Lack of association between schizophrenia and a CAG repeat polymorphism of the hSKCa3 gene in a north eastern US sample.
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Biomedical subjects
Publications and source records attributed to I I Gottesman.
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Relatives of schizophrenia patients have demonstrated several different types of subtle communication disturbances. This study used twin methodology to address the question of whether certain of these disturbances might be reflective of genetic vulnerability. Verbatim interviews from a sample of monozygotic and dizygotic twins in which at least one member of each twin pair had a diagnosis of schizophrenia were rated for three different types of referential communication disturbances. Monozygotic versus dizygotic nonschizophrenic co-twins were compared on each type of disturbance. Associations between the language variables and object sorting test performance also were examined. Differences among subjects in levels of global psychopathology were controlled. Schizophrenic participants showed higher levels of communication disturbance than nonschizophrenic co-twins. One type of communication failure, the "missing information" reference, discriminated monozygotic from dizygotic nonschizophrenic co-twins. This type of failure was associated with specific types of errors on the object sorting test. These findings suggest that missing information references may be an expression of schizophrenia-related genetic vulnerability.
Twin studies have been vital for establishing an important genetic contribution to the etiology of schizophrenia. The five newest studies since 1995 from Europe and Japan have confirmed earlier findings. They yielded probandwise concordance rates of 41-65% in monozygotic (MZ) pairs and 0-28% in dizygotic (DZ) pairs, and heritability estimates of approximately 80-85%. Twin studies are also valuable for investigating the etiological relationships between schizophrenia and other disorders, and the genetic basis of clinical heterogeneity within schizophrenia. Studies of discordant MZ pairs provide further insights into non-inherited factors that contribute to the multifactorial etiology of this disorder. More recently, twin studies have begun to be used to directly investigate molecular genetic and epigenetic processes underlying schizophrenia.
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The polymorphism at the multitude of loci adjacent to human endogenous retrovirus long terminal repeats (LTRs) was analyzed by a technique for whole genome differential display based on the PCR suppression effect that provides selective amplification and display of genomic sequences flanking interspersed repeated elements. This strategy is simple, target-specific, requires a small amount of DNA and provides reproducible and highly informative data. The average frequency of polymorphism observed in the vicinity of the LTR insertion sites was found to be about 12%. The high incidence of polymorphism within the LTR flanks together with the frequent location of LTRs near genes makes the LTR loci a useful source of polymorphic markers for gene mapping.
BACKGROUND: Previous twin studies have supported a genetic contribution to the major categories of psychotic disorders, but few of these have employed operational diagnostic criteria, and no such study has been based on a sample that included the full range of functional psychotic disorders. METHODS: A total of 224 twin probands (106 monozygotic, 118 dizygotic) with a same-sex co-twin and a lifetime history of psychosis was ascertained from the service-based Maudsley Twin Register in London, England. Research Diagnostic Criteria psychotic diagnoses were made on a lifetime-ever basis. Main-lifetime diagnoses of DSM-III-R and International Statistical Classification of Diseases, 10th Revision schizophrenia were also made. Probandwise concordance rates and correlations in liability were calculated, and biometrical model fitting applied. RESULTS: A substantial genetic contribution to variance in liability was confirmed for the major diagnostic categories except Research Diagnostic Criteria depressive psychosis and unspecified functional psychosis, where familial transmission was confirmed, but the relative contribution of genetic and common environmental factors was unclear. Heritability estimates for Research Diagnostic Criteria schizophrenia, schizoaffective disorder, mania, DSM-III-R schizophrenia, and International Statistical Classification of Diseases, 10th Revision schizophrenia were all between 82% and 85%. None of the estimates differed significantly from any other. CONCLUSIONS: Heritability estimates for schizophrenia, schizoaffective disorder, and mania were substantial and similar. Population morbid risk estimates were inferred rather than directly measured, but the results were very similar to those from studies where morbid risks were directly estimated.
In an electroencephalographic (EEG) study of 27 pairs of monozygotic (MZ) twins discordant for schizophrenia, 13 pairs of MZ twins concordant for schizophrenia, 40 pairs of healthy MZ twins, and 91 healthy, unrelated subjects with repeated assessments, we investigated (a) the trait quality of brainwave patterns with respect to interindividual differences, intraindividual stability over time, and within-pair MZ concordance; (b) the EEG characteristics that enable discrimination between affected and unaffected individuals; and (c) the EEG characteristics that reflect the severity of illness. In comparison with healthy control subjects, the MZ twins who were discordant and concordant for schizophrenia exhibited a much lower within-pair EEG concordance, so that EEG abnormalities associated with schizophrenia and manifested differently in the co-twins concordant for schizophrenia seemed to reflect nongenetic, pathological developments of genetically identical brains.
A large sample of identical and fraternal twins who had been reared apart was used to examine the genetic and environmental architecture of the MMPI Subtle-Obvious and Harris-Lingoes subscales. Univariate genetic analyses indicated significant heritability for all 28 of the Harris-Lingoes subscales (estimates ranged from.23 to.61), all five Obvious subscales (estimates ranged from.37 to.56) and four of the five Subtle subscales (estimates ranged from.27 to.35). Two randomly constructed scales were analyzed as controls; neither of these scales showed significant heritability. Exploratory correlational findings suggested that three of the Wiener-Harmon Subtle subscales may tap aspects of psychological health, naivete, or repression. Ma-S may come closest to Wiener and Harmon s intent. Although they apparently diverge from their original purpose, it may be too early to abandon the low face valid items of the Subtle subscales.
Many diseases caused by trinucleotide expansion exhibit increased severity and decreased age of onset (genetic anticipation) in successive generations. Apparent evidence of genetic anticipation in schizophrenia has led to a search for trinucleotide repeat expansions. We have used several techniques, including Southern blot hybridization, repeat expansion detection (RED) and locus-specific PCR to search for expanded CAG/CTG repeats in 12 families from the United Kingdom and 11 from Iceland that are multiplex for schizophrenia and demonstrate anticipation. The unstable DNA theory could also explain discordance of phenotype for schizophrenia in pairs of monozygotic twins, where the affected twin has a greater number of repeats than the unaffected twin. We used these techniques to look for evidence of different CAG/CTG repeat size in 27 pairs of monozygotic twins who are either concordant or discordant for schizophrenia. We have found no evidence of an increase in CAG/CTG repeat size for affected members in the families, or for the affected twins in the MZ twin sample. Southern hybridization and RED analysis were also performed for the twin and family samples to look for evidence of expansion of GAA/TTC repeats. However, no evidence of expansion was found in either sample. Whilst these results suggest that these repeats are not involved in the etiology of schizophrenia, the techniques used for detecting repeat expansions have limits to their sensitivity. The involvement of other trinucleotide repeats or other expandable repeat sequences cannot be ruled out.
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BACKGROUND: The New York High-Risk Project is a study of offspring of patients with schizophrenia (HRSz group) or affective illness (HRAff group) and psychiatrically normal parents (NC group) observed prospectively from childhood to adulthood. We herein present lifetime prevalence and comorbidity rates of Axis I disorders in subjects and their siblings from sample A of the project. METHODS: Schedule for Affective Disorders and Schizophrenia-Lifetime Version interviews conducted with the offspring in adulthood were used to obtain diagnoses of Axis I disorders. RESULTS: Schizophrenia and unspecified psychoses occurred only in the HRSz group. However, schizoaffective and psychotic affective disorders occurred equally in the HRSz and HRAff groups. Total rates of psychosis in these groups were significantly higher than in the NC group. All groups had similar rates of nonpsychotic affective and substance abuse disorders. The HRAff group, however, had significantly more total affective illness than the NC group and tended to have more anxiety disorders than the other groups. Comorbidity rates in the HRSz and HRAff groups were nearly twice those of the NC group. CONCLUSIONS: The familial liabilities to schizophrenia and affective disorders show specificities and commonalities, differing markedly from each other in their expression of some disorders and sharing others. Patterns of comorbidity are generally, although not entirely, similar to these liabilities.
We evaluate the usefulness of 11 key epigenetic concepts from the behavior genetic research paradigm for advancing the field of developmental psychopathology. Key assumptions, empirical examples, and caveats in interpreting results are presented. We emphasize the usefulness of incorporating both dimensional (e.g., temperament trait) and categorical (e.g., diagnosis) variables, environmental measures, direct behavioral assessments, and multiple, theoretically relevant occasions of study into classic twin and family studies. We highlight contemporary techniques for identifying specific chromosomal regions associated with behavioral patterns, and the importance of considering nonmendelizing genetic influences when discerning the panorama of genetic influences on behavior.
The field of behavioral genetics has enormous potential to uncover both genetic and environmental influences on normal and deviant behavior. Behavioral-genetic methods are based on a solid foundation of theories and methods that successfully have delineated components of complex traits in plants and animals. New resources are now available to dissect the genetic component of these complex traits. As specific genes are identified, we can begin to explore how these interact with environmental factors in development. How we interpret such findings, how we ask new questions, how we celebrate the knowledge, and how we use or misuse this knowledge are all important considerations. These issues are pervasive in all areas of human research, and they are especially salient in human behavioral genetics.
Genetic factors make important contributions to the etiologies of schizophrenia. The mode of familial inheritance remains unknown, but it is highly likely that multiple genes and idiosyncratic environmental factors are involved. Rapidly evolving genetic technologies have been applied in the genetic analysis of schizophrenia, and several genomic regions have been posited as harboring susceptibility genes. Currently, the strongest evidence implicates chromosomes 6 and 8, but these linkages are not yet confirmed. In this article we discuss genetic risk factors, gene-environment interaction, the feasibility of genetic testing, psychiatric genetic counseling, and the dangers of genetic discrimination as they apply to schizophrenia. We also address and correct specific misconceptions about the genetics of schizophrenia held by many in the scientific community and in the media, and discuss a blueprint for future genetic research and informed dissemination of findings to the public and to lawmakers.
Given both the rapid rise in the prevalence of HIV infection among adolescent and adult males (0.6%) and females (0.1%) in the United States from 1984 to 1992 and the associations among HIV, injection drug abuse, homosexuality, and sexual promiscuity, it is important to determine whether individuals diagnosed with schizophrenia are at a higher than average risk of HIV infection. Stereotypes from the recent past about sexuality in both male and female patients were examined as an integral part of a literature review. Data from a dozen or so studies conducted since 1990 confirm and strengthen the impressions that persons with schizophrenia should be considered a group with a much higher than average risk for developing HIV/AIDS and that they have special needs for protection as a public health measure. Mental health service providers need to be aware of these findings.