In this issue of Cell, Geng et al. report that mice can undergo embryonic development without cyclins E1 and E2. Fibroblasts derived from the double knockout embryos proliferate normally in culture. However, E type cyclins seem essential for endoreplication and exit from quiescence.
Méndez, J. (2003, August 22). Cell proliferation without cyclin E-CDK2. Cell. Cell Press. https://doi.org/10.1016/S0092-8674(03)00649-4