Multipotent somatic stem cells contribute to the stem cell niche in the Drosophila testis - PubMed (original) (raw)

. 2008 Aug 28;454(7208):1132-6.

doi: 10.1038/nature07173. Epub 2008 Jul 20.

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Multipotent somatic stem cells contribute to the stem cell niche in the Drosophila testis

Justin Voog et al. Nature. 2008.

Abstract

Adult stem cells reside in specialized microenvironments, or niches, that have an important role in regulating stem cell behaviour. Therefore, tight control of niche number, size and function is necessary to ensure the proper balance between stem cells and progenitor cells available for tissue homeostasis and wound repair. The stem cell niche in the Drosophila male gonad is located at the tip of the testis where germline and somatic stem cells surround the apical hub, a cluster of approximately 10-15 somatic cells that is required for stem cell self-renewal and maintenance. Here we show that somatic stem cells in the Drosophila testis contribute to both the apical hub and the somatic cyst cell lineage. The Drosophila orthologue of epithelial cadherin (DE-cadherin) is required for somatic stem cell maintenance and, consequently, the apical hub. Furthermore, our data indicate that the transcriptional repressor escargot regulates the ability of somatic cells to assume and/or maintain hub cell identity. These data highlight the dynamic relationship between stem cells and the niche and provide insight into genetic programmes that regulate niche size and function to support normal tissue homeostasis and organ regeneration throughout life.

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Figures

Figure 1

Figure 1. Somatic stem cell progeny contribute to the hub

a, Schematic diagram of the apical tip of the testis. Hub cells (red) contact SSCs (light grey) and GSCs (green). SSCs produce cyst cells (dark grey) that envelop developing germline cells (green). b-f, Immunofluorescence images of the apical tip of the adult testis from flies heat shocked to generate labelled dividing cells expressing nuclear β-galactosidase (β-gal). Testes were stained with antibodies to DE-cadherin or Fasciclin III (FasIII), β-gal, and Traffic Jam (TJ) or 4,6-diamidino-2-phenylindole (DAPI). b, One day after heat shock, three β-gal+ (arrowheads, green; second panel) and TJ+ somatic cells (red; fourth panel) are near the FasIII+ (blue; third panel) hub (asterisk). c, Five days after heat shock two β-gal+ SSCs (arrowheads, green; right panel) contact hub cells (outline/DE-cadherin, red). A β-gal+ SSC daughter cell (arrow) is also present. d, Lower magnification view of c. β-Gal+ somatic cells (arrows, green) are present along the length of the testis. e, Five days after heat shock, the hub (outline, DE-cadherin, red) contains two β-gal+ cells (arrowheads, green; right panel). f, Fifteen days after heat shock, two β-gal+ hub cells (green, arrowheads; second panel) co-stain with FasIII (blue, outline; third panel) and TJ (red; fourth panel). Scale bars: b, d, 20 μm; c, e, f, 10 μm.

Figure 2

Figure 2. BrdU-labelled cells become incorporated into the apical hub

a, b, d, Immunofluorescence images of testes from wild-type (OregonR) (a, b) or _upd_GAL4-UAS-gfp (d) adult flies fed BrdU. a, Left panel: BrdU+ cells (green) surround the FasIII+ hub (red, outline). Two BrdU+ GSCs (asterisks) and a BrdU+ somatic cell (arrow) are adjacent to the apical hub (outline) after a 1-day chase. Right panel: no BrdU+ hub cells are detected. b, A BrdU+ hub cell (arrow) is present after a 3-day chase (left panel). FasIII (middle panel); BrdU (right panel). c, Hub cells stained with DE-cadherin (red; middle panel) and GFP (green; right panel) in _upd_GAL4-UAS-gfp testis. d, A BrdU+ hub cell (arrow) is detected after a 7-day chase. The middle panel shows the GFP channel; the right panel shows the BrdU channel. Scale bars: 10 μm.

Figure 3

Figure 3. Two populations of mitotically active somatic cells are present near the hub

a-d, Confocal images of _upd_GAL4-UAS-gfp testes. a, b, Testes stained for Vasa (blue; middle panels), phospho-histone-H3 (pHH3, red; right panels) and GFP (green). Phospho-histone-H3+ SSCs (arrowheads) are observed near the hub. c, Testes stained for TJ (blue; middle panel), phospho-histone-H3 (green; right panel) and GFP (green; right panel). The hub is outlined. A mitotic CPC (arrow) surrounds a mitotic GSC (arrowhead). d, Testes stained with TJ (blue; middle panel), phosphohistone-H3 (red; right panel) and GFP (green). A mitotic CPC (arrows) one-cell distance from the hub (outline) is shown. e, Graph depicting marked somatic cell type frequency from all testes assayed at various time points. f, Graph depicting marked somatic cell type frequency from testes containing marked somatic cells at various time points. g-i, A testis 10 days after heat shock stained for β-gal+ (green; bottom panels), DE-cadherin (red) and DAPI (blue). A β-gal+ hub cell (g, indented arrowhead), β-gal+ SSC (h, i, arrowhead) and β-gal+ CPC (i, arrow) are shown. Z-section images (1 μm) are denoted by depth in the lower left corner. Scale bars: 10 μm.

Figure 4

Figure 4. Factors required for SSC maintenance and the SSC-hub cell transition

a, Ten days after heat shock a series of GFP+ late cyst cells (green, arrows) and a single labelled hub cell are present (arrowhead in b). GFP (green), DE-cadherin (red) and DAPI (blue) are shown. b, Higher magnification (×63) of the hub in a (outline, DE-cadherin, red) with a GFP+ hub cell (arrowhead, right panel). c, Five days after heat shock GFP+ germline and somatic cells are maintained near the DE-cadherin+ hub (red). Late GFP+ germline (arrowhead) and somatic cell (arrow) clones are present basally. d, Five days after heat shock GFP+ shgIG29 mutant late somatic cells are present (arrow), but no GFP+ clones are present near the DE-cadherin+ hub (red) at the apical tip. e, f, Fifteen days after heat shock GFP+ hub cells are present from wild-type (e) and shgIG29 (f) somatic clones (arrowheads). GFP+ shgIG29 hub cells display loss of DE-cadherin (red) at the hub interface (inset, DE-cadherin channel). g, h, Testes from 1-day-old _c587_GAL4 (g) and _c587_GAL4/UAS-shgRNAi (h) males stained with DE-cadherin (red) and TJ (green). i, j, Testes from 15-day-old _c587_GAL4 (i) and _c587_GAL4/UAS-shgRNAi (j) males. Note the loss of DE-cadherin (red) and TJ (green) stain in j. k, l, Fifteen days after heat shock distorted GFP+ hub cells are present from esgG66 (k) and esgL2 (l) mutant somatic clones (compare to e). The hub is marked with DE-cadherin (red). m, n, esgshof/CyO; osk/osk (m) and esgshof/esgshof; osk/osk (n) testes stained for FasIII (red, insets) and TJ (green). Scale bars: a, c, d, 20 μm; e-n, 10 μm.

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