(E63) Horses with Undifferentiated Colitis Exhibit Downregulation of a Choline Transporter Gene in Colon and Rectum

Abstract: Background– Acute undifferentiated equine colitis has a high mortality rate. The pathophysiology of colitis at the epithelial level is incompletely understood. Transcriptomic analysis of intestinal tissues can identify cellular pathways altered in colitis. Rectal biopsies in live horses could represent a suitable substitute for colon. Objectives– 1: Characterize the transcriptome of rectal tissue from clinically healthy horses and colitis cases. 2: Determine if downregulated SLC5A7, a gene encoding a high-affinity sodium and chloride-dependent choline transporter, CHT1, in colitis cases persists in a larger dataset and other intestinal tissues (right dorsal colon (RDC), right ventral colon (RVC), cecum). Animals– 11 healthy horses and 5 horses with colitis. Rectal tissue was obtained on all horses, and RDC, RVC, and cecum were obtained in 7 healthy and 4 colitis cases. Methods- An initial pilot RNA-sequencing dataset was obtained in rectal tissues from 3 healthy horses and 3 colitis horses. Subsequent gene expression (qRT-PCR) for SLC5A7 was performed on all samples. Immunofluorescence for CHT1 was performed on rectal tissue from healthy and colitis horses. Results– Horses with colitis had a distinct transcriptomic signature as compared to healthy horses (Figure 1). SLC5A7 was significantly decreased in all tissues from colitis horses by RNA-sequencing and qRT-PCR (Figure 2). CHT1 immunofluorescence was decreased in colitis tissues. Conclusions and clinical importance– Colitis cases demonstrated a shared transcriptome in rectal mucosa/submucosa distinct from clinically healthy horses. SLC5A7 is unexplored in equine colitis but the downregulation observed throughout the colon suggests it may be useful for future diagnostics or therapeutics.