The Expression Of Somatostatins In Zebrafish Pancreas And Effect Of Knockdown On It’s Development

Somatostatins (SS) are a structurally diverse family of peptide hormones, exists almost in all vertebrates.SS exerts a great variety of biological functions, including multiple aspects of growth, development, and metabolism. Somatostatins are produced by a wide variety of cell types and tissues, including epithelial, neuronal, immune, pancreatic islets, gastrointestinal tract, central and peripheral nervous systems, and thyroid tissue. Whole-mount in situ hybridization showed that SSI and SS4 express in zebrafish embryos and SS4 expression was exclusively in the developing pancreas.In former study, we have cloned the cDNA of zebrafish SS3, which temporarily expressed in neural head region, and could maintain its expression in the developing pancreas. In present study, using Two-Color in Situ Hybridization, we compared the co-expression of SS3 with that of the genes encoding various pancreatic hormones, include SS4, ins, gcg and transcription factors isletl. Then, impact of SS3 or/and SS4 functional deficit on zebrafish pancreas development was investigated by knockdown their expression with specific morpholino antisense oligonucleotides.The results of two-color in situ hybridization of SS3 with several pancreatic markers showed that SS3 has an expression domain partial overlapping with that of ins, in some SS3-expressing cells strongly expressing ins at 22 hpf. At 30 hpf and 48 hpf, the ins-expressing cells is mainly in the core region, where SS3-expressing cells at the periphery surrounding ins-expressing cells. At 48 hpf, there are few SS3-expressing cells coexpress isletl-expressing cells; SS3-expressing cells were partial coexpressing with SS4-expressing cells, and the coexpress region were mainly at the periphery. The majority of the SS3-expressing cells were found to coexpress gcg-expressing cells at 48 hpf.SS3 or SS4 expression was knocked down by injected their MOs respectively, then SS4 and SS3 expression were analyzed in morphants embryos. In SS3 morphants, the region of SS4-expressing cells increased; otherwise, in SS4 morphants, the region of SS3-expressing cells increased. However, either in SS3 morphants or SS4 morphants, the cell number of gcg-expressing and the cell number of ins-expressing were not change. While knockdown SS3 and SS4 expression at same time by co-injection with SS3 MO and SS4 MO in embryos, the cell number of gcg-expressing and ins-expressing both were significantly decreased. These results suggested that SS3 and SS4 were likely to regulate each other in developmental pancreas. SS signaling pathway may involve in the formation of endocrinal pancreas during zebrafish embryonic development.