β-Cell-Specific Mafk Overexpression Impairs Pancreatic Endocrine Cell Development
Ahmed M Abdellatif1,2, Hisashi Oishi1,3,4, Takahiro Itagaki1,3
1Department of Anatomy and Embryology, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan.
Abstract:
The MAF family transcription factors are homologs of v-Maf, the oncogenic component of the avian retrovirus AS42. They are subdivided into 2 groups, small and large MAF proteins, according to their structure, function, and molecular size. MAFK is a member of the small MAF family and acts as a dominant negative form of large MAFs. In previous research we generated transgenic mice that overexpress MAFK in order to suppress the function of large MAF proteins in pancreatic β-cells. These mice developed hyperglycemia in adulthood due to impairment of glucose-stimulated insulin secretion. The aim of the current study is to examine the effects of β-cell-specific Mafk overexpression in endocrine cell development. The developing islets of Mafk-transgenic embryos appeared to be disorganized with an inversion of total numbers of insulin+ and glucagon+ cells due to reduced β-cell proliferation. Gene expression analysis by quantitative RT-PCR revealed decreased levels of β-cell-related genes whose expressions are known to be controlled by large MAF proteins. Additionally, these changes were accompanied with a significant increase in key β-cell transcription factors likely due to compensatory mechanisms that might have been activated in response to the β-cell loss. Finally, microarray comparison of gene expression profiles between wild-type and transgenic pancreata revealed alteration of some uncharacterized genes including Pcbd1, Fam132a, Cryba2, and Npy, which might play important roles during pancreatic endocrine development. Taken together, these results suggest that Mafk overexpression impairs endocrine development through a regulation of numerous β-cell-related genes. The microarray analysis provided a unique data set of differentially expressed genes that might contribute to a better understanding of the molecular basis that governs the development and function of endocrine pancreas.
Insights
Overexpressing MAFK in pancreatic beta cells disrupts endocrine development and insulin secretion by altering gene expression. This study reveals MAFK
Area of Science:
- Molecular Biology
- Endocrinology
- Developmental Biology
Background:
- MAF family transcription factors regulate gene expression.
- MAFK, a small MAF protein, acts as a dominant negative regulator of large MAFs.
- Previous studies showed MAFK overexpression in adult pancreatic beta cells causes hyperglycemia.
Purpose of the Study:
- To investigate the effects of beta-cell-specific Mafk overexpression on pancreatic endocrine cell development.
- To understand the molecular mechanisms underlying MAFK's impact on beta-cell function and development.
Main Methods:
- Generation of Mafk-transgenic mice with beta-cell-specific overexpression.
- Analysis of pancreatic islet morphology and cell composition in embryonic and adult stages.
- Quantitative RT-PCR and microarray analysis to assess gene expression changes.
Main Results:
- Mafk overexpression led to disorganized islets and altered insulin/glucagon cell numbers due to reduced beta-cell proliferation.
- Decreased expression of beta-cell-related genes controlled by large MAFs was observed.
- Upregulation of key beta-cell transcription factors and alterations in novel genes (Pcbd1, Fam132a, Cryba2, Npy) were identified.
Conclusions:
- Mafk overexpression during development impairs pancreatic endocrine cell differentiation and function.
- Mafk's regulatory role extends to numerous beta-cell-specific genes, impacting islet development.
- Microarray data provides insights into novel genes involved in pancreatic endocrine development and function.
