Connexin 31.9 is expressed in human pancreatic endocrine beta cells, as well as in exocrine ductal epithelial and vascular endothelial cells.

Connexin 36 (Cx36)-deficient mice exhibit deregulation of insulin secretion and glucose homeostasis. Mouse islet beta cells express Cx36 and connexin 30.2 (Cx30.2). Human beta cells express Cx36; however, it remains unknown whether they express Cx31.9 protein, the ortholog of Cx30.2. To address this question, sections of 23 human pancreatic autopsy samples from both sexes were analyzed by real-time qRT-PCR with oligonucleotides against Cx31.9 and by immunohistochemistry (IHC) with a specific antibody against this connexin. Mean levels of Cx31.9 mRNA were similar to those of Cx36 mRNA, used as a control gene, in all human samples analyzed (n = 7). IHC studies showed that Cx31.9-positive staining was localized to most islet cells in donor samples (15 of 16). The density of Cx31.9 staining per μm2 was calculated from 31 islet images from 10 donor samples. Pancreatic serial sections revealed that the spatial distribution of anti-Cx31.9-labeled cells is similar to that of anti-Cx36- and anti-insulin-positive cells. Moreover, anti-Cx31.9 staining was also localized in anti-CK19-positive epithelial ductal cells and in the endothelial cells of small, medium, and large-diameter vessels. Cx31.9 protein is expressed in endocrine islet beta cells as well as in exocrine ductal epithelial and vascular endothelial cells. In addition, there is a balance of Cx31.9 and Cx36 mRNA levels in the human pancreas.