The pancreas is a gland composed essentially of digestive enzymes-producing acinar cells and hormone-producing endocrine cells. In particular, insulin is one of the best-known pancreatic hormones and it is a member of the large insulin superfamily, a group of evolutionary related proteins that includes also many insulin-like peptides (ILPs) in invertebrates. Although the pancreas has been extensively studied in vertebrates, little information is reported on ILPs and homologues of pancreatic endocrine and exocrine cell types in non-chordate deuterostomes. In order to fill this critical gap in pancreas evolution this thesis concerns the analysis of the orthologues of vertebrate pancreatic genes, both transcriptional factors and terminal differentiation genes, during embryo and larva development in the sea urchin Strongylocentrotus purpuratus, which among the chordate sister group ambulacraria, has proven to be a powerful instrument for evolutionary studies. To this end, the spatial expression of insulin-like molecules found in the sea urchin genome (Splgfl and SpIlgf2) and their predicted receptor (SpInsr) have been extensively studied. The outcomes of this thesis work suggest to rename Splgfl and SpIlgf2 as SpILPI and SpILP2, respectively. Remarkably, SpILPI has been found to be localized in a group of cells of the larval gut in a feeding-dependent fashion. Moreover, after cloning and characterizing the spatial expression of the orthologues of pancreatic transcriptional factors (SpNgn, SpNeuroD, Splsl, SpHnfl, SpPtfla) and exocrine pancreas terminal differentiation genes (SpCpa2L and SpPnlp), I proceeded in investigating the role of some of these genes by functional analysis experiments. During this characterization, several homologues of pancreatic and neuronal cell types have been identified. Notably, putative homologues of acinar cell types, that are clustered in the sea urchin larva stomach, and a peculiar neuronal cell type that secretes a novel neuropeptide were characterized. Finally, the outcome of this study is discussed in a comparative perspective with available data in other animal models in order to make hypotheses on the evolution of insulin-like molecules and pancreatic cell types across metazoan .
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:664282 |
| Date | January 2013 |
| Creators | Perillo, Margherita |
| Publisher | Open University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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