The difference in muscle fiber types is very important to the muscle development and meat quality of broilers. At present, the molecular regulation mechanisms of skeletal muscle fiber‐type transformation in broilers are still unclear. In this study, differentially expressed genes between breast and leg muscles in broilers were analyzed using RNA‐seq. A total of 767 DEGs were identified. Compared with leg muscle, there were 429 upregulated genes and 338 downregulated genes in breast muscle. Gene Ontology (GO) enrichment indicated that these DEGs were mainly involved in cellular processes, single organism processes, cells, and cellular components, as well as binding and catalytic activity. KEGG analysis shows that a total of 230 DEGs were mapped to 126 KEGG pathways and significantly enriched in the four pathways of glycolysis/gluconeogenesis, starch and sucrose metabolism, insulin signalling pathways, and the biosynthesis of amino acids. Quantitative real‐time reverse transcription polymerase chain reaction (qRT‐PCR) was used to verify the differential expression of 7 selected DEGs, and the results were consistent with RNA‐seq data. In addition, the expression profile of MyHC isoforms in chicken skeletal muscle cells showed that with the extension of differentiation time, the expression of fast fiber subunits (types IIA and IIB) gradually increased, while slow muscle fiber subunits (type I) showed a downward trend after 4 days of differentiation. The differential genes screened in this study will provide some new ideas for further understanding the molecular mechanism of skeletal muscle fiber transformation in broilers.

Background: Japanese encephalitis virus is a mosquito-borne neurotropic flavivirus that causes acute viral encephalitis in humans. Pigs are crucial amplifier host of JEV. Recently, increasing evidence has shown that long non-coding RNAs (lncRNAs) play important roles in virus infection. Methods: JEV proliferation was evaluated after overexpression or knockdown of lncRNA-SUSAJ1 using western blotting and reverse-transcription polymerase chain reaction (RT-PCR). C–C chemokine receptor type 1 (CCR1) was found to regulate the expression of lncRNA-SUSAJ1 by inhibitors screen. The expression of lncRNA-SUSAJ1 was detected using RT-PCR after overexpression or knockdown of transcription factor SP1. In addition, the enrichments of transcription factor SP1 on the promoter of lncRNA-SUSAJ1 were analyzed by chromatin immunoprecipitation. Results: In this study, we demonstrated that swine lncRNA-SUSAJ1 could suppress JEV proliferation in PK-15 cells. We also found that CCR1 inhibited the expression of lncRNA-SUSAJ1 via the transcription factor SP1. In addition, knockdown of CCR1 could upregulated the expression of SP1 and lncRNA-SUSAJ1, resulting in resistance to JEV proliferation. Conclusions: These findings illustrate the importance of lncRNAs in virus proliferation, and reveal how this virus regulates lncRNAs in host cells to promote its proliferation.

Objective: Skeletal muscle satellite cells (SMSCs) are significant for the growth, regeneration, and maintenance of skeletal muscle after birth. However, currently, few studies have been performed on the isolation, culture and inducing differentiation of goose muscle satellite cells. Previous studies have shown that C1q and tumor necrosis factor-related protein 3 (CTRP3) participated in the process of muscle growth and development, but its role in the goose skeletal muscle development is not yet clear. This study aimed to isolate, culture, and identify the goose SMSCs in vitro. Additionally, to explore the function of CTRP3 in goose SMSCs.Methods: Goose SMSCs were isolated using 0.25% trypsin from leg muscle (LM) of 15 to 20 day fertilized goose eggs. Cell differentiation was induced by transferring the cells to differentiation medium with 2% horse serum and 1% penicillin streptomycin. Immunofluorescence staining of Desmin and Pax7 was used to identify goose SMSCs. Quantitative realtime polymerase chain reaction and western blot were applied to explore developmental expression profile of CTRP3 in LM and the regulation of CTRP3 on myosin heavy chains (MyHC), myogenin (MyoG) expression and Notch signaling pathway related genes expression.Results: The goose SMSCs were successfully isolated and cultured. The expression of Pax7 and Desmin were observed in the isolated cells. The expression of CTRP3 decreased significantly during leg muscle development. Overexpression of CTRP3 could enhance the expression of two myogenic differentiation marker genes, MyHC and MyoG. But knockdown of CTRP3 suppressed their expression. Furthermore, CTRP3 could repress the mRNA level of Notch signaling pathway-related genes, notch receptor 1, notch receptor 2 and hairy/enhancer-of-split related with YRPW motif 1, which previously showed a negative regulation in myoblast differentiation.Conclusion: These findings provide a useful cell model for the future research on goose muscle development and suggest that CTRP3 may play an essential role in skeletal muscle growth of goose.

Phosphoglycerate dehydrogenase (PHGDH) is the rate-limiting enzyme in the serine synthesis pathway. However, the regulatory role of PHGDH in muscle development is unclear. We report that the expression of PHGDH increased significantly during proliferation of chicken skeletal muscle satellite cells. Knockdown of PHGDH by an siRNA suppressed myoblast proliferation, whereas overexpression of PHGDH enhanced muscle cell proliferation. Furthermore, PHGDH promoted the expression of Forkhead box protein M1 (FoxM1). Knockdown of FoxM1 by an siRNA attenuated the proliferation of chicken muscle cells, whereas its overexpression significantly promoted proliferation. Additionally, siRNA-PHGDH inhibited pcDNA3.1-FoxM1-induced FoxM1 expression in chicken muscle cells. Moreover, PHGDH inhibition overcame the stimulation by pcDNA3.1-FoxM1 of cell cycle-related gene expression. We propose that PHGDH accelerates chicken muscle cell proliferation by increasing FoxM1 expression.

Light is a factor affecting muscle development and meat quality in poultry production. However, few studies have reported on the role of light in muscle development and meat quality in geese. In this experiment, 10 healthy 220-day-old Zhedong white geese were reared for 60 d under a long photoperiod (15L:9D, LL) and short photoperiod (9L:15D, SL). The gastrocnemius muscles were collected after slaughter to evaluate muscle fiber characteristics and meat color, and RNA-seq analysis. The results showed that compared to the LL group, the SL group had large muscle fiber diameter and cross-sectional area, few muscle fibers per unit area, high meat color a* value, and low L* value at 24 h postmortem. On comparing the 2 groups, 70 differentially expressed genes (DEGs) were identified. Compared to the SL group, the LL group had 25 upregulated and 45 downregulated genes. Gene Ontology (GO) enrichment analysis showed that these DEGs were mainly involved in cell, cell part, binding, cellular processes, and single-organism processes. Several significantly enriched athways were identified in the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, such as the calcium and PI3k-Akt signaling pathways. The expression of five randomly selected DEGs was verified using quantitative real-time PCR, and the results were consistent with the RNA-seq data. This study provides a theoretical basis for studying the molecular mechanisms by which light affects muscle development and meat color in geese.

Recently, miR-22 has been suggested to be an important microRNA (miRNA) affecting meat quality. Studies have shown that muscle fatty acid composition and mitochondrial function are closely related to meat quality. The regulatory mechanism of miR-22 on skeletal muscle fatty acid composition and mitochondrial function is not well characterized. Therefore, we aimed to explore the effects of miR-22 on fatty acid composition and mitochondrial function in C2C12 cells. Here, it demonstrate that elevated expression of miR-22 significantly repressed fatty acid elongation and mitochondrial morphology in C2C12 myoblasts, while the knockdown of miR-22 showed opposite results. Furthermore, miR-22 targets the elongase of very long chain fatty acids 6 (ELOVL6) and represses its expression in muscle cells. Knockdown of ELOVL6 mimicked the effect of miR-22 on fatty acid composition and mitochondrial function, while overexpression of ELOVL6 restored the effects of miR-22. These findings indicate that miR-22 downregulates the elongation of fatty acids and mitochondrial morphology by inhibiting ELOVL6 expression in muscle cells, which may provide some useful information for controlling muscle lipid accumulation and mitochondrial function in livestock in the future.