Fig. 1. Localisation of C1A9 and Me(3)K9H3 antibodies to nuclei in mid-cleavage embryos (128-256-nuclei embryos) undergoing facultative heterochromatinisation. (A) Embryo region where the wave of facultative heterochromatinisation is spreading from the bottom left corner to the top right corner. Boxed area B shows nuclei that have completed heterochromatinisaton and contain DAPI-positive chromocenters (see magnified image in B), whereas boxed area C shows nuclei still undergoing heterochromatinisation, many of which have no overt DAPI-positive chromocenters (see arrows pointing to nuclei in C). The nuclei in B are labeled with C1A9 antibody (B') and with the anti-Me(3)K9H3 antiserum (B") and the merged image in B'" shows colocalisation of DAPI-positive chromocenter with C1A9 and Me(3)K9H3 staining. The DAPI-stained nuclei in C were stained with C1A9 antibody (C') and with the anti-Me(3)K9H3 antiserum (C"). Although the pattern of Me(3)K9H3 staining is more spread out in these nuclei compared with those that have completed heterochromatinisation (see C" and B") the merged image in C'" shows that the Me(3)H9H3 pattern largely colocalises with C1A9 staining. Bars, 10 µm.