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Targeted screening for genetic haemochromatosis: a combined phenotype/genotype approach.

OBJECTIVE: To evaluate the clinical utility of a targeted screening approach for the detection of genetic haemochromatosis. METHODS: Screening by measuring fasting serum transferrin saturation (TS) and gene testing was carried out in patients in whom a raised serum alanine amino transferase (ALT) activity and raised random serum TS had been found on routine blood testing. RESULTS: During the 29 month study period, 32 patients homozygous for the C282Y genotype were detected from a catchment population of 330,000 by screening blood samples referred initially for routine laboratory liver function tests. By comparison, during the same period of time and within the same population, only seven patients were found by clinical suspicion alone. The patients in the study, after treatment by venesection, have shown both clinical and biochemical improvement. CONCLUSIONS: The study shows that from a population of patients in whom a routine liver function profile had been requested, it is possible to detect subjects homozygous for the C282Y HFE genotype who have clinical or biochemical markers of iron overload.

D-Alanine Transaminase↗

Genetic polymorphisms and the risk of stroke after cardiac surgery.

BACKGROUND AND PURPOSE: Stroke represents a significant cause of morbidity and mortality after cardiac surgery. Although the risk of stroke varies according to both patient and procedural factors, the impact of genetic variants on stroke risk is not well understood. Therefore, we tested the hypothesis that specific genetic polymorphisms are associated with an increased risk of stroke after cardiac surgery. METHODS: Patients undergoing cardiac surgery utilizing cardiopulmonary bypass surgery were studied. DNA was isolated from preoperative blood and analyzed for 26 different single-nucleotide polymorphisms. Multivariable logistic regression modeling was used to determine the association of clinical and genetic characteristics with stroke. Permutation analysis was used to adjust for multiple comparisons inherent in genetic association studies. RESULTS: A total of 1635 patients experiencing 28 strokes (1.7%) were included in the final genetic model. The combination of the 2 minor alleles of C-reactive protein (CRP; 3'UTR 1846C/T) and interleukin-6 (IL-6; -174G/C) polymorphisms, occurring in 583 (35.7%) patients, was significantly associated with stroke (odds ratio, 3.3; 95% CI, 1.4 to 8.1; P=0.0023). In a multivariable logistic model adjusting for age, the CRP and IL-6 single-nucleotide polymorphism combination remained significantly associated with stroke (P=0.0020). CONCLUSIONS: We demonstrate that common genetic variants of CRP (3'UTR 1846C/T) and IL-6 (-174G/C) are significantly associated with the risk of stroke after cardiac surgery, suggesting a pivotal role of inflammation in post-cardiac surgery stroke.

Aged↗

Utility of the lethargic (lh/lh) mouse model of absence seizures in predicting the effects of lamotrigine, vigabatrin, tiagabine, gabapentin, and topiramate against human absence seizures.

PURPOSE: Traditional methods of preclinical screening have predicted the effects of a putative antiepileptic drug (AED) against human absence seizures by testing its efficacy against clonic seizures in the high-dose pentylenetetrazole (PTZ) model. This high-dose PTZ model correctly predicted the efficacy of ethosuximide (ESM), benzodiazepines, and valproate (VPA) and the lack of efficacy of phenytoin (PHT) and carbamazepine (CBZ). However, the high-dose PTZ model erred in predictions for (a) phenobarbital (PB) (PTZ: efficacy; human: nonefficacy); (b) lamotrigine (LTG) (PTZ: nonefficacy; human: efficacy); (c) vigabatrin (VGB) (PTZ: nonefficacy; human: proabsence effect); and (d) tiagabine (TGB) (PTZ: efficacy; human: possible proabsence). It also appears to have erred in predictions for gabapentin (GBP) (PTZ: efficacy) and topiramate (TPM) (PTZ: efficacy). Because the lh/lh genetic model of absence seizures correctly predicted effects of ESM, clonazepam, VPA, PHT, CBZ, and PB against human absence seizures, we performed this study to test the predictive utility of the lh/lh model for LTG, VGB, TGB, GBP, and TPM. METHODS: Bipolar recording electrodes were implanted bilaterally into frontal neocortex of 8-week-old male lh/lh mice. With the exception of VGB, vehicle or drugs were administered intraperitoneally (i.p.) on alternating days, and an EEG was used to record effects on seizure frequency. With VGB, vehicle was administered i.p. on day 1, and gradually increasing doses of VGB were administered on successive days. Drug and vehicle effects were compared in corresponding 15-min epochs of the 150-min period after administration. RESULTS: LTG (4.8-144 micromol/kg) significantly (p < 0.04) reduced seizure frequency (by 65%) compared with vehicle. In contrast, VGB (0.35-11 mmol/kg) and TGB (0.27-27 micromol/kg) significantly increased seizure frequency (300-700%) and seizure duration (1,700-1,800%; p < 0.001). GBP (18 micromol/kg to 1.8 mmol/kg) and TPM (8.9-295 micromol/kg) had no significant effect on seizure frequency. CONCLUSIONS: In contrast to the high-dose PTZ model, the lh/lh model correctly predicted the antiabsence effect of LTG, the possible proabsence effects of VGB and TGB, and the lack of effect of GBP and TPM. The lh/lh model appears to be superior to the high-dose PTZ model in predicting efficacy of putative AEDs against human absence seizures.

Acetates↗

Prenatal screening for hemoglobinopathies. I. A prospective regional trial.

Prenatal hemoglobinopathy screening was chosen as a model system for the study of patient receptivity to unsolicited genetic information. Providers of prenatal care in Rochester, NY, were offered free testing of all their prenatal patients and genetic counseling of women found positive. The 18,907 prenatal samples tested in a 5-year period represented 35.1% of the pregnancies in the Rochester metropolitan region. A hemoglobinopathy was found in 810 pregnancies (4.3%). Of the 21 different types of hemoglobinopathies detected, the most common were sickle cell trait (59%), hemoglobin C trait (19%), beta-thalassemia trait (11%), and hemoglobin E trait (5%). At the time of phlebotomy, 75% of the pregnancies were of less than 18 wk duration. Sixty-six percent of the pregnancies occurred in patients unaware of their diagnosis, and 80% occurred in patients unaware that they might be at risk for a child with a serious blood disorder. Of the 810 positive pregnancies, 551 (68%) occurred in patients who came for counseling. Of 453 women counseled during their first screened pregnancy, 390 (86%) said they wanted their partners tested and 254 (55%) had their partner tested. In the 77 pregnancies thus found to be at risk, the couple was too late for prenatal diagnosis in 12 cases, and the condition for which the fetus was at risk was too mild in 12 cases. Prenatal diagnosis was offered in the remaining 53 pregnancies and was accepted by 25 couples (47%). These results indicate that unselected patients in the primary care setting in this region, even though pregnant, are receptive to and utilize genetic information.

Adult↗

Generation and mapping of Mus spretus strain-specific markers for rapid genomic scanning.

We describe here a set of genetic markers, based on IRS-PCR amplification difference, that are specifically designed for efficient, high throughput genetic mapping in [(M. domesticus x wild-derived) F1 x M. domesticus] interspecific backcrosses. 146 new genetic loci have been mapped, and strain distribution for these markers has been determined in 96 mouse strains. 103 (81%) of 127 tested markers are present only in one or more wild-derived strains, but absent in 76 other commonly used strains, demonstrating their utility in a variety of mouse pair combinations. Because of the ease of genotyping with this marker set, rapid genome scans for complex genetic trait loci involving crosses between wild-derived strains and other commonly used strains can now be carried out efficiently with large numbers of animals.

Animals↗

The clinical features, course, prognosis and treatment of juvenile arthritis.

The author's classification of juvenile arthritis (JA) differs from most by utilizing both the type of onset and the disease course separated into individual subgroups. The clinical aspects of each are described in detail, along with the special tests and studies to be done to differentiate them. Particular attention is given to the differences between the four subgroups of the pauciarticular onset group. There are different genetic factors for each subgroup and new data on HLA typing utilizing DNA techniques may be helpful in the prognosis of the disease course. The therapy of JA begins with non-steroidal anti-inflammatory drugs, continues with second-line drugs such as gold and penicillamine, and finally leads to the use of immunosuppressive agents. The range of doses, the maximal dose, and the frequency of administration is given for each medication. The long-term prognosis is generally good, with a low death rate, primarily seen in the systemic onset patients. The causes of death vary around the world. Prognosis for continued joint activity and joint function is determined significantly by the type of onset and is worse in the rheumatoid factor positive polyarticular onset group.

Adolescent↗

Genetics of arterial prothrombotic risk states.

Coronary artery disease is a leading cause of death worldwide and the largest killer of men and women in the United States. The pathophysiology of myocardial infarction is multifactorial, and numerous physiologic systems converge to dictate the formation of the two fundamental lesions, thrombosis and atherosclerosis. In this review we address genetic aspects of arterial thrombosis and the key thrombotic factors that have been associated with the increased risk for its development. Specifically, we consider components of coagulation, fibrinolysis, and platelet adhesive receptors, and we review the genetic epidemiology and in vitro laboratory data regarding their risk for the acute coronary syndromes. In combination with traditional risk factor assessment, in the near future these inherited markers can be used to manage patients with vascular disease through a better utilization of invasive or expensive diagnostic testing, as well as pharmacologic intervention.

Blood Coagulation Factors↗

Female illness rates and illness behavior: testing hypotheses about sex differences in health.

Health surveys repeatedly show that females have higher rates of illness, disability days, and health services utilization than do males. Numerous reasons for these sex differences have been hypothesized, based on four general factors thought to differ by sex and to influence self-reported health: genetic characteristics, physical risks, illness behavior, and reporting behavior. This paper briefly reviews these hypotheses, then discusses research strategies to test them. The strategies vary in the type of dependent variables used (medical vs. sociomedical health indicators) and the main method of controlling predictor factors (elimination vs. statistical control). A study was completed in 1978 in the Detroit metropolitan area to (a) explore reasons for sex differences in health and (b) reveal how strongly illness behavior (perception and evaluation of symptoms, propensities to take curative actions or disability days) affects common health indicators, particularly those for the national Health Interview Survey. The study's research design (use of a health diary, and focus on hypotheses about illness behavior) is described.

Adult↗

Modified tobacco mosaic virus particles as scaffolds for display of protein antigens for vaccine applications.

Display of peptides or proteins in an ordered, repetitive array, such as on the surface of a virus-like particle, is known to induce an enhanced immune response relative to vaccination with the "free" protein antigen. The coat protein of Tobacco mosaic virus (TMV) can accommodate short peptide insertions into the primary sequence, but the display of larger protein moieties as genetic fusions to the capsid protein has not been possible. We employed a randomized library approach to introduce a reactive lysine at the externally located amino terminus of the coat protein, which facilitated biotinylation of the capsid. To characterize display of heterologous proteins on the virion surface, we bound a model antigen (green fluorescent protein (GFP)-streptavidin (SA), expressed and purified from plants) to the biotinylated TMV particles, creating a GFP-SA decorated virus particle. A GFP-SA tetramer loading of 26% was obtained, corresponding to approximately 2200 GFP moieties displayed per intact virion. We evaluated the immunogenicity of GFP decorated virions in both mice and guinea pigs and found augmented humoral IgG titers in both species, relative to unbound GFP-SA tetramer. Next, we fused an N-terminal fragment of the Canine oral papillomavirus L2 protein to streptavidin. With TMV display, the L2 protein fragment was significantly more immunogenic than uncoupled antigen when tested in mice. By demonstrating the presentation of whole proteins, this study expands the utility of TMV as a vaccine scaffold beyond that which is possible by genetic manipulation.

Amino Acid Sequence↗

Comparing the performance of exome and genome sequencing for rare disease diagnostics: A randomized implementation effectiveness trial.

PURPOSE: Exome sequencing (ES) and genome sequencing (GS) can improve rare disease diagnosis but are not routinely available in many jurisdictions. To inform implementation, we report on a randomized implementation effectiveness trial comparing ES and GS. METHODS: Eligible trios were randomized to receive ES or GS in the same clinically accredited laboratory. Patient-level data on diagnostic utility and turnaround times were collected. Outcomes were compared statistically between clinically important subgroups. RESULTS: Of 1048 patients, 68.5% had syndromic intellectual disability/developmental delay (ID/DD) and 20.5% had multisystem disorders without ID/DD. Most had prior genetic test(s) that were nondiagnostic (95.5%), and of these, 91.6% included chromosome microarray. Diagnostic yields were 33.8% and 33.6%, for ES (n = 526) and GS (n = 522), respectively. Within sequencing groups, diagnostic results were more frequent among those with ID/DD than those without (P < .005). For routine (ie, nonexpedited) patients (n = 1020), 87.0% were reported in <12 weeks, and the mean turnaround time was 55.5 days (SD: 24.0). Turnaround time for ES and GS did not differ; however, result type (P < .001) and age of onset (P < .005) significantly affected turnaround time. CONCLUSION: Findings provide robust evidence of diagnostic utility and timeliness of ES and GS and will inform policy related to the organization, delivery, and reimbursement of clinical-grade genome diagnostics for rare diseases.

Adolescent↗

Behavioral genetics: concepts for research and practice in language development and disorders.

This paper is an introduction to behavioral genetics for researchers and practitioners in language development and disorders. The specific aims are to illustrate some essential concepts and to show how behavioral genetic research can be applied to the language sciences. Past genetic research on language-related traits has tended to focus on simple etiology (i.e., the heritability or familiality of language skills). The current state of the art, however, suggests that great promise lies in addressing more complex questions through behavioral genetic paradigms. In terms of future goals it is suggested that: (a) more behavioral genetic work of all types should be done--including replications and expansions of preliminary studies already in print; (b) work should focus on fine-grained, theory-based phenotypes with research designs that can address complex questions in language development; and (c) work in this area should utilize a variety of samples and methods (e.g., twin and family samples, heritability and segregation analyses, linkage and association tests, etc.).

Environment↗

Effect of genetic variability on the inflammatory response to periodontal infection.

AIM: To review the association between genetic variability and the inflammatory response induced by periodontal infection. MATERIAL AND METHODS: A search of MEDLINE-PubMed was performed from January 2000 up to and including March 2005. The search included all types of publications, published in English without other limitations. The following search terms were used: "cytokine polymorphism", "gene polymorphism", "periodontitis", "gingivitis", "inflammation" and "host-response". The papers resulting from the above search were used as an additional source for relevant articles. RESULTS: Genetic variability was examined for the correlation to clinical indicators of inflammation such as bleeding on probing (BOP), gingival inflammation, cytokine in gingival crevicular fluid (GCF) and cytokine production by inflammatory cells. According to the current literature, most of the studies found no association between genetic variability and BOP, gingival inflammation or cytokine concentrations in the GCF. These studies were hampered by inappropriate study designs and the use of inflammatory parameters as secondary rather than primary outcome variables. The data suggest that the production of inflammatory mediators by inflammatory cells may be affected by different genetic traits but further studies are needed in order to establish this association. CONCLUSIONS: To date, there is no clear correlation between any of the gene polymorphisms and clinical indicators of inflammation. The powering of studies to reveal associations between single or multiple nucleotide polymorphisms and inflammatory parameters will need to involve a much larger number of subjects than were used in the past. The available data (including the interleukin-1 composite genotype) do not currently support the utility of such tests in the diagnosis and prognostic assessments of periodontal diseases.

Bacteria, Anaerobic↗

Mitochondrial DNA control region sequences from Nairobi (Kenya): inferring phylogenetic parameters for the establishment of a forensic database.

Large forensic mtDNA databases which adhere to strict guidelines for generation and maintenance, are not available for many populations outside of the United States and western Europe. We have established a high quality mtDNA control region sequence database for urban Nairobi as both a reference database for forensic investigations, and as a tool to examine the genetic variation of Kenyan sequences in the context of known African variation. The Nairobi sequences exhibited high variation and a low random match probability, indicating utility for forensic testing. Haplogroup identification and frequencies were compared with those reported from other published studies on African, or African-origin populations from Mozambique, Sierra Leone, and the United States, and suggest significant differences in the mtDNA compositions of the various populations. The quality of the sequence data in our study was investigated and supported using phylogenetic measures. Our data demonstrate the diversity and distinctiveness of African populations, and underline the importance of establishing additional forensic mtDNA databases of indigenous African populations.

Black People↗

Harnessing natural diversity to probe metabolic pathways.

Analyses of cellular processes in the yeast Saccharomyces cerevisiae rely primarily upon a small number of highly domesticated laboratory strains, leaving the extensive natural genetic diversity of the model organism largely unexplored and unexploited. We asked if this diversity could be used to enrich our understanding of basic biological processes. As a test case, we examined a simple trait: the utilization of di/tripeptides as nitrogen sources. The capacity to import small peptides is likely to be under opposing selective pressures (nutrient utilization versus toxin vulnerability) and may therefore be sculpted by diverse pathways and strategies. Hitherto, dipeptide utilization in S. cerevisiae was solely ascribed to the activity of a single protein, the Ptr2p transporter. Using high-throughput phenotyping and several genetically diverse strains, we identified previously unknown cellular activities that contribute to this trait. We find that the Dal5p allantoate/ureidosuccinate permease is also capable of facilitating di/tripeptide transport. Moreover, even in the absence of Dal5p and Ptr2p, an additional activity--almost certainly the periplasmic asparaginase II Asp3p--facilitates the utilization of dipeptides with C-terminal asparagine residues by a different strategy. Another, as-yet-unidentified activity enables the utilization of dipeptides with C-terminal arginine residues. The relative contributions of these activities to the utilization of di/tripeptides vary among the strains analyzed, as does the vulnerability of these strains to a toxic dipeptide. Only by sampling the genetic diversity of multiple strains were we able to uncover several previously unrecognized layers of complexity in this metabolic pathway. High-throughput phenotyping facilitates the rapid exploration of the molecular basis of biological complexity, allowing for future detailed investigation of the selective pressures that drive microbial evolution.

Dipeptides↗

The origin of the genetic code: amino acids as cofactors in an RNA world.

The genetic code, understood as the specific assignment of amino acids to nucleotide triplets, might have preceded the existence of translation. Amino acids became utilized as cofactors by ribozymes in a metabolically complex RNA world. Specific charging ribozymes linked amino acids to corresponding RNA handles, which could basepair with different ribozymes, via an anticodon hairpin, and so deliver the cofactor to the ribozyme. Growing of the 'handle' into a presumptive tRNA was possible while function was retained and modified throughout. A stereochemical relation between some amino acids and cognate anticodons/codons is likely to have been important in the earliest assignments. Recent experimental findings, including selection for ribozymes catalyzing peptide-bond formation and those utilizing an amino acid cofactor, hold promise that scenarios of this major transition can be tested.

Amino Acids↗

Identifying genetic markers to assess the presence of gene-environment interactions.

We analyzed a randomly chosen replicate with the goals of locating the closest markers to the genes involved in the discrete trait and utilizing these as surrogates for the genes in assessing the presence of gene-environment interactions. We screened the markers with an association test prior to using the transmission-disequilibrium test. We performed a segregation analysis, with regressive models and including the selected markers, to understand the underlying genetic mechanism and the role of the environmental factor. We were unsuccessful in locating the relevant markers due to the absence of linkage disequilibrium. Nevertheless, some insights were gained from the methods used.

Chromosome Mapping↗

Genetic determinants of heritable venous thrombosis: genotyping methods for factor V(Leiden)A1691G, methylenetetrahydrofolate reductase C677T, prothrombin G20210A mutation, and algorithms for venous thrombosis investigations.

OBJECTIVES: To implement cost effective and clinically relevant thrombophilic genotyping and homocysteine analysis in our coagulation laboratory. METHODS: We describe genotyping assays for three of the genetic defects associated with hereditary thrombosis: factor V(Leiden) A1691G, methylenetetrahydrofolate reductase C677T, and prothrombin gene G20210A. A second confirmatory assay for factor V(Leiden) using allele specific oligonucleotide polymerase chain reaction is also presented. We suggest an algorithm for the rational integration of the traditional assays routinely used to investigate venous thrombosis with genotyping and plasma homocysteine measurements. RESULTS: These polymerase chain reaction based assays were designed to be performed under identical reaction conditions, permitting simultaneous setup, amplification, digestion, and analysis. CONCLUSIONS: The three genotyping assays presented are robust and relatively easy to perform. Use of an algorithm will ensure efficient resource utilization and minimize unnecessary testing.

5,10-Methylenetetrahydrofolate Reductase (FADH2)↗