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Drosophila Rabex-5 restricts Notch activity in hematopoietic cells and maintains hematopoietic homeostasis.

Reimels TA, Pfleger CM - J. Cell. Sci. (2015)

Bottom Line: Rabex-5 negatively regulates Ras, and we show that Ras activity is responsible for specific Rabex-5 hematopoietic phenotypes.Surprisingly, Ras-independent Notch protein accumulation and transcriptional activity in the lymph gland underlie multiple distinct hematopoietic phenotypes of Rabex-5 loss.Thus, Rabex-5 plays an important role in Drosophila hematopoiesis and might serve as an axis coordinating Ras and Notch signaling in the lymph gland.

View Article: PubMed Central - PubMed

Affiliation: Department of Oncological Sciences, The Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA The Graduate School of Biomedical Sciences, The Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA.

No MeSH data available.


Related in: MedlinePlus

Rabex-5 is required in the medullary zone of the larval lymph gland to restrict Notch accumulation. (A) Schematic depicting primary lobe of the larval lymph gland. Srp-gal4 is expressed across the entire lobe. Dome-gal4 is expressed exclusively in the MZ. Antp-gal4 is expressed exclusively in the PSC. (B) Rabex-5 RNAi in the MZ (dome>GFP, Rabex-5IR) increased Notch fluorescence intensity over the entire lobe compared to that in controls (dome>GFP) 4 days AEL. (C) At 18°C, Rabex-5 RNAi in the MZ (dome>GFP, Rabex-5IR) increased the average number of cells per lobe that strongly express Notch compared to those in controls (dome>GFP). RasV12 expression in the MZ (dome>GFP, RasV12) did not alter the average number of cells per lobe that strongly express Notch. Rabex-5 RNAi in the PSC (antp>GFP, Rabex-5IR) did not change Notch fluorescence intensity over the entire primary lobe (D) or in the PSC (E) compared to those in controls (antp>GFP). (F) Rabex-5 RNAi in the PSC (antp>GFP, Rabex-5IR) had no effect on the average number of cells per lobe that strongly express Notch compared to those in controls (antp>GFP). (G) Rabex-5 RNAi, but not RasV12, in embryonic hemocytes (crq>GFP, Rabex-5IR and crq>GFP, RasV12) increased Notch fluorescence intensity of the primary lobes compared to that of controls (crq>GFP) 5 days AEL. ^P≤0.05, *P≤0.01.
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JCS174433F6: Rabex-5 is required in the medullary zone of the larval lymph gland to restrict Notch accumulation. (A) Schematic depicting primary lobe of the larval lymph gland. Srp-gal4 is expressed across the entire lobe. Dome-gal4 is expressed exclusively in the MZ. Antp-gal4 is expressed exclusively in the PSC. (B) Rabex-5 RNAi in the MZ (dome>GFP, Rabex-5IR) increased Notch fluorescence intensity over the entire lobe compared to that in controls (dome>GFP) 4 days AEL. (C) At 18°C, Rabex-5 RNAi in the MZ (dome>GFP, Rabex-5IR) increased the average number of cells per lobe that strongly express Notch compared to those in controls (dome>GFP). RasV12 expression in the MZ (dome>GFP, RasV12) did not alter the average number of cells per lobe that strongly express Notch. Rabex-5 RNAi in the PSC (antp>GFP, Rabex-5IR) did not change Notch fluorescence intensity over the entire primary lobe (D) or in the PSC (E) compared to those in controls (antp>GFP). (F) Rabex-5 RNAi in the PSC (antp>GFP, Rabex-5IR) had no effect on the average number of cells per lobe that strongly express Notch compared to those in controls (antp>GFP). (G) Rabex-5 RNAi, but not RasV12, in embryonic hemocytes (crq>GFP, Rabex-5IR and crq>GFP, RasV12) increased Notch fluorescence intensity of the primary lobes compared to that of controls (crq>GFP) 5 days AEL. ^P≤0.05, *P≤0.01.

Mentions: To determine which zone of the primary lobe required Rabex-5 to regulate Notch, we knocked down Rabex-5 exclusively in the MZ using dome-gal4 or exclusively in the PSC using antennapedia-gal4 (antp-gal4) (Fig. 6A, Table S1). A significant increase in Notch intensity across the entire lymph gland was seen upon RNAi of Rabex-5 in the MZ (dome>Rabex-5IR, Fig. 6B). Per lobe, the average number of cells with strong Notch expression increased, even when larvae were raised at 18°C to minimize the effect of RNAi (Fig. 6C). Similar to Rabex-5 reduction in the entire primary lobe, Rabex-5 reduction exclusively in the MZ promoted Notch accumulation, supporting a model that Rabex-5 is required to restrict Notch accumulation in the prohemocytes of the MZ. Constitutive Ras activation in the MZ had no effect on Notch expression; at 18°C, RasV12 expression by using dome-gal4 did not significantly alter the average number of cells per lobe that strongly express Notch (dome>RasV12, Fig. 6C).Fig. 6.


Drosophila Rabex-5 restricts Notch activity in hematopoietic cells and maintains hematopoietic homeostasis.

Reimels TA, Pfleger CM - J. Cell. Sci. (2015)

Rabex-5 is required in the medullary zone of the larval lymph gland to restrict Notch accumulation. (A) Schematic depicting primary lobe of the larval lymph gland. Srp-gal4 is expressed across the entire lobe. Dome-gal4 is expressed exclusively in the MZ. Antp-gal4 is expressed exclusively in the PSC. (B) Rabex-5 RNAi in the MZ (dome>GFP, Rabex-5IR) increased Notch fluorescence intensity over the entire lobe compared to that in controls (dome>GFP) 4 days AEL. (C) At 18°C, Rabex-5 RNAi in the MZ (dome>GFP, Rabex-5IR) increased the average number of cells per lobe that strongly express Notch compared to those in controls (dome>GFP). RasV12 expression in the MZ (dome>GFP, RasV12) did not alter the average number of cells per lobe that strongly express Notch. Rabex-5 RNAi in the PSC (antp>GFP, Rabex-5IR) did not change Notch fluorescence intensity over the entire primary lobe (D) or in the PSC (E) compared to those in controls (antp>GFP). (F) Rabex-5 RNAi in the PSC (antp>GFP, Rabex-5IR) had no effect on the average number of cells per lobe that strongly express Notch compared to those in controls (antp>GFP). (G) Rabex-5 RNAi, but not RasV12, in embryonic hemocytes (crq>GFP, Rabex-5IR and crq>GFP, RasV12) increased Notch fluorescence intensity of the primary lobes compared to that of controls (crq>GFP) 5 days AEL. ^P≤0.05, *P≤0.01.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4696494&req=5

JCS174433F6: Rabex-5 is required in the medullary zone of the larval lymph gland to restrict Notch accumulation. (A) Schematic depicting primary lobe of the larval lymph gland. Srp-gal4 is expressed across the entire lobe. Dome-gal4 is expressed exclusively in the MZ. Antp-gal4 is expressed exclusively in the PSC. (B) Rabex-5 RNAi in the MZ (dome>GFP, Rabex-5IR) increased Notch fluorescence intensity over the entire lobe compared to that in controls (dome>GFP) 4 days AEL. (C) At 18°C, Rabex-5 RNAi in the MZ (dome>GFP, Rabex-5IR) increased the average number of cells per lobe that strongly express Notch compared to those in controls (dome>GFP). RasV12 expression in the MZ (dome>GFP, RasV12) did not alter the average number of cells per lobe that strongly express Notch. Rabex-5 RNAi in the PSC (antp>GFP, Rabex-5IR) did not change Notch fluorescence intensity over the entire primary lobe (D) or in the PSC (E) compared to those in controls (antp>GFP). (F) Rabex-5 RNAi in the PSC (antp>GFP, Rabex-5IR) had no effect on the average number of cells per lobe that strongly express Notch compared to those in controls (antp>GFP). (G) Rabex-5 RNAi, but not RasV12, in embryonic hemocytes (crq>GFP, Rabex-5IR and crq>GFP, RasV12) increased Notch fluorescence intensity of the primary lobes compared to that of controls (crq>GFP) 5 days AEL. ^P≤0.05, *P≤0.01.
Mentions: To determine which zone of the primary lobe required Rabex-5 to regulate Notch, we knocked down Rabex-5 exclusively in the MZ using dome-gal4 or exclusively in the PSC using antennapedia-gal4 (antp-gal4) (Fig. 6A, Table S1). A significant increase in Notch intensity across the entire lymph gland was seen upon RNAi of Rabex-5 in the MZ (dome>Rabex-5IR, Fig. 6B). Per lobe, the average number of cells with strong Notch expression increased, even when larvae were raised at 18°C to minimize the effect of RNAi (Fig. 6C). Similar to Rabex-5 reduction in the entire primary lobe, Rabex-5 reduction exclusively in the MZ promoted Notch accumulation, supporting a model that Rabex-5 is required to restrict Notch accumulation in the prohemocytes of the MZ. Constitutive Ras activation in the MZ had no effect on Notch expression; at 18°C, RasV12 expression by using dome-gal4 did not significantly alter the average number of cells per lobe that strongly express Notch (dome>RasV12, Fig. 6C).Fig. 6.

Bottom Line: Rabex-5 negatively regulates Ras, and we show that Ras activity is responsible for specific Rabex-5 hematopoietic phenotypes.Surprisingly, Ras-independent Notch protein accumulation and transcriptional activity in the lymph gland underlie multiple distinct hematopoietic phenotypes of Rabex-5 loss.Thus, Rabex-5 plays an important role in Drosophila hematopoiesis and might serve as an axis coordinating Ras and Notch signaling in the lymph gland.

View Article: PubMed Central - PubMed

Affiliation: Department of Oncological Sciences, The Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA The Graduate School of Biomedical Sciences, The Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA.

No MeSH data available.


Related in: MedlinePlus