title: Polycomb protein Ezh2 regulates pancreatic beta-cell Ink4a/Arf expression and regeneration in diabetes mellitus.
abstract: Proliferation of pancreatic islet beta cells is an important mechanism for self-renewal and for adaptive islet expansion. Increased expression of the Ink4a/Arf locus, which encodes the cyclin-dependent kinase inhibitor p16(INK4a) and tumor suppressor p19(Arf), limits beta-cell regeneration in aging mice, but the basis of beta-cell Ink4a/Arf regulation is poorly understood. Here we show that Enhancer of zeste homolog 2 (Ezh2), a histone methyltransferase and component of a Polycomb group (PcG) protein complex, represses Ink4a/Arf in islet beta cells. Ezh2 levels decline in aging islet beta cells, and this attrition coincides with reduced histone H3 trimethylation at Ink4a/Arf, and increased levels of p16(INK4a) and p19(Arf). Conditional deletion of beta-cell Ezh2 in juvenile mice also reduced H3 trimethylation at the Ink4a/Arf locus, leading to precocious increases of p16(INK4a) and p19(Arf). These mutant mice had reduced beta-cell proliferation and mass, hypoinsulinemia, and mild diabetes, phenotypes rescued by germline deletion of Ink4a/Arf. beta-Cell destruction with streptozotocin in controls led to increased Ezh2 expression that accompanied adaptive beta-cell proliferation and re-establishment of beta-cell mass; in contrast, mutant mice treated similarly failed to regenerate beta cells, resulting in lethal diabetes. Our discovery of Ezh2-dependent beta-cell proliferation revealed unique epigenetic mechanisms underlying normal beta-cell expansion and beta-cell regenerative failure in diabetes pathogenesis.
authors.affiliation: Department of Developmental Biology, Stanford University School of Medicine, Stanford, California 94305, USA.
authors.forename: Hainan
authors.initials: H
authors.lastname: Chen
authors.forename: Xueying
authors.initials: X
authors.lastname: Gu
authors.forename: I-hsin
authors.initials: IH
authors.lastname: Su
authors.forename: Rita
authors.initials: R
authors.lastname: Bottino
authors.forename: Juan L
authors.initials: JL
authors.lastname: Contreras
authors.forename: Alexander
authors.initials: A
authors.lastname: Tarakhovsky
authors.forename: Seung K
authors.initials: SK
authors.lastname: Kim
mesh_terms: D000375:Aging / Q000378:metabolism; D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics / Q000378:metabolism*; D003920:Diabetes Mellitus / Q000378:metabolism*; D000071221:Enhancer of Zeste Homolog 2 Protein; D005260:Female; D017353:Gene Deletion; D005786:Gene Expression Regulation / Q000187:drug effects; D011495:Histone-Lysine N-Methyltransferase / Q000378:metabolism*; D006657:Histones / Q000378:metabolism; D006801:Humans; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D063151:Polycomb Repressive Complex 2; D013311:Streptozocin / Q000494:pharmacology
chemical_list: D000903:Antibiotics, Antineoplastic; C417743:Cdkn2a protein, mouse; D019941:Cyclin-Dependent Kinase Inhibitor p16; D006657:Histones; D013311:Streptozocin; D000071221:Enhancer of Zeste Homolog 2 Protein; C498410:Ezh2 protein, mouse; D011495:Histone-Lysine N-Methyltransferase; D063151:Polycomb Repressive Complex 2