also recruited to DNA damage but much less intensely than WDR76. This work demonstrates the chromatin and DNA damage protein associations of WDR76 and demonstrates the rapid response of WDR76 to laser induced DNA damage. Show less