Home About us Contact
|
Home About us Contact | ||
|
|
||
Complex Disorders (complex + disorders)
Selected AbstractsMixed-effects Logistic Approach for Association Following Linkage Scan for Complex DisordersANNALS OF HUMAN GENETICS, Issue 2 2007H. Xu Summary An association study to identify possible causal single nucleotide polymorphisms following linkage scanning is a popular approach for the genetic dissection of complex disorders. However, in association studies cases and controls are assumed to be independent, i.e., genetically unrelated. Choosing a single affected individual per family is statistically inefficient and leads to a loss of power. On the other hand, because of the relatedness of family members, using affected family members and unrelated normal controls directly leads to false-positive results in association studies. In this paper we propose a new approach using mixed-model logistic regression, in which associations are performed using family members and unrelated controls. Thus, the important genetic information can be obtained from family members while retaining high statistical power. To examine the properties of this new approach we developed an efficient algorithm, to simulate environmental risk factors and the genotypes at both the disease locus and a marker locus with and without linkage disequilibrium (LD) in families. Extensive simulation studies showed that our approach can effectively control the type-I error probability. Our approach is better than family-based designs such as TDT, because it allows the use of unrelated cases and controls and uses all of the affected members for whom DNA samples are possibly already available. Our approach also allows the inclusion of covariates such as age and smoking status. Power analysis showed that our method has higher statistical power than recent likelihood ratio-based methods when environmental factors contribute to disease susceptibility, which is true for most complex human disorders. Our method can be further extended to accommodate more complex pedigree structures. [source] Genetics of anxiety disorders: the complex road from DSM to DNA,DEPRESSION AND ANXIETY, Issue 11 2009Jordan W. Smoller M.D. Sc.D. Abstract Anxiety disorders are among the most common psychiatric disorders, affecting one in four individuals over a lifetime. Although our understanding of the etiology of these disorders is incomplete, familial and genetic factors are established risk factors. However, identifying the specific casual genes has been difficult. Within the past several years, advances in molecular and statistical genetic methods have made the genetic dissection of complex disorders a feasible project. Here we provide an overview of these developments, with a focus on their implications for genetic studies of anxiety disorders. Although the genetic and phenotypic complexity of the anxiety disorders present formidable challenges, advances in neuroimaging and experimental animal models of anxiety and fear offer important opportunities for discovery. Real progress in identifying the genetic basis of anxiety disorders will require integrative approaches that make use of these biologic tools as well as larger-scale genomic studies. If successful, such efforts may yield novel and more effective approaches for the prevention and treatment of these common and costly disorders. Depression and Anxiety, 2009. © 2009 Wiley-Liss, Inc. [source] Detecting genotype combinations that increase risk for disease: Maternal-Fetal genotype incompatibility testGENETIC EPIDEMIOLOGY, Issue 1 2003Janet S. Sinsheimer Abstract Biological mechanisms that involve gene-by-environment interactions have been hypothesized to explain susceptibility to complex familial disorders. Current research provides compelling evidence that one environmental factor, which acts prenatally to increase susceptibility, arises from a maternal-fetal genotype incompatibility. Because it is genetic in origin, a maternal-fetal incompatibility is one possible source of an adverse environment that can be detected in genetic analyses and precisely studied, even years after the adverse environment was present. Existing statistical models and tests for gene detection are not optimal or even appropriate for identifying maternal-fetal genotype incompatibility loci that may increase the risk for complex disorders. We describe a new test, the maternal-fetal genotype incompatibility (MFG) test, that can be used with case-parent triad data (affected individuals and their parents) to identify loci for which a maternal-fetal genotype incompatibility increases the risk for disease. The MFG test adapts a log-linear approach for case-parent triads in order to detect maternal-fetal genotype incompatibility at a candidate locus, and allows the incompatibility effects to be estimated separately from direct effects of either the maternal or the child's genotype. Through simulations of two biologically plausible maternal-fetal genotype incompatibility scenarios, we show that the type-I error rate of the MFG test is appropriate, that the estimated parameters are accurate, and that the test is powerful enough to detect a maternal-fetal genotype incompatibility of moderate effect size. Genet Epidemiol 24:1,13, 2003. © 2003 Wiley-Liss, Inc. [source] Major affective disorders and schizophrenia: a common molecular signature?,HUMAN MUTATION, Issue 9 2006Ann Van Den Bogaert Abstract Psychiatric disorders, including affective disorders (AD) and schizophrenia (SZ) are among the most common disabling brain diseases in Western populations and result in high costs in terms of morbidity as well as mortality. Although their etiology and pathophysiology is largely unknown, family-, twin-, and adoption studies argue for a strong genetic determination of these disorders. These studies indicate that there is between 40 and 85% heritability for these disorders but point also to the importance of environmental factors. Therefore, any research strategy aiming at the identification of genes involved in the development of AD and SZ should account for the complex nature (multifactorial) of these disorders. During the last decade, molecular genetic studies have contributed a great deal to the identification of genetic factors involved in complex disorders. Here we provide a comprehensive review of the most promising genes for AD and SZ, and the methods and approaches that were used for their identification. Also, we discuss the current knowledge and hypotheses that have been formulated regarding the effect of variations on protein functioning as well as recent observations that point to common molecular mechanisms. Hum Mutat 27(9), 833,853, 2006. © 2006 Wiley-Liss, Inc. [source] Hepatopancreatobiliary manifestations and complications associated with inflammatory bowel diseaseINFLAMMATORY BOWEL DISEASES, Issue 9 2010Udayakumar Navaneethan MD Abstract Abstract: Diseases involving the hepatopancreatobiliary (HPB) system are frequently encountered in patients with inflammatory bowel disease (IBD). Hepatobiliary manifestations constitute some of the most common extraintestinal manifestations of IBD. They appear to occur with similar frequency in patients with Crohn's disease or ulcerative colitis. HPB manifestations may occur in following settings: 1) disease possibly associated with a shared pathogenetic mechanism with IBD including primary sclerosing cholangitis (PSC), small-duct PSC/pericholangitis and PSC/autoimmune hepatitis overlap, acute and chronic pancreatitis related to IBD; 2) diseases which parallel structural and physiological changes seen with IBD, including cholelithiasis, portal vein thrombosis, and hepatic abscess; and 3) diseases related to adverse effects associated with treatment of IBD, including drug-induced hepatitis, pancreatitis (purine-based agents), or liver cirrhosis (methotrexate), and reactivation of hepatitis B, and biologic agent-associated hepatosplenic lymphoma. Less common HPB manifestations that have been described in association with IBD include autoimmune pancreatitis (AIP), IgG4-associated cholangitis (IAC), primary biliary cirrhosis (PBC), fatty liver, granulomatous hepatitis, and amyloidosis. PSC is the most significant hepatobiliary manifestation associated with IBD and poses substantial challenges in management requiring a multidisciplinary approach. The natural disease course of PSC may progress to cirrhosis and ultimately require liver transplantation in spite of total proctocolectomy with ileal-pouch anal anastomosis. The association between AIP, IAC, and elevated serum IgG4 in patients with PSC is intriguing. The recently reported association between IAC and IBD may open the door to investigate these complex disorders. Further studies are warranted to help understand the pathogenesis of HPB manifestations associated with IBD, which would help clinicians better manage these patients. An interdisciplinary approach, involving gastroenterologists, hepatologists, and, in advanced cases, general, colorectal, and transplant surgeons is advocated. (Inflamm Bowel Dis 2010) [source] The IBD international genetics consortium provides further evidence for linkage to IBD4 and shows gene-environment interactionINFLAMMATORY BOWEL DISEASES, Issue 1 2005Marie Pierik MD Abstract Background and Aims: The inflammatory bowel diseases (IBDs) Crohn's disease (CD) and ulcerative colitis are complex disorders with an important genetic determinant. One gene associated with CD has been identified: NOD2/CARD15. Two independent genome-wide scans found significant evidence (logarithm of odds [LOD] 3.6) and suggestive evidence (LOD 2.8) for linkage on locus 14q11-12, also known as the IBD4 locus. To further characterize this locus, we assessed gene-environment interaction (IBD4 × smoking) and phenotypic heterogeneity in a large cohort of IBD-affected sibling pairs as part of an ongoing international collaborative effort. Patients and Methods: A total of 733 IBD families, comprising 892 affected sibling pairs, were genotyped for microsatellites D14S261, D14S283, D14S972, and D14S275, spanning the IBD4 locus. Information on gender, ethnicity, age at onset, smoking at diagnosis, extraintestinal manifestations, and disease location was available. Results: A significant distortion in the mean allele sharing (MAS) between affected siblings was observed for CD patients only at each of the four markers (54.6%, 52.8%, 50.4%, and 53.3%, respectively). Maximum linkage for CD was observed at marker D14S261 (multipoint nonparametric linkage score 2.36; P , 0.01; MAS 54.6%). MAS was higher in CD families in which all siblings or at least one sibling smoked compared with nonsmoking CD families (MAS, 58.90%, 57.50%, and 52.80%, respectively). Conclusions: The IBD International Genetics Consortium replicated the IBD4 locus on chromosome 14q for CD and also showed evidence for a gene-environment interaction at this locus. Further studies are needed to explore the mechanism by which smoking influences IBD4. [source] Dialectical behavior therapy for comorbid personality disordersJOURNAL OF CLINICAL PSYCHOLOGY, Issue 2 2008Thomas R. Lynch Abstract Dialectical behavior therapy (DBT) was originally designed as a treatment of emotionally dysregulated, impulsive, and dramatic disorders (e.g., borderline personality disorder) and populations (e.g., parasuicidal women). However, a number of complex disorders represent the dialectical opposite of BPD and related disorders; these disorders are characterized by being overcontrolled, emotionally constricted, perfectionistic, and highly risk-averse. In this article, the authors introduce a recent adaptation of DBT that targets cognitive,behavioral rigidity and emotional constriction and illustrates its application through the case of a man suffering from both paranoid personality disorder and obsessive,compulsive personality disorder. © 2008 Wiley Periodicals, Inc. J Clin Psychol. In Session 64: 1,14, 2008. [source] Suggestive Linkage on Chromosome 1 for a Quantitative Alcohol-Related PhenotypeALCOHOLISM, Issue 10 2002Danielle M. Dick Background Alcohol dependence is a clinically and etiologically heterogeneous disorder. Accordingly, a variety of subtypes of alcohol-dependent individuals have been proposed, and multiple operational definitions of alcohol use, abuse, and dependence have been used in linkage analyses directed toward detecting genes involved in alcohol use and problems. Here, we develop quantitative phenotypes that characterize drinking patterns among both alcoholic and nonalcoholic subjects, and use these phenotypes in subsequent linkage analyses. Methods More than 9000 individuals from alcoholic and control families were administered a semistructured interview and personality questionnaire as part of the initial stage of the Collaborative Study on the Genetics of Alcoholism (COGA). A principal component analysis was conducted on items that captured many of the dimensions of drinking and related behaviors, including aspects of alcohol use, antisocial behavior and affective disturbance when drinking, and personality. Factor scores were computed for all individuals. Nonparametric linkage analyses were conducted on these factor scores, in the initial COGA sample consisting of 987 individuals from 105 extended families, and in a replication sample consisting of 1295 individuals from 157 extended families. Results Three factors were identified, accounting for 68% of the total variance. The most promising regions of linkage appeared for factor 2, on which higher scores indicate a later age of onset of regular drinking and higher harm avoidance. Chromosome 1 yielded consistent evidence of linkage in both samples, with a maximum lod score of 3.3 when the samples were combined for analysis. Consistent suggestion of linkage also was found to chromosome 15. Conclusions Developing novel phenotypes that more accurately model the effect of influential genes may help efforts to detect genes involved in complex disorders. Applying principal component analysis in the COGA sample provided support for some regions of linkage previously reported in COGA, and identified other new, promising regions of linkage. [source] Genetics and the lower urinary tract,,NEUROUROLOGY AND URODYNAMICS, Issue 4 2010Peggy Norton Abstract Many complex disorders have been found to have a heritable component, including lower urinary tract dysfunction. Twin studies have indicated that genetic contributions to urinary incontinence (UI) may be as important as environmental influences. Linkage to chromosome 9 has been demonstrated in families with pelvic organ prolapse and stress UI. An increasing number of incontinence specialists are studying subjects with lower urinary tract dysfunction using single nucleotide polymorphisms, linkage analyses of siblings, and large association studies. These findings have exciting implications for future prevention and treatment of UI. Neurourol. Urodynam. 29:609,611, 2010. © 2010 Wiley-Liss, Inc. [source] Common Susceptibility Variants Examined for Association with Dilated CardiomyopathyANNALS OF HUMAN GENETICS, Issue 2 2010Evadnie Rampersaud Summary Rare mutations in more than 20 genes have been suggested to cause dilated cardiomyopathy (DCM), but explain only a small percentage of cases, mainly in familial forms. We hypothesised that more common variants may also play a role in increasing genetic susceptibility to DCM, similar to that observed in other common complex disorders. To test this hypothesis, we performed case-control analyses on all DNA polymorphic variation identified in a resequencing study of six candidate DCM genes (CSRP3, LDB3, MYH7, SCN5A, TCAP, and TNNT2) conducted in 289 unrelated white probands with DCM of unknown cause and 188 unrelated white controls. In univariate analyses, we identified associated common variants at LDB3 site 10779, LDB3 site 57877, MYH7 sites 16384 and 17404, and TCAP sites 140 and 1735. Multivariate analyses to examine the joint effects of multiple gene variants confirmed univariate results for MYH7 and TCAP and identified a block of nine variants in MYH7 that was strongly associated with DCM. Common variants in genes known to be causative of DCM may play a role in genetic susceptibility to DCM. Our results suggest that examination of common genetic variants may be warranted in future studies of DCM and other Mendelian-like disorders. [source] Mixed-effects Logistic Approach for Association Following Linkage Scan for Complex DisordersANNALS OF HUMAN GENETICS, Issue 2 2007H. Xu Summary An association study to identify possible causal single nucleotide polymorphisms following linkage scanning is a popular approach for the genetic dissection of complex disorders. However, in association studies cases and controls are assumed to be independent, i.e., genetically unrelated. Choosing a single affected individual per family is statistically inefficient and leads to a loss of power. On the other hand, because of the relatedness of family members, using affected family members and unrelated normal controls directly leads to false-positive results in association studies. In this paper we propose a new approach using mixed-model logistic regression, in which associations are performed using family members and unrelated controls. Thus, the important genetic information can be obtained from family members while retaining high statistical power. To examine the properties of this new approach we developed an efficient algorithm, to simulate environmental risk factors and the genotypes at both the disease locus and a marker locus with and without linkage disequilibrium (LD) in families. Extensive simulation studies showed that our approach can effectively control the type-I error probability. Our approach is better than family-based designs such as TDT, because it allows the use of unrelated cases and controls and uses all of the affected members for whom DNA samples are possibly already available. Our approach also allows the inclusion of covariates such as age and smoking status. Power analysis showed that our method has higher statistical power than recent likelihood ratio-based methods when environmental factors contribute to disease susceptibility, which is true for most complex human disorders. Our method can be further extended to accommodate more complex pedigree structures. [source] Refinement of 2q and 7p loci in a large multiplex NTD family,BIRTH DEFECTS RESEARCH, Issue 6 2008Demetra S. Stamm Abstract BACKGROUND: NTDs are considered complex disorders that arise from an interaction between genetic and environmental factors. NTD family 8776 is a large multigenerational Caucasian family that provides a unique resource for the genetic analysis of NTDs. Previous linkage analysis using a genome-wide SNP screen in family 8776 with multipoint nonparametric mapping methods identified maximum LOD* scores of ,3.0 mapping to 2q33.1,q35 and 7p21.1,pter. METHODS: We ascertained an additional nuclear branch of 8776 and conducted additional linkage analysis, fine mapping, and haplotyping. Expression data from lymphoblast cell lines were used to prioritize candidate genes within the minimum candidate intervals. Genomic copy number changes were evaluated using BAC tiling arrays and subtelomeric fluorescent in situ hybridization probes. RESULTS: Increased evidence for linkage was observed with LOD* scores of ,3.3 for both regions. Haplotype analyses narrowed the minimum candidate intervals to a 20.3 Mb region in 2q33.1,q35 between markers rs1050347 and D2S434, and an 8.3 Mb region in 7p21.1,21.3 between a novel marker 7M0547 and rs28177. Within these candidate regions, 16 genes were screened for mutations; however, no obvious causative NTD mutation was identified. Evaluation of chromosomal aberrations using comparative genomic hybridization arrays, subtelomeric fluorescent in situ hybridization, and copy number variant detection techniques within the 2q and 7p regions did not detect any chromosomal abnormalities. CONCLUSIONS: This large NTD family has identified two genomic regions that may harbor NTD susceptibility genes. Ascertainment of another branch of family 8776 and additional fine mapping permitted a 9.1 Mb reduction of the NTD candidate interval on chromosome 7 and 37.3 Mb on chromosome 2 from previously published data. Identification of one or more NTD susceptibility genes in this family could provide insight into genes that may affect other NTD families. Birth Defects Research (Part A), 2008. © 2008 Wiley-Liss, Inc. [source] Approaches to gene identification in neuro-psychiatric and other complex disordersACTA NEUROLOGICA SCANDINAVICA, Issue 2000P. Asherson No abstract is available for this article. [source] Association study of 15 novel single-nucleotide polymorphisms of the T-bet locus among Finnish asthma familiesCLINICAL & EXPERIMENTAL ALLERGY, Issue 7 2004E. Ylikoski Summary Objective T-box expressed in T cells (T-bet) is a transcription factor regulating the commitment of T helper (Th) cells by driving the cells into the Th1 direction. Abnormal Th1/Th2 balance may lead to complex disorders like asthma or autoimmune diseases. Recent studies have suggested that T-bet might be a candidate gene for asthma. This led us to screen 23 Finnish individuals for single-nucleotide polymorphisms (SNPs) in the T-bet locus and study the association between the SNPs and high serum IgE level and asthma. Methods We screened all six exons, adjacent intronic areas and 2 kb of the 5,-flanking region from 23 individuals utilizing WAVEÔ technology. To explore whether T-bet is associated in serum IgE regulation or asthma we genotyped the SNPs in a Finnish asthmatic founder population. The association analyses were made using haplotype pattern mining. Results Fifteen novel SNPs were found in the T-bet gene. Within the Finnish asthmatic founder population, there was no association between T-bet SNPs and high serum IgE level or asthma. Conclusions The genetic variability in the T-bet gene does not play a role in the pathogenesis of human asthma. Our results provide a novel panel of SNPs in T-bet and will help determine whether the SNPs have a functional role in other T cell-mediated diseases. [source] CLINICAL QUESTION: What is the best management strategy for patients with severe insulin resistance?CLINICAL ENDOCRINOLOGY, Issue 3 2010Robert K. Semple Summary Management of severe insulin resistance (IR) is a major clinical challenge in many patients with obesity or lipodystrophy, and also in rarer patients with proven or suspected genetic defects in the insulin receptor or downstream signalling. The latter group can present at any time between birth and early adult life, with a variable clinical course broadly correlated with the severity of IR. Primary insulin signalling defects are usually associated with poor weight gain rather than obesity. Initially, extreme hyperinsulinaemia produces ovarian enlargement and hyperandrogenism in women, and often fasting or postprandial hypoglycaemia. However, any hypoglycaemia gradually evolves into insulin-resistant hyperglycaemia when beta cell function declines. Optimal management of these complex disorders depends on early diagnosis and appropriate targeting of both high and low glucose levels. In newborns, continuous nasogastric feeding may reduce harmful glycaemic fluctuations, and in older patients, acarbose may mitigate postprandial hypoglycaemia. Insulin sensitization, initially with metformin but later with trials of additional agents such as thiazolidinediones, is the mainstay of early therapy, but insulin replacement, eventually with very high doses, is required once diabetes has supervened. Preliminary data suggest that rhIGF-1 can improve survival in infants with the most severe insulin receptor defects and also improve beta cell function in older patients with milder receptoropathies. The utility of newer therapies such as glucagon-like peptide-1 agonists and dipeptidyl peptidase-IV inhibitors remains untested in this condition. Thus, management of these patients remains largely empirical, and there is a pressing need to collate data centrally to optimize treatment algorithms. [source] Growth hormone deficiency and combined pituitary hormone deficiency: does the genotype matter?CLINICAL ENDOCRINOLOGY, Issue 2 2005Mehul T. Dattani Summary The past 12 years have witnessed an explosion in our understanding of the development of the anterior pituitary gland, and of mechanisms that underlie the diagnosis of growth hormone deficiency (GHD) and combined pituitary hormone deficiency (CPHD). The anterior pituitary is the end-product of a carefully orchestrated pattern of expression of signalling molecules and transcription factors that leads to the development of this complex organ secreting six hormones from five different cell types. Naturally occurring and transgenic murine models have demonstrated a role for many of these molecules in the aetiology of GHD/CPHD. These include the transcription factors HESX1, PROP1, POU1F1, LHX3, LHX4, GLI2 and SOX3. Depending upon the expression patterns of these molecules, the phenotype may consist of isolated hypopituitarism, or more complex disorders such as septo-optic dysplasia (SOD) and holoprosencephaly. The phenotype and the mode of inheritance can be highly variable. Novel mutations within the GH-1 and GHRHR genes have also shed light on the phenotype and pathogenesis of isolated GHD (IGHD). To date, genetic mutations have been identified in a modest proportion of patients with IGHD/CPHD and associated syndromes such as SOD. It is, however, clear that many genes remain to be identified, and characterization of these will further elucidate the pathogenesis of these complex conditions. [source] Psychogeriatric Research: A Conceptual Introduction to Aging and Geriatric NeurosciencePSYCHOGERIATRICS, Issue 3 2001Ramón Cacabelos Abstract: Psychogeriatrics (PG) is a multidisciplinary specialty in clinical neuroscience dealing with brain disorders in the elderly population. As any other biomedical field PG has to establish an educational and practical framework in epidemiology, etiopathogenesis, diagnosis, treatment, and social, ethical, and legal issues associated with brain aging and age-related central nervous system disorders. Understanding the molecular basis of aging will help to characterize and differentiate the fundamentals of pathological aging and psychogeriatric ailments. Modern epidemiology of age-related brain disorders have to incorporate novel diagnostic criteria, biological markers, and genetic epidemiology to its methodological armamentarium to avoid bias. Molecular genetics will help to conceptually redefine many psychogeriatric disorders depending upon its genetic component and those interacting environmental factors leading to the phenotypic expression of given diseases. Genetic testing for monogenic and complex/polygenic/multifactorials disorders has to be included in diagnostic protocols since approximately 60 to 80% of major psychogeriatric disorders are genetically driven. It is also important to distinguish mutational genetics from susceptibility genetics in order to establish novel therapeutic strategies and preventive programmes. Genomics, proteomics, and pharmacogenomics are novel fields from which PG can benefit in the areas of etiopathogenesis, diagnosis, and treatment. Drug development in PG requires updated regulations in developed countries. New pharmacological treatments for aging brain disorders are needed. Pharmacogenomics will become an optimal strategy for drug development, contributing to design a molecular psychopharmacology for the elderly, individualizing drug therapy, optimizing efficacy and safety, and reducing unnecessary costs. [source] | |||||||||||||