GSE109495
The large fraction of heterochromatin in Drosophila neurons is simultaneously bound by B-type lamin and HP1a
In most mammalian cell lines, chromatin located at the nuclear periphery is represented by condensed heterochromatin as observed by both microscopy observations and DamID mapping of lamina-associated domains (LADs), enriched in dimethylated Lys9 of histone H3 (H3K9me2). In Drosophila Kc167 cell culture, where LADs were only mapped to the moment, they are neither H3K9me2-enriched, nor overlap with the domains of Heterochromatin Protein 1a (HP1a). Here, using a cell type-specific DamID approach we mapped genome-wide LADs, HP1a and Pc domains from the central brain, Repo-positive glia, Elav-positive neurons and the fat body of Drosophila third instar larvae. Silent or weakly-expressed genes occupy LADs, HP1a and Pc domains, with genes residing in the HP1a-bound LADs expressed at the lowest level. However, a fraction of HP1a domains contain actively expressed genes. The inter-LAD regions that are shared by all cell types are populated by ubiquitously expressed genes, whereas the conserved LADs are less abundant than in mammals. Importantly, in the central brain and in neurons we found strong overlap of HP1a domains with LADs both in the chromosome arms and in pericentromeric regions. In the glia and fat bodies, this overlap was less frequent. Consistent with these results, centromeres appear to reside closer to nuclear lamina in neurons than in Kc167 cells. The discovery of Drosophila peripheral chromatin bound by both HP1a and B-type lamin implies that mechanisms of heterochromatin compaction and attachment to nuclear lamina may be similar in Drosophila and mammals. Overall design: We determined DamID scores for Polycomb (Pc), Lamin Dm0 (Lam) and Heterochromatin Protein 1a (HP1a) normalized by Dam only control, for Drosophila larval central brain, Repo+ glial cells of larval central brain, Elav+ neurons of larval central brain and larval fat bodies. All samples were performed with 2 biological replicates. In case of Dam only control for larval central brain, each biological replicate was performed with 3 technical replicates.