草丁膦对转bar基因水稻GS酶活性和光合功能的影响

喷施草丁膦后,对草丁膦无抗性水稻Cypress(未转bar基因)叶片的谷氨酰胺合成酶(GS)活性先受到抑制,随后叶片内NH 4积累上升,叶绿素含量、PSⅡ原初光化学效率(Fv/Fm)、光能转化效率(ΦPSⅡ)和叶片叶绿素荧光的光化学猝灭系数(qp)下降,光合速率显著降低;最后引起植株死亡.另一方面,Cypress PB-6(转bar基因抗草丁膦水稻)的GS酶活性在喷施草丁膦后虽然先被抑制,但随后能恢复至正常水平,接着NH 4积累下降,草丁膦对叶绿素含量、荧光参数Fv/Fm、ΦPSⅡ、qp的影响被解除,光合速率恢复到正常水平,整个植株生长正常.     

YAP与干细胞及肿瘤

YAP蛋白作为Hippo信号通路中关键成分,在控制生物器官发育和调控细胞生长中起着十分重要的作用。鉴于YAP蛋白的促细胞生长功能以及过表达YAP或YAP上游调控基因失活将引发肿瘤,YAP因此被认为是原癌蛋白。最新的研究表明YAP在维持干细胞特性、抑制干细胞分化及促进成体细胞重编程中也起着十分重要的作用。可见YAP在干细胞和肿瘤细胞中都扮演着重要角色。因此更好地了解和研究YAP蛋白及其信号通路有助于更好地理解干细胞与肿瘤的关系,有助于干细胞治疗的安全应用以及特异性靶向肿瘤治疗药物的开发。     

Dendritic cells derived from pluripotent stem cells:Potential of large scale production

Human pluripotent stem cells(hPSCs), including human embryonic stem cells and human induced pluripotent stem cells, are promising sources for hematopoietic cells due to their unlimited growth capacity and the pluripotency. Dendritic cells(DCs), the unique immune cells in the hematopoietic system, can be loaded with tumor specific antigen and used as vaccine for cancer immunotherapy. While autologous DCs from peripheral blood are limited in cell number, hPSC-derived DCs provide a novel alternative cell source which has the potential for large scale production. This review summarizes recent advances in differentiating hPSCs to DCs through the intermediate stage of hematopoietic stem cells. Step-wise growth factor induction has been used to derive DCs from hPSCs either in suspension cultureof embryoid bodies(EBs) or in co-culture with stromal cells. To fulfill the clinical potential of the DCs derived from hPSCs, the bioprocess needs to be scaled up to produce a large number of cells economically under tight quality control. This requires the development of novel bioreactor systems combining guided EB-based differentiation with engineered culture environment. Hence, recent progress in using bioreactors for hPSC lineage-specific differentiation is reviewed. In particular, the potential scale up strategies for the multistage DC differentiation and the effect of shear stress on hPSC differentiation in bioreactors are discussed in detail.     

云南地方稻waxy基因序列多样性分析

利用特异引物Wx-F/AG-2对来源于云南省16个州市64个县的252份地方稻种waxy基因中含有微卫星序列(CT)n和第一内含子的序列进行PCR扩增并测序。结果表明在268个碱基的序列内检测到4个变异位点:第一内含子上游56位处(CT)n存在(CT)10、(CT)11、(CT)12、(CT)14、(CT)16、(CT)17、(CT)18、(CT)19、(CT)20、(CT)21等10种变异;(CT)11、(CT)18、(CT)17、(CT)12、(CT)10等5种单倍型是云南优势类型,合计占供试材料的92.85%;籼稻以(CT)10、(CT)11、(CT)12为主,而粳稻以(CT)11、(CT)12、(CT)17和(CT)18为主;第一内含子+1位存在G/T变异,81.75%品种是G,T只出现在(CT)16、(CT)17、(CT)18和(CT)20的品种中,其频率在籼稻中为13.48%,粳稻20.86%,水稻16.17%,陆稻22.35%,粘稻10.47%,糯稻42.62%。+86-88位存在ATA/GTA/A--3种变异;+128位处存在(AATT)5和(AATT)6 2种变异。根据这4个变异位点,可将252个云南地方稻种归为16种单倍型,其中Wx4(32.54%)、Wx9(13.89%)、Wx12(12.7%)、Wx5(12.3%)、Wx1(8.33%)、Wx11(7.94%)是主要类型,合计87.7%,其他类型频率较低。籼/粳亚种、水/陆稻和粘/糯中存在单倍型种类和单倍型频率两方面的差异,籼稻/粳稻、水/陆稻和粘/糯稻各亚种或生态型均有独享的单倍型,共享单倍型频率也存在差异,表明亚种间或生态型间发生了一定的遗传分化。单倍型地理分布分析表明,临沧、普洱单倍型种类最丰富,以之为中心向外扩展,单倍型种类有减少的趋势,第一内含子+1位的T主要分布在临沧、普洱、西双版纳、德宏等南部地区。本研究揭示了云南地方稻种群体waxy基因的变异和分布特点。     

Survival of priceless cells: active and passive protection of embryonic stem cells against immune destruction

This review focuses on our current knowledge of the mechanisms employed by embryonic stem (ES) cells to avoid destruction by cell-mediated immune responses. Recently, ES cells have been found to shield themselves against cytotoxic effector cells by expressing CD95L and serine protease inhibitor SPI-6 mediating apoptosis of the cytotoxic cells and inactivation of granzyme B, respectively. These findings are discussed in view of their implications for using ES cell-derived transplants in regenerative medicine as well as for our understanding of early embryonic stages during invasion and implantation.     

Extracellular matrix components direct porcine muscle stem cell behavior

In muscle tissue, extracellular matrix proteins, together with the vasculature system, muscle-residence cells and muscle fibers, create the niche for muscle stem cells. The niche is important in controlling proliferation and directing differentiation of muscle stem cells to sustain muscle tissue. Mimicking the extracellular muscle environment improves tools exploring the behavior of primary muscle cells. Optimizing cell culture conditions to maintain muscle commitment is important in stem cell-based studies concerning toxicology screening, ex vivo skeletal muscle tissue engineering and in the enhancement of clinical efficiency. We used the muscle extracellular matrix proteins collagen type I, fibronectin, laminin, and also gelatin and Matrigel as surface coatings of tissue culture plastic to resemble the muscle extracellular matrix. Several important factors that determine myogenic commitment of the primary muscle cells were characterized by quantitative real-time RT-PCR and immunofluorescence. Adhesion of high PAX7 expressing satellite cells was improved if the cells were cultured on fibronectin or laminin coatings. Cells cultured on Matrigel and laminin coatings showed dominant integrin expression levels and exhibited an activated Wnt pathway. Under these conditions both stem cell proliferation and myogenic differentiation capacity were superior if compared to cells cultured on collagen type I, fibronectin and gelatin. In conclusion, Matrigel and laminin are the preferred coatings to sustain the proliferation and myogenic differentiation capacity of the primary porcine muscle stem cells, when cells are removed from their natural environment for in vitro culture.     

A novel in vitro retinal differentiation model by co-culturing adult human bone marrow stem cells with retinal pigmented epithelium cells

Human retinal pigment epithelium (HRPE) cells are important in maintaining the normal physiology within the neurosensory retina and photoreceptors. Recently, transplantation of HRPE has become a possible therapeutic approach for retinal degeneration. By negative immunoselection (CD45 and glycophorin A), in this study, we have isolated and cultivated adult human bone marrow stem cells (BMSCs) with multilineage differentiation potential. After a 2- to 4-week culture under chondrogenic, osteogenic, adipogenic, and hepatogenic induction medium, these BMSCs were found to differentiate into cartilage, bone, adipocyte, and hepatocyte-like cells, respectively. We also showed that these BMSCs could differentiate into neural precursor cells (nestin-positive) and mature neurons (MAP-2 and Tuj1-positive) following treatment of neural selection and induction medium for 1 month. Furthermore, the plasticity of BMSCs was confirmed by initiating their differentiation into retinal cells and photoreceptor lineages by co-culturing with HRPE cells. The latter system provides an ex vivo expansion model of culturing photoreceptors for the treatment of retinal degeneration diseases.