FoxO1抑制猪骨骼肌MyHC Ⅰ的表达

为研究FoxO1与骨骼肌纤维类型之间的关系,本试验以大白猪为实验材料,利用RT-PCR和Western印迹技术,检测了FoxO1与肌纤维类型标志基因MyHCⅠ、MyHCⅡa、MyHCⅡb和MyHCⅡx在特定骨骼肌中的表达规律,以及调控肌纤维类型关键基因Mef2c和NFAT的表达,并用Wortmannin处理原代培养的猪骨骼肌成肌细胞,检测了FoxO1与肌纤维类型相关基因的表达.结果显示,FoxO1在不同骨骼肌类型中mRNA表达差异不显著(P0.05),其蛋白表达与MyHC各亚型显著相关.Wortmannin处理结果显示,在处理的第3和5d,FoxO1蛋白与MyHCⅡb,MyHCⅡx和NFAT表达显著正相关,而与MyHCⅠ,MyHCⅡa和Mef2c表达显著负相关.结果表明,FoxO1通过抑制MyHCⅠ的表达调控肌纤维类型.     

高糖通过下调FoxO1磷酸化诱导β细胞去分化

胰岛β细胞发生去分化现象是导致其功能减退的机制之一。已有研究证明,FoxO1与β细胞去分化密切相关。然而,高糖是否可通过FoxO1诱导β细胞发生去分化目前尚未见报告。本研究通过不同浓度高糖干预MIN6细胞,采用葡萄糖刺激胰岛素分泌试验（GSIS）检测β细胞功能|实时荧光定量PCR及蛋白免疫印迹、免疫荧光方法检测高糖干预后β细胞内祖细胞标志基因、β细胞标志基因及FoxO1的表达变化。结果显示,不同浓度高糖干预β细胞后,当浓度达到35 mmol/L时,β细胞祖细胞标志基因表达明显增加。且在该浓度时,检测到β细胞标志基因表达明显降低,MIN6细胞葡萄糖刺激胰岛素分泌功能减退,磷酸化FoxO1表达减少。上述结果提示,高糖可诱导胰岛β细胞去分化的发生,其机制可能是通过FoxO1介导。     

外源性重组人睫状神经营养因子抑制成人成肌细胞的体外分化

为探讨外源性重组人睫状神经营养因子(rhCNTF)在成肌细胞分化中的作用,实验观察了0-10 ng/mlrhCNTF对成人成肌细胞体外分化的影响。结果表明,与对照组相比,2.5-10 ng/ml rhCNTF能显著抑制成肌细胞的体外分化(P<0.01),并呈量-效依赖关系,且这种抑制作用是可逆的。Western Blot分析提示,这种抑制作用伴有成肌细胞分化期特异标志myogenin和p21表达量的显著降低(P<0.01),以及成肌细胞增殖期特异标志myf5和desmin表达量的显著增加(P<0.01)。因此可以认为,外源性rhCNTF能可逆地抑制成人成肌细胞的体外分化并保持增殖。     

不同猪品种肌肉组织FoxO1与MyoD基因mRNA的表达及其相关性分析

分别取6月龄八眉猪、长白猪和长×八杂交猪背最长肌,提取总RNA,设计并合成猪FoxO1和MyoD 引物,以β肌动蛋白作为内参,优化反应条件和体系,利用RT-PCR方法检测八眉、长白和长×八杂交猪肌肉组织中FoxO1和MyoD基因mRNA 的表达.结果表明,在不同经济类型猪品种肌肉组织中,FoxO1和MyoD基因mRNA的表达丰度均存在显著差异,FoxO1在八眉猪肌肉组织中的表达普遍高于长白猪（P<0.01）,在杂交组合长×八肌肉组织中的表达也高于长白猪（P<0.01）;而MyoD恰好相反,即在长白猪肌肉组织中的表达普遍高于八眉猪（P<0.01）,在杂交组合长×八肌肉组织中的表达也高于八眉猪（P<0.01）．结果提示,FoxO1和MyoD基因mRNA的表达在肌肉发育中存在负相关（r = 0.728 , P < 0.05）,FoxO1在肌肉组织中的上调作用,可能是造成的MyoD基因mRNA表达降低的原因之一,进而负调控肌肉的发育和骨骼肌的量．     

八眉猪、长白猪及长×八杂交猪肌肉组织中FoxO1基因的表达

分别取6月龄八眉、长白和 (长×八)杂交猪后腿部比目鱼肌、腓肠肌和趾长伸肌, 提取总RNA, 根据人、黑猩猩及大鼠等物种FoxO1基因同源序列设计并合成引物, 以猪b-actin 基因作为内参, 优化反应条件和体系, RT-PCR 单管扩增猪FoxO1基因, 检测八眉、长白和长×八杂交猪不同类型骨骼肌中FoxO1基因mRNA的表达差异。结果表明: 在不同经济类型猪群和不同类型骨骼肌中FoxO1基因mRNA的表达丰度不同, 即在八眉 猪骨骼肌中的表达普遍高于长白猪 (P<0.01), 在杂交组合 (长×八)骨骼肌中的表达也高于长白猪 (P<0.01); 同时在以Ⅰ型纤维为主的比目鱼肌中表达丰度最低(P<0.01), 在以Ⅱb型纤维为主的趾长伸肌中表达丰度最高(P<0.01)。结果提示, FoxO1基因的表达与Ⅰ型肌纤维的含量成反比; 不同经济类型猪品种骨骼肌的发育与FoxO1基因的调控有关。     

FoxO1在病毒感染和炎症发生中的作用

FoxO1是Foxs家族的成员,该家族大多数为转录因子.FoxO1作为Foxs家族的重要转录因子之一,它不仅具有调控转录的作用,也参与许多生理过程,例如糖代谢、细胞凋亡、脂肪代谢、肌细胞的分化、生殖和肿瘤的发生等.近些年,也有越来越多的研究证实FoxO1在病毒感染和炎症发生等过程也具有重要作用,但其中机制还不清楚.本文主要讲述了几种病毒感染及炎症发生期间,FoxO1在其中发挥的重要作用.     

甲基转移酶METTL21C影响鸡骨骼肌细胞成肌的发育

本研究旨在探究甲基转移酶METTL21C在家禽骨骼肌发育分化过程中的作用。采用实时荧光定量PCR (quantitative Real-time PCR, qPCR)检测METTL21C基因在鸡不同组织中的表达情况,绘制其组织表达谱;选取3个时间点,检测其在骨骼肌组织中的表达情况。通过酶消化法从鸡骨骼肌组织中分离得到原代细胞;将METTL21C超表达载体转染至原代鸡骨骼肌细胞,通过qPCR和Western blotting检测Pax7、MyoD、Myf5、MyoG等基因的表达水平。结果显示,METTL21C在心肌和骨骼肌组织中的表达量显著高于其他组织,在胚胎期和幼龄期骨骼肌中的表达呈上升趋势;超表达METTL21C后,成肌相关基因Pax7、MyoD、Myf5、MyoG的表达量显著升高。本研究初步发现甲基转移酶METTL21C具有促进家禽骨骼肌发育分化的作用,为骨骼肌发育的分子机理的研究及相关医学研究提供数据支持。     

外源性瘦素通过丝裂素活化蛋白激酶抑制猪骨骼肌成肌细胞分化

研究瘦素(leptin)对猪骨骼肌成肌细胞分化的影响, 并探讨其可能的作用机制。原代培养猪骨骼肌成肌细胞, 通过倒置显微镜定性观察细胞分化的形态学变化; 肌酸激酶(CK)活性测定法定量分析成肌细胞分化程度; 细胞免疫化学方法分析myogenin的表达情况; 免疫印迹技术(Western Blot)检测丝裂素活化蛋白激酶(mitogen activated protein kinase, MAPK)的表达变化。结果显示, 在猪骨骼肌成肌细胞分化过程中, 外源性leptin减少细胞核融合和肌管形成, 呈浓度和时间依赖性地显著降低CK活性( P < 0.05), 并显著抑制myogenin和MAPK的蛋白表达( P < 0.05)。以上结果说明, leptin抑制猪骨骼肌成肌细胞分化, 并且这种作用可能是通过激活MAPK 信号转导通路实现的。研究结果显示, leptin在骨骼肌成肌细胞分化过程中可能具有重要作用。     

高浓度地塞米松通过下调LMP-1表达抑制大鼠成骨细胞的分化

为探讨地塞米松（dexamethasone,DEX)抑制成骨细胞分化的机制,观察了不同浓度DEX对体外培养大鼠成骨细胞的碱性磷酸酶活性,骨钙素（osteocalcin,OC)合成,I型胶原蛋白表达的影响。并用RT-PCR方法检测了成骨细胞中LIM矿化蛋白1mRNA的表达量,结果显示：低浓度（10^-9mol/L）的DEX能增强碱性磷酸酶的活性、OC的分泌和I型胶原蛋白的表达;而高浓度（10^-7mol/L)的DEX对它们则起抑制作用,并下调成骨细胞正调节因子LMP-1mRNA的表达,上述结果表明,低浓度的DEX促进成骨细胞的分化;高浓度的DEX则抑制成骨细胞的分化,其抑制作用可能是通过下调LMP-1mRNA的表达而实现的。     

Control of mouse myoblast commitment to terminal differentiation by mitogens

Regulation of the transition of mouse myoblasts from proliferation to terminal differentiation was studied with clonal density cultures of a permanent clonal myoblast cell line. In medium lacking mitogenic activity, mouse myoblasts withdraw from the cell cycle, elaborate muscle-specific gene products, and fuse to form multinucleated myotubes. Addition of a purified mitogen, fibroblast growth factor, to mitogen-depleted medium stimulates continued proliferation and prevents terminal differentiation. When mitogens are removed for increasing durations and then refed, mouse myoblasts irreversibly commit to terminal differentiation: after 2–4 h in the absence of mitogens, myoblasts withdraw from the cell cycle, elaborate muscle-specific gene products, and fuse in the presence of mitogens that have been fed back. Population kinetics of commitment determined with ³H-thymidine labeling and autoradiography suggest the following cell-cycle model for mouse myoblast commitment: (1) if mitogens are present in the extracellular environment of myoblasts in G₁ of the cell cycle, the cells enter S and continue through another cell cycle; (2) if mitogens have been absent for 2 or more hours, cells in G₁ do not enter S; the cells commit to differentiate, permanently withdraw from the cell cycle (will not enter S if mitogens are refed), and they subsequently elaborate acetylcholine receptors and fuse (even if mitogens are refed); (3) cells in other phases of the cell cycle continue to transit the cell cycle in the absence of mitogens until reaching the next G₁. The commitment kinetics and experiments with mitotically synchronized cells suggest that the commitment “decision” is made during G₁. Present results do not, however, exclude commitment of some cells in other phases of the cell cycle.     

MiR-15a/b promote adipogenesis in porcine pre-adipocyte via repressing FoxO1

Diabetes and many other metabolism syndromes are closely related to obesity. To reveal the underlying mechan ism of fat deposition, an increasing number of studies are focusing on the functions of miRNAs during adipocytes de velopment. Previous studies have proved that miR15a/b play important roles in multiple physiological processes; however, their functions during adipogenesis remain un clear. To reveal this, we detected the expression profiles of miR15a/b during adipogenesis in porcine preadipocyte, and found that their expression levels increased in the early stage of adipoeyte differentiation and dropped after day 4. Moreover, overexpression of miR15a/b in porcine pre adipocytes promoted adipocyte differentiation and lipid accumulation. Target genes of miR15a/b were predicted and examined, which revealed that Forkhead box protein O1 （FoxO1） is the target gene of miR15a/b. The inhibition of FoxO1 expression level caused by miR15a/b over expression had a positive effect on adipogenesis. Thus, we conclude that miR15a/b promote adipogenesis in porcine preadipocyte via repressing FoxO1.     

BAMBI通过促进ERK1/2磷酸化抑制猪前体脂肪细胞分化

为了研究BAMBI在猪前体脂肪细胞分化过程中的作用,构建了BAMBI慢病毒干扰载体,包装并感染猪前体脂肪细胞,采用油红O染色、油红O提取比色法检测猪前体脂肪细胞分化情况,采用Real-time qPCR、Western blotting检测成脂标志基因mRNA以及蛋白水平表达的变化情况。结果表明,BAMBI慢病毒干扰载体感染前体脂肪细胞后显著降低了BAMBI的表达,shRNA2干扰效率最高,达到了60%以上,干扰BAMBI后能增加猪脂肪细胞的脂质积累,增加了成脂标志基因过氧化物酶体增殖物激活受体γ(Peroxisome proliferator-activated receptorγ,PPARγ)和脂肪酸结合蛋白2(Adipocyte protein 2,ap2)的表达。此外,干扰BAMBI后ERK1/2的磷酸化水平减少了。这些结果表明,BAMBI可能通过促进ERK1/2的磷酸化抑制脂肪细胞分化。     

FHL1 regulates myoblast differentiation and autophagy through its interaction with LC3

Four and a half LIM domain protein 1 (FHL1) belongs to the FHL protein family and is predominantly expressed in skeletal and cardiac muscle. FHL1 acts as a scaffold during sarcomere assembly and plays a vital role in muscle growth and development. Autophagy is key to skeletal muscle development and regeneration, with its dysfunction associated with a range of muscular pathologies and disorders. In this study, we constructed FHL1-silenced or FHL1-overexpressed myoblasts to investigate its role in autophagy during the differentiation of chicken myoblasts into myotubules. Our data showed that FHL1 contributes to myoblast differentiation as measured through MyoG, MyoD, Myh3, and Mb mRNA expression, MyoG and MyHC protein expression and the morphological characteristics of myoblasts. The results showed that FHL1 silencing inhibited the expression of ATG5 and ATG7, meanwhile, immunofluorescence and immunoprecipitation showed that FHL1 and LC3 interacted to regulate the correct formation of autophagosomes. FHL1 inhibition increased cleaved caspase-3 and PARP abundance and promoted myoblast apoptosis. Furthermore, FHL1 rescued skeletal muscle atrophy through regulating the expression of Atrogin-1 and MuRF1. Taken together, these data suggested that FHL1 regulates chicken myoblast differentiation through its interaction with LC3.     

RASSF4 is required for skeletal muscle differentiation

RASSF4, a member of the classical RASSF family of scaffold proteins, is associated with alveolar rhabdomyosarcoma, an aggressive pediatric cancer of muscle histogenesis. However, the role of RASSF4 in normal myogenesis is unknown. We demonstrate here that RASSF4 is necessary for early in vitro myogenesis. Using primary human myoblasts, we show that RASSF4 expression is dramatically increased during in vitro myogenic differentiation, and conversely that RASSF4‐deficient myoblasts cannot differentiate, potentially because of a lack of upregulation of myogenin. In microscopy studies, we show that RASSF4 protein co‐localizes with proteins of the myogenic microtubule‐organizing center (MTOC) both before and after myogenic differentiation. RASSF4‐deficient cells subject to differentiation conditions demonstrate a lack of shape change, suggesting that RASSF4 plays a role in promoting microtubule reorganization and myoblast elongation. In biochemical studies of myotubes, RASSF4 associates with MST1, suggesting that RASSF4 signals to MST1 in the myogenic differentiation process. Expression of MST1 in myoblasts partially reversed the effect of RASSF4 knockdown on differentiation, suggesting that RASSF4 and MST1 coordinately support myogenic differentiation. These data show that RASSF4 is critical for the early steps of myogenic differentiation.     

Linc-smad7 promotes myoblast differentiation and muscle regeneration via sponging miR-125b

Long noncoding RNAs (lncRNAs) are involved in the regulation of skeletal muscle development. In the present study, differentially expressed lncRNAs were identified from RNA-seq data derived from myoblasts and myotubes. We conducted studies to elucidate the function and molecular mechanism of action of Linc-smad7 during skeletal muscle development. Our findings show that Linc-smad7 is upregulated during the early phase of myoblasts differentiation. In in vitro studies, we showed that overexpression of Linc-smad7 promoted the arrest of myoblasts in G1 phase, inhibited DNA replication, and induced myoblast differentiation. Our in vivo studies suggest that Linc-smad7 stimulates skeletal muscle regeneration in cardiotoxin-induced muscle injury. Mechanistically, Linc-smad7 overexpression increased smad7 and IGF2 protein levels. On the contrary, overexpression of miR-125b reduced smad7 and IGF2 protein levels. Results of RNA immunoprecipitation analysis and biotin-labeled miR-125b capture suggest that Linc-smad7 could act as a competing endogenous RNA (ceRNA) for miRNA-125b. Taken together, our findings suggest that the novel noncoding regulator Linc-smad7 regulates skeletal muscle development.