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Expression of Groucho/TLE proteins during pancreas development.

Hoffman BG, Zavaglia B, Beach M, Helgason CD - BMC Dev. Biol. (2008)

Bottom Line: Of note, Tle2 and Tle3 are co-expressed with Gro/TLE interaction domain containing transcription factors that are essential for endocrine pancreas development.We further demonstrate that Tle2 can interact with several of these factors and that Tle2 modulate Arx's repressive activity.Taken together our studies suggest that Gro/TLE proteins play a role in the repression of target genes during endocrine cell specification.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Cancer Endocrinology, BC Cancer Research Center, 675 West 10th Avenue, Vancouver, BC, V5Z 1L3, Canada. bhoffman@bccrc.ca

ABSTRACT

Background: The full-length mammalian homologs of groucho, Tle1, 2, 3, and 4, act as transcriptional corepressors and are recruited by transcription factors containing an eh1 or WRPW/Y domain. Many transcription factors critical to pancreas development contain a Gro/TLE interaction domain and several have been shown to require Gro/TLE interactions for proper function during neuronal development. However, a detailed analysis of the expression patterns of the Gro/TLE proteins in pancreas development has not been performed. Moreover, little is known about the ability of Gro/TLE proteins to interact with transcription factors in the pancreas.

Results: We describe the expression of Gro/TLE family members, and of 34 different transcription factors that contain a Gro/TLE interaction motif, in the pancreas utilizing nine SAGE libraries created from the developing and adult pancreas, as well as the GenePaint database. Next, we show the dynamic expression of Tle1, 2, 3, 4, 5 and 6 during pancreas development by qRT-PCR. To further define the cell-type specificity of the expression of these proteins we use immunofluorescence to co-localize them with Pdx1 at embryonic day 12.5 (E12.5), Ngn3 at E14.5, Pdx1, Nkx2-2, Insulin, Glucagon, Pancreatic polypeptide and Somatostatin at E18.5, as well as Insulin and Glucagon in the adult. We then show that Tle2 can interact with Nkx2-2, Hes1, Arx, and Nkx6-1 which are all critical factors in pancreas development. Finally, we demonstrate that Tle2 modulates the repressive abilities of Arx in a beta-cell line.

Conclusion: Although Tle1, 2, 3, and 4 show overlapping expression in pancreatic progenitors and in the adult islet, the expression of these factors is restricted to different cell types during endocrine cell maturation. Of note, Tle2 and Tle3 are co-expressed with Gro/TLE interaction domain containing transcription factors that are essential for endocrine pancreas development. We further demonstrate that Tle2 can interact with several of these factors and that Tle2 modulate Arx's repressive activity. Taken together our studies suggest that Gro/TLE proteins play a role in the repression of target genes during endocrine cell specification.

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Close-up of the expression of Tle2 and Tle3, as compared to Ngn3 expression, in the E14.5 pancreas. Transverse sections of E14.5 pancreases were analyzed for the expression of (A) Tle2 or (D) Tle3 (green) in relation to (B, E) Ngn3 expression (red). Merged images are shown in (C, F). Blue arrows indicate cells that are Gro/TLE + but not Ngn3+. Yellow arrows indicate cells where the Gro/TLE proteins and Ngn3 co-localize. Green arrows indicate cells expressing Ngn3 only. Sections are shown at ×400.
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Figure 5: Close-up of the expression of Tle2 and Tle3, as compared to Ngn3 expression, in the E14.5 pancreas. Transverse sections of E14.5 pancreases were analyzed for the expression of (A) Tle2 or (D) Tle3 (green) in relation to (B, E) Ngn3 expression (red). Merged images are shown in (C, F). Blue arrows indicate cells that are Gro/TLE + but not Ngn3+. Yellow arrows indicate cells where the Gro/TLE proteins and Ngn3 co-localize. Green arrows indicate cells expressing Ngn3 only. Sections are shown at ×400.

Mentions: During the secondary transition endocrine progenitors lose expression of Notch signaling components, such as Hes1, and begin to express the bHLH factor Ngn3. In neuronal development Tle1 expression is likewise lost during neural specification of progenitors. To see if a similar process occurs in the pancreas we co-localized Tle1-4 with Ngn3 in the E14.5 developing pancreas. Unlike at E12.5 where Tle1-3 were expressed throughout the pancreatic epithelium these factors clearly showed more restricted expression at E14.5 (Figure 4 and Table 4). At this time point Tle1 was absent from the pancreatic epithelium. Tle2 and Tle3 on the other hand both showed scattered expression through the epithelium. Also, both Tle2 and Tle3 co-localized with Ngn3 in a subset of Ngn3 positive cells. Interestingly, cells that were Ngn3 and Tle2 or Tle3 double positive, cells that were Ngn3 positive and Tle2 and Tle3 negative, and cells that were Ngn3 negative and Tle2 and Tle3 positive, were found (Figure 5). Tle4 was again absent from epithelial cells. Tle3 was only found in a restricted set of mesenchymal cells as observed at E12.5, while Tle1, 2, and 4 were widely expressed in the mesenchyme.


Expression of Groucho/TLE proteins during pancreas development.

Hoffman BG, Zavaglia B, Beach M, Helgason CD - BMC Dev. Biol. (2008)

Close-up of the expression of Tle2 and Tle3, as compared to Ngn3 expression, in the E14.5 pancreas. Transverse sections of E14.5 pancreases were analyzed for the expression of (A) Tle2 or (D) Tle3 (green) in relation to (B, E) Ngn3 expression (red). Merged images are shown in (C, F). Blue arrows indicate cells that are Gro/TLE + but not Ngn3+. Yellow arrows indicate cells where the Gro/TLE proteins and Ngn3 co-localize. Green arrows indicate cells expressing Ngn3 only. Sections are shown at ×400.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2551604&req=5

Figure 5: Close-up of the expression of Tle2 and Tle3, as compared to Ngn3 expression, in the E14.5 pancreas. Transverse sections of E14.5 pancreases were analyzed for the expression of (A) Tle2 or (D) Tle3 (green) in relation to (B, E) Ngn3 expression (red). Merged images are shown in (C, F). Blue arrows indicate cells that are Gro/TLE + but not Ngn3+. Yellow arrows indicate cells where the Gro/TLE proteins and Ngn3 co-localize. Green arrows indicate cells expressing Ngn3 only. Sections are shown at ×400.
Mentions: During the secondary transition endocrine progenitors lose expression of Notch signaling components, such as Hes1, and begin to express the bHLH factor Ngn3. In neuronal development Tle1 expression is likewise lost during neural specification of progenitors. To see if a similar process occurs in the pancreas we co-localized Tle1-4 with Ngn3 in the E14.5 developing pancreas. Unlike at E12.5 where Tle1-3 were expressed throughout the pancreatic epithelium these factors clearly showed more restricted expression at E14.5 (Figure 4 and Table 4). At this time point Tle1 was absent from the pancreatic epithelium. Tle2 and Tle3 on the other hand both showed scattered expression through the epithelium. Also, both Tle2 and Tle3 co-localized with Ngn3 in a subset of Ngn3 positive cells. Interestingly, cells that were Ngn3 and Tle2 or Tle3 double positive, cells that were Ngn3 positive and Tle2 and Tle3 negative, and cells that were Ngn3 negative and Tle2 and Tle3 positive, were found (Figure 5). Tle4 was again absent from epithelial cells. Tle3 was only found in a restricted set of mesenchymal cells as observed at E12.5, while Tle1, 2, and 4 were widely expressed in the mesenchyme.

Bottom Line: Of note, Tle2 and Tle3 are co-expressed with Gro/TLE interaction domain containing transcription factors that are essential for endocrine pancreas development.We further demonstrate that Tle2 can interact with several of these factors and that Tle2 modulate Arx's repressive activity.Taken together our studies suggest that Gro/TLE proteins play a role in the repression of target genes during endocrine cell specification.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Cancer Endocrinology, BC Cancer Research Center, 675 West 10th Avenue, Vancouver, BC, V5Z 1L3, Canada. bhoffman@bccrc.ca

ABSTRACT

Background: The full-length mammalian homologs of groucho, Tle1, 2, 3, and 4, act as transcriptional corepressors and are recruited by transcription factors containing an eh1 or WRPW/Y domain. Many transcription factors critical to pancreas development contain a Gro/TLE interaction domain and several have been shown to require Gro/TLE interactions for proper function during neuronal development. However, a detailed analysis of the expression patterns of the Gro/TLE proteins in pancreas development has not been performed. Moreover, little is known about the ability of Gro/TLE proteins to interact with transcription factors in the pancreas.

Results: We describe the expression of Gro/TLE family members, and of 34 different transcription factors that contain a Gro/TLE interaction motif, in the pancreas utilizing nine SAGE libraries created from the developing and adult pancreas, as well as the GenePaint database. Next, we show the dynamic expression of Tle1, 2, 3, 4, 5 and 6 during pancreas development by qRT-PCR. To further define the cell-type specificity of the expression of these proteins we use immunofluorescence to co-localize them with Pdx1 at embryonic day 12.5 (E12.5), Ngn3 at E14.5, Pdx1, Nkx2-2, Insulin, Glucagon, Pancreatic polypeptide and Somatostatin at E18.5, as well as Insulin and Glucagon in the adult. We then show that Tle2 can interact with Nkx2-2, Hes1, Arx, and Nkx6-1 which are all critical factors in pancreas development. Finally, we demonstrate that Tle2 modulates the repressive abilities of Arx in a beta-cell line.

Conclusion: Although Tle1, 2, 3, and 4 show overlapping expression in pancreatic progenitors and in the adult islet, the expression of these factors is restricted to different cell types during endocrine cell maturation. Of note, Tle2 and Tle3 are co-expressed with Gro/TLE interaction domain containing transcription factors that are essential for endocrine pancreas development. We further demonstrate that Tle2 can interact with several of these factors and that Tle2 modulate Arx's repressive activity. Taken together our studies suggest that Gro/TLE proteins play a role in the repression of target genes during endocrine cell specification.

Show MeSH