Figure 1

Overexpression of Wee1 lengthens pre-MBT cell cycles. One-cell stage embryos were microinjected with 2.5 ng mRNA encoding Wee1 or luciferase (control). (A) Embryos were collected at indicated times post-fertilization (hr pf) and analyzed for Wee1 protein by Western analysis. (B) Xenopus embryos injected with 2.5 ng Wee1 or luciferase mRNA were photographed at 4.5 hr pf, when embryos expressing exogenous Wee1 were delayed approximately one cell cycle compared to luciferase controls. (C) Overexpression of Wee1 results in premature tyrosine phosphorylation of Cdks. Embryo lysates were subjected to Western analysis using a phosphoCdk antibody (Cell Signaling Technology). Both phosphorylated p34Cdk1 and p32Cdk2, are recognized by this antibody, which likely accounts for the bands of slower and faster mobility, respectively. Phosphorylation of Cdks was apparent as early as Stage 6 (3 hrs pf) in embryos injected with Wee1. (D) Embryos (n = 10) were collected at the indicated stages, then DNA was isolated and resolved by agarose gel electrophoresis. Approximate timing of the MBT in luciferase expressing control embryos is indicated. E) Embryos were collected at Stage 9 (7 hrs pf), fixed, sectioned, stained with DAPI to visualize nuclear morphology, and photographed. A representative field is shown. scale bar = 50 μm