xCdc4α and xCdc4β block Cyclin E-mediated apoptosis, and this requires an intact F-box domain. Cyclin E mRNA (1 ng) was co-injected with 1 ng of other mRNAs as indicated into one cell of two-cell-stage embryos. (A) Embryos were scored for enlarged cells at stage 9 and apoptotic cells at stage 11 (n = 75-196). (B-M) Representative embryos from each injection are shown; enlarged cells are highlighted with white arrows (B,E-G,K) and shown enlarged in insets. Black arrows highlight apoptotic cells (H,L,M).