Comparative genomics on Sonic hedgehog orthologs

Sonic hedgehog (SHH), Indian hedgehog (IHH), and Desert hedgehog (DHH) are key molecules for the integrome network in oncology and regenerative medicine. Soluble Hedgehog ligands bind to Patched receptor to activate Smoothened seven-transmembrane receptor with Frizzled domain. KIF27 and KIF7 are human homologs of Drosophila Costal-2 (Cos2), associating with Smoothened, GLI homolog, Fused, and microtubule. Smoothened activation leads to GLI1, GLI2, or GLI3-dependent transcription of Hedgehog target genes. Here, comparative proteomics analyses and comparative genomics analyses on SHH orthologs were performed by using bioinformatics. Human SHH representative transcript was assembled by using BX461534 EST, NM_000193.2 RefSeq, AA503654 EST, and AC078834.5 genome sequence. Human SHH mRNA was expressed in fetal brain, infant brain, and also in colorectal cancer. Chimpanzee SHH gene, consisting of three exons, was located within AC147335.2 genome sequence. Human SHH and chimpanzee SHH (462 aa) showed E284G and T416P amino-acid substitutions. Vertebrate SHH orthologs shared the common domain architecture, consisting of N-terminal signal peptide, Hedgehog signaling domain, Hint domain, and C-terminal HPLGMxxxxS motif. Evolutionarily conserved SHH promoter region (nucleotide position 104429-104083 of human genome sequence AC078834.5) was identified. Double bHLH binding sites, CCAAT box, and TATA box were conserved among human SHH promoter, chimpanzee SHH promoter, rat Shh promoter, and mouse Shh promoter.