Vas Nunez, R.P. (Roel) (2016) Men1L/L/ RIP2-CreER: a beta-cell specific mouse model : for pancreatic neuroendocrine tumours under temporal control. thesis, Medicine.
Full text available on request.Abstract
Background Multiple endocrine neoplasia type 1 (MEN1) is a hereditary autosomal dominant syndrome characterised by the occurrence of pancreatic, pituitary and parathyroid neuroendocrine tumours (NETs). It is caused by mutations of the gene MEN1, which codes for the tumour suppressor protein menin. MEN1 mutations are also found in ~40% of sporadic pancreatic NETs. The high mortality rate is principally caused by pancreatic NETs, which are often diagnosed in a metastatic stage and therefore not curable by surgery. Mouse models are important in elucidating mechanisms of MEN1 tumourigenesis and in exploring novel tumour biomarkers and treatments. However, existing models have limitations. Conventional models with germline heterozygous Men1 knockout lack mechanisms of exerting both spatial and temporal control over tumour development. Conditional models with germline homozygous Men1 knockout restricted to specific tissue types use a Cre-LoxP system and a targeted promoter (e.g. UBC9 targeting the whole pancreas and RIP2 targeting pancreatic -cells). Conditional models are of limited use in mechanistic studies of early tumourigenic events, as Men1 knockout occurs from conception and analysis is only feasible in a later, post-embryonic, stage. Temporal control of tissue specific knockout of Men1 has been acquired by fusing a modified oestrogen receptor that selectively binds tamoxifen to Cre constructs. This has been demonstrated earlier using a Men1L/L/UBC9-CreER model, showing islet hyperplasia and increased -cell proliferation one month following tamoxifen administration. Whereas this model is specific for the whole pancreas, for this study MenL/L mice were bred with RIP2-CreER mice to develop a pancreatic NET model under temporal control that is -cell-specific. This study aims to validate its use. Methods We characterised pancreata of 13 male and 16 female Men1L/L/RIP2-CreER mice, harvested at 3.5-4.0, 5.0-5.5, 5.9-6.5 and 7.5-8.5 months of age, following 3 days of tamoxifen administration in the diet at 12-14 weeks of age. Control mice (8 male and 13 female) did not receive tamoxifen. A marker for proliferation, 5-bromo-2-deoxyuridine (BrdU), was administered via the drinking water of both groups prior to culling. Sections of the pancreata were characterised by immunostaining for expression of menin, insulin, glucagon and BrdU. Results We show that 2-4 weeks after tamoxifen treatment in Men1L/L/RIP2-CreER mice menin was largely retained and islets were not significantly enlarged. Conversely, 2.0-2.5 months and longer after tamoxifen administration, menin was largely lost in all islets, the islet area increased >4.2-fold (p<0.005) and -cell proliferation increased >2,5-fold, (p<0.013), whilst -cells proliferation remained unchanged or decreased. No significant differences were observed between males and females. Qualitative analysis confirmed that all tumours were insulin-expressing. Conclusion Men1L/L/RIP2-CreER mice develop insulin-expressing NETs and provide a viable model for temporally controlled -cell-specific Men1 knockout.
| Item Type: | Thesis (Thesis) |
|---|---|
| Supervisor name: | Faculty supervisor: and J.C. Legdeur, Dr. Marie-Cecile Department of Oncology and Ha |
| Supervisor name: | Operational supervisor: and Thakker, Prof. Rajesh V. MD ScD FRCP FRCPath FMedSci FRS |
| Faculty: | Medical Sciences |
| Date Deposited: | 25 Jun 2020 10:40 |
| Last Modified: | 25 Jun 2020 10:40 |
| URI: | https://umcg.studenttheses.ub.rug.nl/id/eprint/138 |
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