本试验旨在探讨日粮中不同水平蛋白质和能量对西门塔尔杂交牛生产性能和经济效益的影响,为生产高质量牛肉、增加养殖经济效益提供依据.试验选取体重、出生日期相近的健康西门塔尔杂交育肥牛(约220 kg)30头,随机分为对照组、试验Ⅰ组和试验Ⅱ组,每组各10头,分别饲喂含不同水平蛋白质和能量的日粮.结果表明:试验Ⅰ组在高能量、高蛋白的水平下净增重为1.93 kg/(头·d),净利润率可达19.5％,比对照组净利润率高13.1％;而试验Ⅱ组在蛋白含量一定、能量水平较高的条件下净增重为1.77 kg/(头·d),净利润率为16.4％,比对照组净利润率高10％.试验组日增重水平显著高于对照组(P<0.05).由此可见,适当地提高全混合颗粒日粮的养分含量,可以明显提升220～350 kg西门塔尔杂交育肥牛的增重效果,使得经济效益最大化.

本试验对水牛SERPINE2基因进行生物信息学分析,探索其在水牛不同组织器官中的表达规律,旨在为研究SERPINE2在水牛生殖过程中的具体调控机制提供理论支持.利用PCR技术克隆水牛SERPINE2基因CDS区的全长序列,在线生物信息学分析程序对SERPINE2进行分析,实时荧光定量PCR技术检测SERPINE2 mRNA在水牛不同组织的表达水平.结果表明:SERPINE2基因CDS区长度为1191 bp,编码397个氨基酸,通过分析相似性结果,发现水牛和牛、绵羊、山羊的相似性为99.6％;系统进化树结果显示,遗传距离最近的是水牛和牛,绵羊次之.在组成SERPINE2蛋白的氨基酸中,缬氨酸含量较高,占氨基酸总数的9.6％.SERPINE2蛋白是一种不稳定的亲水蛋白,SERPINE2有一个信号肽,没有跨膜结构域.SERPINE2蛋白的二级结构中,α-螺旋结构的占比最高,为41.56％.多个器官检测出SERPINE2 mRNA的表达,其中在卵巢的表达量显著高于其他器官,说明SERPINE2基因可能与卵巢生长发育有重大联系.

The proliferation and myogenic differentiation of muscle stem cells (MuSCs) are important factors affecting muscle development and beef quality. There is increasing evidence that circRNAs can regulate myogenesis. We found a novel circRNA, named circRRAS2 that is significantly upregulated in the differentiation phase of bovine MuSCs. Here, we aimed to determine its roles in the proliferation and myogenic differentiation of these cells. The results showed that circRRAS2 was expressed in several bovine tissues. CircRRAS2 inhibited MuSCs proliferation and promoted myoblast differentiation. In addition, chromatin isolation by using RNA purification and mass spectrometry in differentiated muscle cells identified 52 RNA-binding proteins that could potentially bind to circRRAS2, in order to regulate their differentiation. The results suggest that circRRAS2 could be a specific regulator of myogenesis in bovine muscle.HighlightsCircRRAS2 expression is higher in DM cells than in GM cells.CircRRAS2 could significantly inhibit the proliferation and apoptosis of bovine MuSCs.CircRRAS2 promotes the differentiation of bovine MuSCs into myotubes.CircRRAS2 may exert regulatory effects through multiple RNA binding proteins.

【Objective】At present, studies have proved that circRNA plays important roles in the development of bovine muscle, but its molecular regulation mechanism remain elusive. Screening circRNAs related to bovine muscle development can lay a foundation for further elucidating the molecular mechanism of bovine muscle development.【Method】In this study, RNA-seq sequencing results of proliferating (GM) and myogenic differentiation (DM) yellow bovine muscle stem cells (MuSCs) analyzed in the previous stage were used to screen for significantly differentially expressed circRNA, circCEP85L. Tissue samples of heart, liver, spleen, lung, kidney, muscle, intestine and stomach were collected aseptically from fresh yellow fetal calves, and yellow muscle stem cells were isolated and cultured and induced into myogenic differentiation. GM and DM cells cultured in vitro from yellow calves were collected, RNA was extracted and reverse transcribed into cDNA, respectively. Quantitative real time PCR (qRT-PCR) was used to detect the expression of circCEP85L in different tissues and different cell states. Meanwhile, specific primers were designed to amplify the full length of circCEP85L, and the overexpression vector p-circCEP85L was constructed. The plasmid was transfected into MuSCs and overexpressed circCEP85L cell samples were collected. Using overexpression plasmid pCD5-ciR cell samples as control, qRT-PCR, flow cytometry, Western Blot and immunofluorescence were used to detect the effects of overexpression of circCEP85L on proliferation, apoptosis and myogenic differentiation of yellow bovine MuSCs.【Result】The electrophoresis of PCR product proved the existence of circCEP85L. CircCEP85L was expressed in various tissues, and the expression level in DM stage was significantly higher than that in GM stage (P<0.001). To further investigate the effect on circCEP85L scallion MuSCs. The overexpression vector p-circCEP85L was transfected with the control vector pCD5-ciR in vitro cultured yellow bovine MuSCs and the EdU results showed that overexpression of circCEP85L significantly reduced the proportion of EdU positive cells (P<0.001) after continuing the culture for 24 h. Flow cycle analysis showed that overexpression of circCEP85L increased the proportion of cells in G0/G1 phase and significantly decreased the proportion of cells in S phase (P<0.001). Flow cytometry showed that overexpression of circCEP85L significantly inhibited the apoptosis rate of MuSCs (P<0.05). qRT-PCR and western blot were used to detect the expression of proliferation and apoptosis-related genes in MuSCs, respectively. The results showed that overexpression of circCEP85L significantly reduced the mRNA expression levels of proliferation and apoptosis-related genes in bovine MuSCs (P<0.001), and the expression of apoptotic protein BAX was also significantly reduced (P<0.01). In addition, in order to detect the effect of circCEP85L overexpression on myogenic differentiation of cattle MuSCs, the differentiation medium was replaced 24 hours after transfection to induce cell differentiation. Western blot and immunofluorescence results showed that overexpression of circCEP85L significantly promoted the expression level of differentiation marker gene MyH6 (P<0.001), and the number and size of myotubes formed by cell fusion were significantly higher than those of the control group.【Conclusion】The results of this study indicate that circCEP85L affects the growth and development process of skeletal muscle in cattle by inhibiting the proliferation and apoptosis of MuSCs and promoting myogenic differentiation of cells, which is expected to be a key circRNA for subsequent mechanistic studies to regulate the growth and development process of skeletal muscle in cattle.

Myogenesis is an essential process that can affect the yield and quality of beef. Transcriptional studies have shown that histone deacetylase 11 (HDAC11) was differentially expressed in muscle tissues of 6 and 18 month old Longlin cattle, but its role in the regulation of myogenesis remains unclear. This study aimed to determine the role of HDAC11 in the proliferation and differentiation of bovine muscle stem cells (MuSCs). HDAC11 promoted MuSC proliferation by activating Notch signaling and inhibited myoblast differentiation by reducing MyoD1 transcription. In addition, overexpression of HDAC11 inhibited the repair regeneration process of muscle in mice. HDAC11 was found to be a novel key target for the control of myogenesis, and this is a theoretical basis for the development of HDAC11-specific modulators as a new strategy to regulate myogenesis.