title: Characterization of the canine mda-7 gene, transcripts and expression patterns.
abstract: Human melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24) displays potent growth suppressing and cell killing activity against a wide variety of human and rodent cancer cells. In this study, we identified a canine ortholog of the human mda-7/IL-24 gene located within a cluster of IL-10 family members on chromosome 7. The full-length mRNA sequence of canine mda-7 was determined, which encodes a 186-amino acid protein that has 66% similarity to human MDA-7/IL-24. Canine MDA-7 is constitutively expressed in cultured normal canine epidermal keratinocytes (NCEKs), and its expression levels are increased after lipopolysaccharide stimulation. In cultured NCEKs, the canine mda-7 pre-mRNA is differentially spliced, via exon skipping and alternate 5'-splice donor sites, to yield five splice variants (canine mda-7sv1, canine mda-7sv2, canine mda-7sv3, canine mda-7sv4 and canine mda-7sv5) that encode four protein isoforms of the canine MDA-7 protein. These protein isoforms have a conserved N-terminus (signal peptide sequence) and are dissimilar in amino acid sequences at their C-terminus. Canine MDA-7 is not expressed in primary canine tumor samples, and most tumor derived cancer cell lines tested, like its human counterpart. Unlike human MDA-7/IL-24, canine mda-7 mRNA is not expressed in unstimulated or lipopolysaccharide (LPS), concanavalin A (ConA) or phytohemagglutinin (PHA) stimulated canine peripheral blood mononuclear cells (PBMCs). Furthermore, in-silico analysis revealed that canonical canine MDA-7 has a potential 28 amino acid signal peptide sequence that can target it for active secretion. This data suggests that canine mda-7 is indeed an ortholog of human mda-7/IL-24, its protein product has high amino acid similarity to human MDA-7/IL-24 protein and it may possess similar biological properties to human MDA-7/IL-24, but its expression pattern is more restricted than its human ortholog.
authors.affiliation: Scott-Ritchey Research Center, College of Veterinary Medicine, Auburn University, AL, USA.
authors.forename: Maninder
authors.initials: M
authors.lastname: Sandey
authors.affiliation: Department of Pathobiology, College of Veterinary Medicine, Auburn University, AL, USA.
authors.forename: R Curtis
authors.initials: RC
authors.lastname: Bird
authors.affiliation: Department of Human and Molecular Genetics, Virginia Commonwealth University, School of Medicine, Richmond, VA 23298, USA.
authors.forename: Swadesh K
authors.initials: SK
authors.lastname: Das
authors.affiliation: Department of Human and Molecular Genetics, Virginia Commonwealth University, School of Medicine, Richmond, VA 23298, USA; VCU Institute of Molecular Medicine, Virginia Commonwealth University, School of Medicine, Richmond, VA 23298, USA; VCU Massey Cancer Center, Virginia Commonwealth University, School of Medicine, Richmond, VA 23298, USA.
authors.forename: Devanand
authors.initials: D
authors.lastname: Sarkar
authors.affiliation: Radiation Oncology, Washington University School of Medicine, St. Louis, MO 63110, USA.
authors.forename: David T
authors.initials: DT
authors.lastname: Curiel
authors.affiliation: Department of Human and Molecular Genetics, Virginia Commonwealth University, School of Medicine, Richmond, VA 23298, USA; VCU Institute of Molecular Medicine, Virginia Commonwealth University, School of Medicine, Richmond, VA 23298, USA; VCU Massey Cancer Center, Virginia Commonwealth University, School of Medicine, Richmond, VA 23298, USA.
authors.forename: Paul B
authors.initials: PB
authors.lastname: Fisher
authors.affiliation: Scott-Ritchey Research Center, College of Veterinary Medicine, Auburn University, AL, USA; Department of Pathobiology, College of Veterinary Medicine, Auburn University, AL, USA. Electronic address: smithbf@auburn.edu.
authors.forename: Bruce F
authors.initials: BF
authors.lastname: Smith
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D017124:Conserved Sequence; D004247:DNA / Q000235:genetics; D004285:Dogs; D005786:Gene Expression Regulation; D007378:Interleukins / Q000235:genetics*; D015603:Keratinocytes / Q000378:metabolism; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000099180:Interleukin-24
chemical_list: D004247:DNA; D007378:Interleukins; D012333:RNA, Messenger; D000099180:Interleukin-24
keywords: Interleukin-24 (IL-24); Melanoma differentiation associated gene-7 (mda-7); cancer cell lines; canine