Aberrant Regenerating‐Islet Derived (Reg) Gene Expression is an Early Indicator of Colonic Dysplasia in Heterogeneous Nuclear Ribonucleoprotein (Hnrnp I) Knockout Mice

Abstract

ObjectivesReg is an evolutionarily conserved family of proteins with anti‐inflammatory and antimicrobial functions, is mainly involved in the defense of intestinal epithelial cells (IEC). Recent studies indicate that the attenuation of colitis depends on the functions of Reg3b. Here, knockout mice with an IEC‐specific ablation of the Hnrnp I gene (KO) were examined, which exhibited an increased risk of developing spontaneous colitis. The objective of this study is to examine the gene expression of the Reg genes in the KO mice.HypothesisWe hypothesize that epithelial ablation of Hnrnp I in the colon of the KO mice leads to early aberrant expression of Reg3b and Reg3g.MethodsSix weeks old WT and KO mice were sampled for body weight, colon weight and length. Whole colon was opened and jelly‐rolled from distal to proximal end for embedding. Total RNA was extracted for quantification of gene expression using qPCR. Colon tissue sections were examined by hematoxylin‐eosin staining (H&E) for colon morphology and colonic crypt length measurements. Colon localization of Reg proteins was analyzed using immunofluorescent staining. Results were analyzed using the Mann‐Whitney test. Spearman test was used to analyze the correlation. P less than 0.05 is considered significant.ResultsThe expression levels of Reg3b, Reg3g, and Il‐6 in KO mice were significantly lower than WT mice. Furthermore, expression levels of Reg3b and Reg3g are correlated in both WT and KO groups (R=0.95). It is worth mentioning that, in 30% of KO mice, the expression levels of Reg3b and Reg3g are significantly higher than the rest of the KO mice, exhibiting significant dichotomy. Histological analysis showed that the crypt lengths of KO mice were significantly longer than those in the WT mice both in the distal end and proximal colon. More importantly, the KO mice with elevated Reg gene expressions had longer crypt lengths in the distal end. Moreover, KO mice with elongated crypts also exhibited invasive dysplasia in the colon sections.ConclusionsOur results indicate that IECs‐specific Hnrnp I knockout abolished the expression of the Regfamily genes. Further investigations are warranted to determine the potentially detrimental effects from the diminished Reg3 to the overall protection against microbial invasion in the colon. The contradictory upregulation of Reg3b and Reg3g in a subset of the KO mice indicates the extreme responsiveness to the perturbation from the Hnrnp I knockout and may serve as an early indicator of colon dysplasia.