FIGURE 3:

EGFP-Mnk, but not EGFP-RSK, restores developmental block at the midblastula transition in mnk,grp double-mutant embryos. Cellular membranes were stained with anti-spectrin antibody to examine cellularization. (A) Representative phenotype for each genotype in collections of 3- to 5-h-old embryos. The majority of wild-type (w¹¹¹⁸) embryos, mnk,grp double-mutant embryos, and mnk,grp embryos expressing EGFP-RSK cellularized and started to gastrulate. The majority of grp mutant embryos and mnk,grp double-mutant embryos expressing EGFP-Mnk did not show membrane structures stained with α-spectrin. EGFP-Mnk and EGFP-RSK localize to the interphase nucleus (Figures 1 and 7). Severe nuclear aggregation and dropping occurred in mnk,grp embryos expressing EGFP-Mnk, whereas all nuclei stayed on the cortex in mnk,grp embryos expressing EGFP-RSK (α-GFP). Scale bar, 100 μm. (B) Percentages of cellularized embryos in 2- to 3- and 3- to 5-h-old collections. Number of cellularized/total counted embryos is indicated at the top of each data bar.