Expression And Location Study Of ALK1 In Mouse Pancreas

Pancreas is an important complex exocrine and endocrine gland. Exocrine gland, thatmainly produce digestive enzymes is composed by acinar cells and ducts. Endocrine cells aremainly grouped into the islets of Langerhans, which are compact spheroidal clustersembedded in the exocrine cell. Each islet contains four cell types: α-cells, β-cells, δ-cells,γ-cells, which respectively produce glucagon, insulin, somatostatin, pancreatic polypeptide.They play an important role in glucose homeostasis and glycometabolism.Recently, for the attack rates of diabetes mellitus and pancreatic cancer go up, more andmore attention was paid to the study of the molecular mechanism of the pancreasdevelopment. The development of pancreas is a highly concordant process, which is regulatedby many signal systems, of which transforming growth factor-β (TGF-β) signaling pathwayplay a key role, by now, there have been many reports concerned, but little is known about thedetailed mechanism.ALK1 (activin receptor-like kinase1;ACVRL1) is one of the type I transmembraneserine/threonine kinase receptors in TGF-β signaling, which can bind to TGF-β1 or TGF-β3 inthe pathway and then transmit the signal by phosphorylating some Smads proteins. ALK1 isreported to most highly express in endothelial cells, and involved in the regulation of theformation of blood vessels. There has been no report about its expression in pancreas untilnow. As one of the key receptors of TGF-β signaling pathway, it is significative to study theexpression of ALK1 for understanding the mechanism of this pathway during pancreasdevelopment.In order to examine the expression and location of ALK1 during the development ofC57BL/6J mouse, by means of immunihistochemistry and immnohistofluorescence, westained the parraffin slices of E12.5-16.5day, E18.5day embryos, newborn and postprenatal5-week by rabbit polyclonal anti-acvrl1 and polyclonal guinea pig anti-swine insulin. Noexpression was detected in 12.5day, ALK1 was present in mouse pancreas from 13.5d to18.5d, new born and postprenatal 5-week, and exclusively localized to the cells insulinexpressed;Its expression was increase with the development of the mouse pancreas.Besides, in order to confirm these results, we stained the paraffin slices of new bornmouse by polyclonal guinea pig anti-swine insulin and another ALK1 antibody, rabbitpolyclonal anti-TGFβ RI (V-22). The colocation results of immnofluorescence showed thatthese two protein expressed in the same pancreatic cells, and this was consistent with theforegoing. We believe that our finding provide evidences for revealing the molecularmechanism of TGF-βaction in mouse pancreas development.