Transcriptional regulation of the bovine FGFR1 gene facilitates myoblast proliferation under hypomethylation of the promoter

Muscle cells affect the promoting effect of FGF21 on lipid accumulation in porcine adipocytes through AhR/FGFR1 signaling pathway

The intramuscular fat (IMF) content, as an important meat quality trait, can directly affect the tenderness, juiciness, and flavor of pork. Reasonably increasing the IMF content can improve the palatability of pork. Therefore, identification of important factors for the lipid accumulation among muscles is the breakthrough point for improving meat quality. FGF21, identified as a novel metabolic regulator, has been found to regulate glucose and lipid metabolism in 3T3-L1 adipocytes, but its function in porcine adipocytes remains unclear. In this study, we discovered that the administration of recombinant FGF21 protein promotes adipogenic differentiation and increases triglyceride accumulation in porcine adipocytes. While the expression of FGFR1 in adipocytes under muscle conditions is inhibited, affecting the signal transduction of FGF21. This inhibitory effect is accompanied by activation of the AhR signaling pathway. When treated with the AhR antagonist CH223191, there was a partial restoration of FGFR1 expression levels. This indicates that muscle cells suppress the expression of FGFR1 in adipocytes by activating the AhR signaling pathway, thereby affecting the signal transduction of FGF21. Our results reveal the regulatory role of FGF21 in pig adipocyte differentiation and the regulatory mechanism of muscle environment on FGFR1 expression, providing new theoretical basis for IMF content improvement from the perspective of FGF21-FGFR1 signaling transduction.

Genetic Diversity and Selection Signal Analysis of Hu Sheep Based on SNP50K BeadChip

This research is designed to examine the genetic diversity and kinship among Hu sheep, as well as to discover genes associated with crucial economic traits. A selection of 50 unrelated adult male Hu sheep underwent genotyping with the SNP50K BeadChip. Seven indicators of genetic diversity were assessed based on high-quality SNP data: effective population size (Ne), polymorphic information content (PIC), polymorphic marker ratio (PN), expected heterozygosity (He), observed heterozygosity (Ho), effective number of alleles, and minor allele frequency (MAF). Plink software was employed to compute the IBS genetic distance matrix and detect runs of homozygosity (ROHs), while the G matrix and principal component analysis were performed using GCTA software. Selective sweep analysis was carried out using ROH, Pi, and Tajima's D methodologies. This study identified a total of 64,734 SNPs, of which 56,522 SNPs remained for downstream analysis after quality control. The population displayed relatively high genetic diversity. The 50 Hu sheep were ultimately grouped into 12 distinct families, with families 6, 8, and 10 having the highest numbers of individuals, each consisting of 6 sheep. Furthermore, a total of 294 ROHs were detected, with the majority having lengths between 1 and 5 Mb, and the inbreeding coefficient FROH was 0.01. In addition, 41, 440, and 994 candidate genes were identified by ROH, Pi, and Tajima's D methods, respectively, with 3 genes overlapping (BMPR1B, KCNIP4, and FAM13A). These results offer valuable insights for future Hu sheep breeding, genetic assessment, and population management.

IGF2BP1-mediated the stability and protein translation of FGFR1 mRNA regulates myogenesis through the ERK signaling pathway

N6-methyladenosine (m6A) is the most prevalent post-transcriptional modification of RNAs and plays a key regulatory role in various biological processes. As a member of the insulin-like growth factor 2 mRNA-binding proteins (IGF2BPs) family, IGF2BP1 has recently demonstrated its ability to specifically bind m6A-modified sites within mRNAs and effectively regulate their mRNA stability. However, the precise roles of IGF2BP1 in mammalian skeletal muscle development, along with its downstream mRNA targets during myogenesis, have yet to be fully elucidated. Here, we observed that IGF2BP1 expression significantly decreased during myogenic differentiation. Knockdown of IGF2BP1 significantly inhibited myoblast proliferation while promoted myogenic differentiation. In contrast, IGF2BP1 overexpression robustly stimulated myoblast proliferation but suppressed their differentiation. Combined analysis of high-throughput sequencing and RNA stability assays revealed that IGF2BP1 can enhance fibroblast growth factor receptor 1 (FGFR1) mRNA stability and promote its translation in an m6A-dependent manner, thereby regulating its expression level and the Extracellular Signal-Regulated Kinase (ERK) pathway. Additionally, knockdown of FGFR1 rescued the phenotypic changes (namely increased cell proliferation and suppressed differentiation) induced by IGF2BP1 overexpression via attenuating ERK signaling. Taken together, our findings suggest that IGF2BP1 maintains the stability and translation of FGFR1 mRNA in an m6A-dependent manner, thereby inhibiting skeletal myogenesis through activation of the ERK signaling pathway. This study further enriches the understanding of the molecular mechanisms by which RNA methylation regulates myogenesis, providing valuable insights into the role of IGF2BP1-mediated post-transcriptional regulation in muscle development.

Mutations in FGFR1 were associated with growth traits in sheep (Ovis aries)

For its role in the mediation of myoblast proliferation, fibroblast growth factor receptor 1 (FGFR1) was considered a functional candidate gene for growth performance in Tibetan sheep. Via the polymerase chain reaction-restriction fragment length polymorphism (PCR-PFLP) approach, four single nucleotide polymorphisms (SNPs) including g.14752C > T (intron 1), g.45361A > G (intron 7), g.49400A > G (3'UTR region) and g.49587A > T (3'UTR region), were identified in 422 ewes. The association analysis demonstrated that individuals carrying the AA genotype of g.49400A > G had significantly greater withers height, length than those with GG genotype (p < 0.05). Individuals with genotype AA of g.49587A > T had significantly greater weight and chest circumference than those with genotype TT (p < 0.01). Additionally, the individuals with Hap1/1 diplotypes (CAAA-CAAA) were highly significantly associated with weight and chest circumference than Hap1/2 diplotypes (CAAA-CAAT) (p < 0.05). The quantitative real-time polymerase chain reaction (qPCR) analysis revealed that the FGFR1 was detectable expressed in muscle tissues within three different age stage. Remarkably higher mRNA expression was detected at fetal lamb stage as compared with adult ewes (p < 0.01). The outcome of this research confirmed that both g.49400A > G and g.49587A > T of FGFR1 were involved in growth-related traits, which may be considered to be genetic markers for improving the growth traits of Tibetan sheep.

Analysis of Promoter Methylation of the Bovine FOXO1 Gene and Its Effect on Proliferation and Differentiation of Myoblasts

This study aimed to explore the regulatory role of FOXO1 promoter methylation on its transcriptional level and unravel the effect of FOXO1 on the proliferation and differentiation of bovine myoblasts. Bisulfite sequencing polymerase chain reaction (BSP) and real-time quantitative PCR were performed to determine the methylation status and transcript levels of the FOXO1 promoter region at different growth stages. BSP results showed that the methylation level in the calf bovine (CB) group was significantly higher than that in the adult bovine (AB) group (p < 0.05). On the other hand, qRT-PCR results indicated that the mRNA expression level in the AB group was significantly higher than that in the CB group (p < 0.05), suggesting a significant decrease in gene expression at high levels of DNA methylation. CCK-8 and flow cytometry were applied to determine the effect of silencing the FOXO1 gene on the proliferation of bovine myoblasts. Furthermore, qRT-PCR and Western blot were conducted to analyze the expression of genes associated with the proliferation and differentiation of bovine myoblasts. Results from CCK-8 revealed that the short hairpin FOXO1 (shFOXO1) group significantly promoted the proliferation of myoblasts compared to the short-hairpin negative control (shNC) group (p < 0.05). Flow cytometry results showed a significant decrease in the number of the G1 phase cells (p < 0.05) and a significant increase in the number of the S phase cells (p < 0.05) in the shFOXO1 group compared to the shNC group. In addition, the expression of key genes for myoblast proliferation (CDK2, PCNA, and CCND1) and differentiation (MYOG, MYOD, and MYHC) was significantly increased at both mRNA and protein levels (p < 0.05). In summary, this study has demonstrated that FOXO1 transcription is regulated by methylation in the promoter region and that silencing FOXO1 promotes the proliferation and differentiation of bovine myoblasts. Overall, our findings lay the foundation for further studies on the regulatory role of epigenetics in the development of bovine myoblasts.