| Summary: | miRNAs have been widely investigated in terms of cell proliferation and differentiation. However, little is known about their effects on bird growth. Here we characterized the promoter of miR-206 in chicken and found that the preferable promoter was located in 1200 bp upstream of pri-miR-206. In this region, many key transcription factors, including MyoD, c-Myb, CEBPα/β, AP-4, RAP1, Brn2, GATA-1/2/3, E47, Sn, upstream stimulatory factor (USF) and CdxA, were predicted to bind and interact with miR-206 promoter. Overexpression of MyoD sharply increased miR-206 expression in both fibroblast and myoblast cells, and also the regulation in the myoblast cells was much stronger, indicating that miR-206 was regulated by MyoD combined with other muscle specific transcriptional factors. Aiming to further investigate the relationship between miR-206 mutation and transcriptional expression, total of 23 SNPs were identified in the two distinct bird lines by sequencing. Interestingly, the motif bound by MyoD was individually destroyed by G-to-C mutation located at 419 bp upstream of miR-206 precursor. Co-transfecting MyoD and miR-206 promoter in DF-1 cells, the luciferase activity of promoter containing homozygous GG types was significantly higher than CC ones (p < 0.05). Thus, this mutation caused low expression of miR-206. Consistently, eight variants including G-419C mutation exhibited a great effect on birthweight through maker-trait association analysis in F2 population (p < 0.05). Additionally, the regulation of miR-206 on embryo muscle mass mainly by increasing MyoG and muscle creatine kinase (MCK) expression (p < 0.05) with little change in MyoD, TMEM8C and myosin heavy chain (MHC). In conclusion, our findings provide a novel mutation destroying the promoter activity of miR-206 in birds and shed new light to understand the regulation mechanism of miR-206 on the embryonic muscle growth.
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