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Publications (6)0 Total impact

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    ABSTRACT: In response to reported schizophrenia linkage findings on chromosomes 3, 6 and 8, fourteen research groups genotyped 14 microsatellite markers in an unbiased, collaborative (New) sample of 403–567 informative pedigrees per marker, and in the Original sample which produced each finding (the Johns Hopkins University sample of 46–52 informative pedigrees for chromosomes 3 and 8, and the Medical College of Virginia sample of 156–191 informative pedigrees for chromosome 6). Primary planned analyses (New sample) were two-point heterogeneity lod score (lod2) tests (dominant and recessive affected-only models), and multipoint affected sibling pair (ASP) analysis, with a narrow diagnostic model (DSM-IIIR schizophrenia and schizoaffective disorders). Regions with positive results were also analyzed in the Original and Combined samples. There was no evidence for linkage on chromosome 3. For chromosome 6, ASP maximum lod scores (MLS) were 2.19 (New sample, nominal p = .001) and 2.68 (Combined sample, p=.0004). For chromosome 8, maximum lod2 scores (tests of linkage with heterogeneity) were 2.22 (New sample, p=.0014) and 3.06 (Combined sample, p = .00018). Results are interpreted as inconclusive but suggestive of linkage in the latter two regions. We discuss possible reasons for failing to achieve a conclusive result in this large sample. Design issues and limitations of this type of collaborative study are discussed, and it is concluded that multicenter follow-up linkage studies of complex disorders can help to direct research efforts toward promising regions.
    American Journal of Medical Genetics 12/1998; 67(6):580 - 594.
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    ABSTRACT: The present study evaluates evidence for linkage of schizophrenia to chromosome 6p24-p22. An independent sample of 211 families ascertained on the basis of having an affected sib-pair diagnosed with schizophrenia or schizoaffective disorder was assessed with seventeen polymorphic markers spanning a 37cM region. Linkage analysis was performed with parametric and non-parametric methods to test for cosegregation using 4 models of inheritance. Neither two-point nor multipoint non-parametric analyses reached significance at a level less than 0.01 for any markers examined in the region and lod score analyses were not suggestive of linkage. Based on initial findings in the present data set and recently published linkage results, two specific areas were densely covered with markers and tested for linkage disequilibrium. After correcting for multiple comparisons within each locus, no significant deviation from expected allele transmission ratios was observed. The present findings together with the published literature fail to find consistent evidence of a linkage for schizophrenia to a single locus on chromosome 6.
    American Journal of Medical Genetics 12/1996; 67(6):595-610.
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    ABSTRACT: In response to reported schizophrenia linkage findings on chromosomes 3, 6 and 8, fourteen research groups genotyped 14 microsatellite markers in an unbiased, collaborative (New) sample of 403-567 informative pedigrees per marker, and in the Original sample which produced each finding (the Johns Hopkins University sample of 40-52 informative pedigrees for chromosomes 3 and 8, and the Medical College of Virginia sample of 156-191 informative pedigrees for chromosome 6). Primary planned analyses (New sample) were two-point heterogeneity lod score (lod2) tests (dominant and recessive affected-only models), and multipoint affected sibling pair (ASP) analysis, with a narrow diagnostic model schizophrenia and schizoaffective disorders), Regions with positive results were also analyzed in the Original and Combined samples. There was no evidence for linkage on chromosome 3. For chromosome 6, ASP maximum lod scores (MLS) were 2.19 (New sample, nominal p = .001) and. 2.68 (Combined sample, p = .0004). For chromosome 8, maximum lod2 scores (tests of linkage with heterogeneity) were 2.22 (New sample, p = .0014) and 3.06 (Combined sample, p = .00018). Results are interpreted as inconclusive hut suggestive of linkage in the latter two regions. We discuss possible reasons for failing to achieve a conclusive result in this large sample, Design issues and limitations of this type of collaborative study are discussed, and it is concluded that multicenter follow-up linkage studies of complex disorders can help to direct research efforts toward promising regions.
    American Journal of Medical Genetics 11/1996; 67(6):580-594.
  • American Journal of Medical Genetics 01/1996; 67(6):595-610.
  • Psychiatric Genetics - PSYCHIATR GENET. 01/1996; 6(3).
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    C LeDuc, P Miller, J Lichter, P Parry
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    ABSTRACT: Polymorphic microsatellite markers are widely used in molecular analyses. The range of allele sizes and the allele frequencies within a population are important characteristics of the marker. Their determination previously has involved genotyping a large number of individuals. We have developed a technique for defining these characteristics by coamplification of many samples in a DNA pool. Groups of 32 and 42 DNA samples were genotyped and results were compared with those from individual genotype determinations. To improve the accuracy in the estimation of allele frequencies, arithmetic removal of stutter bands was carried out and the consistency of each marker was characterized. This approach was also applied to a group of 94 individuals. All of the work has been done using nonradioactive methods. Potential applications of this technique are in population genetics, high throughput genotyping, and loss of heterozygosity studies.
    PCR methods and applications 07/1995; 4(6):331-6.