External ear microRNA expression profiles during mouse development.

MicroRNAs (miRNAs) comprise a class of approximately 22 nucleotide regulatory non-coding RNAs that play several roles in diverse biological processes. Recent reports suggest that embryonic development in mammals is accompanied by dynamic changes in miRNA expression; however, there is no information regarding the role of miRNAs in the development of the external ear. The aim of this study was to determine the stage-specific expression of miRNAs during mouse external ear development in order to identify potentially implicated miRNAs along with their possible targets. miRNA expression profiles from fetal mice pinnae and back skin tissues at 13.5 dpc and 14.5 dpc were obtained using an Affymetrix GeneChip miRNA 3.0 array. Biological triplicates for both tissues, each collected from a litter averaging 16 fetuses, were analyzed. The results were analyzed with Affymetrix's Transcriptome Analysis Console software to identify differentially expressed miRNAs. We observed differential expression of 40 miRNAs including some predicted to target genes implicated in external ear development, such as mmu-miR-10a, an miRNA known to modulate Hoxa1 mRNA levels, and mmu-miR-200c and mmu-miR-205. To our knowledge, this is the first miRNA expression profiling study of external ear development in mammals. These data could set the basis to understand the implications of miRNAs in normal external ear development.