Type 2 diabetes candidate genes, including PAX5, cause impaired insulin secretion in human pancreatic islets
Karl Bacos, Alexander Perfilyev, Alexandros Karagiannopoulos, Elaine Cowan, Jones K. Ofori, Ludivine Bertonnier-Brouty, Tina Rönn, Andreas Lindqvist, Cheng Luan, Sabrina Ruhrmann, Mtakai Ngara, Åsa Nilsson, Sevda Gheibi, Claire L. Lyons, Jens O. Lagerstedt, Mohammad Barghouth, Jonathan L.S. Esguerra, Petr Volkov, Malin Fex, Hindrik Mulder, Nils Wierup, Ulrika Krus, Isabella Artner, Lena Eliasson, Rashmi B. Prasad, Luis Rodrigo Cataldo, Charlotte Ling
Karl Bacos, Alexander Perfilyev, Alexandros Karagiannopoulos, Elaine Cowan, Jones K. Ofori, Ludivine Bertonnier-Brouty, Tina Rönn, Andreas Lindqvist, Cheng Luan, Sabrina Ruhrmann, Mtakai Ngara, Åsa Nilsson, Sevda Gheibi, Claire L. Lyons, Jens O. Lagerstedt, Mohammad Barghouth, Jonathan L.S. Esguerra, Petr Volkov, Malin Fex, Hindrik Mulder, Nils Wierup, Ulrika Krus, Isabella Artner, Lena Eliasson, Rashmi B. Prasad, Luis Rodrigo Cataldo, Charlotte Ling
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Research Article Endocrinology Metabolism

Type 2 diabetes candidate genes, including PAX5, cause impaired insulin secretion in human pancreatic islets

Abstract

Type 2 diabetes (T2D) is caused by insufficient insulin secretion from pancreatic β cells. To identify candidate genes contributing to T2D pathophysiology, we studied human pancreatic islets from approximately 300 individuals. We found 395 differentially expressed genes (DEGs) in islets from individuals with T2D, including, to our knowledge, novel (OPRD1, PAX5, TET1) and previously identified (CHL1, GLRA1, IAPP) candidates. A third of the identified expression changes in islets may predispose to diabetes, as expression of these genes associated with HbA1c in individuals not previously diagnosed with T2D. Most DEGs were expressed in human β cells, based on single-cell RNA-Seq data. Additionally, DEGs displayed alterations in open chromatin and associated with T2D SNPs. Mouse KO strains demonstrated that the identified T2D-associated candidate genes regulate glucose homeostasis and body composition in vivo. Functional validation showed that mimicking T2D-associated changes for OPRD1, PAX5, and SLC2A2 impaired insulin secretion. Impairments in Pax5-overexpressing β cells were due to severe mitochondrial dysfunction. Finally, we discovered PAX5 as a potential transcriptional regulator of many T2D-associated DEGs in human islets. Overall, we have identified molecular alterations in human pancreatic islets that contribute to β cell dysfunction in T2D pathophysiology.

Authors

Karl Bacos, Alexander Perfilyev, Alexandros Karagiannopoulos, Elaine Cowan, Jones K. Ofori, Ludivine Bertonnier-Brouty, Tina Rönn, Andreas Lindqvist, Cheng Luan, Sabrina Ruhrmann, Mtakai Ngara, Åsa Nilsson, Sevda Gheibi, Claire L. Lyons, Jens O. Lagerstedt, Mohammad Barghouth, Jonathan L.S. Esguerra, Petr Volkov, Malin Fex, Hindrik Mulder, Nils Wierup, Ulrika Krus, Isabella Artner, Lena Eliasson, Rashmi B. Prasad, Luis Rodrigo Cataldo, Charlotte Ling

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Figure 4

T2D-associated expression changes impair insulin secretion.

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T2D-associated expression changes impair insulin secretion. (A) Flow cha...
(A) Flow chart showing strategy for the selection of DEGs for functional follow-up. (B) Ten of the 11 genes selected for functional analysis have T2D-associated DMRs, INSPIRE eQTLs, SNPs associated with T2D or glucose traits, or islet mQTLs annotated to them. (C) mRNA expression of DEGs selected for functional follow-up. ****q < 0.0001, based on a generalized linear model as implemented in DESeq2 (70), with correction for age, sex, purity, and DIC, on expression data on islets from 138 ND controls and 33 individuals with T2D. (D) qPCR quantification of siRNA-mediated knockdown of CHL1, HHATL, OPRD1, and SLC2A2 in human islets (n = 6–8). (E) Effect of knockdown of CHL1, HHATL1, OPRD1, or SLC2A2 on insulin secretion from human islets (n = 6–8). (D and E) *P < 0.05 compared with negative control siRNA (siNC) at the indicated glucose concentration; 2-tailed, paired t test. (F) Representative Western blot showing overexpression of GFP, Barx1, Nefl, Pax5, Pcolce2, and Sfrp1 in virally transduced INS1 β cells. The experiment was performed 3 times. (G–J) Effect of overexpression on insulin secretion (G) and insulin content (H) in absolute values, insulin secretion presented as fold change (I), and total protein (J) (n = 7). (G) **P < 0.01 compared with GFP at 16.7 mM glucose; #P < 0.05 and ##P < 0.01 compared with GFP at 2.8 mM glucose. (H–J) *P < 0.05 and ****P < 0.0001 compared with GFP. Data in G–J were analyzed by 2-tailed, paired t test. Box-and-whisker plots show the median, 25th and 75th percentiles, and minimum and maximum values.