Detection Of Recombination Events Research Articles

The Gene for Human Fibronectin Glomerulopathy Maps to 1q32, in the Region of the Regulation of Complement Activation Gene Cluster

Fibronectin glomerulopathy (GFND) is a newly recognized autosomal dominant disease of the kidney that results in albuminuria, microscopic hematuria, hypertension, renal tubular acidosis type IV, and end-stage renal disease in the 2d to 6th decade of life. The disease is characterized histologically by massive deposits of fibronectin (Fn) present in the subendothelial spaces of renal glomerular capillaries. The cause of human GFND is unknown. In order to localize a candidate gene for GFND, we performed linkage analysis of a large, 193-member pedigree containing 13 affected individuals. Since we had previously excluded the genes for Fn and uteroglobin as candidate genes for GFND, a total-genome search for linkage was performed. Examination of 306 microsatellite markers resulted in a maximum two-point LOD score of 4.17 at a recombination fraction of. 00 for marker D1S249, and a maximum multipoint LOD score of 4.41 for neighboring marker D1S2782. By detection of recombination events, a critical genetic interval of 4.1 cM was identified, which was flanked by markers D1S2872 and D1S2891. These findings confirm that GFND is a distinct disease entity among the fibrillary glomerulopathies. Gene identification will provide insights into the molecular interactions of Fn in GFND, as well as in genetically unaltered conditions.

Recombination activating activity of XRCC1 analogous genes in X-ray sensitive and resistant CHO cell lines

The XRCC1 gene (X-ray repair cross complementing) complements the DNA repair deficiency of the radiation sensitive Chinese hamster ovary (CHO) mutant cell line EM9 but the mechanism of the correction is not elucidated yet. XRCC1 shows substantial homology to the RAG2 gene (recombination activating gene) and we therefore tried to answer question, whether structural similarities (sequence of a putative recombination activating domain, aa 332–362 for XRCC1 and aa 286–316 in RAG2) would reflect similar functions of the homologous, putative recombination activating domain. PCR experiments revealed that no sequence homologous to the structural part of human XRCC1 was present in cDNA of CHO. Differential display demonstrated two putative recombination activating domains in the parental CHO line AA8 and one in the radiosensitive mutant EM9. Southern blot experiments showed the presence of several genes with partial homology to human XRCC1. Recombination studies consisted of expressing amplified target domains within chimeric proteins in recA − bacteria and subsequent detection of recombination events by sequencing the recombinant plasmids. Recombination experiments demonstrated recombination activating activity of all putative recombination activating domains amplified from AA8 and EM9 genomes as reflected by deletions within the insert of the recombinant plasmids. The recombination activating activity of XRCC1 analogues could explain a mechanism responsible for the correction of the DNA repair defect in EM9.

Identification of breakpoints in intergenotypic recombinants of HIV type 1 by bootscanning.

Identification of breakpoints in intergenotypic recombinants of HIV type 1 by bootscanning.

A polymorphic minisatellite sequence in the subtelomeric regions of chromosomes I and V in Leishmania infantum

A minisatellite DNA sequence is described for the first time in Leishmania infantum. It is borne by four chromosomes and consists of an 81-bp repeat unit organised in several clusters. On chromosomes I and V of L. infantum, the clusters are tightly located in the size-variable subtelomeric regions. The organisation of this sequence may be related to that of the subtelomeric interspersed repeat sequences identified in the human genome. The sequencing of seven repeat units, some subcloned from the same cluster, allowed the definition of a consensus sequence of 81 bp, particularly G/C rich (73%). Two subfamilies were clearly defined: one exhibits a 91–95% homology with the consensus sequence; the second one comprises two monomers sharing a 91% homology but only 77% homology with the consensus sequence. The two types of monomers can be found in the same cluster. These data suggest interactions between monomers and a possible role of this sequence in the instability of these regions. Finally, restriction fragment length polymorphisms were revealed by this sequence among various strains of L. infantum. Besides allowing the detection of recombination events in the unstable regions of the chromosomes, this new marker may become a useful tool in the study of the parasite population dynamics in leishmaniasis foci.

Evidence that recombination between reiterated sequences in the Bacillus subtilis chromosome does not occur via unequal crossing over

An experimental system was designed to permit the detection of recombination events occurring via unequal crossing over between sister bacterial chromosomes in Bacillus subtilis. It exploits the fact that during spore development, genetic and metabolic cooperation occurs between two different cell types, only one of which survives. During the early stages of sporulation, the two chromosomes of the developing sporangiole lie in the same cell and recombination between them is possible, in principle. Internal duplications flanking a selectable antibiotic-resistance gene have been introduced into the spoIIIC, spoIVA and spoVJ genes, whose correct expression in the mother cell (non-surviving compartment) is necessary for completion of spore development. After incubation in a sporulation-inducing medium in the absence of selective pressure, these strains sporulate at a low frequency and up to 30% of the progeny are Spo-. They result from mosaic sporangioles, in which only the chromosome segregated into the mother cell compartment of the developing sporangiole contains a reconstituted spo gene. In mosaic sporangioles generated by unequal crossing over between sister bacterial chromosomes, the insertionally inactivated spo gene, segregated into the pre-spore compartment, would carry an extra copy of the duplication initially present. Analysis of the products of 124 independent recombination events giving rise to mosaic sporangioles provided no evidence for the occurrence of unequal crossing over.

Detection of recombination events in human cells using cloned cytomegalovirus DNA fragments as probes

A method is presented for the detection of virus-host interactions at the chromosomal level. This method relies on the analysis of recombinant plasmids carrying specific regions of a viral DNA molecule. Human cytomegalovirus Hin dIII subgenomic fragments were used here as a target for recombination events.

Pregnenolone in the treatment of rheumatoid arthritis.

<h3>Abstract</h3> <i>Acinetobacter baumannii</i> infection poses a major health threat with recurrent treatment failure due to antibiotic resistance, notably to carbapenems. While genomic analyses of clinical strains indicate that homologous recombination plays a major role in the acquisition of antibiotic resistance genes, the underlying mechanisms of horizontal gene transfer often remain speculative. Our understanding of the acquisition of antibiotic resistance is hampered by the lack of experimental systems able to reproduce genomic observations. We here report the detection of recombination events occurring spontaneously in mixed bacterial populations and which can result in the acquisition of resistance to carbapenems. We show that natural transformation is the main driver of intra-, but also inter-strain recombination events between <i>A. baumannii</i> clinical isolates and pathogenic species of <i>Acinetobacter</i>. We observed that interbacterial natural transformation in mixed populations is more efficient at promoting the acquisition of large resistance islands (AbaR4, AbaR1) than when the same bacteria are supplied with large amounts of purified genomic DNA. Importantly, analysis of the genomes of the recombinant progeny revealed large recombination tracts (from 13 to 123 kb) similar to those observed in the genome of clinical isolates. Moreover, we highlight that transforming DNA availability is a key determinant of the rate of recombinants and results from both spontaneous release and interbacterial predatory behavior. In the light of our results, natural transformation should be considered as a leading mechanism of genome recombination and horizontal gene transfer of antibiotic resistance genes in <i>Acinetobacter baumannii</i>. <h3>Importance</h3> <i>Acinetobacter baumannii</i> is a multidrug resistant pathogen responsible for difficult-to-treat hospital-acquired infections. Understanding the mechanisms leading to the emergence of the multi-drug resistance in this pathogen is today crucial. Horizontal gene transfer is assumed to largely contribute to this multidrug resistance. However, in <i>A. baumannii</i>, the mechanisms leading to genome recombination and the horizontal transfer of resistance genes are poorly understood. We bring experimental evidence that natural transformation, a horizontal gene transfer mechanism recently highlighted in <i>A. baumannii</i>, allows the highly efficient interbacterial transfer of genetic elements carrying resistance to last line antibiotic carbapenems. Importantly, we demonstrated that natural transformation, occurring in mixed populations of <i>Acinetobacter</i>, enables the transfer of large resistance island mobilizing multiple resistance genes.