Genetics

Final results of the HEALING IIB trial to evaluate a bio-engineered CD34 antibody coated stent (Genous™Stent) designed to promote vascular healing by capture of circulating endothelial progenitor cells in CAD patients (Article)

Dekker, W.K. den — 2011-07-18T00:00:00Z

Objective: To assess the safety and efficacy of the Genous™ endothelial progenitor cell (EPC) capturing stent in conjunction with HmG-CoA-reductase inhibitors (statins) to stimulate EPC recruitment, in the treatment of patients with de novo coronary artery lesions. Methods and results: The HEALING IIB study was a multi-center, prospective trial, including 100 patients. The primary efficacy endpoint was late luminal loss by QCA at 6-month follow-up (FU). Although statin therapy increased relative EPC levels by 5.6-fold, the angiographic outcome at 6 month FU was not improved in patients with an overall in-stent late luminal loss of 0.76 ± 0.50 mm. The composite major adverse cardiac events (MACE) rate was 9.4%, whereas 6.3% clinically justified target lesion revascularizations (TLRs) were observed. 2 Patients died within the first 30 days after stent implantation due to angiographically verified in-stent thrombosis. At 12 month FU, MACE and TLR increased to 15.6% and 11.5% respectively and stabilized until 24 month FU. 18 Month angiographic FU showed a significant decrease in late luminal loss (0.67 ± 0.54, 11.8% reduction or 10% by matched serial analysis, P = 0.001). Conclusion: The HEALING IIB study suggests that statin therapy in combination with the EPC capture stent does not contribute to a reduction of in-stent restenosis formation for the treatment of de novo coronary artery disease. Although concomitant statin therapy was able to stimulate EPC recruitment, it did not improve the angiographic outcome of the bio-engineered EPC capture stent. Remarkably, angiographic late loss was significantly reduced between 6 and 18 months.

Kinetics of cyclobutane thymine dimer splitting by DNA photolyase directly monitored in the UV (Article)

Thiagarajan, V. — 2011-06-07T00:00:00Z

CPD photolyase uses light to repair cyclobutane pyrimidine dimers (CPDs) formed between adjacent pyrimidines in UV-irradiated DNA. The enzyme harbors an FAD cofactor in fully reduced state (FADH-). The CPD repair mechanism involves electron transfer from photoexcited FADH-to the CPD, splitting of its intradimer bonds, and electron return to restore catalytically active FADH-. The two electron transfer processes occur on time scales of 10-10and 10-9s, respectively. Until now, CPD splitting itself has only been poorly characterized by experiments. Using a previously unreported transient absorption setup, we succeeded in monitoring cyclobutane thymine dimer repair in the main UV absorption band of intact thymine at 266 nm. Flavin transitions that overlay DNA-based absorption changes at 266 nm were monitored independently in the visible and subtracted to obtain the true repair kinetics. Restoration of intact thymine showed a short lag and a biexponential rise with time constants of 0.2 and 1.5 ns. We assign these two time constants to splitting of the intradimer bonds (creating one intact thymine and one thymine anion radical T○-) and electron return from T○-to the FAD cofactor with recovery of the second thymine, respectively. Previous model studies and computer simulations yielded various CPD splitting times between <1 ps and <100 ns. Our experimental results should serve as a benchmark for future efforts to model enzymatic photorepair. The technique and methods developed here may be applied to monitor other photoreactions involving DNA.

The cryptochromes: Blue light photoreceptors in plants and animals (Article)

Chaves, I. — 2011-06-02T00:00:00Z

Cryptochromes are flavoprotein photoreceptors first identified in Arabidopsis thaliana, where they play key roles in growth and development. Subsequently identified in prokaryotes, archaea, and many eukaryotes, cryptochromes function in the animal circadian clock and are proposed as magnetoreceptors in migratory birds. Cryptochromes are closely structurally related to photolyases, evolutionarily ancient flavoproteins that catalyze light-dependent DNA repair. Here, we review the structural, photochemical, and molecular properties of cry-DASH, plant, and animal cryptochromes in relation to biological signaling mechanisms and uncover common features that may contribute to better understanding the function of cryptochromes in diverse systems including in man. Copyright

Preoperative fasting protects mice against hepatic ischemia/reperfusion injury: Mechanisms and effects on liver regeneration (Article)

Verweij, M. — 2011-06-01T00:00:00Z

We show that brief periods of fasting induce functional changes similar to those induced by long-term dietary restriction in mice, and these changes include protection from ischemia/reperfusion (I/R) injury. In this study, we investigated the mechanisms of protection induced by fasting, and we determined the effect on liver regeneration after partial hepatectomy. Partial hepatic ischemia (75 minutes) was induced in ad libitum fed mice and in 1- to 3-day-fasted mice, and one-third or two-thirds hepatectomy was performed in ad libitum fed mice and 3-day-fasted mice. Preoperative fasting for 2 or 3 days significantly decreased hepatocellular I/R injury. Hepatic gene expression of heme oxygenase 1 (HO-1), superoxide dismutase 2 (SOD2), glutathione peroxidase 1 (Gpx1), and glutathione reductase (GSR) was significantly up-regulated in 3-day-fasted mice at the baseline and 6 hours after reperfusion. After reperfusion, p-selectin and interleukin-6 (IL-6) levels were significantly lower, and superoxide radical generation, lipid peroxidation, and neutrophil influx were significantly attenuated in 3-day-fasted mice. Preoperative fasting did not affect liver regeneration after one-third hepatectomy. Hepatic gene expression of IL-6 and transforming growth factor β1 was significantly higher in 3-day-fasted mice before and after one-third hepatectomy. Tumor necrosis factor α expression significantly increased after one-third hepatectomy in 3-day-fasted mice. After a 3-day fast and two-thirds hepatectomy, liver regeneration and subsequent postoperative recovery were compromised. In conclusion, up-regulation of the stress response gene HO-1 and the antioxidant enzymes SOD2, Gpx1, and GSR at the baseline and a better response after reperfusion likely underlie the protection induced by fasting against hepatic I/R injury. Preoperative fasting may be a promising new strategy for protecting the liver against I/R injury during liver transplantation and minor liver resections, although its effect on extended hepatectomy warrants further exploration. Liver Transpl 17:695-704, 2011. © 2011 AASLD.

Gene expression profiling assigns CHEK2 1100delC breast cancers to the luminal intrinsic subtypes (Article)

Nagel, J.H.A. — 2011-05-26T00:00:00Z

CHEK2 1100delC is a moderate-risk cancer susceptibility allele that confers a high breast cancer risk in a polygenic setting. Gene expression profiling of CHEK2 1100delC breast cancers may reveal clues to the nature of the polygenic CHEK2 model and its genes involved. Here, we report global gene expression profiles of a cohort of 155 familial breast cancers, including 26 CHEK2 1100delC mutant tumors. In line with previous work, all CHEK2 1100delC mutant tumors clustered among the hormone receptor-positive breast cancers. In the hormone receptor-positive subset, a 40-gene CHEK2 signature was subsequently defined that significantly associated with CHEK2 1100delC breast cancers. The identification of a CHEK2 gene signature implies an unexpected biological homogeneity among the CHEK2 1100delC breast cancers. In addition, all 26 CHEK2 1100delC tumors classified as luminal intrinsic subtype breast cancers, with 8 luminal A and 18 luminal B tumors. This biological make-up of CHEK2 1100delC breast cancers suggests that a relatively limited number of additional susceptibility alleles are involved in the polygenic CHEK2 model. Identification of these as-yet-unknown susceptibility alleles should be aided by clues from the 40-gene CHEK2 signature.

Quantification of the energy gap in young overweight children. the PIAMA birth cohort study (Article)

Berg, S.W. van den — 2011-05-19T00:00:00Z

Background: Overweight develops gradually as a result of a long term surplus on the balance between energy intake and energy expenditure. Aim of this study was to quantify the positive energy balance responsible for excess body weight gain (energy gap) in young overweight children. Methods. Reported data on weight and height were used of 2190 Dutch children participating in the PIAMA birth cohort study. Accumulated body energy was estimated from the weight gain observed between age 2 and age 5-7. Energy gap was calculated as the difference in positive energy balance between children with and without overweight assuming an energy efficiency of 50%. Results: Ten percent of the children were overweight at the age of 5-7 years. For these children, median weight gain during 4-years follow-up was 13.3 kg, as compared to 8.5 kg in the group of children who had a normal weight at the end of the study. A daily energy gap of 289-320 kJ (69-77 kcal) was responsible for the excess weight gain or weight maintenance in the majority of the children who were overweight at the age of 5-7 years. The increase in daily energy requirement to maintain the 4.8 kilograms excess weight gain among overweight children at the end of the study was approximately 1371 kJ. Conclusions: An energy gap of about 289-320 kJ per day over a number of years can make the difference between normal weight and overweight in young children. Closing the energy gap in overweight children can be achieved by relatively small behavior changes. However, much more effort is required to lose the excess weight gained.

MicroRNAs, the DNA damage response and cancer (Article)

Wouters, M.D. — 2011-05-05T00:00:00Z

Many carcinogenic agents such as ultra-violet light from the sun and various natural and man-made chemicals act by damaging the DNA. To deal with these potentially detrimental effects of DNA damage, cells induce a complex DNA damage response (DDR) that includes DNA repair, cell cycle checkpoints, damage tolerance systems and apoptosis. This DDR is a potent barrier against carcinogenesis and defects within this response are observed in many, if not all, human tumors. DDR defects fuel the evolution of precancerous cells to malignant tumors, but can also induce sensitivity to DNA damaging agents in cancer cells, which can be therapeutically exploited by the use of DNA damaging treatment modalities. Regulation of and coordination between sub-pathways within the DDR is important for maintaining genome stability. Although regulation of the DDR has been extensively studied at the transcriptional and post-translational level, less is known about post-transcriptional gene regulation by microRNAs, the topic of this review. More specifically, we highlight current knowledge about DNA damage responsive microRNAs and microRNAs that regulate DNA damage response genes. We end by discussing the role of DNA damage response microRNAs in cancer etiology and sensitivity to ionizing radiation and other DNA damaging therapeutic agents.

HDAC1 and HDAC2 control the transcriptional program of myelination and the survival of Schwann cells (Article)

Jacobs, B.C. — 2011-04-01T00:00:00Z

Histone deacetylases (HDACs) are major epigenetic regulators. We show that HDAC1 and HDAC2 functions are critical for myelination of the peripheral nervous system. Using mouse genetics, we have ablated Hdac1 and Hdac2 specifically in Schwann cells, resulting in massive Schwann cell loss and virtual absence of myelin in mutant sciatic nerves. Expression of Sox10 and Krox20, the main transcriptional regulators of Schwann cell myelination, was greatly reduced. We demonstrate that in Schwann cells, HDAC1 and HDAC2 exert specific primary functions: HDAC2 activates the transcriptional program of myelination in synergy with Sox10, whereas HDAC1 controls Schwann cell survival by regulating the levels of active Î 2-catenin.

The monocyte transcriptome during pregnancy in multiple sclerosis: Prominent expression of the Fc-receptor CD64 (Article)

Neuteboom, R.F. — 2011-04-01T00:00:00Z

Background: During the third trimester of pregnancy multiple sclerosis (MS) disease activity is reduced. It is not fully understood which factors mediate this disease amelioration. Objective: To study alterations of the monocyte transcriptome during pregnancy in MS patients, using a genomewide approach to identify differentially regulated genes. Methods: Women with MS and healthy controls were longitudinally studied, including a visit before pregnancy. Results: RNA-microarray analysis was performed in six patients. We found a significant increase of CD64 (Fc gamma receptor 1a, FcgR1a) during the third trimester compared with baseline, confirmed by RT-PCR in a group of ten patients. Analysis with Ingenuity software was performed using all genes expression of which was altered at least 1.5-fold in at least five out of six patients. Major networks that were altered during MS pregnancy were: cell-to-cell signalling and interaction, immune response, and cell signalling. From the genes selected for Ingenuity analysis, seven additional candidate genes, selected for their biological interest, were tested using RT-PCR in ten patients with MS and nine controls. We found an increased expression of JAK2 and STAT1 directly postpartum in patients with MS and in controls. Conclusion: The increased CD64 expression during pregnancy is indicative of enhanced innate immune functions.

Tumour-specific methylation of PTPRG intron 1 locus in sporadic and Lynch syndrome colorectal cancer (Article)

Roon, E.H.J. van — 2011-03-01T00:00:00Z

DNA methylation is a hallmark in a subset of right-sided colorectal cancers. Methylation-based screening may improve prevention and survival rate for this type of cancer, which is often clinically asymptomatic in the early stages. We aimed to discover prognostic or diagnostic biomarkers for colon cancer by comparing DNA methylation profiles of right-sided colon tumours and paired normal colon mucosa using an 8.5 k CpG island microarray. We identified a diagnostic CpG-rich region, located in the first intron of the protein-tyrosine phosphatase gamma gene (PTPRG) gene, with altered methylation already in the adenoma stage, that is, before the carcinoma transition. Validation of this region in an additional cohort of 103 sporadic colorectal tumours and 58 paired normal mucosa tissue samples showed 94% sensitivity and 96% specificity. Interestingly, comparable results were obtained when screening a cohort of Lynch syndrome-associated cancers. Functional studies showed that PTPRG intron 1 methylation did not directly affect PTPRG expression, however, the methylated region overlapped with a binding site of the insulator protein CTCF. Chromatin immunoprecipitation (ChIP) showed that methylation of the locus was associated with absence of CTCF binding. Methylation-associated changes in CTCF binding to PTPRG intron 1 could have implications on tumour gene expression by enhancer blocking, chromosome loop formation or abrogation of its insulator function. The high sensitivity and specificity for the PTPRG intron 1 methylation in both sporadic and hereditary colon cancers support biomarker potential for early detection of colon cancer.

Assessing the role of the cadherin/catenin complex at the Schwann cell-axon interface and in the initiation of myelination (Article)

Lewallen, K.A. — 2011-02-23T00:00:00Z

Myelination is dependent on complex reciprocal interactions between the Schwann cell (SC) and axon. Recent evidence suggests that the SC-axon interface represents a membrane specialization essential for myelination; however, the manner in which this polarized-apical domain is generated remains a mystery. The cell adhesion molecule N-cadherin is enriched at the SC-axon interface and colocalizes with the polarity protein Par-3. The asymmetric localization is induced on SC-SC and SC-axon contact. Knockdown of N-cadherin in SCs cocultured with DRG neurons disrupts Par-3 localization and delays the initiation of myelination. However, knockdown or overexpression of neuronal N-cadherin does not influence the distribution of Par-3 or myelination, suggesting that homotypic interactions between SC and axonal N-cadherin are not essential for the events surrounding myelination. To further investigate the role of N-cadherin, mice displaying SC-specific gene ablation of N-cadherin were generated and characterized. Surprisingly, myelination is only slightly delayed, and mice are viable without any detectable myelination defects. β-Catenin, a downstream effector of N-cadherin, colocalizes and coimmunoprecipitates with N-cadherin on the initiation of myelination. To determine whether β-catenin mediates compensation on N-cadherin deletion, SC-specific gene ablation of β-catenin was generated and characterized. Consistent with our hypothesis, myelination is more severely delayed than when manipulating N-cadherin alone, but without any defect to the myelin sheath. Together, our results suggest that N-cadherin interacts with β-catenin in establishing SC polarity and the timely initiation of myelination, but they are nonessential components for the formation and maturation of the myelin sheath. Copyright

RNF12 activates Xist and is essential for X chromosome inactivation (Article)

Barakat, T.S. — 2011-02-15T00:00:00Z

In somatic cells of female placental mammals, one of the two X chromosomes is transcriptionally silenced to accomplish an equal dose of X-encoded gene products in males and females. Initiation of random X chromosome inactivation (XCI) is thought to be regulated by X-encoded activators and autosomally encoded suppressors controlling Xist. Spreading of Xist RNA leads to silencing of the X chromosome in cis. Here, we demonstrate that the dose dependent X-encoded XCI activator RNF12/RLIM acts in trans and activates Xist. We did not find evidence for RNF12-mediated regulation of XCI through Tsix or the Xist intron 1 region, which are both known to be involved in inhibition of Xist. In addition, we found that Xist intron 1, which contains a pluripotency factor binding site, is not required for suppression of Xist in undifferentiated ES cells. Analysis of female Rnf12-/- knockout ES cells showed that RNF12 is essential for initiation of XCI and is mainly involved in the regulation of Xist. We conclude that RNF12 is an indispensable factor in up-regulation of Xist transcription, thereby leading to initiation of random XCI.

A Functional Role for Tumor Cell Heterogeneity in a Mouse Model of Small Cell Lung Cancer (Article)

Calbo, J. — 2011-02-15T00:00:00Z

Small cell lung cancer (SCLC) is the lung neoplasia with the poorest prognosis, due to its high metastatic potential and chemoresistance upon relapse. Using the previously described mouse model for SCLC, we found that the tumors are often composed of phenotypically different cells with either a neuroendocrine or a mesenchymal marker profile. These cells had a common origin because they shared specific genomic aberrations. The transition from neuroendocrine to mesenchymal phenotype could be achieved by the ectopic expression of oncogenic RasV12. Crosstalk between mesenchymal and neuroendocrine cells strongly influenced their behavior. When engrafted as a mixed population, the mesenchymal cells endowed the neuroendocrine cells with metastatic capacity, illustrating the potential relevance of tumor cell heterogeneity in dictating tumor properties.

BLM-DNA2-RPA-MRN and EXO1-BLM-RPA-MRN constitute two DNA end resection machineries for human DNA break repair (Article)

Nimonkar, A.V. — 2011-02-15T00:00:00Z

Repair of dsDNA breaks requires processing to produce 3′-terminated ssDNA. We biochemically reconstituted DNA end resection using purified human proteins: Bloom helicase (BLM); DNA2 helicase/nuclease; Exonuclease 1 (EXO1); the complex comprising MRE11, RAD50, and NBS1 (MRN); and Replication protein A (RPA). Resection occurs via two routes. In one, BLM and DNA2 physically and specifically interact to resect DNA in a process that is ATP-dependent and requires BLM helicase and DNA2 nuclease functions. RPA is essential for both DNA unwinding by BLM and enforcing 5′ → 3′ resection polarity by DNA2. MRN accelerates processing by recruiting BLM to the end. In the other, EXO1 resects the DNA and is stimulated by BLM, MRN, and RPA. BLM increases the affinity of EXO1 for ends, and MRN recruits and enhances the processivity of EXO1. Our results establish two of the core machineries that initiate recombinational DNA repair in human cells.

RNF12 activates Xist and is essential for X chromosome inactivation (Article)

Barakat, T.S. — 2011-02-15T00:00:00Z

In somatic cells of female placental mammals, one of the two X chromosomes is transcriptionally silenced to accomplish an equal dose of X-encoded gene products in males and females. Initiation of random X chromosome inactivation (XCI) is thought to be regulated by X-encoded activators and autosomally encoded suppressors controlling Xist. Spreading of Xist RNA leads to silencing of the X chromosome in cis. Here, we demonstrate that the dose dependent X-encoded XCI activator RNF12/RLIM acts in trans and activates Xist. We did not find evidence for RNF12-mediated regulation of XCI through Tsix or the Xist intron 1 region, which are both known to be involved in inhibition of Xist. In addition, we found that Xist intron 1, which contains a pluripotency factor binding site, is not required for suppression of Xist in undifferentiated ES cells. Analysis of female Rnf12-/-knockout ES cells showed that RNF12 is essential for initiation of XCI and is mainly involved in the regulation of Xist. We conclude that RNF12 is an indispensable factor in up-regulation of Xist transcription, thereby leading to initiation of random XCI.

Overexpression of full-length ETV1 transcripts in clinical prostate cancer due to gene translocation (Article)

Gasi, D. — 2011-02-07T00:00:00Z

ETV1 is overexpressed in a subset of clinical prostate cancers as a fusion transcript with many different partners. However, ETV1 can also be overexpressed as a full-length transcript. Full-length ETV1 protein functions differently from truncated ETV1 produced by fusion genes. In this study we describe the genetic background of full-length ETV1 overexpression and the biological properties of different full-length ETV1 isoforms in prostate cancer. Break-apart FISH showed in five out of six patient samples with overexpression of full-length ETV1 a genomic rearrangement of the gene, indicating frequent translocation. We were able to study the rearrangements in more detail in two tumors. In the first tumor 59′-RACE on cDNA showed linkage of the complete ETV1 transcript to the first exon of a prostate-specific two exon ncRNA gene that maps on chromosome 14 (EST14). This resulted in the expression of both full-length ETV1 transcripts and EST14-ETV1 fusion transcripts. In chromosome spreads of a xenograft derived from the second prostate cancer we observed a complex ETV1 translocation involving a chromosome 7 fragment that harbors ETV1 and fragments of chromosomes 4 and 10. Further studies revealed the overexpression of several different full-length transcripts, giving rise to four protein isoforms with different N-terminal regions. Even the shortest isoform synthesized by full-length ETV1 stimulated in vitro anchorage-independent growth of PNT2C2 prostate cells. This contrasts the lack of activity of even shorter N-truncated ETV1 produced by fusion transcripts. Our findings that in clinical prostate cancer overexpression of full-length ETV1 is due to genomic rearrangements involving different chromosomes and the identification of a shortened biologically active ETV1 isoform are highly relevant for understanding the mechanism of ETV1 function in prostate cancer.

Virtual reality for embryonic measurements requiring depth perception (Article)

Rousian, M. — 2011-02-01T00:00:00Z

Two real-time three-dimensional images of first-trimester pregnancies visualized using virtual reality (VR) are presented. Inherently three-dimensional structures, like the umbilical cord and limbs, can be efficiently and accurately measured using VR.

Osteoarthritis induction leads to early and temporal subchondral plate porosity in the tibial plateau of mice: an in vivo micro CT study. (Article)

Botter, S.M. — 2011-02-01T00:00:00Z

Abstract: In osteoarthritis (OA) changes occur both in cartilage and subchondral bone. The subchondral bone plate facilitates normal crosstalk between articular cartilage and trabecular subchondral bone, and adaptive changes in the plate due to OA may therefore disturb crosstalk homeostasis. To investigate these changes over time we examined the cartilage-subchondral bone interface using a combined approach of histology and in vivo micro CT. Male C57Bl/6 mice (n=8), aged 16 weeks, received intra-articular injections with collagenase in one joint to induce instability-related OA and saline into the contralateral knee joint (controls). At 2, 4, 6, 10 and 14 weeks post-injection, changes in the tibial subchondral bone plate and subchondral trabeculae were analyzed. At two weeks post-injection, collagenase injected joints had significantly more cartilage damage and osteophytosis than control joints. Osteoclast activity directly underneath the subchondral bone plate was significantly elevated (Oc.S./BS controls: 7.60± 0.81%; OA: 11.07± 0.79%), causing the plate to become thinner and creating a large increase in subchondral bone plate porosity (cumulative porosity volume controls: 0.05e-3 ± 0.04e-3 mm(3) ; OA: 2.52e-3 ± 0.69e-3 mm(3) ). At four weeks post-injection, the previously formed perforations disappeared, coinciding with a significant rise in osteoblast activity in the subchondral trabecular bone (bone formation rate controls: 0.30± 0.03, OA: 0.62± 0.13 μm(2) /μm(3) *day). The current study provides for the first time quantitative longitudinal data on the dynamic changes in the subchondral bone plate after OA induction. The development of plate perforations may enhance mutual interaction between subchondral trabeculae, bone marrow cells and the articular cartilage in OA.

Final results of a phase IIa, randomised, open-label trial to evaluate the percutaneous intramyocardial transplantation of autologous skeletal myoblasts in congestive heart failure patients: The SEISMIC trial (Article)

Duckers, H.J. — 2011-02-01T00:00:00Z

Aims: The SEISMIC study was an open-label, prospective, randomised study to assess the safety and feasibility of percutaneous myoblast implantation in heart failure patients with implanted cardioverter-defibrillators (ICD). Methods and results: Patients were randomised 2:1 to autologous skeletal myoblast therapy vs. optimal medical treatment. The primary safety end-point was defined as the incidence of procedural and device related serious adverse events, whereas the efficacy endpoints were defined as the change in global LVEF by MUGA scan, change in NYHA classification of heart failure and in the distance achieved during a six-minute walk test (6MW) at 6-month follow-up. Forty subjects were randomised to the treatment arm (n=26), or to the control arm (n=14). There were 12 sustained arrhythmic events and one death after episodes of ventricular tachycardia (VT) in the treatment group and 14 events in the control group (P=ns). At 6-month follow-up, 6MW distance improved by 60.3±54.1 meters in the treated group as compared to no improvement in the control group (0.4±185.7 meters; P=ns). In the control group, 28.6% experienced worsening of heart failure status (4/14), while 14.3% experienced an improvement in NYHA classification (2/14). In the myoblast-treatment arm, one patient experienced a deterioration in NYHA classification (8.0%), whereas five patients improved one or two classes (20.0%; P=0.06). However, therapy did not improve global LVEF measured by MUGA at 6-month follow-up. Conclusions: These data indicate that implantation of myoblasts in patients with HF is feasible, appears to be safe and may provide symptomatic relief, though no significant effect was detected on global LVEF.

Visualizing RAD51-mediated joint molecules: Implications for recombination mechanism and the effect of sequence heterology (Article)

Ristic, D. — 2011-01-17T00:00:00Z

The defining event in homologous recombination is the exchange of base-paired partners between a single-stranded (ss) DNA and a homologous duplex driven by recombinase proteins, such as human RAD51. To understand the mechanism of this essential genome maintenance event, we analyzed the structure of RAD51-DNA complexes representing strand exchange intermediates at nanometer resolution by scanning force microscopy. Joint molecules were formed between substrates with a defined ssDNA segment and homologous region on a double-stranded (ds) partner. We discovered and quantified several notable architectural features of RAD51 joint molecules. Each end of the RAD51-bound joints had a distinct structure. Using linear substrates, a 10-nt region of mispaired bases blocked extension of joint molecules in all examples observed, whereas 4nt of heterology only partially blocked joint molecule extension. Joint molecules, including 10nt of heterology, had paired DNA on either side of the heterologous substitution, indicating that pairing could initiate from the free 3′end of ssDNA or from a region adjacent to the ss-ds junction. RAD51 filaments covering joint ss-dsDNA regions were more stable to disassembly than filaments covering dsDNA. We discuss how distinct structural features of RAD51-bound DNA joints can play important roles as recognition sites for proteins that facilitate and control strand exchange.