title: Altered MENIN expression disrupts the MAFA differentiation pathway in insulinoma.
abstract: The protein MENIN is the product of the multiple endocrine neoplasia type I (MEN1) gene. Altered MENIN expression is one of the few events that are clearly associated with foregut neuroendocrine tumours (NETs), classical oncogenes or tumour suppressors being not involved. One of the current challenges is to understand how alteration of MENIN expression contributes to the development of these tumours. We hypothesised that MENIN might regulate factors maintaining endocrine-differentiated functions. We chose the insulinoma model, a paradigmatic example of well-differentiated pancreatic NETs, to study whether MENIN interferes with the expression of v-MAF musculoaponeurotic fibrosarcoma oncogene homologue A (MAFA), a master glucose-dependent transcription factor in differentiated β-cells. Immunohistochemical analysis of a series of human insulinomas revealed a correlated decrease in both MENIN and MAFA. Decreased MAFA expression resulting from targeted Men1 ablation was also consistently observed in mouse insulinomas. In vitro analyses using insulinoma cell lines showed that MENIN regulated MAFA protein and mRNA levels, and bound to Mafa promoter sequences. MENIN knockdown concomitantly decreased mRNA expression of both Mafa and β-cell differentiation markers (Ins1/2, Gck, Slc2a2 and Pdx1) and, in parallel, increased the proliferation rate of tumours as measured by bromodeoxyuridine incorporation. Interestingly, MAFA knockdown alone also increased proliferation rate but did not affect the expression of candidate proliferation genes regulated by MENIN. Finally, MENIN variants with missense mutations detected in patients with MEN1 lost the WT MENIN properties to regulate MAFA. Together, our findings unveil a previously unsuspected MENIN/MAFA connection regarding control of the β-cell differentiation/proliferation balance, which could contribute to tumorigenesis.
authors.affiliation: INSERM U1052/CNRS UMR5286/Université de Lyon, Lyon1 UMR-S1052, Cancer Research Center of Lyon, Lyon F-69008, France Service de Génétique Moléculaire et Clinique, Hospices Civils de Lyon, Hôpital Edouard Herriot, Lyon F-69437, France UMR 3347/CNRS, U1021/INSERM, Institut Curie, Orsay F-91405, France Service Central d'Anatomie et Cytologie Pathologiques, Hospices Civils de Lyon, Hôpital Edouard Herriot, Lyon F-69437, France Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA.
authors.forename: Z
authors.initials: Z
authors.lastname: Hamze
authors.forename: C
authors.initials: C
authors.lastname: Vercherat
authors.forename: A
authors.initials: A
authors.lastname: Bernigaud-Lacheretz
authors.forename: W
authors.initials: W
authors.lastname: Bazzi
authors.forename: R
authors.initials: R
authors.lastname: Bonnavion
authors.forename: J
authors.initials: J
authors.lastname: Lu
authors.forename: A
authors.initials: A
authors.lastname: Calender
authors.forename: C
authors.initials: C
authors.lastname: Pouponnot
authors.forename: P
authors.initials: P
authors.lastname: Bertolino
authors.forename: C
authors.initials: C
authors.lastname: Roche
authors.forename: R
authors.initials: R
authors.lastname: Stein
authors.forename: J Y
authors.initials: JY
authors.lastname: Scoazec
authors.forename: C X
authors.initials: CX
authors.lastname: Zhang
authors.forename: M
authors.initials: M
authors.lastname: Cordier-Bussat
mesh_terms: D000328:Adult; D000368:Aged; D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D018278:Carcinoma, Neuroendocrine / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D002454:Cell Differentiation; D049109:Cell Proliferation; D047369:Chromatin Immunoprecipitation; D005260:Female; D005947:Glucose / Q000494:pharmacology; D006801:Humans; D007124:Immunoenzyme Techniques; D050417:Insulin-Secreting Cells / Q000378:metabolism / Q000473:pathology; D007340:Insulinoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D051473:Maf Transcription Factors, Large / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008875:Middle Aged; D010190:Pancreatic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured
chemical_list: C485159:MAFA protein, human; C105373:MEN1 protein, human; D051473:Maf Transcription Factors, Large; C484898:Men1 protein, mouse; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D005947:Glucose
keywords: MAFA; MEN1; MENIN; differentiation; endocrine tumour; insulinoma