Characterizing Differential Pectoralis Muscle miRNA Transcriptional Profiles Between Modern and Legacy Gallus Broiler Lines

Modern meat-type chickens (broilers) exhibit enhanced growth, especially of the skeletal muscle, relative to their legacy counterparts. Comparative studies of modern and legacy broiler chickens provide an opportunity to identify genes and pathways affected by this human-directed evolution.   We previously used messenger RNA sequencing to compare the transcriptomes of a modern and a legacy broiler line to identify differentially enriched genes in the breast muscle at days 6 and 21 post-hatch. This study expands our transcriptional profiling to identify important genes and pathways that may be affected by miRNA regulation.  At day 6 post-hatch 20 miRNAs, including several associated with, cell proliferation, metabolism, myogenic growth and development were differentially enriched between the two lines.  The miRNA profiles between lines at day 21 post-hatch identified only 7 miRNAs differentially enriched nearly all of which remain enriched from the D6 samples.  Several differentially enriched myomiRs and other miRNAs that may play a role in regulation of myogenic growth and differentiation were identified between the modern and legacy broiler lines.  Specifically, differences in the ratios of several miRs enriched in Ross samples, such as miR-146a, miR-194, miR-215, may affect the myostatin signaling pathway.  Additionally, miRs enriched in the legacy line, such as miR-193a, are associated with cell cycle and the Akt/PI3k signaling pathway.  These differentially enriched miRs help to further clarify the transcriptional profiles of these two broiler lines and further elucidate the effects of human directed selective pressures on domesticated organisms.