Breast muscle weight (BrW) is one of the most important economic traits in chicken, and directional breeding for that results in both phenotypic and genetic changes. The Jingxing yellow chicken, including an original (without human-driven selection) line and a selected line (based on selection for increased intramuscular fat content), were used to dissect the genetic architecture and key variants associated with BrW. We detected 1069 high-impact single nucleotide polymorphisms (SNPs) with high conserved score and significant frequency difference between two lines. Based on the annotation result, the ECM-receptor interaction and fatty acid biosynthesis were enriched, and muscle-related genes, including MYOD1, were detected. By performing genome-wide association study for the BrW trait, we defined a major haplotype and two conserved SNPs that affected BrW. By integrated genomic and transcriptomic analysis, IGF2BP1 was identified as the crucial gene associated with BrW. In conclusion, these results offer a new insight into chicken directional selection and provide target genetic markers by which to improve chicken BrW.

Triglyceride (TG) content in chicken muscle tissue signifies intramuscular fat (IMF) content, which is important for improving meat quality. However, the genetic basis of TG deposition in chicken is still unclear. Using 520 chickens from an artificially selected line with significantly increased IMF content and a control line, a genome-wide association study (GWAS) with TG content reports a region of 802 Kb located in chromosome 1. The XP-EHH and gene expression analysis together reveal that the solute carrier family 16 member A7 (SLC16A7) gene is the key candidate gene associated with TG content in chicken muscle tissue. Furthermore, the weighted gene co-expression network analysis (WGCNA) confirmed the regulatory effects of SLC16A7 on promoting TG deposition by de novo lipogenesis (DNL). Functional verification of SLC16A7 in vitro also supports this view, and reveals that this effect mainly occurs in myocytes. Our data highlight a potential IMF deposition pathway by DNL, induced by SLC16A7 in chicken myocytes. These findings will improve the understanding of IMF regulation in chicken and guide the formulation of breeding strategies for high-quality chicken.

Objective: Global consumption for chicken meat is steadily increasing. Carcass traits (e.g., slaughter weight [SW], eviscerated weight [EW]) are important economic traits for the meat production in chickens. Detection of genetic variants for these traits contributes to elucidating the genetic mechanism and accelerating genetic improvement.Methods: In this study, we performed a genome-wide association study on SW, EW, and thigh muscle weight (ThW), as well as the relative weight of these traits in 565 Sanhuang (SH) chickens. Additionally, genetic estimation has been conducted based on wholegenome variants for carcass traits. Finally, we compared the expression abundance of candidate genes to validate the function on carcass traits.Results: Except the percentage of SW (SP, 0.08), other traits were detected with moderate to high heritability (0.20−0.50). A high genetic correlation (0.72−0.93) was found among the carcass traits (SW, EW, and ThW). A total of 311 single-nucleotide polymorphisms and 73 candidate genes (e.g., IGF2BP1, BMP3, ACSL5) were identified significant association with carcass traits. IGF2BP1 was detected a causal role in EW and ThW, GIP, SNF8, and PHOSPHO1 were also located within the same genomic peak. CCND2 was related to SP and significantly expressed in commercial broilers and SH chickens. Lipid metabolism and immune function were simultaneously altered as a result of the selection for carcass traits. The genes ACSL5 and RASGEF1B were also significantly up-regulated in breast muscle in commercial broilers compared to SH chickens. Additionally, the transcriptomic profile of 73 candidate genes was constructed in multi-tissues, and a total of 17 genes (e.g., IGF2BP1, RASGEF1B, BMP3) were defined as differentially expressed genes between commercial broilers and SH chickens.Conclusion: In general, the findings in this study could facilitate the understandings of genetic mechanisms of carcass traits in chickens, and provide important variants and genes set for genomic breeding.

Chickens are a primary source of protein in the human diet, with demand increasing annually. However, research on genes that promote chicken meat development remains relatively limited. Therefore, in this study, breast muscle samples (pectoralis major, n = 10 per group) from chickens at five developmental stages (D1, D35, D70, D105, and D140) were selected to investigate genetic-level changes and identify additional genes influencing chicken meat development. Differential expression analysis between adjacent stages (|FC| > 1.5, p < 0.05) revealed 42 differentially expressed genes (DEGs) shared across four comparisons, primarily enriched in muscle development pathways such as focal adhesion, the regulation of the actin cytoskeleton, and Wnt signaling. Weighted gene coexpression network analysis (WGCNA) revealed that four modules were significantly correlated with body weight and breast muscle weight phenotypes. By integrating the hub genes of the four modules and the DEGs, we identified key genes, including MEGF10, MYOM2, TM4SF1, HNMT, NR4A3, and Wnt5a. Furthermore, we conducted a comparative analysis of key gene expression trends across commercial broilers (CBs) and Beijing You (BJY) chickens. MYOM2 and Wnt5a exhibited distinct expression patterns during the early developmental stage of Xianju (XJ) chickens, suggesting that these genes may be critical factors distinguishing XJ chicken breast muscle development from that of other breeds. In all three chicken breeds analyzed, the expression levels of HNMT and MEGF10 gradually decreased with increasing age, indicating that their functions are universal in poultry muscle development. In summary, our findings revealed key regulatory genes that influence breast muscle development, offering candidate targets for marker-assisted selection in poultry breeding programs.

Objective: Chicken embryos are typically incubated in complete darkness, overlooking the potential influence of rhythmic light exposure. This study aimed to investigate the effects of a 12-hour light/12-hour dark rhythmic light environment on liver development and lipid metabolism in chicken embryos, providing a foundation for regulating poultry physiology through light manipulation.Methods: Fertile eggs were incubated under two lighting conditions: a 12 h light/12 h dark cycle (LD group) and constant darkness (DD group). Embryos or chicks were sampled at embryonic days 12 (E12), 14 (E14), 16 (E16), 18 (E18), 20 (E20), and day 1 post-hatch (D1). Body weight, liver weight, and residual yolk weight were recorded. Liver morphology and lipid accumulation were evaluated using H&E and Oil Red O staining. Hepatic levels of triglycerides (TG), total cholesterol (TC), free fatty acids, fatty acid synthase (FAS), and acetyl-CoA carboxylase (ACC) were measured. Expression of lipid metabolism-related genes was assessed by real-time quantitative polymerase chain reaction.Results: Embryo weight, liver weight, liver index, and residual yolk weight did not differ significantly between groups. However, liver tissues in the LD group exhibited earlier maturation of liver plate structures and increased lipid droplet accumulation. TG concentration was significantly higher at E12 and D1, TC at E12 and E18, and ACC at E12, E16, and E18 in the LD group (p<0.05). Furthermore, lipid synthesis genes (ACC, FAS, SCD1, SREBP-1c, ELOVL6) were upregulated, while lipid degradation genes (CPT1, PPARα, MTTP) were downregulated at specific embryonic stages in the LD group (p<0.05).Conclusion: Rhythmic light exposure under a 12 h light/12 h dark cycle promoted liver development and lipid accumulation by modulating expression of lipid metabolism genes such as ACC, FAS, and CPT1. These findings highlight the potential of light rhythm as a strategy to optimize embryonic development and lipid metabolism in poultry.