Determining Differential Expression Patterns of MicroRNAs in Mammalian Skin by In Situ Hybridization

MicroRNAs are small non-coding RNAs that regulate gene expression posttranscriptionally (Bartel, 2009). Several different microRNAs have been implicated in regulatory pathways of skin morphogenesis, stem cells, skin cancer, and other skin diseases. A subset of microRNAs have been found to be differentially expressed in distinct skin lineages, namely epidermis and hair follicle (Yi et al., 2006). Characterization of the spatial and temporal expression patterns of these microRNAs can provide a basis to investigate their functions during development as well as in skin diseases including skin cancer. During my thesis study, I employed in situ hybridization to characterize the differential expression of four discrete microRNAs: miR-203, miR-143, miR-125b, and miR-205 in mammalian skin. My results demonstrated that miR-203 is highly expressed in differentiating skin lineages, miR-143 is enriched in the transient amplifying cells in hair follicle matrix, miR-125b and miR-205 are enriched in skin stem cells. I also cloned three regions upstream of miR-205 and analyzed their promoter activity in cultured keratinocytes. Together, my study shows that miRNAs are differentially expressed in distinct skin lineages and provides a basis to analyze their functions in the future