Functional annotation of differentially expressed fetal cardiac microRNA targets: implication for microRNA-based cardiovascular therapeutics.

Gene expression pattern of a failing heart depicts remarkable similarity with developing fetal heart. Elucidating genetic as well as epigenetic mechanisms regulating the gene expression during cardiac development will improve our understanding of cardiovascular diseases. In the present study, we aimed to validate and characterize differentially expressed known microRNAs (miRNA) obtained from next generation sequencing data of two fetal cardiac developmental stages (days 4th and 14th) from chicken (G. gallus domesticus) using bioinformatic approaches. Potential mRNA targets of individual miRNA were identified and classified according to their biological, cellular, and molecular functions. Functional annotation of putative target genes was performed to predict their association with cardiovascular diseases. We identified a total of 19 differentially expressed miRNAs between 4th and 14th day sample from the data sets obtained by next generation sequencing. A total of nearly 1522 potential targets ranging from 15 to 270 for each miRNA were predicted out of which 1221 were unique, while 301 were overlapping. Gene ontology and KEGG analysis revealed that majority of these target genes regulate critical cellular and molecular processes including transcriptional regulation, protein transport, signal transduction, matrix remodeling, Ras signaling, MAPK signaling, and TGF-beta signaling pathways indicating the complex nature of microRNA-mediated gene regulation during cardiogenesis. We found a significant association between potential target genes and cardiovascular diseases validating a link between fetal cardiac miRNAs and regulation of cardiovascular disease-related genes. These important findings may lay a foundation for further understanding the regulatory mechanisms operative in gene re-programming in the failing heart.