الفهرس 
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Abstract
The current work was conducted to characterize the key milestones defining and factors controlling pancreatic development in mice using wild type and genetically modified mice. The specimens were collected from the different mice groups during pre- and postnatal life and processed for immunohistochemical analysis. The obtained results revealed that the prenatal development of the pancreas passed into two major sequential phases; primary and secondary phases. In the primary transition, the pancreatic primordia of E9.5 mouse embryos appeared in the form of two epithelial domains budding from the endodermal lining of the foregut and contained low number of hormone+ cells. The secondary transition was observed in E13.5 mouse embryos and onwards during which the developing pancreas revealed marked expansion and differentiation of its forming elements. The secondary transition ended by formation of clustered cellular masses of endocrine cells with insulin+ β-cells filling the core of the islet surrounded by three types of other hormone+ cells. The analyses of Mafa knockout and Mafb knockout single and compound mutant mice was performed and revealed that Mafb have a dominant role during development for maintenance of thenumbers of insulin+ and glucagon+ cells and Mafa for β-cell maturation, however with minor contribution to their development. In addition, the contribution of Mafb for the production of insulin in adult pancreas was examined using Mafaand Mafb knockoutcompoundmutants. The effect of small Maf Mafk on pancreatic endocrine activity was examined during development. The β-cellspecific Mafk overexpression had resulted in impairment in endocrine development through alteration of the gene expression of many important genes for endocrine development and function. Microarray analysis was performed to reveal the changes in whole genomic profiles. Three novel genes with uncharacterized roles during pancreatic development were reported in the current work namely Npy, Cryba2 and Fam132a. A further investigation of the role played by these genes might enhance the current knowledge about factors governing pancreatic development.