A Depleted Pool (IMAGE) Brown University Caption Mice lacking the gene for the protein TAF4b (right) produce fewer undifferentiated germ cells (green) than mice with the gene (left). This leads to a decreased ability to keep sperm production going after about a month or so of initial fertility. Credit Freiman lab/Brown University Usage Restrictions with credit License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.