Tissue Expression Analysis and Characterization of Smad3 Promoter in Bovine Myoblasts and Preadipocytes

Long non-coding RNA (LncRNA) and epigenetic factors: their role in regulating the adipocytes in bovine

Investigating the involvement of long non-coding RNAs (lncRNAs) and epigenetic processes in bovine adipocytes can provide valuable new insights into controlling adipogenesis in livestock. Long non-coding RNAs have been associated with forming chromatin loops that facilitate enhancer-promoter interactions during adipogenesis, as well as regulating important adipogenic transcription factors like C/EBPα and PPARγ. They significantly influence gene expression regulation at the post-transcriptional level and are extensively researched for their diverse roles in cellular functions. Epigenetic modifications such as chromatin reorganization, histone alterations, and DNA methylation subsequently affect the activation of genes related to adipogenesis and the progression of adipocyte differentiation. By investigating how fat deposition is epigenetically regulated in beef cattle, scientists aim to unravel molecular mechanisms, identify key regulatory genes and pathways, and develop targeted strategies for modifying fat deposition to enhance desirable traits such as marbling and meat tenderness. This review paper delves into lncRNAs and epigenetic factors and their role in regulating bovine adipocytes while focusing on their potential as targets for genetic improvement to increase production efficiency. Recent genomics advancements, including molecular markers and genetic variations, can boost animal productivity, meeting global demands for high-quality meat products. This review establishes a foundation for future research on understanding regulatory networks linked to lncRNAs and epigenetic changes, contributing to both scholarly knowledge advancement and practical applications within animal agriculture.

miR-33a Inhibits the Differentiation of Bovine Preadipocytes through the IRS2-Akt Pathway

Several microRNAs (miRNAs) are known to participate in adipogenesis. However, their role in this process, especially in the differentiation of bovine preadipocytes, remains to be elucidated. This study was intended to clarify the effect of microRNA-33a (miR-33a) on the differentiation of bovine preadipocytes by cell culture, real-time fluorescent quantitative PCR (qPCR), Oil Red staining, BODIPY staining, and Western blotting. The results indicate that overexpression of miR-33a significantly inhibited lipid droplet accumulation and decreased the mRNA and protein expression of adipocyte differentiation marker genes such as peroxisome proliferator-activated receptor gamma (PPARγ), sterol regulatory element-binding protein 1 (SREBP1), and fatty acid-binding protein 4 (FABP4). In contrast, the interference expression of miR-33a promoted lipid droplet accumulation and increased the expression of marker genes. Additionally, miR-33a directly targeted insulin receptor substrate 2 (IRS2) and regulated the phosphorylation level of serine/threonine kinase (Akt). Furthermore, miR-33a inhibition could rescue defects in the differentiation of bovine preadipocytes and the Akt phosphorylation level caused by small interfering IRS2 (si-IRS2). Collectively, these results indicate that miR-33a could inhibit the differentiation of bovine preadipocytes, possibly through the IRS2-Akt pathway. These findings might help develop practical means to improve the quality of beef.

Effect of genetic variants in the SMAD1 and SMAD5 genes promoter on growth and beef quality traits in cattle

The SMAD1 and SMAD5 genes belong to mothers against decapentaplegic proteins family, which participate in the BMP pathway to control skeletal myogenesis and growth. In the present study, we analyzed the associations between polymorphisms of SMAD1 and SMAD5 genes promoter and important economical traits in Qinchuan cattle. Four SNPs in the SMAD1 gene promoter and three SNPs in the SMAD5 promoter were identified by sequencing of 448 Qinchuan cattles. Allelic and frequency analyses of these SNPs resulted in eight haplotypes both in the promoters of the two genes promoter and identified potential cis-regulatory transcription factor (TF) components. In addition, correlation analysis showed that cattle SMAD1 promoter activity of individuals with Hap4 (P < 0.01) was stronger than that of individuals with Hap2. while the transcriptional activity of individuals with Hap3 within SMAD5 gene promoter was significantly (P < 0.01) higher followed by H2. Uniformly, diplotypes H4-H6 of SMAD1 gene and H1-H3 of SMAD5 gene performed significant (P < 0.01) associations with body measurement and improved carcass quality traits. All these results have indicated that polymorphisms in SMAD1 and SMAD5 genes promoter could impact the transcriptional regulation and then affect muscle content in beef cattle. Moreover, both the SMAD1 and SMAD5 genes were expressed ubiquitously in 10 tissues and had higher expression in the longissimus thoracis tissue from 6-month-old and 12-month-old cattle than in cattle of other ages. We can conclude that SMAD1 and SMAD5 genes may play an important role in muscle growth and development, and the variants mapped within SMAD1 and SMAD5 genes can be utilized in molecular marker-assisted selection for cattle carcass quality and body measurement traits in breed improvement programs of Qinchuan cattle.

MiR-33a plays an crucial role in the proliferation of bovine preadipocytes

Preadipocyte proliferation is a critical and precisely orchestrated procedure in adipogenesis, which is highly regulated by microRNAs (miRNAs). A previous study identified that the expression of miR-33a is different in intramuscular fat (IMF) tissues from steers and bulls. In the present study, miR-33a was overexpressed in bovine preadipocytes, and a total of 781 differentialy expressed genes were found, including 348 upregulated and 433 downregulated genes. Gene Ontology and Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway analyses of the differentially expressed genes enriched cell division and cell cycle respectively. MiR-33a overexpression decreased the rate of preadipocyte proliferation. Synchronously, the mRNA and protein expression levels of proliferation-related marker genes, including cyclin B1 (CCNB1) and proliferating cell nuclear antigen (PCNA), were decreased. In contrast, inhibiting miR-33a increased the rate of preadipocyte proliferation, and expression levels of CCNB1 and PCNA. Furthermore, based on luciferase reporter assays, miR-33a targeted directly cyclin-dependent kinase 6 (CDK6)-3'UTR and inhibited CDK6 protein expression. Interestingly, the silencing of CDK6 inhibited bovine preadipocyte proliferation and proliferation-related genes. Therefore, miR-33a inhibits the proliferation of bovine preadipocytes. CDK6 is the target gene of miR-33a and may be involved in the effects of miR-33a on bovine preadipocyte proliferation.

Transcriptional regulation of adipogenic marker genes for the improvement of intramuscular fat in Qinchuan beef cattle

The intramuscular fat content plays a crucial role in meat quality traits. Increasing the degree of adipogenesis in beef cattle leads to an increase in the content of intramuscular fat. Adipogenesis a complex biochemical process which is under firm genetic control. Over the last three decades, the Qinchuan beef cattle have been extensively studied for the improvement of meat production and quality traits. In this study, we reviewed the literature regarding adipogenesis and intramuscular fat deposition. Then, we summarized the research conducted on the transcriptional regulation of key adipogenic marker genes, and also reviewed the roles of adipogenic marker genes in adipogenesis of Qinchuan beef cattle. This review will elaborate our understanding regarding transcriptional regulation which is a vital physiological process regulated by a cascade of transcription factors (TFs), key target marker genes, and regulatory proteins. This synergistic action of TFs and target genes ensures the accurate and diverse transmission of the genetic information for the accomplishment of central physiological processes. This information will provide an insight into the transcriptional regulation of the adipogenic marker genes and its role in bovine adipogenesis for the breed improvement programs especially for the trait of intramuscular fat deposition.

Transcription factors regulate adipocyte differentiation in beef cattle

Intramuscular fat (IMF) content is a critical factor affecting meat flavor, juiciness, tenderness, and color. Therefore, the improvement of IMF content is one of the hotspots of animal science research. Fat deposition is the result of a combination of increased number of fat cells and cellular hypertrophy. In addition, transcription factors can influence the number of adipocytes and regulate lipid metabolism. The progress of the transcription factors regulating adipocyte differentiation in beef cattle, including IMF cell sources, and promoting or inhibiting adipogenic differentiation of transcription factors is reviewed in this paper.

Genetic variants in the TORC2 gene promoter and their association with body measurement and carcass quality traits in Qinchuan cattle

The TORC2 gene is responsible for nutrient metabolism, gluconeogenesis, myogenesis and adipogenesis through the PI3K-Akt, AMPK, glucagon and insulin resistance signaling pathways. Sequencing of PCR amplicons explored three novel SNPs at loci g.16534694G>A, g.16535011C>T, and g.16535044A>T in the promoter region of the TORC2 gene in the Qinchuan breed of cattle. Allelic and genotypic frequencies of these SNPs deviated from Hardy-Weinberg equilibrium (HWE) (P < 0.05). SNP1 genotype GG, SNP2 genotype CT and SNP3 genotype AT showed significantly (P <0.05) larger body measurement and improved carcass quality traits. Haplotype H1 (GCA) showed significantly (p<0.01) higher transcriptional activity (51.44%) followed by H4 (ATT) (34.13%) in bovine preadipocytes. The diplotypes HI-H3 (GG-CC-AT), H1-H2 (GG-CT-AT) and H3-H4 (GA-CT-TT) showed significant (P<0.01) associations with body measurement and improved carcass quality traits. Analysis of the relative mRNA expression level of the TORC2 gene in different tissues within two different age groups revealed a significant increase (P<0.01) in liver, small intestine, muscle and fat tissues with growth from calf stage to adult stage. We can conclude that variants mapped within TORC2 can be used in marker-assisted selection for carcass quality and body measurement traits in breed improvement programs of Qinchuan cattle.

DNA Methylation and Transcription Factors Competitively Regulate SIRT4 Promoter Activity in Bovine Adipocytes: Roles of NRF1 and CMYB

Sirtuin 4 (SIRT4) belongs to the mitochondrial sirtuin protein family, a class of NAD⁺-dependent protein deacylases that remove post-translational acyl modifications from cellular substrates during the regulation of various biological pathways. SIRT4 has been shown to regulate lipid homeostasis. However, the mechanism by which the bovine SIRT4 gene is transcriptionally regulated remains unknown. To explore the molecular mechanism of SIRT4 expression, we obtained a 400-kb fragment of the 5'-regulatory region of bovine SIRT4 by molecular cloning, which contained a CpG island. Electrophoretic mobility shift assays and luciferase reporter gene assays identified the nuclear respiratory factor 1 (NRF1) and myb proto-oncogene protein (CMYB) binding sites as transcriptional repression and activation sites in the SIRT4 promoter region, respectively. We further verified that NRF1 and CMYB bind to the SIRT4 promoter using chromatin immunoprecipitation assays. In addition, from DNA methylation and reporter gene assays, results revealed that SIRT4 promoter activity was enhanced by demethylation. Further, NRF1-mediated transcriptional inhibition and CMYB-mediated transcriptional activation of SIRT4 expression were strengthened by demethylation during bovine adipocyte differentiation. Taken together, our results shed light on the mechanism underlying the promoter methylation and transcriptional regulation of SIRT4 expression in bovine adipocytes.

Bioinformatics Analysis and Competitive Regulation by Transcription Factors of SIRT5 at the Core Promoter Region Using Bovine Adipocytes

Sirtuin 5 (SIRT5) belongs to the mitochondrial sirtuin family, which constitutes a highly conserved family of nicotinamide adenine dinucleotide NAD⁺-dependent deacetylases and ADP-ribosyltransferases that play an important regulatory role in stress resistance and metabolic homeostasis. SIRT5, a member of the mitochondrial sirtuins, has been confirmed to exhibit deacetylase, desuccinylase, and demalonylase enzymatic activities. First, we showed that SIRT5 was expressed at the highest level in the bovine testis, followed by longissimus thoracis and subcutaneous adipose tissue, using real-time quantitative PCR and mRNA levels of SIRT5 during adipocyte differentiation, which increased before the first day and then decreased rapidly. To explore the molecular regulation of bovine SIRT5 expression, we cloned a 2-kb fragment of the 5'-regulatory region and the functional proximal minimal promoter of bovine SIRT5. Electrophoretic mobility shift assays and luciferase reporter assays identified Kruppel-like factor 2 (KLF2), CCAAT enhancer binding protein beta (CEBPβ), peroxisome proliferator-activated receptor alpha (PPARα), myogenic differentiation 1 (MYOD), and nuclear respiratory factor 1 (NRF1) binding sites as transcriptional activators or repressors in the core promoter region of SIRT5. In brief, our study focused on the mechanism underlying the transcriptional regulation of SIRT5 expression in bovine adipocytes.