Comparative integromics on FZD7 orthologs: conserved binding sites for PU.1, SP1, CCAAT-box and TCF/LEF/SOX transcription factors within 5'-promoter region of mammalian FZD7 orthologs.

Canonical WNT signals are transduced through Frizzled (FZD) family receptor and LRP5/LRP6 co-receptor to upregulate MYC, CCND1, FGF20, JAG1, WISP1 and DKK1 genes, while non-canonical WNT signals are transduced through FZD family receptor and PTK7/ROR2/RYK co-receptor to activate RHOA/RHOU/RAC/CDC42, JNK, PKC, NFAT and NLK signaling cascades. FZD7, expressed in the normal gastrointestinal tract, is upregulated in esophageal cancer, gastric cancer, colorectal cancer, and hepatocellular carcinoma. Here, chimpanzee FZD7 and cow Fzd7 genes were identified and characterized by using bioinformatics (Techint) and human intelligence (Humint). Chimpanzee FZD7 and cow Fzd7 genes were identified within NW_001232110.1 and AC173037.2 genome sequences, respectively. Chimpanzee FZD7 and cow Fzd7 showed 100% and 97.2% total-amino-acid identity with human FZD7. All of the nine amino-acid residues substituted between human FZD7 and human FzE3 were identical to those of human FZD7 in chimpanzee, cow, mouse and rat FZD7 orthologs. Functional analyses using FzE3 with multiple cloning artifacts and/or sequencing errors are invalid. FZD7 orthologs were seven-transmembrane proteins with extracellular Frizzled domain, leucine zipper motif around the 5th transmembrane domain, and cytoplasmic DVL- and PDZ-binding motifs. Ser550 and Ser556 of FZD7 orthologs were putative aPKC phosphorylation sites. Dimerization and Ser550/556 phosphorylation were predicted as regulatory mechanisms for the signaling through FZD7. Transcriptional start site of human FZD7 gene was 735-bp upstream of NM_003507.1 RefSeq 5'-end. In addition to gastrointestinal cancer, hepatocellular cancer and pancreatic cancer, human FZD7 mRNAs were expressed in blastocysts, undifferentiated embryonic stem (ES) cells, ES-derived endodermal progenitors, ES-derived neural progenitors, fetal cochlea, retinal pigment epithelium, olfactory epithelium, regenerating liver, and multiple sclerosis. Comparative genomics analyses revealed that the binding sites for PU.1, SP1/Krüppel-like, CCAAT-box, and TCF/LEF/SOX transcription factors were conserved among 5'-promoter regions of mammalian FZD7 orthologs.