Blood Stem Cells in a Rush (IMAGE) Technische Universität Dresden Caption Mende et al. show that a balanced progression through the early and the late G1 cell cycle phase is a key regulator of hematopoietic stem cell function in vivo. In their study, a shortening of the G1 cell cycle phase transit time by the overexpression of CCND1/CDK4 significantly improved hematopoietic stem cell function compared to controls. However, a dramatic reduction of the duration of G1 progression mediated by CCNE1/CDK2 overexpression resulted in the rapid loss of stem cell function. The figure is a metaphoric depiction of the finding that the timing of G1 phase transition is pivotal for human hematopoietic stem cell fate choices. Credit Image by Nicole Mende. Usage Restrictions None 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.