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Normal proliferation and tumorigenesis but impaired pancreatic function in mice lacking the cell cycle regulator sei1.

Fernandez-Marcos PJ, Pantoja C, Gonzalez-Rodriguez A, Martin N, Flores JM, Valverde AM, Hara E, Serrano M - PLoS ONE (2010)

Bottom Line: Sei1- fibroblasts did not show abnormalities regarding proliferation or susceptibility to neoplastic transformation, nor did we observe defects on Cdk4 complexes or E2f activity.These defects were associated to nuclear accumulation of the cell-cycle inhibitors p21(Cip1) and p27(Kip1) in islet cells.We conclude that Sei1 plays an important role in pancreatic beta-cells, which supports a functional link between Sei1 and the core cell cycle regulators specifically in the context of the pancreas.

View Article: PubMed Central - PubMed

Affiliation: Tumor Suppression Group, Spanish National Cancer Research Centre (CNIO), Madrid, Spain.

ABSTRACT
Sei1 is a positive regulator of proliferation that promotes the assembly of Cdk4-cyclin D complexes and enhances the transcriptional activity of E2f1. The potential oncogenic role of Sei1 is further suggested by its overexpression in various types of human cancers. To study the role of Sei1, we have generated a mouse line deficient for this gene. Sei1- fibroblasts did not show abnormalities regarding proliferation or susceptibility to neoplastic transformation, nor did we observe defects on Cdk4 complexes or E2f activity. Sei1- mice were viable, did not present overt pathologies, had a normal lifespan, and had a normal susceptibility to spontaneous and chemically-induced cancer. Pancreatic insulin-producing cells are known to be particularly sensitive to Cdk4-cyclin D and E2f activities, and we have observed that Sei1 is highly expressed in pancreatic islets compared to other tissues. Interestingly, Sei1- mice present lower number of islets, decreased beta-cell area, impaired insulin secretion, and glucose intolerance. These defects were associated to nuclear accumulation of the cell-cycle inhibitors p21(Cip1) and p27(Kip1) in islet cells. We conclude that Sei1 plays an important role in pancreatic beta-cells, which supports a functional link between Sei1 and the core cell cycle regulators specifically in the context of the pancreas.

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Pancreatic islets in Sei1- mice.(A) Levels of mRNA expression of the Sertad family members Sei1, Sertad2 and Sertad3, as well as, the pancreatic islet gene Kir6.2, were measured using qRT-PCR in total mRNA from isolated pancreatic islets of wt (n = 4) and Sei1- (n = 2) male mice. (B–F) Paraffin sections of pancreas (n = 4 per genotype) of the indicated genotypes were stained with antibodies against insulin (B and C), p27Kip1 (D) or p21Cip1 (E). (B) Number of islets relative to the total area of the pancreas. (C) Ratio between the β-cell islet area and the total pancreas area. (D) p27Kip1- or (E) p21Cip1-positive nuclei relative to total β-cell area. (F) Representative examples of the indicated stainings. The dotted lines mark the limits of the pancreatic islets. Values correspond to the average and s.d. Statistical differences were determined by the Student's t-test; *p<0.05; **p<0.01; and ***p<0.001.
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pone-0008744-g008: Pancreatic islets in Sei1- mice.(A) Levels of mRNA expression of the Sertad family members Sei1, Sertad2 and Sertad3, as well as, the pancreatic islet gene Kir6.2, were measured using qRT-PCR in total mRNA from isolated pancreatic islets of wt (n = 4) and Sei1- (n = 2) male mice. (B–F) Paraffin sections of pancreas (n = 4 per genotype) of the indicated genotypes were stained with antibodies against insulin (B and C), p27Kip1 (D) or p21Cip1 (E). (B) Number of islets relative to the total area of the pancreas. (C) Ratio between the β-cell islet area and the total pancreas area. (D) p27Kip1- or (E) p21Cip1-positive nuclei relative to total β-cell area. (F) Representative examples of the indicated stainings. The dotted lines mark the limits of the pancreatic islets. Values correspond to the average and s.d. Statistical differences were determined by the Student's t-test; *p<0.05; **p<0.01; and ***p<0.001.

Mentions: To further reinforce a role of Sei1 in β-cells, we evaluated the expression of Sei1, Sertad2 and Sertad3 in isolated pancreatic islets (being Sertad2 the closest paralog of Sei1). Interestingly, the mRNA levels of Sei1, Sertad2 and Sertad3 were similar in wt islets, and no compensatory changes in Sertad2 or Sertad3 were observed in Sei1- islets (Fig. 8A). As a control for the isolation of islets, we detected the transcript for Kir6.2 (also known as Kcnj11), which is expressed in the islets but not in the exocrine pancreas [24] and no changes were observed associated to the status of Sei1 (Fig. 8A). Of note, compared with a large set of tissues (a total of 17 tissues), islets presented the highest levels of Sei1 expression (Suppl. Fig. S1). Moreover, the ratio between the levels of Sei1 and Sertad2 mRNAs was also maximal in the islets (Suppl. Fig. S1). Therefore, it can be concluded that the levels of Sei1 in islets are uniquely high.


Normal proliferation and tumorigenesis but impaired pancreatic function in mice lacking the cell cycle regulator sei1.

Fernandez-Marcos PJ, Pantoja C, Gonzalez-Rodriguez A, Martin N, Flores JM, Valverde AM, Hara E, Serrano M - PLoS ONE (2010)

Pancreatic islets in Sei1- mice.(A) Levels of mRNA expression of the Sertad family members Sei1, Sertad2 and Sertad3, as well as, the pancreatic islet gene Kir6.2, were measured using qRT-PCR in total mRNA from isolated pancreatic islets of wt (n = 4) and Sei1- (n = 2) male mice. (B–F) Paraffin sections of pancreas (n = 4 per genotype) of the indicated genotypes were stained with antibodies against insulin (B and C), p27Kip1 (D) or p21Cip1 (E). (B) Number of islets relative to the total area of the pancreas. (C) Ratio between the β-cell islet area and the total pancreas area. (D) p27Kip1- or (E) p21Cip1-positive nuclei relative to total β-cell area. (F) Representative examples of the indicated stainings. The dotted lines mark the limits of the pancreatic islets. Values correspond to the average and s.d. Statistical differences were determined by the Student's t-test; *p<0.05; **p<0.01; and ***p<0.001.
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Related In: Results  -  Collection

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pone-0008744-g008: Pancreatic islets in Sei1- mice.(A) Levels of mRNA expression of the Sertad family members Sei1, Sertad2 and Sertad3, as well as, the pancreatic islet gene Kir6.2, were measured using qRT-PCR in total mRNA from isolated pancreatic islets of wt (n = 4) and Sei1- (n = 2) male mice. (B–F) Paraffin sections of pancreas (n = 4 per genotype) of the indicated genotypes were stained with antibodies against insulin (B and C), p27Kip1 (D) or p21Cip1 (E). (B) Number of islets relative to the total area of the pancreas. (C) Ratio between the β-cell islet area and the total pancreas area. (D) p27Kip1- or (E) p21Cip1-positive nuclei relative to total β-cell area. (F) Representative examples of the indicated stainings. The dotted lines mark the limits of the pancreatic islets. Values correspond to the average and s.d. Statistical differences were determined by the Student's t-test; *p<0.05; **p<0.01; and ***p<0.001.
Mentions: To further reinforce a role of Sei1 in β-cells, we evaluated the expression of Sei1, Sertad2 and Sertad3 in isolated pancreatic islets (being Sertad2 the closest paralog of Sei1). Interestingly, the mRNA levels of Sei1, Sertad2 and Sertad3 were similar in wt islets, and no compensatory changes in Sertad2 or Sertad3 were observed in Sei1- islets (Fig. 8A). As a control for the isolation of islets, we detected the transcript for Kir6.2 (also known as Kcnj11), which is expressed in the islets but not in the exocrine pancreas [24] and no changes were observed associated to the status of Sei1 (Fig. 8A). Of note, compared with a large set of tissues (a total of 17 tissues), islets presented the highest levels of Sei1 expression (Suppl. Fig. S1). Moreover, the ratio between the levels of Sei1 and Sertad2 mRNAs was also maximal in the islets (Suppl. Fig. S1). Therefore, it can be concluded that the levels of Sei1 in islets are uniquely high.

Bottom Line: Sei1- fibroblasts did not show abnormalities regarding proliferation or susceptibility to neoplastic transformation, nor did we observe defects on Cdk4 complexes or E2f activity.These defects were associated to nuclear accumulation of the cell-cycle inhibitors p21(Cip1) and p27(Kip1) in islet cells.We conclude that Sei1 plays an important role in pancreatic beta-cells, which supports a functional link between Sei1 and the core cell cycle regulators specifically in the context of the pancreas.

View Article: PubMed Central - PubMed

Affiliation: Tumor Suppression Group, Spanish National Cancer Research Centre (CNIO), Madrid, Spain.

ABSTRACT
Sei1 is a positive regulator of proliferation that promotes the assembly of Cdk4-cyclin D complexes and enhances the transcriptional activity of E2f1. The potential oncogenic role of Sei1 is further suggested by its overexpression in various types of human cancers. To study the role of Sei1, we have generated a mouse line deficient for this gene. Sei1- fibroblasts did not show abnormalities regarding proliferation or susceptibility to neoplastic transformation, nor did we observe defects on Cdk4 complexes or E2f activity. Sei1- mice were viable, did not present overt pathologies, had a normal lifespan, and had a normal susceptibility to spontaneous and chemically-induced cancer. Pancreatic insulin-producing cells are known to be particularly sensitive to Cdk4-cyclin D and E2f activities, and we have observed that Sei1 is highly expressed in pancreatic islets compared to other tissues. Interestingly, Sei1- mice present lower number of islets, decreased beta-cell area, impaired insulin secretion, and glucose intolerance. These defects were associated to nuclear accumulation of the cell-cycle inhibitors p21(Cip1) and p27(Kip1) in islet cells. We conclude that Sei1 plays an important role in pancreatic beta-cells, which supports a functional link between Sei1 and the core cell cycle regulators specifically in the context of the pancreas.

Show MeSH
Related in: MedlinePlus