神经组织特异表达绿色荧光蛋白转基因小鼠的脑组织形态观察

目的 建立神经组织特异表达绿色荧光蛋白的转基因小鼠,为神经系统的形态学观察提供可以荧光示踪的工具动物.方法 把增强型绿色荧光蛋白(EGFP) 因插入血小板源性生长因(PDGF)B-链启动子下游构建转基因载体,用显微注射的方法建立转基因C57BL/6J小鼠.PCR鉴定转基因小鼠的基因表型,对阳性转基因小鼠的脑组织进行矢状面冷冻切片,分别进行HE染色,显微镜观察组织结构,荧光体视镜及荧光显微镜观察绿色荧光蛋白(GFP)在神经组织的表达.结果 在8个首建品系中筛选出1个神经组织高表达绿色荧光蛋白的转基因小鼠系.观察到绿色荧光蛋白在大脑皮层、海马、丘脑、小脑及脑干等部位表达.结论 建立了稳定遗传的神经组织特异表达绿色荧光蛋白转基因小鼠品系,为神经系统的生理学及病理学研究提供了可以荧光示踪的模型动物.     

绿色荧光蛋白转基因小鼠神经干细胞的培养与鉴定

目的:体外分离、培养及鉴定绿色荧光蛋白(green fluorescent protein,GFP)转基因小鼠神经干细胞(neu- ral stem cells,NSCs),为利用其示踪研究NSCs分化机制奠定基础。方法:从新生GFP小鼠海马组织分离NSCs,采用无血清培养、扩增及传代;免疫荧光和免疫细胞化学染色鉴定NSCs和神经细胞;荧光显微镜下观察GFP表达情况。结果:新生GFP小鼠大脑海马组织分离的NSCs具有自我增殖及分化成神经元、星形胶质细胞和少突胶质细胞的能力;连续传代后,神经球和分化后细胞的GFP表达不受影响。结论:成功分离并获得了GFP新生小鼠NSCs,该细胞具有自我更新能力和多向分化潜能,且稳定表达GFP。因此,源自GFP转基因小鼠的NSCs可以作为研究NSCs多向分化机制的有效示踪工具。     

增强型绿色荧光蛋白基因转染小鼠胚胎干细胞及其无血清神经细胞诱导

目的构建表达绿色荧光蛋白的小鼠胚胎干细胞(MES)克隆,观察基因转染对MES细胞增殖和无血清诱导为nestin阳性神经前体细胞(NPCs)的影响。方法原代分离小鼠胚胎成纤维细胞并经丝裂霉素-C处理作为饲养层细胞。质粒的转化、抽提、纯化。电穿孔法基因转染,MES细胞克隆的NBT／BCIP染色,NPCs的nestin免疫组织化学染色。结果EGFP基因转染后可得到表达绿色荧光蛋白的MES细胞克隆,采用N2或ITSF无血清条件培养基可将其定向诱导为nestin阳性的并能发绿色荧光的NPCs。基因转染后的MES细胞增殖、神经前体细胞诱导率和未转染组相比均无明显下降,但NPCs绿色荧光的表达较诱导前明显下降。结论基因转染对ES细胞的增殖和神经分化无明显影响。     

绿色荧光蛋白转基因小鼠来源肌卫星细胞的体外培养及体内示踪

目的:从绿色荧光蛋白转基因小鼠中分离培养肌卫星细胞(MSCs)并进行体内示踪.方法:利用差速贴壁结合克隆分选方法,分离了MSCs,并于体外进行培养传代、鉴定及分化.检测所获MSCs的生长曲线及细胞周期并与来源于野生型鼠的同代MSCs进行比较.将绿色荧光蛋白标记的MSCs注射到裸鼠胫前肌,于注射后当时、注射后1周、2周、3周和4周利用二维荧光成像平台进行体内示踪.结果:MSCs被成功分离、传代及鉴定.来源于绿色荧光蛋白(GFP)标记或未标记小鼠MSCs的生长曲线、细胞周期及肌原性分化等无差别.MSCs注射后4周内可以动态观察到注射部位的绿色荧光信号并获得组织学证实.结论:来源于GFP转基因小鼠的MSCs在生长和增殖特性上与未转基因来源的MSCs相似,在体内可以通过二维荧光成像平台进行可靠的、无创性的示踪.     

ENK与CaBPs在PPE-GFP转基因小鼠视网膜细胞中的共存

目的:以PPE-GFP转基因小鼠为研究工具,观察绿色荧光蛋白(GFP)阳性的脑啡肽(ENK)能神经元与钙结合蛋白D28K(CB)、钙视网膜蛋白(CR)和小白蛋白(PV)等钙结合蛋白(CaBPs)成员在视网膜的分布及共存情况。方法:利用免疫组织化学和免疫荧光双标染色的方法。结果:GFP阳性的ENK能细胞主要分布在视网膜内核层内缘,少量分布在节细胞层。所有的GFP阳性细胞均与神经元标志物NSE共存,但不与星形胶质细胞标志物GFAP共存。GFP与CB、CR和PV均有部分共存,其中GFP/CB共存神经元占GFP阳性细胞的8.65%,占CB阳性细胞的5.84%;GFP/CR共存神经元占GFP阳性细胞的18.18%,占CR阳性细胞的14.28%,且共存细胞仅见于内核层;GFP/PV共存细胞占GFP阳性细胞的68.75%,占PV阳性细胞的91.67%,共存细胞主要位于内核层,少量见于节细胞层。结论:ENK能神经元在视网膜内具有板层特异性的分布特点和与钙结合蛋白成员有不同的共存模式,上述结果为深入研究小鼠视网膜ENK能神经元的功能意义提供了形态学依据。     

绿色荧光蛋白转基因小鼠不同源性间充质干细胞原代培养及生物学特性比较

 目的： 探讨绿色荧光蛋白转基因小鼠脐带和骨髓源性间充质干细胞 （MSCs）的体外分离培养方法、生物学特性、表面标志及多向分化潜能。方法：应用Ⅱ型胶原酶消化培养法分离脐带MSCs及密度梯度离心法分离骨髓MSCs进行体外培养。在倒置显微镜下观察2种细胞的生长特点,运用生长曲线和MTT法检测其原代细胞增殖能力,台盼蓝法测定细胞传代成活率,采用流式细胞术测定2种第3代（P3）细胞DNA周期及表面标志物的表达,并比较其向成脂细胞和成骨细胞的分化潜能。结果：酶消化法分离培养的脐带MSCs 1 d后,细胞贴壁呈成纤维形,2 d后呈漩涡状生长且增殖明显,3 d后达80%融合即可传代;应用密度梯度离心法分离骨髓MSCs,体外培养4 d后,细胞贴壁呈圆形、梭形和多角形生长,5 d后呈克隆样生长且增殖明显,7 d后达80%融合即可传代。原代培养的脐带MSCs生长曲线近似“S”形,骨髓MSCs 生长曲线较平缓;MTT法显示脐带MSCs在3～5 d增殖较明显,骨髓MSCs 7 d后细胞增殖较明显。2种P3细胞传代成活率均为96%以上,G0/G1期细胞均为85%以上,无明显差异（P>0.05）;2种P3细胞CD44、CD90和CD105阳性率均为(60.7±2.3)%以上高表达,CD45、CD19、CD14和CD79a均为(25.6±4.8)%低表达,两者无明显差异（P>0.05）;2种MSCs在体外均具有向成骨细胞和成脂细胞分化的潜能,脐带MSCs向成骨及成脂细胞分化率均为90%以上,与骨髓MSCs的分化潜能比较有显著差异（P<0.05）。结论：脐带MSCs较骨髓MSCs具有较强的增殖能力及分化潜能。绿色荧光蛋白转基因小鼠的脐带MSCs可作为较好干细胞示踪的细胞源。     

Mito-cpYFP cDNA转基因小鼠的建立及其自由基分布规律的初步探讨

目的:利用可实时动态测量超氧阴离子自由基的环状排列黄色荧光蛋白(circularly permuted yellow fluorescent protein,cpYFP)构建可实时动态监测活体动物体内自由基的转基因动物模型。方法:应用转基因技术将载有可定位于线粒体内的cpYFP(mitochondria-targeted cpYFP,mito-cpYFP)的载体pRP(Exp)-CAGGmitocpYFP注射到C57BL/6小鼠的受精卵中,采用PCR及RT-PCR的方法鉴定阳性小鼠,通过荧光观察自由基的分布并辅助鉴定阳性小鼠。结果:PCR、RT-PCR及荧光观察结果表明mito-cpYFP cDNA转基因小鼠构建成功。通过与野生型C57BL/6小鼠交配,得到F1、F2和F3代的新生幼鼠共计494只,其中,阳性幼鼠为255只,阳性率为51.6%。转基因阳性鼠体内出现了绿色荧光,其解剖伤口、肠道、脑部及口腔黏膜等荧光明显,而肾脏、肝脏及胸腺等荧光则较弱,耻骨联合部和膀胱出现绿色荧光,但约0.5 h后消失。结论:我们成功制备了可稳定表达并遗传mito-cpYFP的转基因小鼠品系。在活体动物体内,自由基在黏膜层含量较多。此模型可研究自由基在生物体内的含量及分布规律,为后续生物自由基作为信号分子在机体内传导途径的研究提供有效的工具。     

转基因小鼠的插入突变与基因克隆——方法,成就与展望

转基因技术成为研究基因的四维时空中的表达特性和功能的一种重要手段，在新基因的功能鉴定及人类疾病模型的建立中得到了重要的应用。由于转基因插入内源基因组往往引起内源基因的插入突变，这种突变占转基因小鼠“产品”的５￣１０％，比自发突变率要高得多；更为重要的是，利用已知ＤＮＡ序列的转基因作为探讨可以对具有一定突变表型的、发生插入突变的内源基因进行染色体定位和分离，从而开辟了一条利用外源基因的基因诱陷作用而     

胚胎干细胞与四倍体互补产生转基因小鼠

目的 将四倍体胚胎补偿技术与转基因相结合，构建基因打靶载体转化的胚胎干细胞(ESCs)，获得小概率的同源重组事件，进而直接得到所要的突变品系。 方法 通过电穿孔的方法将增强型绿色荧光蛋白（EGFP）表达质粒转入ESCs，用G418筛选获得EGFP-ESCs。另外，通过电融合获得四倍体囊胚细胞，显微注射法将19～21个EGFP-ESCs注入每个四倍体囊胚腔，分别移植到假孕2.5d雌鼠子宫或假孕0.5d的输卵管内。 结果 获得稳定表达的EGFP-ESCs，染色体数目正常 (2n＝40条)；四倍体细胞融合率为95.07%，囊胚发育率为95%；共获得410个重构囊胚；移植后未得到出生小鼠，但共观察到了151个着床位点，子宫移植的着床率为29.41%，输卵管移植的着床率为64.37%，获得的胚胎中EGFP蛋白有散在的表达。 结论 稳定表达的EGFP-ESCs参与到了转基因胎鼠的发育中；本实验中输卵管移植的着床率高于子宫移植的着床率。     

液压转基因技术用于脂肪肝大鼠的肝脏转基因实验

目的 探讨液压转基因技术（HDT）应用于大鼠脂肪肝转基因的条件、方法。 方法 以不同速度将不同体积、浓度的绿色荧光蛋白基因质粒pEGFP-C1一次性注射到脂肪肝大鼠尾静脉,于注射后不同时间取大鼠（各4只）各肝叶制备冷冻切片,在波长488nm的荧光显微镜下观察、计数各肝叶绿色荧光蛋白阳性细胞。 结果 在pEGFP-C1浓度为33mg/L、注射速度为2ml/s、注射液体积为大鼠体重的8.5%条件下,注射质粒后6h,各肝叶绿色荧光蛋白阳性细胞比例最高,其中,蒂状叶的绿色荧光蛋白阳性细胞约占18%,左叶约占14%、中叶约占12.5%、右叶约占10%,尾状叶约占8%。转基因后24h绿色荧光蛋白的表达量逐渐减少,至72h时各肝叶均难以检出绿色荧光蛋白阳性细胞。 结论 大鼠尾静脉液压转基因技术可用于脂肪肝大鼠的肝脏转基因研究,转基因的适宜条件为：质粒溶液浓度33mg/L,注射量占大鼠体重的8.5%,注射速度为2ml/s,观察转基因效果的适宜时间是转基因后6～24h。     

A comparative approach to somatic cell nuclear transfer in the rhesus monkey

BACKGROUND: Despite the potential utility of primate somatic cell nuclear transfer (SCNT) to biomedical research and to the production of autologous embryonic stem (ES) cells for cell- or tissue-based therapy, a reliable method for SCNT is not yet available. Employing the rhesus monkey as a clinically relevant animal model, we have compared a conventional electrofusion method for SCNT with a one-step micromanipulation (OSM) method. METHODS: A prospective, randomized trial was conducted using only oocytes that were mature [metaphase II (MII)] at collection and a fibroblast-like cell line as nuclear donor cells (fetal fibroblasts). The embryos produced were characterized for in vitro developmental potential, cell number, karyotype and expression of nuclear mitotic apparatus (NuMA) and OCT-4. RESULTS: An in vitro blastocyst development rate of 24.4% was achieved with the OSM method, significantly higher than the 12.2% obtained following electrofusion. SCNT-produced embryos expressed normal karyotypes, cell numbers and NuMA and OCT-4 proteins in most cases. SCNT with male nuclear donor cells resulted in the production of male, SCNT blastocysts, eliminating the possibility of a parthenogenetic origin. Of the four fibroblast cell lines tested as nuclear donor cells, two supported the routine production of blastocysts following SCNT. CONCLUSIONS: The application of a modified SCNT technique (OSM) followed by embryo culture in hamster embryo culture medium-10 (HECM-10) allows, for the first time, the routine production of SCNT blastocysts, most of which appear normal by immunochemical, cytochemical and in vitro developmental criteria. These embryos will provide a resource for isolating ES cells and for studies of nuclear reprogramming by monkey cytoplasts.     

Reprogramming following somatic cell nuclear transfer in primates is dependent upon nuclear remodeling

BACKGROUND: Somatic cell nuclear transfer (SCNT) requires cytoplast-mediated reprogramming of the donor nucleus. Cytoplast factors such as maturation promoting factor are implicated based on their involvement in nuclear envelope breakdown (NEBD) and premature chromosome condensation (PCC). Given prior difficulties in SCNT in primates using conventional protocols, we hypothesized that the ability of cytoplasts to induce nuclear remodeling was instrumental in efficient reprogramming. METHODS: NEBD and PCC in monkey (Macaca mulatta) SCNT embryos were monitored by lamin A/C immunolabeling. RESULTS: Initially, a persistent lamin A/C signal from donor cell nuclei after fusion with cytoplasts was observed indicative of incomplete NEBD following SCNT and predictive of developmental arrest. We then identified fluorochrome-assisted enucleation and donor cell electrofusion as likely candidates for inducing premature cytoplast activation and a consequent lack of nuclear remodeling. Modified protocols designed to prevent premature cytoplast activation during SCNT showed robust NEBD and PCC. Coincidently, over 20% of SCNT embryos reconstructed with fetal fibroblasts progressed to blastocysts. Similar results were obtained with other somatic cells. Reconstructed blastocysts displayed patterns of Oct-4 expression similar to fertilized embryos reflecting successful reprogramming. CONCLUSIONS: Our results represent a significant breakthrough in elucidating the role of nuclear remodeling events in reprogramming following SCNT.     

Serial cloning of pigs by somatic cell nuclear transfer: restoration of phenotypic normality during serial cloning.

Somatic cell nuclear transfer (scNT) is a useful way to create cloned animals. However, scNT clones exhibit high levels of phenotypic instability. This instability may be due to epigenetic reprogramming and/or genomic damage in the donor cells. To test this, we produced transgenic pig fibroblasts harboring the truncated human thrombopoietin (hTPO) gene and used them as donor cells in scNT to produce first-generation (G1) cloned piglets. In this study, 2,818 scNT embryos were transferred to 11 recipients and five G1 piglets were obtained. Among them, a clone had a dimorphic facial appearance with severe hypertelorism and a broad prominent nasal bridge. The other clones looked normal. Second-generation (G2) scNT piglets were then produced using ear cells from a G1 piglet that had an abnormal nose phenotype. We reasoned that, if the phenotypic abnormality of the G1 clone was not present in the G2 and third-generation (G3) clones, or was absent in the G2 clones but reappeared in the G3 clones, the phenotypic instability of the G1 clone could be attributed to faulty epigenetic reprogramming rather than to inherent/accidental genomic damage to the donor cells. Blastocyst rates, cell numbers in blastocyst, pregnancy rates, term placenta weight and ponderal index, and birth weight between G1 and G2 clones did not differ, but were significantly (P < 0.05) lower than control age- and sex-matched piglets. Next, we analyzed global methylation changes during development of the preimplantation embryos reconstructed by donor cells used for the production of G1 and G2 clones and could not find any significant differences in the methylation patterns between G1 and G2 clones. Indeed, we failed to detect the phenotypic abnormality in the G2 and G3 clones. Thus, the phenotypic abnormality of the G1 clone is likely to be due to epigenetic dysregulation. Additional observations then suggested that expression of the hTPO gene in the transgenic clones did not appear to be the cause of the phenotypic abnormality in the G1 clones and that the abnormality was acquired by only a few of the G1 clone's cells during its gestational development.     

Embryo development after successful somatic cell nuclear transfer to in vitro matured human germinal vesicle oocytes

BACKGROUND: Somatic cell nuclear transfer (SCNT) involves the transfer of somatic cell nuclei into enucleated oocytes. Because human in vivo matured oocytes are scarcely available, we investigated whether in vitro matured (IVM) germinal vesicle (GV) oocytes could also support preimplantation development of human cloned embryos. METHODS: Three groups were used for SCNT: in vitro matured GV oocytes (IVM oocytes), 'in vivo' matured oocytes (in vivo oocytes) and 'failed fertilized' oocytes after routine-ICSI (FF oocytes). After removal of the chromosome-spindle complex, cumulus cell nuclei were injected, and oocytes were artificially activated and cultured. RESULTS: In total 61, 54 and 45 metaphase II oocytes were used for SCNT in the three groups, respectively. Survival and pronuclear rates were 59, 78 and 58% and 61, 64 and 50%, respectively. Of the 22 activated IVM oocytes, 13 cleaved to the 2-cell stage, whereby 2 morulae were formed. For the in vivo oocytes, 17 of 27 activated oocytes cleaved to the 2-cell stage and 1 morula was observed. Cleavage to the 2-cell stage in the group of FF oocytes was compromised. CONCLUSIONS: To our knowledge, this is the first report describing development of cloned human embryos using IVM oocytes and non-autologous transfer using a conventional method of SCNT.     

Development of human cloned blastocysts following somatic cell nuclear transfer with adult fibroblasts

Nuclear transfer stem cells hold considerable promise in the field of regenerative medicine and cell-based drug discovery. In this study, a total of 29 oocytes were obtained from three young (20-24 years old) reproductive egg donors who had been successful in previous cycles. These oocytes, deemed by intended parents to be in excess of their reproductive needs, were donated for research without financial compensation by both the egg donor and intended parents after receiving informed consent. All intended parents successfully achieved ongoing pregnancies with the oocytes retained for reproductive purposes. Mature oocytes, obtained within 2 hours following transvaginal aspiration, were enucleated using one of two methods, extrusion or aspiration, after 45 minutes of incubation in cytochalasin B. Rates of oocyte lysis or degeneration did not differ between the two methods. Somatic cell nuclear transfer (SCNT) embryos were constructed using two established adult male fibroblast lines of normal karyotype. High rates of pronuclear formation (66%), early cleavage (47%), and blastocyst (23%) development were observed following incubation in standard in vitro fertilization culture media. One cloned blastocyst was confirmed by DNA and mitochondrial DNA fingerprinting analyses, and DNA fingerprinting of two other cloned blastocysts indicated that they were also generated by SCNT. Blastocysts were also obtained from a limited number of parthenogenetically activated oocytes. This study demonstrates, for the first time, that SCNT can produce human blastocyst-stage embryos using nuclei obtained from differentiated adult cells and provides new information on methods that may be needed for a higher level of efficiency for human nuclear transfer.     

Cloning adult farm animals: a review of the possibilities and problems associated with somatic cell nuclear transfer

In 1997, Wilmut et al. announced the birth of Dolly, the first ever clone of an adult animal. To date, adult sheep, goats, cattle, mice, pigs, cats and rabbits have been cloned using somatic cell nuclear transfer. The ultimate challenge of cloning procedures is to reprogram the somatic cell nucleus for development of the early embryo. The cell type of choice for reprogramming the somatic nucleus is an enucleated oocyte. Given that somatic cells are easily obtained from adult animals, cultured in the laboratory and then genetically modified, cloning procedures are ideal for introducing specific genetic modifications in farm animals. Genetic modification of farm animals provides a means of studying genes involved in a variety of biological systems and disease processes. Moreover, genetically modified farm animals have created a new form of 'pharming' whereby farm animals serve as bioreactors for production of pharmaceuticals or organ donors. A major limitation of cloning procedures is the extreme inefficiency for producing live offspring. Dolly was the only live offspring produced after 277 attempts. Similar inefficiencies for cloning adult animals of other species have been described by others. Many factors related to cloning procedures and culture environment contribute to the death of clones, both in the embryonic and fetal periods as well as during neonatal life. Extreme inefficiencies of this magnitude, along with the fact that death of the surrogate may occur, continue to raise great concerns with cloning humans.     

Production of interspecific somatic cell hybrids using polyethylene glycol

Summary A procedure routinely used in our laboratory for the production of human-mouse and pig-mouse somatic cell hybrids using polyethylene glycol is presented. Presumably, one should be able to employ the same procedure for the production of other interspecific somatic cell hybrids.     

Factors affecting survival of reconstructed mouse embryos after nuclear transfer

Reconstruction of mouse embryos was performed by injection of donor genetic material from differentiated cells of various types (cumulus cells, cardiomyocytes, and epithelial cells) into recipient cells (mature oocytes and zygotes). A medium for microsurgery was selected, which enhanced survival of both embryonic and somatic cells during the reconstructive manipulations. Special preparation of somatic cells to transplantation was carried out, which employed factors synchronizing the cells in a certain phase of the cell cycle in order to enhance their capacity to maintain the development of reconstructed embryos. The processes of nucleus reprogramming in specialized cells under the action of cytoplasmic factors of oocytes and zygotes were examined. During in vitro culturing of reconstructed embryos, the most successful development was observed in embryos implanted with donor material from cumulus cells. Mouse embryos reconstructed with a certain genome and subsequent production and use of stem cells are considered as the model system for developing the basic principles of replacement therapy.__________This revised version was published online in July 2005 with the addition of the issue title and article categoryTranslated from Kletochnye Tekhnologii v Biologii i Meditsine, Vol. 1, No. 1, pp. 47–51, January, 2005     

Developmental competence of human in vitro aged oocytes as host cells for nuclear transfer

BACKGROUND: Improving human nuclear transfer (NT) efficiencies is paramount for the development of patient-specific stem cell lines, although the opportunities remain limited owing to difficulties in obtaining fresh mature oocytes. METHODS: Therefore, the developmental competence of aged, failed-to-fertilize human oocytes as an alternate cytoplasmic source for NT was assessed and compared with use of fresh, ovulation-induced oocytes. To further characterize the developmental potential of aged oocytes, parthenogenetic activation, immunocytochemical analysis of essential microtubule proteins involved in meiotic and mitotic division, and RT-PCR in single oocytes (n = 6) was performed to determine expression of oocyte-specific genes [oocyte-specific histone 1 (H1FOO), growth differentiation factor 9 (GDF9), bone morphogenetic protein 15 (BMP15), zygote arrest 1 (ZAR1)] and microtubule markers [nuclear mitotic arrest (NuMA), minus-end directed motor protein HSET and the microtubule kinesin motor protein EG5]. RESULTS: For NT, enucleation and fusion rates of aged oocytes were significantly lower compared with fresh oocytes (P < 0.05). Cleavage rates and subsequent development were poor. In addition, parthenote cleavage was low. Immunocytochemical analysis revealed that many oocytes displayed aberrant expression of NuMA and EG5, had disrupted meiotic spindles and tetrapolar spindles. One of the six oocytes misexpressed GDF9, BMP15 and ZAR1. Two oocytes expressed EG5 messenger RNA (mRNA), and HSET and NuMA were not detectable. RT-PCR of mRNA for oocyte specific genes and microtubule markers in single aged oocytes. CONCLUSIONS: Thus, aneuploidy and spindle defects may contribute to poor parthenogenetic development and developmental outcomes following NT.