Fig. 3.

Mdg1/ERdj4 protein pattern in the developing gastrointestinal tract. a Schematic drawing of the digestive avian tract with the glandular rich proventriculus located directly before the muscular gizzard. b At day 2.5 (HH-stage 17), longitudinal section of the pharyngeal arches. The ectodermal (ect), the endodermal linings (end), and arterial endothelium (*) are Mdg1/ERdj4 positive. Scale bar 100 µm. c HH-stage 17, coronal section. The endothelial lining of the aorta (ao), the coelomic epithelium (ce), and the endoderm-derived, apical, epithelial zone of the oesophagus (*) are Mdg1/ERdj4 positive. Scale bar 100 µm. d HH-stage 17, intestinal tract in the abdominal region (it). The apical border of the epithelium contains high amounts of Mdg1/ERdj4 protein. In the basal zone, the protein is focussed to a fine-lined border (arrow). Scale bar 50 µm. e Embryonic day 4, intestinal tract in the abdominal region (it). The protein pattern observed at HH-stage 17 is maintained (see d). Scale bar 50 µm. Immunostaining of the proventriculus (f–h) and the gizzard (i–l) at day 10, 14, and 18, respectively. × 10 magnifications (f–l), corresponding × 40 magnifications of the indicated rectangles are shown in f′–l′. Arrowheads mark the peritoneum; asterisk marks smooth muscle cells forming layers of the tunica muscularis (f) and the lamina muscularis mucosae (f′). Arrows point to the luminal epithelium of the gizzard (i, i′, k′). Note the microvilli in k′ (arrow)