Rat small intestine expresses the reelin–Disabled‐1 signalling pathway

Expression of reelin, reelin receptors [apolipoprotein E receptor 2 (ApoER2) and very low density lipoprotein receptor (VldlR)] and the Disabled-1 (Dab1) protein was investigated in rat intestinal mucosa. Intestinal reelin and Dab1 mRNA levels were maximal in the early stages of life, reaching adult levels in 1-month-old rats. Expression of reelin mRNA was restricted to fibroblasts, whereas mRNAs of Dab1, ApoER2, VldlR and integrins alpha3 and beta1 were observed in enterocytes, crypts and fibroblasts. Reelin protein was only observed in isolated intestinal fibroblasts and in a cell layer subjacent to the villus epithelium, which seems to be composed of myofibroblasts because it also reacted to alpha-smooth muscle actin. The Disabled-1 and VldlR protein signals were detected in the crypt and villus cells, and they were particularly abundant in the terminal web domain of the enterocytes. The ApoER2 protein signal was detected in the upper half of the villi but not in the crypts. This is the first report showing that rat intestinal mucosa expresses the reelin-Disabled-1 signalling system.