State of art and limitations in genetic engineering to induce stable chondrogenic phenotype

Current protocols for chondrocyte expansion and chondrogenic differentiation of stem cells fail to reduce phenotypic loss and to mitigate hypertrophic tendency. To this end, cell genetic manipulation is gaining pace as a means of generating cells with stable chondrocyte phenotype. Herein, we provide an overview of candidate genes that either induce cartilage regeneration or inhibit cartilage degeneration. We further discuss in vitro, ex vivo and in vivo viral transduction and non-viral transfection strategies for targeted cells (chondrocytes, mesenchymal stem cells, induced pluripotent stem cells and synovial cells), along with the most representative results obtained in pre-clinical models and in clinical trials. We highlight current challenges and associated risks that slowdown clinical acceptance and commercialisation of gene transfer technologies.     

Ciona intestinalis NADH dehydrogenase NDX confers stress-resistance and extended lifespan on Drosophila

An assembled cDNA coding for the putative single-subunit NADH dehydrogenase (NDX) of Ciona intestinalis was introduced into Drosophila melanogaster. The encoded protein was found to localize to mitochondria and to confer rotenone-insensitive substrate oxidation in organello. Transgenic flies exhibited increased resistance to menadione, starvation and temperature stress, and manifested a sex and diet-dependent increase in mean lifespan of 20–50%. However, NDX was able only weakly to complement the phenotypes produced by the knockdown of complex I subunits.     

Linkage relationships between regulatory and structural gene loci involved in zein synthesis in maize

Summary The synthesis of at least 15 zein polypeptides is under the control of regulatory gene loci. One of these, Opaque-2 (chromosome 7, position 16) strongly reduces the zein accumulation without modifying the zein molecular components. The linkage relationship between the regulatory gene 02 and the 5 structural loci (Zp1, Zp2, Zp3, Zp6, Zp12) segregating with sample Mendelian ratios have been studied. Zp1, Zp2, Zp3 are closely linked to each other; moreover this gene cluster is located on chromosome 7 at 5.5 cM from the Opaque-2 locus. The structural loci Zp6 and Zp12 are not linked with each other, with the 02 locus or with Zp1, Zp2, Zp3. From our data it follows that the zein structural genes are located in at least three positions on the maize genome. The scattering in the genome of the genes controlled by the Opaque-2 locus suggests a transacting role for this regulatory element.     

Gene delivery by lentivirus vectors

The capacity to efficiently transduce nondividing cells, shuttle large genetic payloads, and maintain stable long-term transgene expression are attributes that have brought lentiviral vectors to the forefront of gene delivery vehicles for research and therapeutic applications in a clinical setting. Our discussion initiates with advances in lentiviral vector development and how these sophisticated lentiviral vectors reflect improvements in safety, regarding the prevention of replication competent lentiviruses (RCLs), vector mobilization, and insertional mutagenesis. Additionally, we describe conventional molecular regulatory systems to manage gene expression levels in a spatial and temporal fashion in the context of a lentiviral vector. State of the art technology for lentiviral vector production by transient transfection and packaging cell lines are explicitly presented with current practices used for concentration, purification, titering, and determining the safety of a vector stock. We summarize lentiviral vector applications that have received a great deal of attention in recent years including the generation of transgenic animals and the stable delivery of RNA interference molecules. Concluding remarks address some of the successes in preclinical animals, and the recent transition of lentiviral vectors to human clinical trials as therapy for a variety of infectious and genetic diseases.     

A reassessment of explanations for discordant introgressions of mitochondrial and nuclear genomes

Hybridization is increasingly recognized as a significant evolutionary process, in particular because it can lead to introgression of genes from one species to another. A striking pattern of discordance in the amount of introgression between mitochondrial and nuclear markers exists such that substantial mitochondrial introgression is often found in combination with no or little nuclear introgression. Multiple mechanisms have been proposed to explain this discordance, including positive selection for introgressing mitochondrial variants, several types of sex‐biases, drift, negative selection against introgression in the nuclear genome, and spatial expansion. Most of these hypotheses are verbal, and have not been quantitatively evaluated so far. We use individual‐based, multilocus, computer simulations of secondary contact under a wide range of demographic and genetic scenarios to evaluate the ability of the different mechanisms to produce discordant introgression. Sex‐biases and spatial expansions fail to produce substantial mito‐nuclear discordance. Drift and nuclear selection can produce strong discordance, but only under a limited range of conditions. In contrast, selection on the mitochondrial genome produces strong discordance, particularly when dispersal rates are low. However, commonly used statistical tests have little power to detect this selection. Altogether, these results dismiss several popular hypotheses, and provide support for adaptive mitochondrial introgression.     

Tomato contains two differentially expressed genes encoding B-type phytochromes,neither of which can be considered an ortholog of Arabidopsis phytochrome B

Tomato (Solanum lycopersicon L.) contains two B-type phytochrome genes (PHYB1 and PHYB2). Fragments of these two PHYB were cloned following amplification by the polymerase chain reaction of a portion of their relatively well conserved 5 coding regions. Polypeptides encoded by these gene fragments exhibit 90% sequence identity. These two PHYB are independently expressed in organ-specific fashion. In mature plants, PHYB2 mRNA is most abundant in fruit and PHYB1 mRNA in expanded leaves. A phylogenetic analysis fails to establish which tomato PHYB is orthologous to either Arabidopsis PHYB or PHYD, the latter being a second B-type phytochrome. Instead, this analysis indicates that following the divergence of the Solanaceae and Brassicaceae from one another, a PHYB gene duplicated independently in each lineage. Consequently, Arabidopsis PHYB mutants cannot be considered strictly equivalent to the tomato tri mutants, which appear to be mutated at the PHYB1 locus. Similarly, other putative PHYB mutants might not be equivalent to those described for Arabidopsis and tomato. This situation complicates efforts to determine PHYB function because there might be no one answer to this question.Abbreviations PCR polymerase chain reaction - PHY undesignated phytochrome gene - PHYA, PHYB, etc phytochrome gene(s) of the A, B, etc. type This research was supported by USDA NRICGP grant 93-00939 and by NATO travel grant CRG 931183. It was initiated when two of us (L.H.P., M.-M.C.-P.) spent a sabbatical year at the Institut National de la Recherche Agronomique in Versailles, France. L.H.P. gratefully acknowledges support provided by a senior guest fellowship from the Ministère de l'enseignement superieur et de la recherche during his stay in Versailles. L.H.P. and M.-M.C.-P thank all of their colleagues in Versailles for their warm hospitality and their willingness to share their expertise with us. We also thank Russell Malmberg, Richard Meagher and Robert Price for helpful discussions concerning the interpretation of molecular phylogenies.     

新型PEI衍生物的体外表征及对巨噬细胞的转染效果研究

目的:以PEI1.8kDa为基础连接戊二醛合成新型可降解PEI衍生物GPEI后,研究GPEI包裹质粒转染巨噬细胞后对巨噬细胞合成蛋白及表型的影响。方法:合成GPEI后,检测了GPEI质粒聚合物的粒径及电位,并通过透射电镜观察聚合物形态,通过免疫荧光、WB、RT-PCR、Elisa及Transwell实验检测巨噬细胞RNA、蛋白、终产物水平变化及表型改变。结果:GPEI能够包裹质粒,形成100 nm左右带有正电荷的聚合物,WB、RT-PCR结果表明GPEI转染较PEI25kDa有优势(P0.05),巨噬细胞转染后6天持续分泌PGI2(P0.05)。结论:以PEI1.8kDa为基础合成的GPEI能够包裹PTGIS质粒并将其转染进巨噬细胞后对巨噬细胞的表型有明显影响。     

长白猪、枫泾猪和它们的杂种后代Ag—NOR的研究

4头枫泾猪,3头长白猪和5头长白×枫泾杂一代的NOR平均数分别为3.88、2和2.95。33头长白×枫泾杂二代猪(杂一代互交后代),其中7头黑猪的NOR众数为4,平均数为3.85;9头白猪的NOR众数为2,平均数为2.25;14头白猪的NOR众数为3,平均数为2.86;3头花猪的NOR众数分别为4.3、3,平均数为3.65、3.00和3.08。根据长白、枫泾和长白×枫泾杂一代和杂二代的NOR数目的区别和变化,NOR的遗传符合孟德尔定律。根据NOR数目与毛色的高度相关,提出了决定猪的黑白毛色的基因位于8号染色体并与NOR连锁的假设。猪的毛色除由位于8号染色体上的毛色基因所决定外,还应受其它基因位点的影响。     

Functional polymorphism in porcine CYP2E1 gene: Its association with skatole levels

Raising intact male pigs would have a significant economic impact on the pork industry. However, the presence of skatole (a major cause of boar taint) in meat from intact male pigs could be highly objectionable to consumer. The excessive accumulation of skatole in fat is a major cause of boar taint, and is associated with defective expression of cytochrome P4502E1 (CYP2E1). In pigs, it has been found that CYP2E1 is negatively correlated with accumulation of skatole. The searching for polymorphism of CYP2E1 and the relevant functional analysis would help develop a genetic marker for the selection of pigs with low skatole levels in fat. The aim of this study was to measure the expression pattern of CYP2E1 mRNA in various tissues of the pig, to identify genetic polymorphisms, and to evaluate the functional relevance of polymorphic sites with respect to the skatole level in fat. We show herein that a substitution of G → A at base 1423 of the CYP2E1 gene in the liver causes a significant decrease in the expressed CYP2E1 level. Our data suggest that the G → A substitute might be at least partially responsible for a high level of skatole in pigs. We believe that this is an important step toward the selection of genetic markers for boar taint by lowering fat levels of skatole in fat.