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The meat production of broilers is crucial to economic benefits of broiler industries, while the slaughter performance of broilers is directly determined by skeletal muscle development. Hence, the broiler breeding for growth traits shows a great importance. As a kind of small noncoding RNA, microRNA (miRNA) can regulate the expression of multiple genes and perform a wide range of regulation in organisms. Currently, more and more studies have confirmed that miRNAs are closely associated with skeletal muscle development of chickens. Based on our previous miR-seq analysis (accession number: PRJNA668199), miR-460b-5p was screened as one of the key miRNAs probably involved in the growth regulation of chickens. However, the regulatory effect of miR-460b-5p on the development of chicken skeletal muscles is still unclear. Therefore, miR-460b-5p was further used for functional validation at the cellular level in this study. The expression pattern of miR-460b-5p was investigated in proliferation and differentiation stages of chicken primary myoblasts. It was showed that the expression level of miR-460b-5p gradually decreased from the proliferation stage (GM 50%) to the lowest at 24 h of differentiation. As differentiation proceeded, miR-460b-5p expression increased significantly, reaching the highest and stabilizing at 72 h and 96 h of differentiation. Through mRNA quantitative analysis of proliferation marker genes, CCK-8 and Edu assays, miR-460b-5p was found to significantly facilitate the transition of myoblasts from G1 to S phase and promote chicken myoblast proliferation. mRNA and protein quantitative analysis of differentiation marker genes, as well as the indirect immunofluorescence results of myotubes, revealed that miR-460b-5p significantly stimulated myotube development and promote chicken myoblast differentiation. In addition, the target relationship was validated for miR-460b-5p according to the dual-luciferase reporter assay and mRNA quantitative analysis, which indicates that miR-460b-5p was able to regulate RBM19 expression by specifically binding to the 3′ UTR of RBM19. In summary, miR-460b-5p has positive regulatory effects on the proliferation and differentiation of chicken myoblasts, and RBM19 is a target gene of miR-460b-5p. [ABSTRACT FROM AUTHOR]

This study was conducted in two steps to determine the effects of in ovo injection of zinc acetate (ZAC) on some gene expression associated with embryonic growth and development, and with growth and carcass characteristics of the resultant chicks. In the first step the effect of in ovo injection of ZAC on the expression of insulin-like growth factors (IGFs:IGF-I and IGF-I), myogenic regulatory factors (MRFs) and metallothionein (MT) genes was examined, and in the step two, the associations between genes expression with fertility, embryonic mortality, hatchability, body weight (BW) and relative organ weight on day of hatch, and body weight (BW) and feed conversion ratio (FCR) a week after hatching were investigated. Seven hundred twenty fertile eggs (n=720) were randomly divided into 4 treatment groups consisted of: 1) noninjected (NI) group, 2) sham group (group injected with deionized water (DW)), and 3) and 4) groups injected with 3.64 and 5.23 M ZAC, respectively. On day 3 of incubation the eggs were injected with 50 µL of each treatment into the albumen. On day 5 of the incubation and on hatch day, liver and breast muscle of the chicks were removed and immediately stored at -80 °C until RNA extraction and real time-PCR analysis. In ovo ZAC injection increased myogenic differentiation factor both in embryo and breast muscle. MT mRNA expression was also increased by ZAC injection. Hatchability was lower in ZAC groups and early embryonic mortality was higher in sham control (SHC) and ZAC groups. Injection of ZAC improved both BW and FCR during the first week of rearing, and increased the relative weights of liver and breast muscle. In conclusion, in ovo injection of ZAC increased some of gene expressions of tissues and BW7 during the first week, but decreased hatchability. Hence, lower doses of ZAC are recommended to use in further experiments. [ABSTRACT FROM AUTHOR]