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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 negative regulation of Notch is required for proper regulation of hematopoiesis during development. (A) In a Rabex-5ex42/ex42 background, DpN and SerBd-3 (Rabex-5ex42/ex42; DpN/+ and Rabex-5ex42/ex42; SerBd-3/+) increased larval lethality compared to that in controls (Rabex-5ex42/ex42). Dl7 (Rabex-5ex42/ex42; Dl7/+) suppressed larval lethality. (B) In a Rabex-5ex42/ex42 background 14 days AEL, DpN and SerBd-3 (Rabex-5ex42/ex42; DpN/+ and Rabex-5ex42/ex42; SerBd-3/+) increased the incidence of melanotic masses and Dl7 (Rabex-5ex42/ex42; Dl7/+) decreased the incidence of melanotic masses compared to those in controls (Rabex-5ex42/ex42). (C) In a Rabex-5ex42/ex42 background 6 days AEL, DpN (Rabex-5ex42/ex42; DpN/+) increased the percentage of larvae with lamellocytes compared to that in controls (Rabex-5ex42/ex42). Dl7 (Rabex-5ex42/ex42; Dl7/+) decreased the percentage of larvae with lamellocytes. SerBd-3 (Rabex-5ex42/ex42; SerBd-3/+) did not alter the percentage of larvae with lamellocytes compared to that in controls (Rabex-5ex42/ex42). (D) Summary of Rabex-5ex42/ex42 genetic interactions with Notch, Delta and Serrate. (E) Notch RNAi in hemocytes (srp>GFP, NIR) did not affect the area of the primary lymph gland lobes at 21°C but reduced the enlarged lymph glands (srp>GFP, NIR, Rabex-5IR) resulting from Rabex-5 RNAi (srp>GFP, Rabex-5IR) to control area (srp>GFP) 7 days AEL. DAPI staining is shown in blue. Scale bars: 50 μm; ^P≤0.05, *P≤0.01.
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JCS174433F8: Rabex-5 negative regulation of Notch is required for proper regulation of hematopoiesis during development. (A) In a Rabex-5ex42/ex42 background, DpN and SerBd-3 (Rabex-5ex42/ex42; DpN/+ and Rabex-5ex42/ex42; SerBd-3/+) increased larval lethality compared to that in controls (Rabex-5ex42/ex42). Dl7 (Rabex-5ex42/ex42; Dl7/+) suppressed larval lethality. (B) In a Rabex-5ex42/ex42 background 14 days AEL, DpN and SerBd-3 (Rabex-5ex42/ex42; DpN/+ and Rabex-5ex42/ex42; SerBd-3/+) increased the incidence of melanotic masses and Dl7 (Rabex-5ex42/ex42; Dl7/+) decreased the incidence of melanotic masses compared to those in controls (Rabex-5ex42/ex42). (C) In a Rabex-5ex42/ex42 background 6 days AEL, DpN (Rabex-5ex42/ex42; DpN/+) increased the percentage of larvae with lamellocytes compared to that in controls (Rabex-5ex42/ex42). Dl7 (Rabex-5ex42/ex42; Dl7/+) decreased the percentage of larvae with lamellocytes. SerBd-3 (Rabex-5ex42/ex42; SerBd-3/+) did not alter the percentage of larvae with lamellocytes compared to that in controls (Rabex-5ex42/ex42). (D) Summary of Rabex-5ex42/ex42 genetic interactions with Notch, Delta and Serrate. (E) Notch RNAi in hemocytes (srp>GFP, NIR) did not affect the area of the primary lymph gland lobes at 21°C but reduced the enlarged lymph glands (srp>GFP, NIR, Rabex-5IR) resulting from Rabex-5 RNAi (srp>GFP, Rabex-5IR) to control area (srp>GFP) 7 days AEL. DAPI staining is shown in blue. Scale bars: 50 μm; ^P≤0.05, *P≤0.01.

Mentions: Rabex-5 knockdown, however, was sufficient to increase the percentage of circulating crystal cells (Fig. 3E). Given the instructive role of Notch signaling in crystal cell specification (Duvic et al., 2002; Lebestky et al., 2003; Mandal et al., 2007; Krzemien et al., 2010) and the reported roles in lamellocyte differentiation (Duvic et al., 2002; Small et al., 2014), we further investigated the involvement of Notch. Encouragingly, genetic modification of certain Notch signaling components changed the Rabex-5- crystal cell phenotype (Fig. 4H, summarized in Fig. 8D). The Rabex-5- crystal cell phenotype was strongly suppressed by a dominant-negative allele of Notch ligand Serrate (Ser), SerBd-3, consistent with reported effects of this allele on crystal cells (Lebestky et al., 2003). The crystal cell phenotype was subtly suppressed by a loss-of-function allele of Notch ligand Delta (Dl), Dl7, and enhanced by Notch duplication (DpN).


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

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

Rabex-5 negative regulation of Notch is required for proper regulation of hematopoiesis during development. (A) In a Rabex-5ex42/ex42 background, DpN and SerBd-3 (Rabex-5ex42/ex42; DpN/+ and Rabex-5ex42/ex42; SerBd-3/+) increased larval lethality compared to that in controls (Rabex-5ex42/ex42). Dl7 (Rabex-5ex42/ex42; Dl7/+) suppressed larval lethality. (B) In a Rabex-5ex42/ex42 background 14 days AEL, DpN and SerBd-3 (Rabex-5ex42/ex42; DpN/+ and Rabex-5ex42/ex42; SerBd-3/+) increased the incidence of melanotic masses and Dl7 (Rabex-5ex42/ex42; Dl7/+) decreased the incidence of melanotic masses compared to those in controls (Rabex-5ex42/ex42). (C) In a Rabex-5ex42/ex42 background 6 days AEL, DpN (Rabex-5ex42/ex42; DpN/+) increased the percentage of larvae with lamellocytes compared to that in controls (Rabex-5ex42/ex42). Dl7 (Rabex-5ex42/ex42; Dl7/+) decreased the percentage of larvae with lamellocytes. SerBd-3 (Rabex-5ex42/ex42; SerBd-3/+) did not alter the percentage of larvae with lamellocytes compared to that in controls (Rabex-5ex42/ex42). (D) Summary of Rabex-5ex42/ex42 genetic interactions with Notch, Delta and Serrate. (E) Notch RNAi in hemocytes (srp>GFP, NIR) did not affect the area of the primary lymph gland lobes at 21°C but reduced the enlarged lymph glands (srp>GFP, NIR, Rabex-5IR) resulting from Rabex-5 RNAi (srp>GFP, Rabex-5IR) to control area (srp>GFP) 7 days AEL. DAPI staining is shown in blue. Scale bars: 50 μm; ^P≤0.05, *P≤0.01.
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JCS174433F8: Rabex-5 negative regulation of Notch is required for proper regulation of hematopoiesis during development. (A) In a Rabex-5ex42/ex42 background, DpN and SerBd-3 (Rabex-5ex42/ex42; DpN/+ and Rabex-5ex42/ex42; SerBd-3/+) increased larval lethality compared to that in controls (Rabex-5ex42/ex42). Dl7 (Rabex-5ex42/ex42; Dl7/+) suppressed larval lethality. (B) In a Rabex-5ex42/ex42 background 14 days AEL, DpN and SerBd-3 (Rabex-5ex42/ex42; DpN/+ and Rabex-5ex42/ex42; SerBd-3/+) increased the incidence of melanotic masses and Dl7 (Rabex-5ex42/ex42; Dl7/+) decreased the incidence of melanotic masses compared to those in controls (Rabex-5ex42/ex42). (C) In a Rabex-5ex42/ex42 background 6 days AEL, DpN (Rabex-5ex42/ex42; DpN/+) increased the percentage of larvae with lamellocytes compared to that in controls (Rabex-5ex42/ex42). Dl7 (Rabex-5ex42/ex42; Dl7/+) decreased the percentage of larvae with lamellocytes. SerBd-3 (Rabex-5ex42/ex42; SerBd-3/+) did not alter the percentage of larvae with lamellocytes compared to that in controls (Rabex-5ex42/ex42). (D) Summary of Rabex-5ex42/ex42 genetic interactions with Notch, Delta and Serrate. (E) Notch RNAi in hemocytes (srp>GFP, NIR) did not affect the area of the primary lymph gland lobes at 21°C but reduced the enlarged lymph glands (srp>GFP, NIR, Rabex-5IR) resulting from Rabex-5 RNAi (srp>GFP, Rabex-5IR) to control area (srp>GFP) 7 days AEL. DAPI staining is shown in blue. Scale bars: 50 μm; ^P≤0.05, *P≤0.01.
Mentions: Rabex-5 knockdown, however, was sufficient to increase the percentage of circulating crystal cells (Fig. 3E). Given the instructive role of Notch signaling in crystal cell specification (Duvic et al., 2002; Lebestky et al., 2003; Mandal et al., 2007; Krzemien et al., 2010) and the reported roles in lamellocyte differentiation (Duvic et al., 2002; Small et al., 2014), we further investigated the involvement of Notch. Encouragingly, genetic modification of certain Notch signaling components changed the Rabex-5- crystal cell phenotype (Fig. 4H, summarized in Fig. 8D). The Rabex-5- crystal cell phenotype was strongly suppressed by a dominant-negative allele of Notch ligand Serrate (Ser), SerBd-3, consistent with reported effects of this allele on crystal cells (Lebestky et al., 2003). The crystal cell phenotype was subtly suppressed by a loss-of-function allele of Notch ligand Delta (Dl), Dl7, and enhanced by Notch duplication (DpN).

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