• Ring finger protein 43 is a 90kDa protein containing a transmembrane domain, a protease-associated domain, an ectodomain, and a cytoplasmic RING domain. Ring finger protein 43 acts as a negative regulator of the Wnt signaling pathway by mediating the ubiquitination, endocytosis, and subsequent degradation of Wnt receptor complex components Frizzled on both canonical and non-canonical Wnt signaling pathways. Expressed in fetal kidney, fetal lung, and in colon cancer tissues, hepatocellular carcinomas, and lung adenocarcinomas. Mutations in this gene have been reported in multiple tumor cells, including colorectal and endometrial cancers. Acts as a tumor suppressor in the intestinal stem cell zone by inhibiting the Wnt signaling pathway, thereby restricting the size of the intestinal stem cell zone.

Gene targeting strategy for B-hRNF43 mice. The exons 2-6 of mouse Rnf43 gene that encode extracellular domain and part of transmembrane domain are replaced by human counterparts in B-hRNF43 mice. The genomic region of mouse Rnf43 gene that encodes cytoplasmic portion is retained. The promoter, 5’UTR and 3’UTR region of the mouse gene are also retained. The chimeric RNF43 expression is driven by endogenous mouse Rnf43 promoter, while mouse Rnf43 gene transcription and translation will be disrupted. 

Strain specific analysis of RNF43 mRNA expression in wild-type C57BL/6JNifdc mice and B-hRNF43 mice by RT-PCR. Liver RNA were isolated from wild-type C57BL/6JNifdc mice (+/+) and homozygous B-hRNF43 mice (H/H), then cDNA libraries were synthesized by reverse transcription, followed by PCR with mouse or human RNF43 primers. Mouse Rnf43 mRNA was detectable in wild-type mice. Human RNF43 mRNA was detectable only in homozygous B-hRNF43 mice (H/H) but not in wild-type mice. 

Western blot analysis of RNF43 protein expression in homozygous B-hRNF43 mice. Various tissue lysates were collected from wild-type C57BL/6JNifdc mice (+/+) and homozygous B-hRNF43 mice (H/H), and then analyzed by western blot with anti-RNF43 antibody (ThermoFisher, PA5-79930). 40 μg total proteins were loaded for western blotting analysis. RNF43 was detected in liver, colon and lung in wild-type mice and homozygous B-hRNF43 mice, as the antibody is cross-recognized between human and mouse RNF43.