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Accelerated Proliferation and Differential Global Gene Expression in Pancreatic Islets of Five-Week-Old Heterozygous Men1 Mice: Men1 Is a Haploinsufficient Suppressor
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences. Uppsala University, Science for Life Laboratory, SciLifeLab. (Endokrin tumörbiologi)
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology. Uppsala University, Science for Life Laboratory, SciLifeLab. (Endokrin tumörbiologi)
Uppsala University, Science for Life Laboratory, SciLifeLab. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Endocrine Surgery.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences. Uppsala University, Science for Life Laboratory, SciLifeLab. (Endokrin tumörbiologi)
2012 (English)In: Endocrinology, ISSN 0013-7227, E-ISSN 1945-7170, Vol. 153, no 6, 2588-2598 p.Article in journal (Refereed) Published
Abstract [en]

Individuals carrying heterozygous (hz) MEN1 (Multiple Endocrine Neoplasia Syndrome Type 1) germ line mutations develop endocrine tumors as a result of somatic loss of the wild-type (wt) allele. However, endocrine cell proliferation has been observed despite wt allele retention, indicating haploinsufficiency. To study downstream molecular effects of the hz haplotype, a germ line Men1 hz mouse model was used to explore differences in global endocrine pancreatic gene expression. Because islet cells of 5-wk-old hz mice express Menin from the retained wt Men1 allele, these were isolated after collagenase digestion of the pancreas, and used for global gene expression array. Wild-type littermates were used for comparison. Array findings were corroborated by quantitative PCR, Western blotting, in situ proximity ligation assay, and immunohistochemistry. The hz islets show increased proliferation: the Ki-67 index was twice as high as in wt islets (3.48 vs. 1.74%; P = 0.024). The microarray results demonstrated that several genes were differentially expressed. Some selected genes were studied on the protein level, e.g. the cytoskeletal regulator myristoylated alanine-rich protein kinase C substrate (Marcks) was significantly less expressed in hz islets, using in situ proximity ligation assay and Western blotting (P < 0.001 and P < 0.01, respectively). Further, gene ontology analysis showed that genes with higher mRNA expression in the hz endocrine pancreas were associated with e.g. chromatin maintenance and apoptosis. Lower mRNA was observed for genes involved in growth factor binding. In conclusion, despite retained Menin expression, proliferation was accelerated, and numerous genes were differentially expressed in the endocrine pancreas of 5-wk-old hz Men1 mice, corroborating the hypothesis that MEN1 is a haploinsufficient suppressor.

Place, publisher, year, edition, pages
2012. Vol. 153, no 6, 2588-2598 p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:uu:diva-174062DOI: 10.1210/en.2011-1924ISI: 000304370700011PubMedID: 22492302OAI: oai:DiVA.org:uu-174062DiVA: diva2:526214
Available from: 2012-05-10 Created: 2012-05-10 Last updated: 2017-12-07Bibliographically approved
In thesis
1. The MEN 1 Pancreas: Tumor Development and Haploinsufficiency
Open this publication in new window or tab >>The MEN 1 Pancreas: Tumor Development and Haploinsufficiency
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Multiple Endocrine Neoplasia Type I Syndrome (MEN 1) is a monogenic autosomal dominantly inherited cancer syndrome caused by a heterozygous loss of the MEN1 gene, predisposing for endocrine cell proliferation and tumor formation. MEN 1 carriers classically develop tumors in endocrine organs; the parathyroids, the endocrine pancreas, and the pituitary. Other organs, endocrine and non-endocrine, may also be affected. The most common cause of death in MEN 1 is pancreatic endocrine tumor (PNET), which exhibit inactivation of both MEN1 alleles. The increased proliferation prior to loss of the wild-type allele indicates haploinsufficiency, and little is known concerning the mechanisms behind MEN 1 PNET development. The MEN1 protein, menin, lacking homology with other known proteins, is involved in several aspects of transcriptional regulation and chromatin organization.

We report differential expression and subcellular localization of transcription factors important in pancreatic development, in human and mouse MEN 1 pancreas, compared to non-MEN 1 pancreas. A predominantly cytoplasmic localization of Neurogenin3 and NeuroD1 was observed in tumors as well as in MEN 1 non-tumorous pancreas.

Notch signaling factor expression and localization were examined in the pancreas of a heterozygous Men1 mouse model, and compared with that of wild-type littermates. Nuclear Hes1 was lost in tumors, concomitant to weaker Notch1 NICD expression, and further, analyzed using qPCR, it was shown that Notch1 was less expressed in heterozygous islets compared to wild-type islets.

Performing a global gene expression array, we identified differential gene expression in five-week-old heterozygous Men1 mouse islets, compared to islets from wild-type littermates. The array results for a subset of the differentially regulated genes were corroborated using qPCR, western blotting and in situ PLA. We additionally observed significantly accelerated proliferation in islets from young heterozygous animals.

It is often problematic to determine prognosis for individual patients with PNET. This is especially true in the group of patients with well differentiated endocrine carcinomas. In the absence of metastases, morphological signs of malignancy are frequently lacking. We evaluated the expression of nuclear and cytoplasmic survivin in a clinically characterized patient material (n=111), and a high nuclear survivin expression proved to be a significant negative prognostic factor for survival.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. 69 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 792
Keyword
MEN 1, PNET, tumor development, haploinsufficiency, survivin
National Category
Cancer and Oncology Endocrinology and Diabetes
Research subject
Endocrinology and Diabetology
Identifiers
urn:nbn:se:uu:diva-175033 (URN)978-91-554-8415-6 (ISBN)
Public defence
2012-09-28, Enghoffsalen, Ingång 50, Akademiska Sjukhuset, UPPSALA, 13:15 (English)
Opponent
Supervisors
Available from: 2012-08-31 Created: 2012-05-31 Last updated: 2013-01-22Bibliographically approved

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Lejonklou, Margareta HBarbu, AndreeaStålberg, PeterSkogseid, Britt

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