LncRNA lncMGR regulates skeletal muscle development and regeneration by recruiting CDK9 and sponging miRNAs.

Long non-coding RNAs (lncRNAs) play an essential role in vertebrate myogenesis and muscle diseases. However, the dynamic expression patterns, biological functions, and mechanisms of lncRNAs in skeletal muscle development and regeneration remain largely unknown. In this study, a novel lncRNA (named lncMGR) was differentially expressed during breast muscle development in fast- and slow-growing chickens. Functionally, lncMGR promoted myoblast differentiation, inhibited myoblast proliferation in vitro, and promoted myofiber hypertrophy and injury repair in vivo. Mechanistically, lncMGR increased the mRNA and protein expression of skeletal muscle myosin heavy chain 1 A (MYH1A) via both transcriptional and post-transcriptional regulation. Nuclear lncMGR recruited cyclin-dependent kinase 9 (CDK9) to the core transcriptional activation region of the MYH1A gene to activate MYH1A transcription. Cytoplasmic lncMGR served as a competitive endogenous RNA (ceRNA) to competitively absorb miR-2131-5p away from MYH1A and subsequently protected the MYH1A from miR-2131-5p-mediated degradation. Besides miR-2131-5p, cytoplasmic lncMGR could also sponge miR-143-3p to reconcile the antagonist between the miR-2131-5p/MYH1A-mediated inhibition effects and miR-143-3p-mediated promotion effects on myoblast proliferation, thereby inhibiting myoblast proliferation. Collectively, lncMGR could recruit CDK9 and sponge multiple miRNAs to regulate skeletal muscle development and regeneration, and could be a therapeutic target for muscle diseases.

Genome-Wide Genetic Structure of Henan Indigenous Chicken Breeds.

There are five indigenous chicken breeds in Henan Province, China. These breeds have their own unique phenotypic characteristics in terms of morphology, behavior, skin and feather color, and productive performance, but their genetic basis is not well understood. Therefore, we analyzed the genetic structure, genomic diversity, and migration history of Henan indigenous chicken populations and the selection signals and genes responsible for Henan gamecock unique phenotypes using whole genome resequencing. The results indicate that Henan native chickens clustered most closely with the chicken populations in neighboring provinces. Compared to other breeds, Henan gamecock's inbreeding and selection intensity were more stringent. TreeMix analysis revealed the gene flow from southern chicken breeds into the Zhengyang sanhuang chicken and from the Xichuan black-bone chicken into the Gushi chicken. Selective sweep analysis identified several genes and biological processes/pathways that were related to body size, head control, muscle development, reproduction, and aggression control. Additionally, we confirmed the association between genotypes of SNPs in the strong selective gene LCORL and body size and muscle development in the Gushi-Anka F2 resource population. These findings made it easier to understand the traits of the germplasm and the potential for using the Henan indigenous chicken.

Evolutionary analysis and functional characterization reveal the role of the insulin-like growth factor system in a diversified selection of chickens (Gallus gallus).

The insulin-like growth factor (IGF) system plays an indispensable role in embryonic and postnatal development in mammals. However, the effects of the system on growth, carcass, and egg-laying traits, and diversified selection have not been systematically studied in chickens. In the present study, firstly the composition and gene structures of the chicken IGF system were investigated using phylogenetic tree and conserved synteny analysis. Then the effects of the genetic variations in the IGF system genes on breeding of specialized varieties were explored by principal component analysis. In addition, the spatiotemporal expression properties of the genes in this system were analyzed by RT-qPCR and the functions of the genes in egg production performance and growth were explored by association study. Moreover, the effects of IGF-binding proteins 3 (IGFBP3) on skeletal muscle development in chicken were investigated by cell cycle analysis, 5-ethynyl-2'-deoxyuridine (EdU) and Cell Counting Kit-8 (CCK-8) assays. The results showed that the chicken IGF system included 13 members which could be classified into 3 groups based on their amino acid sequences: IGF binding proteins 1 to 5 and 7 (IGFBP1-5 and 7) belonged to the first group; IGF 1 and 2 (IGF1 and IGF2), and IGF 1 and 2 receptor (IGF1R and IGF2R) belonged to the second group; and IGF2 binding proteins 1-3 (IGF2BP1-3) belonged to the third group. The IGF2BP1 and 3, and IGFBP2, 3, and 7 genes likely contributed more to the formation of both the specialized meat-type and egg-type lines, whereas IGFBP1 and 5 likely contributed more to the formation of the egg-type lines. The SNPs in the IGF2BP3 and IGFBP2 and 5 genes were significantly associated with egg number, and SNPs in the IGFBP3 promoter region were significantly associated with body weight, breast muscle weight and leg muscle weight. The IGFBP3 inhibited proliferation but promoted differentiation of chicken primary myoblasts (CPMs). These results provide insights into the roles of the IGF system in the diversified selection of chickens. The SNPs associated with egg-laying performance, growth, and carcass traits could be used as genetic markers for breeding selection of chickens in the future.