FIG. 4.

Mitotic chromosomes are methylated homogeneously and show defects in chromosome condensation. Larval neuroblast chromosome preparations were stained with various antibodies, as indicated. Bars, 2 μm. (A) Immunodetection of 5-methylcytosine (5mC) revealed widespread DNA methylation in Dnmt3a-overexpressing flies, while no DNA methylation was detectable in flies overexpressing the catalytically inactive control. (B) Immunodetection of histone H3 indicated that the distribution of nucleosomes was not affected by DNA hypermethylation. (C) The localization of the centromere identifier protein Cid was not altered by genomic hypermethylation. However, the pairwise staining pattern of the centromere was disrupted in Dnmt3a-overexpressing flies. Note the frequent overcondensation of hypermethylated mitotic chromosomes.