Intramuscular fat (IMF) deposition is a critical determinant of beef quality, yet the regulatory role of preadipocyte-derived exosomes remains unclear. Exosomes (HC-Exo and CRSC-Exo) were isolated from preadipocytes of Haoyue Beef Cattle (HC) and Chinese Red Steppe Cattle (CRSC), breeds with distinct IMF contents. HC-Exo significantly enhanced preadipocyte proliferation and differentiation, increasing lipid droplet formation and triglyceride synthesis, alongside elevated expression levels of peroxisome proliferator-activated receptor γ (PPARγ) and CCAAT enhancer binding protein alpha (C/EBPα). MiRNA sequencing identified 580 differentially expressed miRNAs, with miR-26a twice as abundant in HC-Exo versus CRSC-Exo. Integrated bioinformatics analyses, including KEGG, GO, and dual-luciferase reporter assays, identified glycogen synthase kinase-3B (GSK3B) as a direct target of miR-26a. Functional validation demonstrated that miR-26a mimics enhanced adipogenesis by suppressing GSK3B expression, while GSK3B overexpression inhibited differentiation. These findings establish exosomal miR-26a as a novel regulator of intramuscular adipogenesis, providing molecular insights for improving beef quality.

In this study, we successfully isolated and cultured bovine skeletal muscle satellite cells (bSMSCs) and induced muscle cell formation in vitro. Skeletal muscle satellite cells (SMSCs) were isolated from the deep tissues of foetal bovine hind limbs and differentiated with 2% horse serum in vitro. The transcriptome sequencing results revealed a total of 1030 differentially expressed genes (DEGs) in the middle stage of differentiation (day 3) compared with the predifferentiation stage (day 0). A total of 374 DEGs were identified in the postdifferentiation stage (day 7) compared with the middle differentiation stage (day 3). We further investigated the regulatory effects of the DEG nerve growth factor (NGF) on the proliferation and myogenic differentiation of bSMSCs. The overexpression of NGF increased the mRNA and protein expression levels of myosin heavy chain (MyHC) and myogenin (MyoG), which are myoblast development markers, whereas NGF knockdown had the opposite effect; however, NGF did not affect the expression of the proliferation marker paired box gene 7 (Pax7) in bSMSCs. In addition, functional enrichment analysis of the DEGs revealed that the PI3K/Akt signalling pathway was significantly enriched in the DEGs and that NGF regulates myogenesis through the activation of the PI3K/Akt signalling pathway. Our results revealed that NGF was shown to be a putative regulator that controls myogenesis by activating the PI3K/Akt signalling pathway. The study provided a reference for further studies on the molecular mechanism of myogenic differentiation, regulatory network establishment, and beef quality improvement.

Copy number variations (CNV) are important genetic variations. The endogenous factors cobalamin receptor (CUBN) and MIA SH3 domain ER-derived factor 3 (MIA3) are associated with bone/muscle development and intramuscular fat deposition. There have been no reports on the effects of CUBN and MIA3 CNVs on growth traits of Chinese cattle. This study aimed to determine the correlation between the CUBN and MIA3 CNVs and growth traits in Chinese cattle. qRT-PCR was used to detect the distribution of CUBN and MIA3 CNV and the expression levels of their mRNA, and correlation analysis was conducted between CNV and growth traits. The CUBN was differentially expressed in different breeds of cattle, and CUBN CNV correlated significantly with body height, hip height, body slanting length, and hip width of Grassland Red cattle (CYH); eye muscle area of Yanbian cattle (YB) and Yan Yellow cattle (YH). MIA3 showed no CNV in CYH and YB cattle, and only one deletion type occurred in YH cattle. CUBN and MIA3 mRNA have different expression patterns in different cattle breeds and tissues. In conclusion, CUBN CNV is correlated significantly with growth traits in Chinese cattle and is a novel molecular marker that could be exploited in cattle breeding.

Fatty acid composition (FA) is an important indicator of meat quality in beef cattle. We investigated potential functional candidate genes for FA in beef cattle by integrating genomic and transcriptomic dataset through multiple strategies. In this study, we observed 65 SNPs overlapping with five candidate genes (CCDC57, FASN, HDAC11, ALG14, and ZMAT4) using two steps association based on the imputed sequencing variants. Using multiple traits GWAS, we further identified three significant SNPs located in the upstream of FASN and one SNP (chr19:50779529) was embedded in FASN. Of those, two SNPs were further identified as the cis-eQTL based on transcriptomic analysis of muscle tissues. Moreover, the knockdown of FASN yielded a significant reduction in intracellular triglyceride content in preadipocytes and impeded lipid droplet accumulation in adipocytes. RNA-seq analysis of preadipocytes with FASN interference revealed that the differentially expressed genes were enriched in cell differentiation and lipid metabolic pathway. Our study underscored the indispensable role of FASN in orchestrating adipocyte differentiation, and fatty acid metabolism. The integrative analysis with multiple strategies may contribute to the understanding of the genetic architecture of FA in farm animals. Multiple strategies association revealed candidate genes for fatty acid composition in cattle and function validation of FASN.

Yanbian cattle are a native cattle breed originating from the Yanbian Korean Autonomous Prefecture in Jilin Province, northeastern China. Developed over centuries through natural and artificial selection under cold climatic conditions, this breed is highly adapted to harsh environments, including low temperatures, rugged terrain, and sparse forage. Here, we constructed a high-quality chromosome-level genome assembly for Yanbian cattle using HiFi, Hi-C and RNA-seq data. The genome sequence was anchored to 30 chromosomes, with a total genome length of 2.8 Gb, a contig N50 of 86.41 Mb and a scaffold N50 of 111.08 Mb. Short-read data showed the average 99.56% mapping ratio to the assembly, validating base-level accuracy. Also, 93% complete BUSCOs verified the integrity of the assembled genome. 51.94% repetitive elements of the genome and 20,421 protein-coding genes were annotated. This Yanbian cattle genome serves as an indispensable resource for bovine genomic studies and local breed conservation, enabling both evolutionary insights and genetic characteristic analyses.

Chinese red steppe cattle, a highly developed breed for their meat and milk, are not well known about the formation mechanisms for high-quality beef. Furthermore, many fundamental investigations of cattle are hampered by deficient full-length cDNAs. Here, we utilized ONT full-length transcript sequencing from 9 bovine preadipocytes during 3 periods to find 2502 novel genes and 3253 novel transcriptomes, further improving the quality of reference genome annotation. At the same time, based on diverse expression patterns in 3 periods (early, middle and late), we identified 754 significantly differentially expressed genes (DEGs) and 932 significantly differentially expressed transcripts (DETs) in the first contrast group (0d_vs_4d), 197 significantly DEGs and 297 significantly DETs in the second contrast group (0d_vs_8d), 465 and 555 significantly DEGs and DETs in the third contrast group (4d_vs_8d). These DEGs mainly enriched the pathways related to cell differentiation such as Wnt signaling pathway and positive regulation of fat cell differentiation. A total of 35,616 alternative splicing (AS) events were detected, in which 111, 109 and 101 significantly different AS events were found in the group 0d_vs_4d, 0d_vs_8d and 4d_vs_8d respectively. In particular, two essential DEGs, N4BP2L1 and PRKAA1 related to cell differentiation were shown to take part in distinct AS events and were therefore considered as key candidate genes for improving fat deposition and meat quality in Chinese red steppe cattle. These findings provide novel insights into the adipocyte differentiation in cattle and metabolic processes that regulate fat storage, which is essential for optimizing growth and production.

Background: Cultivated meat, an alternative to conventional meat, has substantial potential for alleviating environmental and ethical concerns. This method of manufacturing meat involves the isolation of skeletal muscle satellite cells (SMSCs) from donor animals, after which they proliferate in vitro and differentiate into primitive muscle fibers. The aim of this research was to evaluate how the insulin-like growth factor 1 (IGF1) gene regulates the myogenic differentiation of bovine skeletal muscle satellite cells (bSMSCs). Methods: bSMSCs isolated from newborn calves were cultured to the third generation in vitro and differentiated into myoblasts via the serum withdrawal method. An overexpression lentivirus and siRNA targeting the IGF1 gene were constructed and transduced into bSMSCs, which were subsequently analyzed via real-time fluorescence quantitative PCR(qRT-PCR) and Western blots. The mRNA and protein levels of the myogenic differentiation markers myosin heavy chain (MyHC) and myogenin (MyoG) were determined. Results: The results revealed that the lentivirus overexpressing the IGF1 gene significantly increased the expression of MyHC and MyoG, whereas the expression of both the MyHC and MyoG mRNAs and proteins was strongly reduced by si-IGF1. Conclusions: IGF1 positively regulates the myogenic differentiation of bSMSCs. This study provides a reference for further elucidating the molecular mechanism by which the IGF1 gene regulates the myogenic differentiation of bSMSCs via the PI3K/Akt signaling pathway and lays a foundation for establishing a regulatory network of bovine muscle growth and development.

Retraction: "MicroRNA-205 affects mouse granulosa cell apoptosis and estradiol synthesis by targeting CREB1," by Pengju Zhang, Jun Wang, Hongyan Lang, Weixia Wang, Xiaohui Liu, Haiyan Liu, Chengcheng Tan, Xintao Li, Yumin Zhao, Xinghong Wu, J Cell Biochem. 2018; 120: 8466-8474: The above article, published online on 16 December 2018 in Wiley Online Library () has been retracted by agreement between the journal's Editor in Chief, Christian Behl, and Wiley Periodicals LLC. The retraction has been agreed following an investigation based on allegations raised by third parties. Several flaws and inconsistencies between results presented and experimental methods described were found. Furthermore, multiple image duplications as well as image elements that were published previously in a different scientific context were found in Figures 2, 3, and 5. Thus, the editors consider the conclusions of this article to be invalid. The authors did not respond when asked to collaborate during the investigation and confirm the retraction.

[目的]了解黑毛和牛与延边牛杂交的效果.[方法]对不同阶段(6、12、18、24月龄)F1、F2代体重、体高、体斜长、胸围、管围等指标进行测定.[结果]F2代公牛6、12、18、24月龄体重均显著高于F1代(P<0.05),不同月龄F2代母牛体重与F1代无显著差异;18月龄F2代公牛体斜长显著高于F1代(P<0.05);不同月龄F2代无论公牛还是母牛胸围均显著高于F1代(P<0.05);F2代公牛腹围在6月龄、12月龄、18月龄均显著高于F1代(P<0.05);F2代母牛各月龄腹围均显著高于F1代(P<0.05);F2代公牛6月龄十字部高、24月龄管围显著高于F1代(P<0.05);F2代母牛在18月龄十字部高显著高于F1代(P<0.05).[结论]F2代具有良好的杂交优势,黑毛和牛改良延边牛是切实可行的,该品种的杂交潜力较大.

Animal skeletal muscle growth is regulated by a complex molecular network including some non-coding RNAs (ncRNAs). In this paper, we review the non-coding RNAs related to the growth and development of common animal skeletal muscles, aiming to provide a reference for the in-depth study of the role of ncRNAs in the development of animal skeletal muscles, and to provide new ideas for the improvement of animal production performance.

Background: The regulatory genes related to lipid metabolism affect the intramuscular fat (IMF) content and improve meat quality traits.Mediator Complex Subunit 4 (MED4), a vitamin D receptor protein, affects vitamin D, livestock growth, carcass traits, and triglyceride deposition.However, the physiological function of the MED4 gene on bovine adipocyte differentiation remains unknown.Methods: This study explored the function of the MED4 gene in preadipocyte differentiation in Chinese Red Steppe cattle.The overexpression plasmid and the interference sequences of the MED4 gene were constructed to detect the effects of the MED4 gene on adipogenesis and biomakers using quantitative polymerase chain reaction and western blotting.Results: The MED4 gene had significantly high expression during preadipocyte differentiation (p < 0.05).Overexpression of the MED4 gene increased the expression of the PPARγ gene, a preadipocyte differentiation biomarker, improved cellular lipid droplets and triglycerides accumulation, and positively accelerated adipocyte maturation (p < 0.05).Interference of the MED4 gene can negatively regulate preadipocyte differentiation.Conclusion: This study showed that the MED4 gene may affect the preadipocyte differentiation and adipogenesis in Chinese Red Steppe cattle by regulating the PPARγ gene.

旨在研究采用日系黑毛牛冻精对地方品种延边牛级进杂交改良效果.选择18月龄体质健康、体况相近、膘情较好的F1代和F2代的阉公牛各20头,统一饲养管理,饲喂至30月龄.宰后排酸5 d,采集左侧胴体背最长肌12～13肋间西冷部位,对其肉品质、营养品质、风味物质和质构特性进行测定,分析利用日系黑毛牛冻精对延边牛杂交的改良效果.结果表明,F2代肌内脂肪含量显著高于F1代(P＜0.05),提高2.74％,增幅10.4％;F1代和F2代剪切力值均小于42.83 N,均达到嫩级别,且F2代嫩度显著高于F1代(P＜0.05);F2代肌苷酸含量显著高于F1代(P＜0.05);其余测定性状差异不显著,但从数值上F2代肉质优于F1代.综上,F2代肉更嫩、肌内脂肪沉积更优、风味更佳,表现出良好杂交优势,为培育雪花牛肉生产专门化种群提供理论依据.

为了研究中国草原红牛F-框蛋白32(FBXO32)基因多态性与肉质性状之间的相关性,试验选取120头中国草原红牛为研究对象,采用PCR产物直接测序法检测FBXO32基因内含子4的多态性,利用SPSS 19.0软件对多态性位点与离心失水率、滴水损失率、压榨水分、肌肉嫩度、肌内脂肪含量、初水分含量、蛋白质含量、大理石花纹评分、熟肉率、眼肌面积、pH24值指标进行相关性分析.结果表明:在FBXO32基因第4内含子g.16336603处检测到一个C/T突变位点,TT型为优势基因型,等位基因T为优势基因,该位点在所测群体中处于哈迪-温伯格平衡状态(P＞0.05);CC基因型离心失水率显著低于TT和TC基因型(P＜0.05),肌内脂肪含量和大理石花纹评分显著高于TT和TC基因型(P＜0.05),pH24值高于TT和TC基因型,其中与TC基因型差异显著(P＜0.05);但3个基因型的滴水损失率、压榨水分、肌肉嫩度、初水分含量、蛋白质含量、眼肌面积及熟肉率均差异不显著(P＞0.05).说明FBXO32基因可作为中国草原红牛品种选育标记.

为探究中国草原红牛介体复合物亚基4(MED4)基因多态性及其对草原红牛肉质性状的影响,实验以118头20月龄的草原红牛为研究对象,采用PCR测序的方法对草原红牛MED4基因第7外显子的多态性进行研究,利用SPASS 20.0软件分析MED4基因SNP位点与肉质性状的相关性.结果表明:草原红牛MED4基因第7外显子存在A268G、A420G突变,经卡方检验发现2处突变位点均处于Hardy-Weinberg不平衡状态,2处突变位点的遗传杂合度(He)相对较低,多态信息含量(PIC)介于0.25和0.5之间,属中度多态;对不同基因型对应个体的生产性状进行关联分析,发现A268G位点与肉质性状无显著相关,而A420G位点不同基因型个体间肌肉嫩度、pH和蛋白质含量存在显著差异.本实验可为MED4基因标记在草原红牛生产中的利用提供初步参考依据.

为探究延黄牛CD44基因及短支链酰基辅酶A脱氢酶（ACADSB）基因多态性及其与肉质性状的相关性，选取54头延黄牛为研究对象，采用PCR扩增产物Sanger测序技术检测单核苷酸多态性（SNP）位点，利用“牛等家养动物群体遗传分析工具V1.0”评价延黄牛群体遗传结构，利用SPSS 19.0软件分析基因多态性与肉质性状的相关性。结果：延黄牛CD44基因外显子17 g.65736591处存在C/T突变，延黄牛ACADSB基因外显子1 g.42806106处存在A/G突变；卡方检验显示，检测到的SNP位点在延黄牛群体中均处于Hardy-Weinberg平衡状态（P＞0.05）,且在延黄牛群体中变异较小，均属于中度多态（多态信息含量为0.25～0.5）;关联分析结果显示，延黄牛CD44基因SNP位点不同基因型间的肉质性状均无显著差异（P＞0.05）,ACADSB基因SNP位点不同基因型间在压榨水分、解冻损失率及肉红度（A）值间存在显著性差异（P＜0.05,P＜0.01）,而在其他肉质性状间无显著差异，初步说明CD44和ACADSB基因有望作为延黄牛肉质性状的优良候选基因。

[目的]研究中国草原红牛丙酮酸脱氢酶激酶4(pyruvate dehydrogenase kinase 4,PDK4)基因多态性与肉质性状的关系.[方法]挑选120头中国草原红牛为研究对象,采用Sanger测序法检测PDK4基因第1～11外显子的单核苷酸多态性(SNP)位点,分析SNP位点的基因型频率、基因频率及群体遗传参数等.利用SPSS 21.0软件对中国草原红牛PDK4基因SNP位点多态性与肉质性状(熟肉率、肉嫩度、失水率、pH、滴水损失、肌内脂肪含量、初水分含量、蛋白质含量)进行关联分析.[结果]在中国草原红牛PDK4基因外显子8和外显子11上共检测到3个SNPs;PDK4基因第8外显子57 bp处存在1个SNP位点(G57C),且引起编码氨基酸的改变,存在GG、GC和CC 3种基因型;PDK4基因第11外显子在330和389 bp处存在2个SNPs位点(G330T和C389T),在G330T位点上存在GG、GT和TT 3种基因型;在C389T位点上存在CC、CT和TT 3种基因型.卡方适合性检验结果显示,中国草原红牛第8外显子G57C位点偏离Hardy-Weinberg平衡状态(P＜0.05),第11外显子的G330T和C398T符合Hardy-Weinberg平衡状态(P＞0.05);群体遗传参数分析发现,第8外显子G57C突变位点属于低度多态性位点(PIC＜0.25),等位基因数为1.1429,表明其在中国草原红牛中的变异较小;第11外显子G330T和C398T属于中度多态性位点(0.25＜PIC＜0.5),等位基因数分别为1.6431和1.6447,说明该遗传标记能够提供遗传信息.关联分析结果表明,PDK4基因第8外显子中G57C位点GG和CC基因型个体肌内脂肪含量显著高于GC基因型(P＜0.05);第11外显子G330T位点GG基因型滴水损失和初水分量显著高于GT基因型(P＜0.05);GG基因型肉嫩度显著高于TT基因型(P＜0.05);GT基因型肌内脂肪含量显著高于TT基因型(P＜0.05),C389T处CT基因型失水率显著低于TT基因型(P＜0.05).[结论]PDK4基因多态性与中国草原红牛肉质性状相关,可作为肉质性状的候选基因.

In order to study the effect of prolonged fattening period on meat production performance of wojin black cattle 60,12-month-old Woking black steers with similar body weight and good body condition were randomly divided into two groups（control group and experimental group） with 30 head in each group, the control group was fattened up to 30 months old, and the treatment group was fattened up to 36 months old.The results showed that the premortem live weight, carcass weight, net meat rate and intermuscular fat thickness of the 36-month-old group were significantly higher than those of the 30-month-old group（P＜0.05）,but the slaughter rate, eye muscle area and backfat thickness were not significantly different（P＞0.05） The tenderness increased significantly（P＜0.05）and the water-holding capacity increased, but the difference was not significant（P＞0.05）.In conclusion, proper prolongation of fattening period can improve slaughter performance and meat color and tenderness of wojin black steers.

The study of the genes associated with economically important traits in livestock is one important aspect of the breeding. In order to investigate the expression difference of genes associated with growth traits and meat quality traits of the Wojin Black cattle and the Steppes Red cattle, 3 male Wojin Black cattle and 3 male Steppes Red cattle aged 18 month were randomly selected. After slaughter, the liver tissue, subcutaneous fat and longissimus dorsi muscle tissue of cattle were harvested for extraction of total RNA. Real time fluorescent quantitative PCR was used to detect the expression difference of IGF1, H-FABP, GH, GHR, Myf5, MSTN, LPL, ACSL1, PPARγ between two cattle breeds mentioned above. The results showed that the expression of both IGF1 and H-FABP genes were the highest in the liver and muscle tissues of Wojin Black cattle, and no significant difference in the expression of IGF1 genes in the fat tissues of the two cattle breeds（P＞0.05）; The expression of GH, GHR and MyoG genes was the highest in the liver tissues of Steppes Red cattle, and the highest in the muscles of Wojin Black cattle; The expression of Myf5, MSTN and ACSL1 genes were not detected in liver tissues of 2 cattle breeds, and the expression of Myf5 and MSTN genes was significantly higher in muscles of Wojin Black cattle compared with Steppes Red cattle（P＞0.05）, and the expression of ACSL1 genes were the highest in fat tissues of Wojin black cattle; The expression of PPAR γ and LPL genes was the highest in the liver tissues of Steppes Red cattle, and the highest in the adipose tissues of Wojin Black cattle.

为研究中国草原红牛丙酮酸脱氢酶激酶4(Pyruvate Dehydrogenase Kinase 4,PDK4)基因功能,本研究克隆了PDK4基因编码区序列(CDS),从mRNA水平检测PDK4基因在中国草原红牛各组织及其前体脂肪细胞成脂分化过程中的表达差异,最后进行生物信息学分析.根据NCBI公布的牛PDK4基因序列(登录号:NM_001101883.1)设计引物,PCR扩增和克隆测序,获得草原红牛PDK4基因完整CDS序列,应用生物信息学软件分析蛋白理化性质和结构,预测蛋白信号肽和磷酸化位点及构建系统进化树;通过实时荧光定量PCR检测PDK4基因在中国草原红牛各组织中mRNA的相对表达量及PDK4基因在前体脂肪细胞分化过程中mRNA水平上的表达情况.结果显示:本研究成功获得中国草原红牛PDK4基因CDS序列,长度为1223 bp,编码407个氨基酸,与野牦牛同源性较高(99.8％),与埃及果蝠的同源性较低(89.7％).PDK4基因在草原红牛心脏、肝脏、脾脏、肺脏、肾脏、胃、十二指肠、背最长肌和脂肪中均显著表达,其中在背最长肌中的表达量显著高于其他组织.成脂分化结果表明,PDK4基因mRNA表达量在0～4 d呈上升趋势,4～6 d之间无显著差异.

为探究雪花型沃金黑牛宰后成熟期间滴水损失率情况,对同一饲养条件、健康无病、发育正常、30月龄的沃金黑牛母牛、阉牛各9头,均取背最长肌西冷部位在宰后成熟24 h、48 h、72 h、96 h、120 h和144 h测定肌肉的滴水损失率.结果表明,随着宰后成熟时间的增加,沃金黑牛母牛和阉牛肉的滴水损失率显著增加(P<0.05);从性别来看,阉牛的滴水损失率低于母牛.