P135 MAJOR GENE REGULATORS AFFECTED IN COLON AND BLOOD OF DEXTRAN SODIUM SULFATE ACUTE COLITIS MURINE MODEL
Authors: Yarani Reza , Palasca Oana , Doncheva Nadezhda Tsankova , Anthon Christian , Pilecki Bartosz , Litman Thomas , Holmskov Uffe , Jensen Lars Juhl , Gorodkin Jan , Pociot Flemming 
Published: January 2020

Abstract

Background
Dextran sulfate sodium (DSS) ulcerative colitis (UC) murine models have long been used for in vivo studies. DSS is a negatively charged polysaccharide with colitogenic properties. Although the mechanisms by which DSS induces intestinal inflammation are not fully understood, there are several good reasons why the DSS chemical colitis model for investigating the immunopathogenesis mechanism of UC is widely used. These include strong phenotypic clinical manifestations which emulate numerous clinical and histopathological features of human UC, ease of use, low mortality rate and high reproducibility. Here, by using high-throughput RNA sequencing analysis we set to investigate the major predicted gene regulators (GRs) affected by differentially expressed genes in the DSS treated UC model in order to obtain regulatory insights into the pathogenic mechanisms of UC development.

Methods
A DSS-induced mouse model of UC was established. Total RNA from colon tissue and blood of 3 healthy and 3 DSS-treated mice was extracted and sequenced by Illumina HiSeq 4000. Gene expression levels were obtained by mapping and quantification to the annotated mouse genome. Subsequently, differential gene expression analysis between DSS-treated and control mice both in colon and blood was performed. Ingenuity pathway analysis software (IPA®, Qiagen) was used to predict/identify major GRs affected by significantly differentially expressed genes (SDEGs, FC &gt; |2|, p ≤0.05) in both colon and blood.

Results
Our analysis revealed how many and which major GRs are affected in DSS-treated mice and also the direction of change as compared to healthy (untreated) mice. In colon, 595 activated and 198 inhibited major GRs (p-value of overlap ≤0.05) in relation to ∼ 3180 SDEGs were identified, while in blood, we identified 205 activated and 62 inhibited GRs (in relation to ∼650 SDEGs). Colon and blood share 181 activated and 41 inhibited GRs. Identified GRs include transcription regulators, cytokines, transmembrane receptors and enzymes that mainly contribute to the development of inflammatory/immune responses. In colon and blood, the top 10 activated and inhibited regulators with the highest positive and negative activation z-score with target molecules as well as expression in the datasets are indicated in Figure 1a and 1b, respectively.

Conclusion
In this study, we analyzed linkage of GRs to SDEGs through coordinated expression and identified potential major regulators that have significant effect on UC pathogenic-related gene expression. These GRs seem to be the key regulators of transcriptomic changes induced by inflammation. These findings expand our molecular understanding of putative new targets that may be important in the pathophysiology of UC and provide biological insights into the observed expression changes between the UC and healthy controls.