Fig. 2. HP1 and dmH3K9 are upregulated on both male and female X chromosomes in JIL-1 null mutants. (A-C) Confocal images of whole-mount polytene nuclei from male and female third instar larvae. The X chromosome is indicated by X; the chromocenter by an arrow. (A,B) Triple labeling with anti-HP1 (red) and anti-dmH3K9 (green) antibodies, and with Hoechst (DNA, blue), of female (A) and male (B) wild-type (wt) and JIL-1^z2 homozygous (z2/z2) mutant polytene nuclei. (A) In the female, both HP1 and dmH3K9 are upregulated on the X chromosome, and to a lesser degree on the autosomes in JIL-1^z2 homozygous nuclei. (B) In the male, both HP1 and dmH3K9 are upregulated on the X chromosome, and to a lesser degree on the autosomes in JIL-1^z2 homozygous nuclei. (C) Triple labeling with anti-HP1 (red) and anti-MSL1 (green) antibodies, and with Hoechst (DNA, blue), of male wild-type (wt) and JIL-1^z2 homozygous (z2/z2) mutant polytene nuclei. MSL-1 labeling identifies the male X chromosome. (D) Identification of the female X chromosome by a GFP-lacI fusion protein targeted to 256 lacO repeats inserted into the 4D5 interband region of polytene X chromosomes in a JIL-1^z2 homozygous (z2/z2) mutant. The preparation was triple labeled with anti-dmH3K9 (red) and anti-GFP (green) antibodies, and with Hoechst (DNA, blue). The position of the lacO repeats identifying the X chromosome is indicated (arrowhead). Composite images (comp) are shown to the left.