Treatment of Spontaneous Tumors With Algorithmically Controlled Electroporation.

OBJECTIVE: To study the safety and efficacy of algorithmically controlled electroporation (ACE) against spontaneous equine melanoma. METHODS: A custom temperature sensing coaxial electrode was paired with a high voltage pulse generation system with integrated temperature feedback controls. Computational modeling and ex vivo studies were conducted to evaluate the system's ability to achieve and maintain target temperatures. Twenty-five equine melanoma tumors were treated with a 2000 V protocol consisting of a 2-5-2 waveform, 45 °C temperature set point, and integrated energized times of 0.005 s, 0.01 s, or 0.02 s (2500x, 5000x, and 10000x 2 µs pulses, respectively). Patients returned 20-50 days post treatment to determine the efficacy of the treatment. RESULTS: ACE temperature control algorithms successfully achieved and maintained target temperatures in a diverse population of spontaneous tumors with significant variation in tissue impedance. All treatments were completed successfully without and without adverse events. Complete response rates greater than 93% were achieved in all treatment groups. CONCLUSION: ACE is a safe and effective treatment for spontaneous equine melanoma. The temperature control algorithm enabled rapid delivery of electroporation treatments without prior knowledge of tissue electrical or thermal properties and could adjust to real time changes in tissue properties. SIGNIFICANCE: Real time temperature control in electroporation procedures enables treatments near critical structures where thermal damage is contraindicated. Unlike standard approaches, ACE protocols do not require extensive pretreatment planning or knowledge of tissue properties to determine an optimal energy delivery rate and they can account for changes in tissue state (e.g., perfusion) in real time to simultaneously minimize treatment time and potential for thermal damage.

Integrated Time Nanosecond Pulse Irreversible Electroporation (INSPIRE): Assessment of Dose, Temperature, and Voltage on Experimental and Clinical Treatment Outcomes.

OBJECTIVE: This study sought to investigate a novel strategy using temperature-controlled delivery of nanosecond pulsed electric fields as an alternative to the 50-100 microsecond pulses used for irreversible electroporation. METHODS: INSPIRE treatments were carried out at two temperatures in 3D tumor models using doses between 0.001 s and 0.1 s. The resulting treatment zones were quantified using viability staining and lethal electric field intensities were determined numerically. Computational modeling was then used to determine parameters necessary for INSPIRE treatments to achieve equivalent treatment zones to clinical electroporation treatments and evaluate the potential for these treatments to induce deleterious thermal damage. RESULTS: Lethal thresholds between 1109 and 709 V/cm were found for nominal 0.01 s treatments with pulses between 350 ns and 2000 ns at physiological temperatures. Further increases in dose resulted in significant decreases in lethal thresholds. Given these experimental results, treatment zones comparable to clinical electroporation are possible by increasing the dose and voltage used with nanosecond duration pulses. Temperature-controlled simulations indicate minimal thermal cell death while achieving equivalent treatment volumes to clinical electroporation. CONCLUSION: Nanosecond electrical pulses can achieve comparable outcomes to traditional electroporation provided sufficient electrical doses or voltages are applied. The use of temperature-controlled delivery may minimize thermal damage during treatment. SIGNIFICANCE: Intense muscle stimulation and the need for cardiac gating have limited irreversible electroporation. Nanosecond pulses can alleviate these challenges, but traditionally have produced significantly smaller treatment zones. This study suggests that larger ablation volumes may be possible with the INSPIRE approach and that future in vivo studies are warranted.

Repurposing antimalarial aminoquinolines and related compounds for treatment of retinal neovascularization.

Neovascularization is the pathological driver of blinding eye diseases such as retinopathy of prematurity, proliferative diabetic retinopathy, and wet age-related macular degeneration. The loss of vision resulting from these diseases significantly impacts the productivity and quality of life of patients, and represents a substantial burden on the health care system. Current standard of care includes biologics that target vascular endothelial growth factor (VEGF), a key mediator of neovascularization. While anti-VGEF therapies have been successful, up to 30% of patients are non-responsive. Therefore, there is a need for new therapeutic targets, and small molecule inhibitors of angiogenesis to complement existing treatments. Apelin and its receptor have recently been shown to play a key role in both developmental and pathological angiogenesis in the eye. Through a cell-based high-throughput screen, we identified 4-aminoquinoline antimalarial drugs as potent selective antagonists of APJ. The prototypical 4-aminoquinoline, amodiaquine was found to be a selective, non-competitive APJ antagonist that inhibited apelin signaling in a concentration-dependent manner. Additionally, amodiaquine suppressed both apelin-and VGEF-induced endothelial tube formation. Intravitreal amodaiquine significantly reduced choroidal neovascularization (CNV) lesion volume in the laser-induced CNV mouse model, and showed no signs of ocular toxicity at the highest doses tested. This work firmly establishes APJ as a novel, chemically tractable therapeutic target for the treatment of ocular neovascularization, and that amodiaquine is a potential candidate for repurposing and further toxicological, and pharmacokinetic evaluation in the clinic.

Structure-Guided Strategy for the Development of Potent Bivalent ERK Inhibitors.

ERK is the effector kinase of the RAS-RAF-MEK-ERK signaling cascade, which promotes cell transformation and malignancy in many cancers and is thus a major drug target in oncology. Kinase inhibitors targeting RAF or MEK are already used for the treatment of certain cancers, such as melanoma. Although the initial response to these drugs can be dramatic, development of drug resistance is a major challenge, even with combination therapies targeting both RAF and MEK. Importantly, most resistance mechanisms still rely on activation of the downstream effector kinase ERK, making it a promising target for drug development efforts. Here, we report the design and structural/functional characterization of a set of bivalent ERK inhibitors that combine a small molecule inhibitor that binds to the ATP-binding pocket with a peptide that selectively binds to an ERK protein interaction surface, the D-site recruitment site (DRS). Our studies show that the lead bivalent inhibitor, SBP3, has markedly improved potency compared to the small molecule inhibitor alone. Unexpectedly, we found that SBP3 also binds to several ERK-related kinases that contain a DRS, highlighting the importance of experimentally verifying the predicted specificity of bivalent inhibitors. However, SBP3 does not target any other kinases belonging to the same CMGC branch of the kinome. Additionally, our modular click chemistry inhibitor design facilitates the generation of different combinations of small molecule inhibitors with ERK-targeting peptides.

Hybrid origins and the earliest stages of diploidization in the highly successful recent polyploid Capsella bursa-pastoris.

Whole-genome duplication (WGD) events have occurred repeatedly during flowering plant evolution, and there is growing evidence for predictable patterns of gene retention and loss following polyploidization. Despite these important insights, the rate and processes governing the earliest stages of diploidization remain poorly understood, and the relative importance of genetic drift, positive selection, and relaxed purifying selection in the process of gene degeneration and loss is unclear. Here, we conduct whole-genome resequencing in Capsella bursa-pastoris, a recently formed tetraploid with one of the most widespread species distributions of any angiosperm. Whole-genome data provide strong support for recent hybrid origins of the tetraploid species within the past 100,000-300,000 y from two diploid progenitors in the Capsella genus. Major-effect inactivating mutations are frequent, but many were inherited from the parental species and show no evidence of being fixed by positive selection. Despite a lack of large-scale gene loss, we observe a decrease in the efficacy of natural selection genome-wide due to the combined effects of demography, selfing, and genome redundancy from WGD. Our results suggest that the earliest stages of diploidization are associated with quantitative genome-wide decreases in the strength and efficacy of selection rather than rapid gene loss, and that nonfunctionalization can receive a "head start" through a legacy of deleterious variants and differential expression originating in parental diploid populations.

Utility of Stepping, Walking, and Head Impulses for Screening Patients for Vestibular Impairments.

OBJECTIVE: To determine if some common screening tests predict scores on detailed, objective diagnostic tests of the vestibular system. STUDY DESIGN: Sixty patients with vestibular disorders were compared with 60 asymptomatic controls. SETTING: Vestibular diagnostic laboratory, tertiary care center. SUBJECTS AND METHODS: Subjects were screened with head impulse tests, Fukuda stepping tests while walking and marching in place, and tandem walking tests with eyes open and closed. All subjects underwent bithermal caloric tests and Dix-Hallpike maneuvers; patients underwent low-frequency sinusoidal tests of the vestibulo-ocular reflex in darkness and cervical vestibular evoked myogenic potentials. RESULTS: On tandem walking tests, patients differed significantly from controls, but receiver operating characteristic scores were < 0.80. On Fukuda tests, patients turned significantly more than controls for walking but not marching, but receiver operating characteristic values were considerably less than 0.80. On head impulse tests, patients with bithermal caloric weakness (≥20% and <60%) did not differ from controls, but patients with severe bithermal caloric weakness (≥60%) differed significantly from controls. Receiver operating characteristic values were >0.80 only for subjects with severe bithermal caloric weakness and were highest, at 0.88, for subjects with severe weakness and age ≥ 60 years. CONCLUSIONS: The Fukuda test is a poor screening test because it does not correlate well with objective test findings. Tandem walking is best used for screening older patients for vestibular disorders. Positive findings on a head impulse test are probably consistent with severe peripheral vestibular impairment and may be most useful in older patients. In younger patients with vertigo, negative results on head impulse tests may not be informative.

Cochlear implant electrode misplacement: incidence, evaluation, and management.

OBJECTIVES/HYPOTHESIS: To review the presentation and management of improper electrode array placement, and to help guide clinical decision-making. STUDY DESIGN: Retrospective case series. METHODS: Pediatric and adult cochlear implant patients managed from January 2001 to present whose electrode arrays were not placed properly within the cochlea or extended beyond the cochlea into the internal auditory canal or adjacent structures. RESULTS: Four patients, three pediatric and one adult, were identified from over 824 cases (< 1%) managed over the study duration. All cases had normal cochlear anatomy. These cases were initially identified due to poor auditory skill development or absent behavioral responses following implantation, which prompted imaging. Two patients presented several years after surgery. Sites of improper placement included the eustachian tube, vestibule, internal carotid artery canal, and internal auditory canal (IAC). Intraoperative findings and management are reviewed. CONCLUSIONS: Electrode array malpositioning is a rare, but serious and correctable complication in cochlear implant surgery. A multidisciplinary approach, including prompt audiologic evaluation and imaging, is important, particularly when benefit from the implant is limited or absent. Management of electrode arrays in the IAC may be more challenging.

Stimulation of Activin A/Nodal signaling is insufficient to induce definitive endoderm formation of cord blood-derived unrestricted somatic stem cells.

INTRODUCTION: Unrestricted somatic stem cells (USSC) derived from umbilical cord blood are an attractive alternative to human embryonic stem cells (hESC) for cellular therapy. USSC are capable of forming cells representative of all three germ line layers. The aim of this study was to determine the potential of USSC to form definitive endoderm following induction with Activin A, a protein known to specify definitive endoderm formation of hESC. METHODS: USSC were cultured for (1) three days with or without 100 ng/ml Activin A in either serum-free, low-serum or serum-containing media, (2) three days with or without 100 ng/ml Activin A in combination with 10 ng/ml FGF4 in pre-induction medium, or (3) four days with or without small molecules Induce Definitive Endoderm (IDE1, 100 nM; IDE2, 200 nM) in serum-free media. Formation of definitive endoderm was assessed using RT-PCR for gene markers of endoderm (Sox17, FOXA2 and TTF1) and lung epithelium (surfactant protein C; SPC) and cystic fibrosis transmembrane conductance regulator; CFTR). The differentiation capacity of Activin A treated USSC was also assessed. RESULTS: Activin A or IDE1/2 induced formation of Sox17+ definitive endoderm from hESC but not from USSC. Activin A treated USSC retained their capacity to form cells of the ectoderm (nerve), mesoderm (bone) and endoderm (lung). Activin A in combination with FGF4 did not induce formation of Sox17+ definitive endoderm from USSC. USSC express both Activin A receptor subunits at the mRNA and protein level, indicating that these cells are capable of binding Activin A. CONCLUSIONS: Stimulation of the Nodal signaling pathway with Activin A or IDE1/2 is insufficient to induce definitive endoderm formation from USSC, indicating that USSC differ in their stem cell potential from hESC.

Generation of induced pluripotent stem cell lines from Friedreich ataxia patients.

Friedreich ataxia (FRDA) is an autosomal recessive disorder characterised by neurodegeneration and cardiomyopathy. It is caused by a trinucleotide (GAA) repeat expansion in the first intron of the FXN gene that results in reduced synthesis of FXN mRNA and its protein product, frataxin. We report the generation of induced pluripotent stem (iPS) cell lines derived from skin fibroblasts from two FRDA patients. Each of the patient-derived iPS (FA-iPS) cell lines maintain the GAA repeat expansion and the reduced FXN mRNA expression that are characteristic of the patient. The FA-iPS cells are pluripotent and form teratomas when injected into nude mice. We demonstrate that following in vitro differentiation the FA-iPS cells give rise to the two cell types primarily affected in FRDA, peripheral neurons and cardiomyocytes. The FA-iPS cell lines have the potential to provide valuable models to study the cellular pathology of FRDA and to develop high-throughput drug screening assays. We have previously demonstrated that stable insertion of a functional human BAC containing the intact FXN gene into stem cells results in the expression of frataxin protein in differentiated neurons. As such, iPS cell lines derived from FRDA patients, following correction of the mutated gene, could provide a useful source of immunocompatible cells for transplantation therapy.

The challenge of developmentally appropriate care: predictive genetic testing in young people for familial adenomatous polyposis.

Predictive genetic tests for familial adenomatous polyposis (FAP) are routinely offered to young people during early adolescence. While this is not controversial, due to the medical benefit conferred by the test, it is nonetheless challenging as a consequence of the stage of life of the young people, and the simultaneous involvement of multiple family members. Despite these challenges, it is possible to ensure that the test is offered in such a way that it actively acknowledges and facilitates young people's developing autonomy and psychosocial well-being. In this paper we present findings from ten in-depth interviews with young people who have undergone predictive genetic testing for FAP (four male, six female; five gene-positive, five gene-negative; aged 10-17 years at the time of their predictive test; aged 12-25 years at the time of their research interview). We present five themes that emerged from the interviews which highlight key ethical challenges associated with such testing. These are: (1) the significance of the test; (2) young people's lack of involvement in the decision to be tested; (3) young people's limited understanding; (4) provision of the blood test at the first visit; and (5) group testing of family members. We draw on these themes to make eight recommendations for future practice. Together, these recommendations highlight the importance of providing developmentally appropriate care to young people undergoing predictive genetic testing for FAP.

Advanced pediatric mastoiditis with and without intracranial complications.

OBJECTIVES/HYPOTHESIS: Recently, several groups have noticed an increase in cases of advanced pediatric mastoiditis and intracranial complications. The objective of this study was to review the bacteriology of advanced mastoiditis in pediatric patients, with the hypothesis that a difference in bacteriology might explain the development of an intracranial complication. STUDY DESIGN: Retrospective chart review. METHODS: All pediatric patients with coalescent mastoiditis requiring surgery treated at a tertiary care children's hospital between 2002 and 2007 were reviewed. Every patient included was treated either with mastoidectomy alone (for coalescent mastoiditis without an intracranial complication) or with transtemporal craniotomy (for coalescent mastoiditis with an intracranial complication). All patients had surgical specimens sent for pathology, Gram stain, and aerobic and anaerobic cultures. RESULTS: One hundred eight pediatric patients with coalescent mastoiditis were identified: 58 (53%) presented with coalescent mastoiditis alone, 17 (16%) presented with coalescent mastoiditis and an intracranial complication, and 33 (31%) were excluded because they were treated with myringotomy and tubes alone, had incomplete data, or had an unclear diagnosis. Streptococcus pneumoniae was the most commonly cultured organism in patients with and without intracranial complications. Anaerobic isolates were present in 29.4% of patients with intracranial complications and 5.7% of patients without intracranial complications (P = .015). CONCLUSIONS: Nearly a quarter of pediatric patients with coalescent mastoiditis presented with a simultaneous intracranial complication. There was an increased incidence of anaerobic organisms in patients with intracranial complications compared to those without, indicating the importance of culture and antibiotic coverage appropriate for anaerobes. This series demonstrates the role of aggressive surgical management and close collaboration with the infectious disease service for long-term intravenous antibiotic therapy in treating pediatric patients with advanced mastoiditis.

Facial Nerve Grading System 2.0.

OBJECTIVE: To present an updated version of the original Facial Nerve Grading Scale (FNGS), commonly referred to as the House-Brackmann scale. STUDY DESIGN: Controlled trial of grading systems using a series of 21 videos of individuals with varying degrees of facial paralysis. RESULTS: The intraobserver and interobserver agreement was high among the original and revised scales. Nominal improvement is seen in percentage of exact agreement of grade and reduction of instances of examiners differing by more then one grade when using FNGS 2.0. FNGS 2.0 also offers improved agreement in differentiating between grades 3 and 4. CONCLUSION: FNGS 2.0 incorporates regional scoring of facial movement, providing additional information while maintaining agreement comparable to the original scale. Ambiguities regarding use of the grading scale are addressed.

Southern Ocean deep-water carbon export enhanced by natural iron fertilization.

The addition of iron to high-nutrient, low-chlorophyll regions induces phytoplankton blooms that take up carbon. Carbon export from the surface layer and, in particular, the ability of the ocean and sediments to sequester carbon for many years remains, however, poorly quantified. Here we report data from the CROZEX experiment in the Southern Ocean, which was conducted to test the hypothesis that the observed north-south gradient in phytoplankton concentrations in the vicinity of the Crozet Islands is induced by natural iron fertilization that results in enhanced organic carbon flux to the deep ocean. We report annual particulate carbon fluxes out of the surface layer, at three kilometres below the ocean surface and to the ocean floor. We find that carbon fluxes from a highly productive, naturally iron-fertilized region of the sub-Antarctic Southern Ocean are two to three times larger than the carbon fluxes from an adjacent high-nutrient, low-chlorophyll area not fertilized by iron. Our findings support the hypothesis that increased iron supply to the glacial sub-Antarctic may have directly enhanced carbon export to the deep ocean. The CROZEX sequestration efficiency (the amount of carbon sequestered below the depth of winter mixing for a given iron supply) of 8,600 mol mol(-1) was 18 times greater than that of a phytoplankton bloom induced artificially by adding iron, but 77 times smaller than that of another bloom initiated, like CROZEX, by a natural supply of iron. Large losses of purposefully added iron can explain the lower efficiency of the induced bloom(6). The discrepancy between the blooms naturally supplied with iron may result in part from an underestimate of horizontal iron supply.

Cell-mediated rejection results in allograft loss after liver cell transplantation.

Liver cell transplantation in humans has been impeded by invariable loss of the graft. It is unclear whether graft loss is due to an immune response against donor hepatocytes. Transplantation with ABO-matched liver cells was performed in a patient with Crigler-Najjar type 1. After successful engraftment, there was a gradual loss of graft function. Solid-phase enzyme immunoassay testing and cell-complement cytotoxicity assays detecting preformed antibodies directed toward class I and/or class II human leukocyte antigen (HLA) molecules were negative. In contrast, a striking host alloresponse to either the HLA-B39 or C7 antigen was found, suggesting that a vigorous response to a defined mismatched HLA antigen contributed to graft loss in our patient. This study provides evidence that a T-cell-mediated immune mechanism could be responsible for human liver cell transplant graft loss. This finding warrants confirmation in future liver cell transplants in humans.

Asymptomatic individuals at genetic risk of haemochromatosis take appropriate steps to prevent disease related to iron overload.

BACKGROUND/AIMS: If community screening for hereditary haemochromatosis is to be considered, compliance with preventative measures and absence of significant psychological morbidity must be demonstrated. METHODS: Workplace screening for the HFE C282Y mutation and then clinical care for C282Y homozygotes was instituted. Data were collected on understanding of test results, perceived health status and anxiety for C282Y homozygotes compared with controls. Uptake of clinical care, compliance and response to treatment and changes in diet were monitored for up to 4 years for C282Y homozygotes. RESULTS: After 11 307 individuals were screened, 40/47 (85%) newly identified C282Y homozygotes completed questionnaires 12 months after diagnosis compared with 79/126 (63%) of controls. Significantly more C282Y homozygotes correctly remembered their test result compared with controls (95 vs 51%, P<0.0001). No significant difference in perceived health status was observed within or between the two groups at 12 months compared with baseline. Anxiety levels decreased significantly for C282Y homozygotes at 12 months compared with before testing (P<0.05). Forty-five of the 47 (95.8%) C282Y homozygotes accessed clinical care for at least 12 months. All 22 participants requiring therapeutic venesection complied with treatment for at least 12 months (range 12-47 months). CONCLUSION: Individuals at a high genetic risk of developing haemochromatosis use clinical services appropriately, maintain their health and are not 'worried well'. Population genetic screening for haemochromatosis can be conducted in the work place in a way that is acceptable and beneficial to participants.

"You're one of us now": young people describe their experiences of predictive genetic testing for Huntington disease (HD) and familial adenomatous polyposis (FAP).

There has been much debate about the psychosocial effects of predictive genetic testing in minors. The majority of this debate has been theoretical, with little empirical evidence published. We conducted in-depth interviews with 18 young people who had undergone testing, to explore the range of harms and benefits that they perceived were associated with their tests. Participants were eight individuals who were tested for Huntington disease (two gene-positive, six gene-negative) and ten who were tested for familial adenomatous polyposis (five gene-positive, five gene-negative). At the time of their test they ranged from 10 to 25 years of age. When interviewed they ranged from 14 to 26 years of age. Harms described included knowledge of future illness, witnessing distress in parents, negative effects on family relationships and friendships, effects upon employment and school, experiencing regret, feeling guilty and having to confront difficult issues. Benefits included knowledge of gene-negative status, relief from uncertainty, witnessing relief in parents, feeling able to plan for the future, positive effects on family relationships and friendships, feeling empowered and experiencing a sense of clarity about what is important in life. Harms were described in relation to gene-negative test results, as were benefits in relation to gene-positive test results. The testing process itself had several positive and negative effects for young people, distinct from the actual test result. Future research concerning the effects of predictive genetic testing in young people must remain broad and should aim to measure the beneficial as well as the harmful effects that resonate for young people themselves.

High incidence of complex chromosome abnormality in cleavage embryos from patients with repeated implantation failure.

OBJECTIVE: To analyze the chromosome abnormalities observed in the course of preimplantation aneuploidy screening using comparative genomic hybridization (CGH) on single blastomeres in relation to maternal age and previous IVF history. DESIGN: Retrospective analytical study. SETTING: A large IVF unit and the research laboratory of an associated clinical genetics unit. PATIENT(S): Twenty-eight women referred for aneuploidy screening of cleavage embryos. INTERVENTION(S): Blastomere biopsy. MAIN OUTCOME MEASURE(S): The incidence of aneuploidy and complex abnormality in human cleavage embryos. RESULT(S): The incidence in embryos of aneuploidy for one to two chromosomes was significantly increased with advanced maternal age, but was independent of any history of recurrent implantation failure. In comparison, the incidence of complex chromosome abnormality (which involves three or more chromosomes) was independent of maternal age but significantly increased in embryos from patients with a history of recurrent implantation failure. CONCLUSION(S): The incidence of complex abnormality in healthy cleavage embryos is independent of maternal age but is increased in patients with a history of recurrent implantation failure. These results suggest that the pathology underlying complex abnormality is different from that resulting in aneuploidy of one to two chromosomes but particularly relevant to women with recurrent implantation failure.

Chromatin-binding regions of EBNA1 protein facilitate the enhanced transfection of Epstein-Barr virus-based vectors.

Epstein-Barr virus (EBV)-based vectors can stably maintain large genomic fragments in mammalian cells, offering great potential for the treatment/correction of many acquired and inherited disorders. Numerous studies report marked increases in the transfection efficiency of EBV-based vectors after delivery into cell lines constitutively expressing Epstein-Barr nuclear antigen-1 (EBNA1), compared with cells not expressing EBNA1. We employ a novel strategy, involving the transfection of mRNA encoding EBNA1, to transiently express EBNA1 protein in human cells. Subsequently we show that the transfection efficiency of a 21-kb EBVbased vector is improved significantly when codelivered with mRNA encoding EBNA1. Similar increases in transfection efficiency were observed after delivery of the plasmid into cells constitutively expressing EBNA1. We also investigate the mechanism by which EBNA1 facilitates the transfection of EBV-based vectors, using mRNA encoding modified versions of the protein. Previous studies suggest that the EBNA1 DNA-binding domain (DBD), together with the nuclear localization signal (NLS), may enhance transfection of EBV plasmids by facilitating their nuclear transport. We demonstrate that an EBNA1 derivative comprising only the NLS and DBD does not facilitate transfection of EBV-based vectors. However, cells expressing an EBNA1 derivative devoid of a functional NLS but retaining the chromatin-binding regions, domains A and B, enhances plasmid transfection efficiency by up to 10-fold. Moreover, a variant of EBNA1 comprising two copies of domain A fused to the DBD enhances DNA transfection to an even greater extent than wild-type EBNA1. We therefore propose that EBNA1-mediated transfection of EBV-based vectors is dependent on the presence of chromatin- binding regions and the DBD, but not the NLS.

Gross genomic rearrangements involving deletions in the CFTR gene: characterization of six new events from a large cohort of hitherto unidentified cystic fibrosis chromosomes and meta-analysis of the underlying mechanisms.

Gross genomic rearrangements involving deletions in the CFTR gene have recently been found to account for approximately 20% of unidentified cystic fibrosis (CF) chromosomes in both French and Italian patients. Using QMPSF and walking quantitative DHPLC, six novel mutations (three simple deletions, two complex deletions with short insertions of 3-6 bp, and a complex deletion with a 182 bp inverted downstream sequence) were characterized by screening 274 unidentified CF chromosomes from 10 different countries. These lesions increase the total number of fully characterized large CFTR genomic rearrangements involving deletions to 21. Systematic analysis of the 42 associated breakpoints indicated that all 21 events were caused by nonhomologous recombination. Whole gene complexity analysis revealed a significant correlation between regions of low sequence complexity and the locations of the deletion breakpoints. Known recombination-promoting motifs were noted in the vicinity of the breakpoints. A total of 11 simple deletions were potentially explicable in terms of the classical model of replication slippage. However, the complex deletions appear to have arisen via multiple mechanisms; three of the five complex deletions with short insertions and both examples of large inverted insertions (299 and 182 bp, respectively) can be explained by either a model of serial replication slippage in cis (SRScis) or SRS in trans (SRStrans). Finally, the nature and distribution of large genomic rearrangements in the CFTR gene were compared and contrasted with those of two other genes, DMD and MSH2, with a view to gaining a broader understanding of DNA sequence context in mediating the diverse underlying mutational mechanisms.