Comprehensive analysis of localization of 78 solute carrier genes throughout the subsections of the rat gastrointestinal tract

Solute carriers (SLCs), the second largest super-family of membrane proteins in the human genome, transport amino acids, sugars, fatty acids, inorganic ions, essential metals and drugs over membranes. To date no study has provided a comprehensive analysis of SLC localization along the entire GI tract. The aim of the present study was to provide a comprehensive, segment-specific description of the localization of SLC genes along the rat GI tract by employing bioinformatics and molecular biology methods. The Unigene database was screened for rat SLC entries in the intestinal tissue. Using qPCR we measured expression of the annotated genes in the GI tract divided into the following segments: the esophagus, the corpus and the antrum of the stomach, the proximal and distal parts of the duodenum, ileum, jejunum and colon, and the cecum. Our Unigene-derived gene pool was expanded with data from in-house tissue panels and a literature search. We found 44 out of 78 (56%) of gut SLC transcripts to be expressed in all GI tract segments, whereas the majority of remaining SLCs were detected in more than five segments. SLCs are predominantly expressed in gut regions with absorptive functions although expression was also found in segments unrelated to absorption. The proximal jejunum had the highest number of differentially expressed SLCs. In conclusion, SLCs are a crucial molecular component of the GI tract, with many of them expressed along the entire GI tract. This work presents the first overall road map of localization of transporter genes in the GI tract.