Characterization of the canine mda-7 gene, transcripts and 2 expression patterns
Authors
Maninder Sandey, R. Curtis Bird, Swadesh K. Das, Devanand Sarkar, David T. Curiel, Paul B. Fisher, Bruce F. Smith
Institution
Auburg Uni
Country
United States
Year
2014
Journal
Gene
Abstract
Human melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24) displays potent growth sup- pressing and cell killing activity against a wide variety of human and rodent cancer cells. In this study, we iden- tified 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 humanMDA-7/IL-24. CanineMDA-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 alter- nate 5′-splice donor sites, to yield five splice variants (canine mda-7sv1, canine mda-7sv2, canine mda-7sv3, ca- nine 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 se- quences 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 phytohemagglu- tinin (PHA) stimulated canine peripheral blood mononuclear cells (PBMCs). Furthermore, in-silico analysis re- vealed 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 caninemda-7 is indeed an ortholog of humanmda-7/IL-24, its protein product has high amino acid similarity to humanMDA-7/IL-24 protein and itmay possess similar biological prop- erties to human MDA-7/IL-24, but its expression pattern is more restricted than its human ortholog.