Connexin 36 is Expressed in Beta and Connexins 26 and 32 in Acinar Cells at the End of the Secondary Transition of Mouse Pancreatic Development and Increase During Fetal and Perinatal Life

Abstract

To identify when during fetal development connexins (Cxs) 26 (Cx26) 32 (Cx32), and 36 (Cx36) begin to be expressed, as well as to characterize their spatial distribution, real time polymerase chain reaction and immunolabeling studies were performed. Total RNA from mouse pancreases at 13 and 18 days postcoitum (dpc) and 3 days postpartum (dpp) was analyzed. In addition, pancreatic sections of mouse at 13, 14, 15, 16, 18 dpc and 3 dpp and of rat at term were double labeled with either anti-insulin or anti-a-amylase and anti-Cx26 or -Cx32 or -Cx36 antibodies and studied with confocal microscopy. From day 13 dpc, Cxs 26, 32, and 36 transcripts were identified and their levels increased with age. At 13-14 dpc, Cxs 26 and 32 were localized in few acinar cells, whereas Cx36 was distributed in small beta cell clumps. From day 14 dpc onwards, the number of labeled cells and relative immunofluorescent reactivity of all three Cxs at junctional membranes of the respective cell types increased. Cxs 26 and 32 colocalized in fetal acinar cells. In rat pancreas at term, a similar connexin distribution was found. Relative Cxs levels evaluated by immunoblotting also increased (two-fold) in pancreas homogenates from day 18 dpc to 3 dpp. The early cell specific, wide distribution, and age dependent expression of Cxs 26, 32, and 36 during fetal pancreas ontogeny suggests their possible involvement in pancreas differentiation and prenatal maturation. Anat Rec, 295:980-990, 2012. V C 2012 Wiley Periodicals, Inc.

Cx36 Is a Target of Beta2/NeuroD1, Which Associates with Prenatal Differentiation of Insulin-producing β Cells

“…To this end, we used a luciferase reporter system to test different regions of the Gjd2 promoter, chromatin immunoprecipitation assays to evaluate the binding of Beta2/NeuroD1 to this promoter, and cell transfections, as well as site-directed mutagenesis, to assess the effects of Beta2/NeuroD1 on Cx36 expression. The data show that Gjd2 is (1) expressed early in the development of the mouse pancreas, as reported in the chicken (Berthoud et al 2004), and in a recent report (Pérez-Armendariz et al 2012) published since the submission of this study; (2) encodes the cognate Cx36 protein at the time of the second wave of b-cell differentiation; (3) is a hitherto nonidentified target of Beta2/NeuroD1, which controls its expression by direct binding to the Gjd2 promoter.…”

Cellular communication and heterogeneity in pancreatic islet insulin secretion dynamics

“…Further, Cx36 has been identified as a possible regulator of β-cell differentiation and maturation [46, 47]. Because Cx36 plays such a critical role in islet dynamics and function, it is not surprising that it would support islet development and fitness as well.…”

Maturation of Stem Cell-Derived Beta-cells Guided by the Expression of Urocortin 3

“…Therefore, beta-cells can be considered mature when they are able to maintain blood glucose at normal levels in response to intermittent feeding and fasting, a state which is gradually acquired and only fully achieved after weaning [76,77]. [56,77], ZNT8 [126], MAFA [73], Cx36 [127], PCSK1 and PCSK2 [128], MAFB [129], PAX4 [47], NEUROD [48], Islet1 [46], NGN3 [52], NKX6.1 [42], GLUT2 [130], and Pdx1 [58] is shown.…”