Figure 1.

FRAP analysis of chromatin components in the developing mouse embryo reveals a decrease in chromatin mobility of H2A-GFP. (A) Experimental setup for FRAP in embryos. Zygotes were collected and microinjected with in vitro transcribed mRNA and cultured until the indicated developmental stages, when they were subjected to FRAP. After imaging acquisition, embryos were cultured until the blastocyst stage, and their development was scored. (B) A representative nucleus of an eight-cell stage embryo expressing H2A-GFP during a FRAP experiment is shown. The bleached region is represented by a rectangle. Bar, 10 μm. (C) Representative single FRAP curves of H2A-GFP at the two-cell (red) and eight-cell (blue) stages. The bleach time point is indicated by an arrow. Recovery of H2A-GFP is significantly faster at the two-cell stage compared with the eight-cell stage. (D) Recovery curves of H2A-GFP at the two-cell (red) and eight-cell (blue) stages. Recovery was quantified in the bleached area over a 60-sec period, and the curves were normalized to zero to account for differences in bleach depth between experiments. Individual points are mean ± SEM, and mean values were fit into an exponential curve. (E) Estimated mobile fractions (±SEM) of H2A-GFP in two-cell and eight-cell stage embryos.