H3-K9 trimethylation in dsetdb1G19561 ovaries is abolished in a germ-cell-specific manner.
(A) Colocalization of H3K9me3 signals with dSETDB1 signals and DAPI-dense spots. A boxed area is enlarged into individual or merged channels, together with a schematic illustration of the relative positions of individual signals (the right-most panel). Dotted circles indicate nuclear boundaries. (B) Loss of H3K9me3 signals in the inner region of the anterior germarium (the ‘inner’ germarium) in the dsetdb1G19561 germarium. Different cell populations in the germarium were stained either for VASA (upper panel) or Fas III (lower panel). (C) Diagram of the Drosophila germarium (upper panel). TF, terminal filament; CC, cap cell; GSC, germline-stem cell; ISC, inner-sheath cell; CB, cystoblast; Cc, cystocyte; SSC, somatic stem cell; FC, follicle cell. Subregions of the germarium (1, 2a, 2b, and 3) are indicated. Typical H3K9me3 pattern in a mutant germarium (lower panel), where the signal is absent from the inner germarium (dashed boundary in green; see text) but intact in the outer germarium (the region in between grey and green boundaries). (D) H3K9me3 signals are abolished in the VASA-positive primordial germ cells in the third-instar larval ovary of the dsetdb1 mutant. Dashed lines (red in B and white in D) indicate the boundaries of VASA-positive cells. Germaria in A-C are outlined by dashed lines. The nuclei were counterstained with 4′,6-diamidino-2-phenylindole (DAPI; blue). Arrows and arrowheads in B (right panel) and C (lower panel) indicate H3K9me3 signals detected in the nurse cells and somatic cells of the outer germarium of the dsetdb1 mutant. Scale bars, 10 µm.