| Summary: | <p>Abstract</p> <p>Background</p> <p>A deletion mutation in the growth hormone receptor (<it>GHR</it>) gene results in the inhibition of skeletal muscle growth and fat deposition in dwarf chickens. We used microarray techniques to determine microRNA (miRNA) and mRNA expression profiles of <it>GHR</it> in the skeletal muscles of 14-day-old embryos as well as 7-week-old deletion-type dwarf and normal-type chickens. Our aim was to elucidate the miRNA regulation of <it>GHR</it> expression with respect to growth inhibition and fat deposition.</p> <p>Results</p> <p>At the same developmental stages, different expression profiles in skeletal muscles of dwarf and normal chickens occurred for four miRNAs (miR-1623, miR-181b, let-7b, and miR-128). At different developmental stages, there was a significant difference in the expression profiles of a greater number of miRNAs. Eleven miRNAs were up-regulated and 18 down-regulated in the 7-week-old dwarf chickens when compared with profiles in 14-day-old embryos. In 7-week-old normal chickens, seven miRNAs were up-regulated and nine down-regulated compared with those in 14-day-old embryos. In skeletal muscles, 22 genes were up-regulated and 33 down-regulated in 14-day-old embryos compared with 7-week-old dwarf chickens. Sixty-five mRNAs were up-regulated and 108 down-regulated in 14-day-old embryos as compared with 7-week-old normal chickens. Thirty-four differentially expressed miRNAs were grouped into 18 categories based on overlapping seed and target sequences. Only let-7b was found to be complementary to its target in the 3′ untranslated region of <it>GHR</it>, and was able to inhibit its expression. Kyoto Encyclopedia of Genes and Genomes pathway analysis and quantitative polymerase chain reactions indicated there were three main signaling pathways regulating skeletal muscle growth and fat deposition of chickens. These were influenced by let-7b-regulated <it>GHR</it>. Suppression of the cytokine signaling 3 (<it>SOCS3</it>) gene was found to be involved in the signaling pathway of adipocytokines.</p> <p>Conclusions</p> <p>There is a critical miRNA, let-7b, involved in the regulation of <it>GHR</it>. <it>SOCS3</it> plays a critical role in regulating skeletal muscle growth and fat deposition <it>via</it> let-7b-mediated <it>GHR</it> expression.</p>
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