Ultraviolet radiation-induced differential microRNA expression in the skin of hairless SKH1 mice, a widely used mouse model for dermatology research

Cutaneous squamous cell carcinoma (cSCC) is the most common type of non-melanoma skin cancer that can metastasize. The major etiological factor associated with cSCC is Ultraviolet radiation (UVR) with a limited understanding of its molecular mechanism. It was hypothesized that there is a direct effect of UVR on modulation of microRNAs (miRNAs), a novel class of short noncoding RNAs which affects translation and stability of mRNAs. To test the hypothesis, the dorsal skin of the SKH1 mice (6-7 week old) was exposed to acute and chronic doses of UVR. In miRNA array profiling, we found differential expression (log fold change>1) of miR-25-5p between untreated and acute UVR treated (4kJ/m(2)) SKH1 mice skin. However, differential expression (>1 log fold) of miR-144-3p, miR-33-5p, miR-32-5p, miR-1983, miR-136-5p, miR-142-3p, miR-376a-3p, miR-142-5p, miR-3968, and miR-29b-3p was observed between untreated and chronically UVR treated mice skin. Differentially expressed selected miRNAs (miR-32-5p, miR-33-5p, miR-144-3p, and miR-376a-3p) were further validated in real time PCR using miRNA specific primers. Web based data mining, for the prediction of potential miRNA associated gene pathways in miRBase database revealed a link with important pathways (PI3K-Akt, MAPK, Wnt, transcriptional misregulation, and other oncogenic pathway) associated with cSCC. Furthermore, findings of PI3K-Akt pathway genes affected due to chronic UVR were confirmed using cDNA array.