The SSBP3 co-regulator is required for glucose homeostasis, pancreatic islet architecture, and beta-cell identity
Objective: Transcriptional complex activity drives the development and function of pancreatic islet cells to allow for proper glucose regulation. Prior studies from our lab and others highlighted that the LIM-homeodomain transcription factor (TF), Islet-1 (Isl1), and its interacting co-regulator, Ld...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Elsevier
2023-10-01
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| Series: | Molecular Metabolism |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S2212877823001199 |
| _version_ | 1797690208874921984 |
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| author | Eliana Toren Jessica D. Kepple Kristen V. Coutinho Samuel O. Poole Iztiba M. Deeba Tanya H. Pierre Yanping Liu Maigen M. Bethea Chad S. Hunter |
| author_facet | Eliana Toren Jessica D. Kepple Kristen V. Coutinho Samuel O. Poole Iztiba M. Deeba Tanya H. Pierre Yanping Liu Maigen M. Bethea Chad S. Hunter |
| author_sort | Eliana Toren |
| collection | DOAJ |
| description | Objective: Transcriptional complex activity drives the development and function of pancreatic islet cells to allow for proper glucose regulation. Prior studies from our lab and others highlighted that the LIM-homeodomain transcription factor (TF), Islet-1 (Isl1), and its interacting co-regulator, Ldb1, are vital effectors of developing and adult β-cells. We further found that a member of the Single Stranded DNA-Binding Protein (SSBP) co-regulator family, SSBP3, interacts with Isl1 and Ldb1 in β-cells and primary islets (mouse and human) to impact β-cell target genes MafA and Glp1R in vitro. Members of the SSBP family stabilize TF complexes by binding directly to Ldb1 and protecting the complex from ubiquitin-mediated turnover. In this study, we hypothesized that SSBP3 has critical roles in pancreatic islet cell function in vivo, similar to the Isl1::Ldb1 complex. Methods: We first developed a novel SSBP3 LoxP allele mouse line, where Cre-mediated recombination imparts a predicted early protein termination. We bred this mouse with constitutive Cre lines (Pdx1- and Pax6-driven) to recombine SSBP3 in the developing pancreas and islet (SSBP3ΔPanc and SSBP3ΔIslet), respectively. We assessed glucose tolerance and used immunofluorescence to detect changes in islet cell abundance and markers of β-cell identity and function. Using an inducible Cre system, we also deleted SSBP3 in the adult β-cell, a model termed SSBP3Δβ-cell. We measured glucose tolerance as well as glucose-stimulated insulin secretion (GSIS), both in vivo and in isolated islets in vitro. Using islets from control and SSBP3Δβ-cell we conducted RNA-Seq and compared our results to published datasets for similar β-cell specific Ldb1 and Isl1 knockouts to identify commonly regulated target genes. Results: SSBP3ΔPanc and SSBP3ΔIslet neonates present with hyperglycemia. SSBP3ΔIslet mice are glucose intolerant by P21 and exhibit a reduction of β-cell maturity markers MafA, Pdx1, and UCN3. We observe disruptions in islet cell architecture with an increase in glucagon+ α-cells and ghrelin+ ε-cells at P10. Inducible loss of β-cell SSBP3 in SSBP3Δβ-cell causes hyperglycemia, glucose intolerance, and reduced GSIS. Transcriptomic analysis of 14-week-old SSBP3Δβ-cell islets revealed a decrease in β-cell function gene expression (Ins, MafA, Ucn3), increased stress and dedifferentiation markers (Neurogenin-3, Aldh1a3, Gastrin), and shared differentially expressed genes between SSBP3, Ldb1, and Isl1 in adult β-cells. Conclusions: SSBP3 drives proper islet identity and function, where its loss causes altered islet-cell abundance and glucose homeostasis. β-Cell SSBP3 is required for GSIS and glucose homeostasis, at least partially through shared regulation of Ldb1 and Isl1 target genes. |
| first_indexed | 2024-03-12T01:56:15Z |
| format | Article |
| id | doaj.art-80b6b8aa66f947929240244c5b9225e4 |
| institution | Directory Open Access Journal |
| issn | 2212-8778 |
| language | English |
| last_indexed | 2024-03-12T01:56:15Z |
| publishDate | 2023-10-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Molecular Metabolism |
| spelling | doaj.art-80b6b8aa66f947929240244c5b9225e42023-09-08T04:33:24ZengElsevierMolecular Metabolism2212-87782023-10-0176101785The SSBP3 co-regulator is required for glucose homeostasis, pancreatic islet architecture, and beta-cell identityEliana Toren0Jessica D. Kepple1Kristen V. Coutinho2Samuel O. Poole3Iztiba M. Deeba4Tanya H. Pierre5Yanping Liu6Maigen M. Bethea7Chad S. Hunter8Comprehensive Diabetes Center and Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, AL 35294, USAComprehensive Diabetes Center and Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, AL 35294, USAComprehensive Diabetes Center and Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, AL 35294, USAComprehensive Diabetes Center and Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, AL 35294, USAComprehensive Diabetes Center and Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, AL 35294, USAComprehensive Diabetes Center and Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, AL 35294, USAComprehensive Diabetes Center and Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, AL 35294, USAComprehensive Diabetes Center and Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, AL 35294, USACorresponding author. 1825 University Boulevard, SHEL 1211, University of Alabama at Birmingham, Birmingham, AL 35294, USA.; Comprehensive Diabetes Center and Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, AL 35294, USAObjective: Transcriptional complex activity drives the development and function of pancreatic islet cells to allow for proper glucose regulation. Prior studies from our lab and others highlighted that the LIM-homeodomain transcription factor (TF), Islet-1 (Isl1), and its interacting co-regulator, Ldb1, are vital effectors of developing and adult β-cells. We further found that a member of the Single Stranded DNA-Binding Protein (SSBP) co-regulator family, SSBP3, interacts with Isl1 and Ldb1 in β-cells and primary islets (mouse and human) to impact β-cell target genes MafA and Glp1R in vitro. Members of the SSBP family stabilize TF complexes by binding directly to Ldb1 and protecting the complex from ubiquitin-mediated turnover. In this study, we hypothesized that SSBP3 has critical roles in pancreatic islet cell function in vivo, similar to the Isl1::Ldb1 complex. Methods: We first developed a novel SSBP3 LoxP allele mouse line, where Cre-mediated recombination imparts a predicted early protein termination. We bred this mouse with constitutive Cre lines (Pdx1- and Pax6-driven) to recombine SSBP3 in the developing pancreas and islet (SSBP3ΔPanc and SSBP3ΔIslet), respectively. We assessed glucose tolerance and used immunofluorescence to detect changes in islet cell abundance and markers of β-cell identity and function. Using an inducible Cre system, we also deleted SSBP3 in the adult β-cell, a model termed SSBP3Δβ-cell. We measured glucose tolerance as well as glucose-stimulated insulin secretion (GSIS), both in vivo and in isolated islets in vitro. Using islets from control and SSBP3Δβ-cell we conducted RNA-Seq and compared our results to published datasets for similar β-cell specific Ldb1 and Isl1 knockouts to identify commonly regulated target genes. Results: SSBP3ΔPanc and SSBP3ΔIslet neonates present with hyperglycemia. SSBP3ΔIslet mice are glucose intolerant by P21 and exhibit a reduction of β-cell maturity markers MafA, Pdx1, and UCN3. We observe disruptions in islet cell architecture with an increase in glucagon+ α-cells and ghrelin+ ε-cells at P10. Inducible loss of β-cell SSBP3 in SSBP3Δβ-cell causes hyperglycemia, glucose intolerance, and reduced GSIS. Transcriptomic analysis of 14-week-old SSBP3Δβ-cell islets revealed a decrease in β-cell function gene expression (Ins, MafA, Ucn3), increased stress and dedifferentiation markers (Neurogenin-3, Aldh1a3, Gastrin), and shared differentially expressed genes between SSBP3, Ldb1, and Isl1 in adult β-cells. Conclusions: SSBP3 drives proper islet identity and function, where its loss causes altered islet-cell abundance and glucose homeostasis. β-Cell SSBP3 is required for GSIS and glucose homeostasis, at least partially through shared regulation of Ldb1 and Isl1 target genes.http://www.sciencedirect.com/science/article/pii/S2212877823001199DiabetesGlucose homeostasisPancreatic isletTranscription factorCo-regulatorGene regulation |
| spellingShingle | Eliana Toren Jessica D. Kepple Kristen V. Coutinho Samuel O. Poole Iztiba M. Deeba Tanya H. Pierre Yanping Liu Maigen M. Bethea Chad S. Hunter The SSBP3 co-regulator is required for glucose homeostasis, pancreatic islet architecture, and beta-cell identity Molecular Metabolism Diabetes Glucose homeostasis Pancreatic islet Transcription factor Co-regulator Gene regulation |
| title | The SSBP3 co-regulator is required for glucose homeostasis, pancreatic islet architecture, and beta-cell identity |
| title_full | The SSBP3 co-regulator is required for glucose homeostasis, pancreatic islet architecture, and beta-cell identity |
| title_fullStr | The SSBP3 co-regulator is required for glucose homeostasis, pancreatic islet architecture, and beta-cell identity |
| title_full_unstemmed | The SSBP3 co-regulator is required for glucose homeostasis, pancreatic islet architecture, and beta-cell identity |
| title_short | The SSBP3 co-regulator is required for glucose homeostasis, pancreatic islet architecture, and beta-cell identity |
| title_sort | ssbp3 co regulator is required for glucose homeostasis pancreatic islet architecture and beta cell identity |
| topic | Diabetes Glucose homeostasis Pancreatic islet Transcription factor Co-regulator Gene regulation |
| url | http://www.sciencedirect.com/science/article/pii/S2212877823001199 |
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