Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2011 Aug 15;10(16):2628-34.
doi: 10.4161/cc.10.16.17059. Epub 2011 Aug 15.

Regulation of Adult Stem Cell Behavior by Nutrient Signaling

Affiliations
Free PMC article

Regulation of Adult Stem Cell Behavior by Nutrient Signaling

Lei Wang et al. Cell Cycle. .
Free PMC article

Abstract

Adult stem cells play an essential role throughout life, maintaining tissue and organ function by providing a reservoir of cells for homeostasis and repair. Maintenance and activity of adult stem cells have been the focus of numerous studies that have revealed stem cell-intrinsic factors and signals from the local microenvironment that regulate stem cell behavior. A growing body of work has provided evidence that circulating, systemic factors also contribute to the regulation of stem cell behavior in numerous tissues. We have demonstrated that Drosophila male germline stem cells (GSCs) and intestinal stem cells (ISCs) respond to changes in nutrient availability, specifically amino acids. Furthermore, we have shown that insulin signaling plays an important role in mediating the effects of changes in nutritional conditions. Notably, insulin signaling is cell-autonomously required within male GSCs for maintenance. Here we discuss our data regarding the effects and mechanisms by which changes in systemic nutritional conditions may influence the maintenance and activity of adult stem cells via insulin signaling.

Figures

Figure 1
Figure 1
Starvation-induced changes are distinct from aging-related changes to the niche. (A) Quantification of the average number of GSCs per testis in flies fed (dark green) or starved (light green) for 15 d. Genotypes analyzed were w, upd-GAL4 (hub driver) outcrossed to w1118 (upd-GAL4/+) and w, upd-GAL4, UAS-GFP; UAS-upd, TM2. Starvation-induced GSC loss was not significantly different between the two genotypes using two-way ANOVA. Error bars represent 95% confidence interval of the mean. Number of testes analyzed for each genotype is as follows: upd-GAL4/+ fed n = 36, starved n = 37; upd-GAL4, UAS-GFP; UAS-upd, TM2 fed n = 27, starved n = 35. (B and C) Immunofluorescence images of the testes from flies fed (B) or starved (C) for 15 d and stained with antibodies against E-cadherin (E-cad). Note expression of E-cad in hub cells is not affected by starvation. (D) Immunofluorescence image of the testis containing dInR339 mutant clones stained with antibodies against FasIII (green), GFP (green), STAT92E (red) and DAPI (blue). Arrow indicates a GFP+ dInR339/dInR339 mutant GSC (D′) that is also positive for STAT92E (D″). Arrowhead indicates a wild-type (GFP) GSC that is also STAT92E+. Scale bars, 20 µm.
Figure 2
Figure 2
The total number of intestinal stem cells (ISCs) and esg+ progenitor cells in the posterior midguts (PMG) respond dynamically to nutrient availability. (A–D) Immunofluorescence images of PMGs from GbeSu(H)lacZ; esg-GFP flies stained with antibodies against GFP to mark ISC/EBs (green), antibodies against βGAL to mark activated Notch signaling (red) in EBs and DAPI to mark DNA (blue). ISCs are identified as GFP+/βGAL cells as indicated by arrowheads in (A) and its inset showing the βGAL channel only. Guts shown were from newly eclosed flies fed for 3 d as control (A), control flies that were starved for additional 15 d (B), control flies that were continuously fed for additional 15 d (C) or control flies that were starved 15 d then refed for 4 d (D). Scale bars, 50 µm. (E) Quantification of the total number of ISCs and Esg-GFP+ cells in the PMGs from flies described in (A–D). To estimate the total number of cells per PMG, the number of ISCs and Esg-GFP+ cells in each immunofluorescence image were measured, normalized to a defined gut area, then adjusted to the total area of each PMG. Number of guts examined, from left to right: 32, 32, 32, 31. Error bars represent 95% confidence interval of the mean. **p < 0.01 by Student t-test.
Figure 3
Figure 3
dILP expression in the Drosophila testis. (A) Immunofluorescence image of a testis (genotype w; dILP2-GAL4;UAS-GFPNLS) showing GFP+, dILP2 expressing cells (green) and DAPI marking DNA (blue). Apical tip (*), mitotic amplification zone (bar), sperm (arrowhead), late cyst cells expressing dILP2 (arrows). Scale bar, 100 µm. (B and B′) Immunofluorescence image of the basal end of a testis (genotype: w; dILP3-LacZ) stained with antibodies against β-galactosidase (β-gal, green) to highlight dILP3-expressing cells, Eyes absent (Eya; red) to mark late cyst cells and DAPI (blue). (B′) β-gal expression. Eya+/β-gal late cyst cell (arrowhead). Eya+/β-gal+ late cyst cell (arrow). Scale bars, 50 µm. (C and D) Quantitative RT-PCR (qPCR) showing relative mRNA abundance for dILP2 and 3 (C) and 4E-BP (D) in testes from fed, starved and refed flies. mRNA levels were normalized to GAPDH2 and expression is shown relative to the level in fed flies at 20 d (C) or to the level in fed flies at 15 d (D). Error bars represent the statistical range across triplicate measurements.
Figure 4
Figure 4
Inactivating dFOXO results in fewer GSCs in the Drosophila testis that are insensitive to starvation. (A) Quantification of the average number of GSCs per testis in flies fed (dark green) or starved (light green) for 20 d. Flies analyzed were control (dFOXO21/+), transheterozygous dFOXO mutants (dFOXO21/dFOXO25) and those expressing an RNAi transgene against dFOXO in the hub using the upd-GAL4 driver (upd > dFOXORNAi). The total numbers of testes analyzed (n) were: control fed n = 37, starved n = 33; dFOXO21/dFOXO25 fed n = 26, starved n = 42; upd > dFOXORNAi fed n = 32, starved n = 32. Error bars represent 95% confidence interval of the mean. Asterisks indicate statistically significant difference (p < 0.001) using Student t-test. (B) Immunofluorescence image of testes, in which early germ cells are expressing GFP (green; B and B″) stained with antibodies that recognize dFOXO (red; B and B″). dFOXO are expressed in germ cells, including GSCs (GFP+, arrows), in somatic cells (GFP, arrowheads) and in the hub (asterisk). Note the strong enrichment of dFOXO in the hub (B″). (Genotype: w;UAS-GFPmCD8;nanos-GAL4).

Similar articles

See all similar articles

Cited by 17 articles

See all "Cited by" articles

Publication types

LinkOut - more resources

Feedback