Genome-wide analysis of the rat colon reveals site-specific differences in histone modifications and proto-oncogene expression

Results/Conclusion: Globally, RNA-Seq results indicated that 9,866 genes were actively expressed, of which 540 genes were differentially expressed between the proximal and distal colon. With regard to differentially expressed genes, a high correlation was observed between H3K4me3-Seq and RNA-Seq data, with 96% of the canonical pathways being similarly affected in the H3K4me3-Seq and RNA-Seq data sets. Gene ontology analysis indicated that colonic crypt location significantly impacted both chromatin and transcriptional regulation of genes involved in cell transformation, lipid metabolism, lymphatic development and immune cell trafficking. Gene function analysis indicated that the PI3-Kinase signaling pathway was regulated in a site-specific manner, e.g., pathway proto-oncogenes, c-Jun, c-Fos and ATF, were up-regulated in the distal colon. Middle and long non-coding RNAs (lncRNAs) were also detected in the colon, including select lncRNAs formerly only detected in the rat nervous system. In summary, distinct combinatorial patterns of histone modifications exist in the proximal versus distal colon. These site-specific differences may explain the differential effects of chemoprotective agents on cell transformation in the ascending (proximal) and descending (distal) colon.