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. 2010 Jun 16;151(8):4024–4030. doi: 10.1210/en.2009-1251

Multiple Endocrine Neoplasia Type 1 Deletion in Pancreatic α-Cells Leads to Development of Insulinomas in Mice

H-C Jennifer Shen 1, Kris Ylaya 1, Klaus Pechhold 1, Arianne Wilson 1, Asha Adem 1, Stephen M Hewitt 1, Steven K Libutti 1
PMCID: PMC2940531  PMID: 20555035

Abstract

The pancreatic α- and β-cells are critical components in regulating blood glucose homeostasis via secretion of glucagon and insulin, respectively. Both cell types are typically localized in the islets of Langerhans. However, little is known about the roles of paracrine interactions that contribute to their physiological functions. The lack of suitable cell lines to study α- and β-cells interactions have led us to develop an α-cell-specific Cre-expressing transgenic line utilizing a glucagon promoter sequence, the Glu-Cre transgenic mouse. Here, we demonstrate that the Glu-Cre could specifically and efficiently excise floxed target genes in adult islet α-cells. We further showed that deletion of the tumor suppressor gene, multiple endocrine neoplasia type 1 (Men1), in α-cells led to tumorigenesis. However, to our surprise, the lack of Men1 in α-cells did not result in glucagonomas but rather β-cell insulinomas. Because deletion of the Men1 alleles was only present in α-cells, our data suggested that cross communication between α- and β-cells contributes to tumorigenesis in the absence of Men1. Together, we believed that the new model systems described here will allow future studies to decipher cellular interactions between islet α- and β-cells in a physiological context.

Deficiency of menin protein in islet α-cells unexpectedly leads to β-cell insulinomas in mice, providing a model to better understand cellular interactions between α- and β-cells.

One major function of the pancreas is to regulate blood glucose homeostasis via insulin and glucagon hormones produced in the islets of Langerhans. Failure to maintain glucose homeostasis can lead to disease states, such as hypoglycemia, hyperglycemia, and diabetes mellitus. Specifically, oversecretion of insulin by the β-cells in pancreatic islets can cause life-threatening hypoglycemia, whereas insulin-production insufficiency leads to glucose intolerance and often rapidly progresses toward overt hyperglycemia and diabetes mellitus. Thus, the insulin-secreting β-cells have received much focus in published research, due in large part to their role in the pathogenesis of diabetes. However, glucagon-secreting α-cells, somatostatin-secreting δ-cells, and pancreatic polypeptide-secreting cells all coexist with β-cell in the islets of Langerhans, forming effective functional units. However, much is to be learned about the functions of these other cells types, especially the glucagon secreting α-cells, which cooperate with β-cells in maintaining normal blood glucose levels within a very small range (1).

Anatomically, the different hormone-secreting endocrine cells are scattered throughout the human islets. The close proximity of β-cells to all other endocrine cells has suggested that unique paracrine interactions are important for islet functions (2). In contrast to human islets, rodent β-cells are localized in the center of islets, whereas other endocrine cells are arranged on the outside, forming a mantle (2). It is thus unclear if paracrine interactions among the different islet cells involve islet microcirculation and/or direct cell-cell interactions (2,3). Tools developed to specifically target each islet cell subtype would undoubtedly help to reveal unidentified characteristics of the endocrine pancreas.

To further our understanding of α-cell-specific roles during development and pathological states, we described here an α-cell-specific Cre-expressing transgenic line, the Glu-Cre mouse. We demonstrated that Glu-Cre can efficiently excise alleles flanked by loxP sites in approximately 83% of α-cells in the adult pancreas. Using the Glu-Cre transgenic mice, we performed proof-of-principle experiments to inactivate a known tumor suppressor gene, multiple endocrine neoplasia type 1 (Men1) (4,5,6,7). The objective was to determine whether tumorigenesis would occur in islet α-cell, given that inactivation of Men1 in specific endocrine cell types has led to the development of insulinomas, prolactinomas, and parathyroid neoplasia (8,9,10,11). To our surprise, inactivation of Men1 in glucagon-producing α-cells led to β-cell insulinomas. Together, these results suggested a novel role for α-cells in regulating β-cell proliferation and provided new experimental platforms for dissecting the characteristics of endocrine pancreas.

Materials and Methods

Ethics statement

The National Cancer Institute is accredited by Association for Assessment and Accreditation of Laboratory Animal Care International and follows the Public Health Service Policy for the Care and Use of Laboratory Animals. Animal care was provided in accordance with the procedures outlined in the Guide for Care and Use of Laboratory Animals from the National Research Council. All animal experiments were conducted in accordance with National Institutes of Health approved protocols and guidelines.

Animals and genotyping

The Glu-Cre transgenic mice were generated as described (12). Tissue expression of Glu-Cre was evaluated in offspring from crosses of the Glu-Cre transgenic mice with Z/AP reporter mice (13). All mice were genotyped by PCR using DNA isolated from tail snips or fluorescence-activated cell sorted (FACS)-purified endocrine islet cell subsets. Genotyping for the Glu-Cre transgene, Men1 deleted and floxed alleles was performed as previously described (12,14).

Histological analysis

The pancreatic tissue was processed for frozen histological analysis by embedding tissues in Tissue-Tek OCT freezing medium and by formalin-fixed paraffin embedding (FFPE). Frozen (10–20 μm) and FFPE pancreas sections (5 μm) were routinely stained with Mayer’s hematoxylin and eosin for histopathological analysis. For all histological analysis, Glu-Cre;Men1 f/f mice were compared with age-matched control genotypes of Glu-Cre, Men1 f/f, Men1 f/+, and Glu-Cre;Men1 f/+ mice.

For immunostaining, polyclonal guinea pig antiswine insulin (1:500; Dako, Carpinteria, CA), rabbit antihuman glucagon (1:500; Dako), rabbit anti-Cre recombinase (1:500; Covance, Emeryville, CA), and rabbit antimenin (1:150; Bethyl Laboratories, Montgomery, TX) were used. For immunohistochemical staining, FFPE sections were incubated on tissue sections either 1 h at room temperature or overnight at 4 C after blocking with the ready-to-use serum-free protein block (Dako) and 3% hydrogen peroxide. Antigen retrival was performed in 10 mm citrate buffer (pH 6.0) for 7.5 min at 125 C. The EnVision+ system (Dako) followed by DAB+ chromogen (Dako) addition was used for antigen detection. Sections were counterstained in Mayer’s hematoxylin, mounted and photographed using a Zeiss Axioplan 2ie, outfitted with an Axiocam HRc digital camera (Carl Zeiss MicroImaging, Thornwood, NY). Immunofluorescent staining was performed as described and imaged using a Zeiss Axiovert fluorescence microscope (14). Alkaline phosphotase (AP) stain was performed on frozen sections as described (13). Nuclear fast red (Dako) was used to counter stain for AP sections. For image quantification, multiple and adjacent serial sections were stained for glucagon and AP to approximate the percentage of glucagon-positive α-cells that are also positive for AP.

Islet isolation, dissociation, and flow cytometry

Pancreatic islet cells were isolated as described previously (12). Briefly, pancreata were digested with collagenase and gradient centrifuged. Hand-picked islets were dissociated into single cell suspensions, fixed, and stained for insulin and glucagon before being sorted by a FACSAria cell sorter (BD Biosciences, San Jose, CA). No preferential loss of a particular cell type during islet cell isolation process was observed (15). Genomic DNA was extracted from sorted islet cell subsets and subjected to genotyping. For each animal that underwent islet cell sorting procedure, the number of insulin-positive cells plus the number of glucagon-positive cells was considered the total number of islet cells. The percentage of glucagon-positive cells was determined by dividing the number of glucagon-positive cells by the total number of islet cells for each animal.

Insulin and glucose measurements

Plasma insulin levels were determined as described previously (14). For glucose tolerance tests, mice were fasted for 15 h before receiving ip injection of sterile-filtered d-glucose (2 g/kg of fasted body weight) at time 0. Blood glucose values were measured immediately before and 15, 30, 60, and 120 min after glucose injections. Blood was collected via a tail snip, and a glucometer (Ascensia Contour; Bayer HealthCare, Mishawaka, IN) was used to determine the blood glucose level.

Results

Generation of α-cell-specific knockout of Men1 in endocrine pancreas

The α-cell-specific Cre transgenic line (Glu-Cre) was generated using a rat glucagon promoter sequence to direct Cre recombinase expression (12). To determine the Cre recombinase expression in Glu-Cre transgenic mice, we used an antibody against Cre recombinase and bred the Glu-Cre transgenic line with the Z/AP reporter mice (13). Expression of Cre recombinase was absent in Glu-Cre;Z/AP pups at the time of birth (postnatal d 1) (data not shown) but was detected in α-cells and not in other cells of the islets by immunostaining in Glu-Cre;Men1 f/+ mice at 6 wk of age (Fig. 1A). The ability of Cre to excise floxed alleles was confirmed when positive alkaline phosophotase staining was observed in α-cells of Glu-Cre;Z/AP pancreas at 5 months of age (Fig. 1B). We further determined that the Glu-Cre line efficiently targets α-cells, because approximately 83% of glucagon-positive cells expressed the reporter product, AP by histochemical staining.

Figure 1.

Figure 1

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Histological analyses of Cre recombinase expression in pancreatic islets. A, Immunofluorescent staining of Cre recombinase using a Cre antibody in Glu-Cre;Men1 f/+ mice at 6 wk of age. Left, Insulin staining (green) was used to identify islet, and glucagon (red) was used to confirm presence of α-cells. Right, Closely adjacent frozen section was used to identify Cre-positive cells (red) in the same islet, 4′,6-diamidino-2-phenylindole (DAPI) (blue) nuclear stain was used to visualize the islet morphology. B, Using the Glu-Cre;Z/AP reporter mice at 5 months of age, AP and glucagon (dark brown) staining of islets are shown, with insets indicated zoom-in positive staining for each.

Inactivation of Men1 in endocrine cells has been shown to develop cell type-specific endocrine tumors in several mouse models of MEN1 (8,9,10,11). Thus, we hypothesized that loss of Men1 in glucagon-producing α-cells might lead to glucagonomas, as documented in some MEN1 patients (6,7,16). The Glu-Cre transgenic mice were next bred with mice in which exons 3 and 8 of the Men1 alleles were flanked by loxP sites (flox or f) (17,18). At the time of weaning (3–4 wk after birth), the expected Mendelian frequencies for all genotypes were obtained (data not shown). Deletion of the Men1 alleles was confirmed using genomic DNA isolated from FACS-purified glucagon-expressing cells at 4 months of age (Fig. 2A). However, no obvious histological abnormalities were observed in mouse pancreases lacking Men1 in α-cells (Glu-Cre;Men1 f/f) at this age. We further confirmed the lack of menin protein expression in glucagon-positive cells of Glu-Cre;Men1 f/f pancreas (Fig. 2B) but not in control Glu-Cre pancreas (data not shown) by immunohistological staining. At 13–14 months of age, histological analysis of Glu-Cre;Men1 f/f (n = 6) pancreas revealed either hyperplastic islets (n = 4) or large tumors (n = 2), when compared with age-matched control genotypes (wild type, n = 1; Glu-Cre, n = 2; Men1 f/+ and Men1 f/f, n = 5) (Fig. 2C).

Figure 2.

Figure 2

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Generation of Glu-Cre;Men1 f/f mice. A, Deletion of the Men1 alleles in 4-month-old mouse pancreas. Genotyping PCR using genomic DNA isolated from pancreatic endocrine insulin-positive β-cells (I) and glucagon-positive α-cells (G). The presence of deleted Men1 allele (del; 638 bp) was only detected in Glu-Cre;Men1 f/f, but not in wild type (Wt) and Men1 f/f pancreas. Positive (pos) and negative (neg) controls are as indicated. B, Glucagon and menin protein expression in Glu-Cre;Men1 f/f islets at 13 months of age by immunohistochemical staining. Dark brown color indicated positive cytoplasmic staining for glucagon (left) and nuclear staining for menin (middle, noting nonspecific light brown staining in both endocrine and exocrine tissues). Negative control (neg. control) is shown to demonstrate background staining without glucagon and menin antibodies. Arrowheads pointed to examples of glucagon-positive cells lacking menin, in which cell nuclei lack the dark brown positive menin staining in the middle panel. C, Hematoxylin and eosin staining of representative Glu-Cre;Men1 f/f animals with hyperplastic islets (i) and tumors (iv) at 13–14 months of age. Normal-sized islets (ii and v) are indicated by arrows, whereas hyperplastic islets (iii) and insulinomas tumors (vi) filled with blood islands are indicated by arrowheads.

Analysis of Glu-Cre;Men1 f/f mice

MEN1 patients are predisposed to develop various pancreatic neuroendocrine tumors, such as gastrinomas, insulinomas, and glucagonomas (6,7). Because insulin and glucagon are the two major hormones secreted by the endocrine pancreas, we next performed immunohistochemical staining against insulin and glucagon to determine the type of neuroendocrine tumors found in Glu-Cre;Men1 f/f animals. All normal-sized islets, hyperplastic islets, and tumors were stained positive for insulin (Fig. 3, A–D). As expected, glucagon-positive α-cells were found to localize at the outer ring of pancreatic islets but appeared to be hyperproliferative in some islets (Fig. 3F). In contrast, glucagon-positive cells appeared to be scarcely and randomly localized within hyperplastic islets or insulinomas (Fig. 3, G and H).

Figure 3.

Figure 3

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Representative immunohistological staining of insulin (A–D) and glucagon (E–H) on Glu-Cre;Men1 f/f mouse pancreas. The entire pancreas section stained for insulin (A) and glucagon (E) is shown. Scale bars, 0.5 mm. B–D and F–H, Magnified areas of A and E. Scale bars, 0.05 mm, except for D and H, where scale bars, 0.1 mm. For the glucagon staining, nonspecific light brown background color was observed in some islets.

Our observation that insulinomas developed due to the loss of Men1 in glucagon-secreting α-cells led us to hypothesize that either α-cell trans-differentiate into β-cells before tumor development or paracrine signaling between α- and β-cells contributed to β-cells hyperplasia. To test our hypothesis, we next isolated α- and β-cells by FACS when Glu-Cre;Men1 f/f animals were at 14–16 months of age. Using genomic DNA extracted from α- and β-cells, we were able to detect deletion of the Men1 alleles in α-cells but not in β-cells, suggesting that α-cells did not trans-differentiate into β-cells (Fig. 4A). Interestingly, we noted a slight increase in the number of glucagon cells in Glu-Cre;Men1 f/f mice when compared with age-matched control genotype (Fig. 4B). Physiologically, the Glu-Cre;Men1 f/f mice demonstrated normal glucose control, because their plasma insulin levels and glucose tolerance were comparable with control genotypes (please see Supplemental Figs. 1 and 2 and Supplemental Table 1, published on The Endocrine Society’s Journals Online web site at http://endo.endojournals.org). Together, we provided evidence to suggest that loss of Men1 in pancreatic α-cells leads to β-cell insulinomas via paracrine interactions.

Figure 4.

Figure 4

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Analysis of 14- to 16-month-old Glu-Cre;Men1 f/f pancreatic islets. A, Deletion of the Men1 alleles in islet glucagon-positive α-cells (G), but not in insulin-positive β-cells (I), in two Glu-Cre;Men1 f/f mice. Control genotypes (Glu-Cre and Men1 f/+), positive (pos) and negative (neg) controls are as indicated. B, Slight increase in the percentage of glucagon cells in pancreatic islets of Glu-Cre;Men1 f/f mice (n = 4), when compare with age-matched Glu-Cre mice (n = 2).

Discussion

MEN1 patients are known to develop multiple endocrine tumors primarily affecting parathyroid, pituitary, and pancreatic islets (6,7). Several mouse models of MEN1 have been generated to better understand the etiology of MEN1 tumor development (18,19,20). Specifically in the pancreas, we and others have inactivated Men1 in specific cells of endocrine and exocrine pancreas, and most of the pancreatic lesions developed in these conditional knockout mice were pancreatic insulinomas (8,9,10,14). Surprisingly, the model described here targeting loss of Men1 alleles in islet α-cells also led to insulinomas. However, there is one major distinction, in that the tumors found in Glu-Cre;Men1 f/f mice were rare, perhaps one to two tumor nodules visible to naked eyes per mouse, in contrast to the high penetrance of islet tumors in other pancreatic mouse models of Men1. Together, these data suggested that perhaps menin, the protein product of Men1, is not a critical proliferation regulator for α-cell as it is for β-cells. Alternatively, other proliferation regulators present in α-cells, but less so in β-cells, could be compensating for the Men1 loss. The onset of Cre recombinase expression and the fact that α-cells only represent about 10% of islet cell population might also explain the tumor scarcity in Glu-Cre;Men1 f/f mice.

It remains to be determined how loss of the Men1 alleles in α-cell could lead to tumors of β-cell origin. Because α- and β-cells are functionally and anatomically associated with each other, we believe our data suggested that cross talk between α- and β-cells may contribute to this process. Given the onset of Cre recombinase expression in the Glu-Cre transgenic mice, the process is necessarily postnatal, after islet cells differentiated into distinct α- and β-cell types. However, given that not all islets in Glu-Cre;Men1 f/f became hyperplastic or formed tumors, we reasoned that additional genetic events need to occur to initiate tumorigenesis in the absence of menin. We further noted a slight increase in glucagon-positive α-cells in Glu-Cre;Men1 f/f pancreas. However, only a few glucagon-positive cells could be found in Glu-Cre;Men1 f/f insulinomas. We thus speculated that dynamic changes in α-cell numbers might be related to the regulation of β-cell proliferation. Recent development of innovative method to isolate and purify the few α-cells during the tumor progression in the Glu-Cre;Men1 f/f mouse model would help to precisely address this question (21). In addition, the use of specific makers for α- and β-cells, such as MafA and MafB, might help to better understand the interactions between these endocrine cells in this model system.

In contrast to our finding, a similar knockout of Men1 in glucagon cells by Lu et al. (22) provided plausible evidence to suggest that cell trans-differentiation was involved in islet tumor development. In this study, the authors used a Cre transgenic line that inactivated the Men1 alleles specifically in α-cells during embryogenesis (23,24) and observed that both glucagonomas and insulinomas development in these mice lacking menin in α-cells. Several lines of experiments further suggested that insulinoma tumors were derived from trans-differentiated glucagon-expressing cells. In this model system, tumors developed consistently, and onset of tumor formation was much earlier than the Glu-Cre;Men1 f/f described here. These major distinctions could be the result of the different Cre transgenic lines and different mouse strain used (25,26). Although the mechanistic pathway that led to tumor formation in our model system has yet to be determined, it is confirmatory that menin deficiency in α-cells eventually leads to insulinoma development.

In our model system, tumor latency and rarity would be the major challenges to overcome to delineate the molecular mechanisms involved. Nonetheless, our example of using Glu-Cre to delete Men1 is only one of potentially many that can expand our understanding of α-cells in a physiological context. In contrast to the only other α-cell-specific Cre-expressing mice (23,24), our Glu-Cre mice do not exhibit Cre expression in embryos, thus allowing deletion of the target gene after birth and avoidance of embryonic lethality if the target gene is essential for embryogenesis. Because α-cell is a critical component in the regulation of glucose homeostasis, this Glu-Cre transgenic line will provide an important tool to further our knowledge of α-cells and their interactions with other islet cells.

Supplementary Material

[Supplemental Data]
en.2009-1251_index.html (798B, html)

Acknowledgments

We thank Dr. S. M. Hewitt, members of the Tissue Array Research Program laboratory and Dr. J. Wiest for providing the space and resources to complete this project during the transition of Dr. S. K. Libutti’s laboratory move to the Albert Einstein College of Medicine.

Footnotes

This work was supported by funds from the Intramural Research Program of the National Institutes of Health, National Cancer Institute, Center for Cancer Research.

Disclosure Summary: The authors have nothing to disclose.

First Published Online June 16, 2010

Abbreviations: AP, Alkaline phosphotase; FACS, fluorescence-activated cell sorted; FFPE, formalin-fixed paraffin embedding; Men1, multiple endocrine neoplasia type 1.

References

  1. Gromada J, Franklin I, Wollheim CB 2007 α-Cells of the endocrine pancreas: 35 years of research but the enigma remains. Endocr Rev 28:84–116 [DOI] [PubMed] [Google Scholar]
  2. Cabrera O, Berman DM, Kenyon NS, Ricordi C, Berggren PO, Caicedo A 2006 The unique cytoarchitecture of human pancreatic islets has implications for islet cell function. Proc Natl Acad Sci USA 103:2334–2339 [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Bonner-Weir S, Orci L 1982 New perspectives on the microvasculature of the islets of Langerhans in the rat. Diabetes 31:883–889 [DOI] [PubMed] [Google Scholar]
  4. Chandrasekharappa SC, Guru SC, Manickam P, Olufemi SE, Collins FS, Emmert-Buck MR, Debelenko LV, Zhuang Z, Lubensky IA, Liotta LA, Crabtree JS, Wang Y, Roe BA, Weisemann J, Boguski MS, Agarwal SK, Kester MB, Kim YS, Heppner C, Dong Q, Spiegel AM, Burns AL, Marx SJ 1997 Positional cloning of the gene for multiple endocrine neoplasia-type 1. Science 276:404–407 [DOI] [PubMed] [Google Scholar]
  5. Lemmens I, Van de Ven WJ, Kas K, Zhang CX, Giraud S, Wautot V, Buisson N, De Witte K, Salandre J, Lenoir G, Pugeat M, Calender A, Parente F, Quincey D, Gaudray P, De Wit MJ, Lips CJ, Höppener JW, Khodaei S, Grant AL, Weber G, Kytölä S, Teh BT, Farnebo F, Thakker RV 1997 Identification of the multiple endocrine neoplasia type 1 (MEN1) gene. The European consortium on MEN1. Hum Mol Genet 6:1177–1183 [DOI] [PubMed] [Google Scholar]
  6. Marx S, Spiegel AM, Skarulis MC, Doppman JL, Collins FS, Liotta LA 1998 Multiple endocrine neoplasia type 1: clinical and genetic topics. Ann Intern Med 129:484–494 [DOI] [PubMed] [Google Scholar]
  7. Trump D, Farren B, Wooding C, Pang JT, Besser GM, Buchanan KD, Edwards CR, Heath DA, Jackson CE, Jansen S, Lips K, Monson JP, O'Halloran D, Sampson J, Shalet SM, Wheeler MH, Zink A, Thakker RV 1996 Clinical studies of multiple endocrine neoplasia type 1 (MEN1). QJM 89:653–669 [DOI] [PubMed] [Google Scholar]
  8. Bertolino P, Tong WM, Herrera PL, Casse H, Zhang CX, Wang ZQ 2003 Pancreatic β-cell-specific ablation of the multiple endocrine neoplasia type 1 (MEN1) gene causes full penetrance of insulinoma development in mice. Cancer Res 63:4836–4841 [PubMed] [Google Scholar]
  9. Biondi CA, Gartside MG, Waring P, Loffler KA, Stark MS, Magnuson MA, Kay GF, Hayward NK 2004 Conditional inactivation of the MEN1 gene leads to pancreatic and pituitary tumorigenesis but does not affect normal development of these tissues. Mol Cell Biol 24:3125–3131 [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Crabtree JS, Scacheri PC, Ward JM, McNally SR, Swain GP, Montagna C, Hager JH, Hanahan D, Edlund H, Magnuson MA, Garrett-Beal L, Burns AL, Ried T, Chandrasekharappa SC, Marx SJ, Spiegel AM, Collins FS 2003 Of mice and MEN1: insulinomas in a conditional mouse knockout. Mol Cell Biol 23:6075–6085 [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Libutti SK, Crabtree JS, Lorang D, Burns AL, Mazzanti C, Hewitt SM, O'Connor S, Ward JM, Emmert-Buck MR, Remaley A, Miller M, Turner E, Alexander HR, Arnold A, Marx SJ, Collins FS, Spiegel AM 2003 Parathyroid gland-specific deletion of the mouse Men1 gene results in parathyroid neoplasia and hypercalcemic hyperparathyroidism. Cancer Res 63:8022–8028 [PubMed] [Google Scholar]
  12. Shen HC, Adem A, Ylaya K, Wilson A, He M, Lorang D, Hewitt SM, Pechhold K, Harlan DM, Lubensky IA, Schmidt LS, Linehan WM, Libutti SK 2009 Deciphering von Hippel-Lindau (VHL/Vhl)-associated pancreatic manifestations by inactivating Vhl in specific pancreatic cell populations. PLoS One 4:e4897 [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Lobe CG, Koop KE, Kreppner W, Lomeli H, Gertsenstein M, Nagy A 1999 Z/AP, a double reporter for cre-mediated recombination. Dev Biol 208:281–292 [DOI] [PubMed] [Google Scholar]
  14. Shen HC, He M, Powell A, Adem A, Lorang D, Heller C, Grover AC, Ylaya K, Hewitt SM, Marx SJ, Spiegel AM, Libutti SK 2009 Recapitulation of pancreatic neuroendocrine tumors in human multiple endocrine neoplasia type I syndrome via Pdx1-directed inactivation of Men1. Cancer Res 69:1858–1866 [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Pechhold K, Zhu X, Harrison VS, Lee J, Chakrabarty S, Koczwara K, Gavrilova O, Harlan DM 2009 Dynamic changes in pancreatic endocrine cell abundance, distribution, and function in antigen-induced and spontaneous autoimmune diabetes. Diabetes 58:1175–1184 [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Bergman L, Boothroyd C, Palmer J, Grimmond S, Walters M, Teh B, Shepherd J, Hartley L, Hayward N 2000 Identification of somatic mutations of the MEN1 gene in sporadic endocrine tumours. Br J Cancer 83:1003–1008 [DOI] [PMC free article] [PubMed] [Google Scholar]
  17. Ma W, Tessarollo L, Hong SB, Baba M, Southon E, Back TC, Spence S, Lobe CG, Sharma N, Maher GW, Pack S, Vortmeyer AO, Guo C, Zbar B, Schmidt LS 2003 Hepatic vascular tumors, angiectasis in multiple organs, and impaired spermatogenesis in mice with conditional inactivation of the VHL gene. Cancer Res 63:5320–5328 [PubMed] [Google Scholar]
  18. Crabtree JS, Scacheri PC, Ward JM, Garrett-Beal L, Emmert-Buck MR, Edgemon KA, Lorang D, Libutti SK, Chandrasekharappa SC, Marx SJ, Spiegel AM, Collins FS 2001 A mouse model of multiple endocrine neoplasia, type 1, develops multiple endocrine tumors. Proc Natl Acad Sci USA 98:1118–1123 [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Bertolino P, Tong WM, Galendo D, Wang ZQ, Zhang CX 2003 Heterozygous Men1 mutant mice develop a range of endocrine tumors mimicking multiple endocrine neoplasia type 1. Mol Endocrinol 17:1880–1892 [DOI] [PubMed] [Google Scholar]
  20. Loffler KA, Biondi CA, Gartside M, Waring P, Stark M, Serewko-Auret MM, Muller HK, Hayward NK, Kay GF 2007 Broad tumor spectrum in a mouse model of multiple endocrine neoplasia type 1. Int J Cancer 120:259–267 [DOI] [PubMed] [Google Scholar]
  21. Pechhold S, Stouffer M, Walker G, Martel R, Seligmann B, Hang Y, Stein R, Harlan DM, Pechhold K 2009 Transcriptional analysis of intracytoplasmically stained, FACS-purified cells by high-throughput, quantitative nuclease protection. Nat Biotechnol 27:1038–1042 [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Lu J, Herrera PL, Carreira C, Bonnavion R, Seigne C, Calender A, Bertolino P, Zhang CX 2010 α-Cell-specific Men1 ablation triggers the transdifferentiation of glucagon-expressing cells and insulinoma development. Gastroenterology 138:1954–1965 [DOI] [PubMed] [Google Scholar]
  23. Herrera PL 2000 Adult insulin- and glucagon-producing cells differentiate from two independent cell lineages. Development 127:2317–2322 [DOI] [PubMed] [Google Scholar]
  24. Herrera PL, Nepote V, Delacour A 2002 Pancreatic cell lineage analyses in mice. Endocrine 19:267–278 [DOI] [PubMed] [Google Scholar]
  25. Doetschman T 2009 Influence of genetic background on genetically engineered mouse phenotypes. Methods Mol Biol 530:423–433 [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Yoshiki A, Moriwaki K 2006 Mouse phenome research: implications of genetic background. ILAR J 47:94–102 [DOI] [PubMed] [Google Scholar]

Associated Data

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Supplementary Materials

[Supplemental Data]
en.2009-1251_index.html (798B, html)
en.2009-1251_1.pdf (98.8KB, pdf)

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