Differential levels of nuclear import factors in the two halves of an early embryo affect gastrulation timing.

(A) Experimental approach. One blastomere of a two-cell stage X. laevis embryo was co-microinjected with mRNA to alter nuclear import factor levels and fluorescently labeled dextran as a cell tracer. Embryos were allowed to develop to different stages to assess effects on developmental progression. (B) Microinjections were performed as shown in (A) with 250 pg GFP mRNA, 175 pg NTF mRNA, or 250 pg importin α mRNA + 250 pg GFP-LB3 mRNA. These amounts, that maximally affect nuclear size [13, 24], were used in all experiments. Microinjected two-cell embryos were allowed to develop to 13 hpf gastrula. Representative vegetal pole images are shown. Blastopore area was measured and averaged for 7–13 embryos per condition. Blastopore closure appeared symmetric in all conditions. Error bars represent SD. *** p<0.005, * p<0.05.