9318007 Kim Although it has been known since the 1920's that retinol, a form of vitamin A, is absolutely essential for sperm production, it is still unknown as to why retinol is required. Clearly, retinol is a signaling molecule that uses protein mediators to control the expression of genes critical for sperm production. In this proposal, two important protein mediators that work together, kinases and phosphatases which modulate the activity of proteins that control the retinol-regulated gene expression, will be investigated using the testis. The information gained will be useful to formulate strategies to either increase or decrease male reproductive efficiency. ***
