Recombination ectopic

Two reasons could explain the failure of soluble SI SCF to induce long term growth of hematopoietic cells on stroma. One might be the production of inadequate levels of protein by SI stroma and by SESl and MMCE cells ectopically expressing SI SCF. The other could be an antagonistic function of the mutated SI SCF compared to the membrane-bound isoform. To test for these possibilities we added recombinant soluble SCF, that is produced as a cleavage product of mb SCF, to TEl feeder cocultures. 

Most of the information concerning recombination between repeated sequences has been derived from studies in the yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe,5 although some classes of ectopic recombination have also been studied in mammalian cells.6 The yeast studies indicate that the rates of ectopic recombination are surprisingly high (similar to the rates of classical recombination) and that the rates of these events are much higher in meiosis than in mitosis. Conversion events involving repeats on nonhomologous chromosomes are associated... 

Fig. 2. Classes of recombination events. The rectangles represent repeated genes. Thin lines represent one pair of homologs, and thick lines represent another. Arrows indicate recombinational interactions. The different types of recombination are as follows C, classical QC, quasi-classical H, heterochromosomal SC, sister chromatid USC, unequal sister chromatid and I, intrachromatid. All types of recombination except classical are considered ectopic sister chromatid, unequal sister chromatid, and intrachromatid recombinations are defined as intrachromosomal events.

Whereas all of the methods discussed thus far concern ectopic interactions between artificially constructed repeats, there have also been a number of studies designed to examine recombination between naturally occurring repeated sequences. Recombination between both dispersed and tandemly repeated sequences has been examined, and some of the approaches used are described below. 

From studies done primarily in S. cerevisiae, it is clear that ectopic recombination events occur at frequencies that are high relative to mutation frequencies. These events, therefore, are likely to be important in concerted evolution and perhaps in other types of evolutionarily important processes (e.g., genome rearrangements). The genetic control of ectopic recombination as well as the effects of repeat size and/or sequence heterogeneity on the frequency and types of ectopic recombination are active areas of investigation. 

A concept where the fnnctionally important expression of one gene can resnlt in the ectopic expression of a neighboring gene, resnlfing in apparent expression similarity between tissues. See de Marco, A. and de Marco, V., Bacteria co-transformed with recombinant proteins and chaperones cloned in independent plasmids are suitable for expression tuning, J. Biotechnol. 109, 45-52, 2004 Yanai, L, Korbel, J.O., Boue, S. et al.. Similar gene expression profiles do not imply similar tissue functions. Trends Genet. 22, 132-138, 2006. 

Barlow, A.J., Francis-West, P.H. 1997. Ectopic application of recombinant BMP-2 and BMP-4 can change patterning of developing chick facial primordia. Development 124, 391-398. 

Musculoskeletal A rare case of extraspinal ectopic bone growth has been reported after the use of rhBMP-2 (Infuse Bone Graft), a recombinant human version of bone morphogenetic protein 2 f5" ]. 

Uludag, H., D Augusta, D., Golden, J., Li, J., Timony, G., Riedel, R., and Wozney, J.M. Implantation of recombinant human bone morphogenetic proteins with biomaterial carriers a correlation between protein pharmacokinetics and osteoinduction in the rat ectopic model. /. Biomed. Mater. Res. 50 227-238, 2000. 

Kato, M., Namikawa, T., Terai, H. et al. 2006. Ectopic hone formation in mice associated with a lactic acid/ dioxanone/ethylene glycol copolymer-tricalcium phosphate composite with added recombinant human bone morphogenetic protein-2. Biomaterials 27 3927-33. 

A number of delivery systems have been developed for the controlled release of bone morphogenic protein-2 (BMP-2). For example, calcimn phosphate cement-based materials have shown the ability to deliver recombinant human bone morphogenic protein-2 (rhBMP-2) to increase alkaline phosphatase (ALP) activity in MC3T3-E1 cells in vitro,and enhance bone formation both ectopically and in an ulna osteotomy model. In addition to cement-based systems, polymeric materials have also been heavily researched as potential delivery vehicles of BMP-2. Saito et al. have developed a temperature sensitive poly(D,L-lactic acid-polyethylene glycol) (PLA-PEG) block copolymer as an... 

Recombinant plasmids specific for bacteria, yeast, and even mammalian cells have been generated in the laboratory and exploited for a variety of basic and applied research applications. Specifically, recombinant expression plasmids can be constructed in order to express the ectopic protein encoded by the foreign (trans) gene in the appropriate host cell. Recombinant plasmids of mammalian cells are based on viruses, rather than on episomal DNA. Only the DNA replication function of the virus is incorporated into the plasmid, so that the plasmid is replicated without producing the active virus. In the ease of human cells, simian virus 40 (SV40) is commonly used to generate recombinant DNA. 

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