Biomedical subjects

Elene Haralambous

Publications and source records attributed to Elene Haralambous.

3 recordsLinked to original sources

PubMed2006

Development of a genotyping microarray for Usher syndrome.

BACKGROUND: Usher syndrome, a combination of retinitis pigmentosa (RP) and sensorineural hearing loss with or without vestibular dysfunction, displays a high degree of clinical and genetic heterogeneity. Three clinical subtypes can be distinguished, based on the age of onset and severity of the hearing impairment, and the presence or absence of vestibular abnormalities. Thus far, eight genes have been implicated in the syndrome, together comprising 347 protein-coding exons. METHODS: To improve DNA diagnostics for patients with Usher syndrome, we developed a genotyping microarray based on the arrayed primer extension (APEX) method. Allele-specific oligonucleotides corresponding to all 298 Usher syndrome-associated sequence variants known to date, 76 of which are novel, were arrayed. RESULTS: Approximately half of these variants were validated using original patient DNAs, which yielded an accuracy of >98%. The efficiency of the Usher genotyping microarray was tested using DNAs from 370 unrelated European and American patients with Usher syndrome. Sequence variants were identified in 64/140 (46%) patients with Usher syndrome type I, 45/189 (24%) patients with Usher syndrome type II, 6/21 (29%) patients with Usher syndrome type III and 6/20 (30%) patients with atypical Usher syndrome. The chip also identified two novel sequence variants, c.400C>T (p.R134X) in PCDH15 and c.1606T>C (p.C536S) in USH2A. CONCLUSION: The Usher genotyping microarray is a versatile and affordable screening tool for Usher syndrome. Its efficiency will improve with the addition of novel sequence variants with minimal extra costs, making it a very useful first-pass screening tool.

DNA↗

PubMed2006

Factor H, a regulator of complement activity, is a major determinant of meningococcal disease susceptibility in UK Caucasian patients.

Defence against Neisseria meningitidis involves complement-mediated bactericidal activity. Factor H (fH) down-regulates complement activation. A putatively functional single-nucleotide-polymorphism (SNP) exists within a presumed nuclear-factor-kappa-B responsive element (NF-kB) in the fH gene (C-496T). Genetic and functional investigations were carried out to determine whether C-496T has a role in meningococcal disease (MD) susceptibility. Genetic susceptibility was investigated in 2 independent studies, a case-control and family-based transmission-disequilibrium-test (TDT), using 2 separate cohorts of UK Caucasian patients. MD susceptibility was both genetically associated with the C/C homozygous genotype (OR = 2.0, 95% CI 1.3 - 3.2, p = 0.001) and linked to the C allele (p = 0.04), the association being most significant in serogroup C infected patients (OR = 2.9, 95% CI 1.6 - 5.5, p = 0.0002). FH serum concentrations were also associated with C-496T genotype, with highest fH concentrations in C/C homozygous individuals (p = 0.01). Functional studies showed NF-kappa-B binding to the C-496T-containing region and that pre-incubation of fH with meningococci reduced bactericidal activity and increased meningococci B and C survival in blood. This study shows that C-496T is both associated and linked with MD and that individuals possessing the fH C-496T C/C genotype are more likely to have increased serum fH protein levels, have reduced bactericidal activity against meningococci and be at an increased risk of contracting MD.

Adolescent↗

PubMed2003

Role of functional plasminogen-activator-inhibitor-1 4G/5G promoter polymorphism in susceptibility, severity, and outcome of meningococcal disease in Caucasian children.

OBJECTIVE: Meningococcal sepsis invariably is associated with coagulopathy. We have previously reported an association between mortality rate in meningococcal disease and the functional 4G/5G promoter polymorphism of the plasminogen-activator-inhibitor (PAI)-1 gene in a small patient cohort. In a much larger cohort, we aimed to confirm these results and further investigate the role of the 4G/5G polymorphism in determining susceptibility, outcome, and complications of disease.DESIGN Susceptibility was investigated in two separate studies, a case-control study and a family-based transmission study, each test using a separate patient cohort. Severity was investigated using clinical diagnosis, the presence of vascular complications, Pediatric Risk of Mortality (PRISM)-predicted morality, and actual mortality. SETTING: University hospital and laboratories. SUBJECTS: Subjects were 510 UK pediatric patients, 210 parents of patients, and 155 UK Caucasian controls. INTERVENTIONS: DNA extraction and 4G/5G PAI-1 genotyping was carried out using published techniques. MEASUREMENTS AND MAIN RESULTS: Predicted mortality distribution differed significantly between genotypes (p =.05) with a significantly higher median PRISM in the 4G/4G (41.1%) than the 4G/5G (23.4%) and 5G/5G (19.0%) genotyped patients combined (p =.02). Actual mortality rate was significantly associated with both genotype (chi-square = 14.8, p =.001) and allele frequencies (chi-square = 14.0, p <.0001), with more deaths in the 4G/4G (28.4%) than the 4G/5G and 5G/5G genotyped patients combined (14.9%; chi-square = 7.9; p =.005; risk ratio, 1.9; 95% confidence interval, 1.2-3.0). Logistic regression indicated a 40% and 91% reduction in the odds of dying if a patient was either 4G/5G or 5G/5G, respectively, in comparison to a 4G homozygous patient. When analyzed by clinical diagnosis, the association with death was found only in the sepsis group (chi-square = 18.7, p <.0001; risk ratio, 2.7; 95% confidence interval, 1.6-4.6). In survivors of disease, a significantly higher proportion of 4G/4G patients suffered from vascular complications (chi-square = 6.7, p =.03; risk ratio, 2.4; 95% confidence interval, 1.1-5.0). The 4G/5G polymorphism was not associated or linked with susceptibility (case-control result, p =.6; family-based transmission study results, p =.2). CONCLUSIONS: This study confirms that Caucasian pediatric patients carrying the functional PAI-1 4G/4G genotype are at an increased risk of developing vascular complications and dying from meningococcal disease.

Adolescent↗