799 INTESTINAL RBM47 DELETION PROMOTES SPONTANOUS POLYPOSIS THROUGH UP-REGULATED EPITHELIAL PROLIFERATION, ALTERNATIVE SPLICING OF TJP1 BUT MITIGATES COLITIS-ASSOCAITED TUMORIGENESIS VIA ANTI-OXIDATIVE ADAPTATION AND REDUCED INFLAMMATION

Abstract

Background RNA-binding motif protein 47 (RBM47) is a requisite cofactor in APOBEC1-dependent C-to-U RNA editing whose RNA targets are unknown. Aims Because Apobec-1 knockout mice are protected against polyposis in the ApcMin background, we asked if intestine-specific Rbm47 knockout mice (Rbm47IKO) exhibit altered tumor susceptibility, either spontaneously or in different murine cancer models. Results 86% (6/7) of 12-month old chow-fed Rbm47IKOmice developed spontaneous intestinal and colonic polyps (Fig 1A), compared to 10% (1/10) aged Rbm47floxcontrols. RNA-seq showed upregulated proliferation, glutathione metabolism, and anti-oxidative pathways in Rbm47 IKOintestine. QPCR revealed reduced abundance of the long Tjp1 mRNA isoform (Tjp1+) in Rbm47 IKOmice (Fig 1B), which was further reduced in polyp vs uninvolved tissue (11.8±0.2 vs 15.1±1.2, P=.03) in aged Rbm47 IKOmice. In support, we observed decreased Rbm47 mRNA (–DCT 0.97±2.79 vs 3.47±2.58, P Conclusion Rbm47IKOmice demonstrate spontaneous polyposis through upregulating proliferation and modifying Tjp1 alternative RNA splicing, with increased proximal intestinal polyposis in the ApcMin/+ background. By contrast, Rbm47IKOmice are protected against AOM-DSS-driven colitis-associated colon tumorogenesis by augmenting antioxidant capacity, over-expression of Il-33, and decreasing inflammatory activity. These contrasting phenotypes suggest that RBM47 exerts pathway-specific effects on intestinal tumorigenesis as a genetic modifier of growth, proliferation and inflammatory pathways. Download : Download high-res image (81KB) Download : Download full-size image Figure 1 . A: dissecting microscope images (left) and hematoxylin and eosin staining sections (right) of spontaneous polypogenesis in small intestine and colon of 12-month old chowfed Rbm47 IKOmice. B: Relative abundance of long Tjp1 mRNA isoform (Tjp1+) by quantitative RT-PCR in young adult mice jejunum. C: Rbm47 mRNA expression and relative abundance of Tjp1+ isoform by quantitative RT-PCR in human colorectal cancer tissue vs paired normal tissue. D: Comparison of overall survival among colorectal cancer patients with different levels of Rbm47 mRNA expression in tumor tissue using the cancer genome atlas (TCGA) database. Download : Download high-res image (71KB) Download : Download full-size image Figure 2 . A: Macroscopic illustration of colitis-associated colon tumors in mice treated with AOM)-DSS. B: left; the HE stained microscopic sections illustrate abundance of crypt abscess formation (yellow arrowheads) within dysplastic lesions of colon in AOM-DSS treated mice. Middle; F4/80 immunohistochemical staining of dysplastic lesions of colon in AOM-DSS treated mice. Right: Relative mRNA expression of inflammatory genes by quantitative RTPCR in dysplastic lesions of AOM-DSS treated mice. C: Relative mRNA expression of genes related to interleukin 33 by quantitative RT-PCR in dysplastic lesions of AOM-DSS treated mice. D: Macroscopic illustration of proximal small intestine tumors in mice with Apc Min/+background.