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C J MacLean

Publications and source records attributed to C J MacLean.

At least 19 recordsLinked to original sources
PubMed2002

Genome-wide scans of three independent sets of 90 Irish multiplex schizophrenia families and follow-up of selected regions in all families provides evidence for multiple susceptibility genes.

From our linkage study of Irish families with a high density of schizophrenia, we have previously reported evidence for susceptibility genes in regions 5q21-31, 6p24-21, 8p22-21, and 10p15-p11. In this report, we describe the cumulative results from independent genome scans of three a priori random subsets of 90 families each, and from multipoint analysis of all 270 families in ten regions. Of these ten regions, three (13q32, 18p11-q11, and 18q22-23) did not generate scores above the empirical baseline pairwise scan results, and one (6q13-26) generated a weak signal. Six other regions produced more positive pairwise and multipoint results. They showed the following maximum multipoint H-LOD (heterogeneity LOD) and NPL scores: 2p14-13: 0.89 (P = 0.06) and 2.08 (P = 0.02), 4q24-32: 1.84 (P = 0.007) and 1.67 (P = 0.03), 5q21-31: 2.88 (P= 0.0007), and 2.65 (P = 0.002), 6p25-24: 2.13 (P = 0.005) and 3.59 (P = 0.0005), 6p23: 2.42 (P = 0.001) and 3.07 (P = 0.001), 8p22-21: 1.57 (P = 0.01) and 2.56 (P = 0.005), 10p15-11: 2.04 (P = 0.005) and 1.78 (P = 0.03). The degree of 'internal replication' across subsets differed, with 5q, 6p, and 8p being most consistent and 2p and 10p being least consistent. On 6p, the data suggested the presence of two susceptibility genes, in 6p25-24 and 6p23-22. Very few families were positive on more than one region, and little correlation between regions was evident, suggesting substantial locus heterogeneity. The levels of statistical significance were modest, as expected from loci contributing to complex traits. However, our internal replications, when considered along with the positive results obtained in multiple other samples, suggests that most of these six regions are likely to contain genes that influence liability to schizophrenia.

Chromosome Mapping↗
PubMed2000

The trimmed-haplotype test for linkage disequilibrium.

Single-marker linkage-disequilibrium (LD) methods cannot fully describe disequilibrium in an entire chromosomal region surrounding a disease allele. With the advent of myriad tightly linked microsatellite markers, we have an opportunity to extend LD analysis from single markers to multiple-marker haplotypes. Haplotype analysis has increased statistical power to disclose the presence of a disease locus in situations where it correctly reflects the historical process involved. For maximum efficiency, evidence of LD ought to come not just from a single haplotype, which may well be rare, but in addition from many similar haplotypes that could have descended from the same ancestral founder but have been trimmed in succeeding generations. We present such an analysis, called the "trimmed-haplotype method." We focus on chromosomal regions that are small enough that disequilibrium in significant portions of them may have been preserved in some pedigrees and yet that contain enough markers to minimize coincidental occurrence of the haplotype in the absence of a disease allele: perhaps regions 1-2 cM in length. In general, we could have no idea what haplotype an ancestral founder carried generations ago, nor do we usually have a precise chromosomal location for the disease-susceptibility locus. Therefore, we must search through all possible haplotypes surrounding multiple locations. Since such repeated testing obliterates the sampling distribution of the test, we employ bootstrap methods to calculate significance levels. Trimmed-haplotype analysis is performed on family data in which genotypes have been assembled into haplotypes. It can be applied either to conventional parent-affected-offspring triads or to multiplex pedigrees. We present a method for summarizing the LD evidence, in any pedigree, that can be employed in trimmed-haplotype analysis as well as in other methods.

Alleles↗
PubMed2000

Clinical features of schizophrenia and linkage to chromosomes 5q, 6p, 8p, and 10p in the Irish Study of High-Density Schizophrenia Families.

OBJECTIVE: Schizophrenia is clinically heterogeneous. Recent linkage studies suggest that multiple genes are important in the etiology of schizophrenia. The authors examined the hypothesis of whether the clinical variability in schizophrenia is due to genetic heterogeneity. METHOD: Using data from the Irish Study of High-Density Schizophrenia Families (N=265 pedigrees; N=1,408 individuals), the authors attempted to predict, from major symptoms and signs of psychosis, evidence for linkage within families for schizophrenia-related disorders to chromosomal regions 5q21-5q31, 6p24-6p22, 8p22-8p21, and 10p15-10p11. RESULTS: No substantial evidence was found for associations between clinical features of schizophrenia and linkage to chromosomes 5q, 6p, or 10p. However, affected individuals from families with evidence for linkage to 8p had significantly more affective deterioration, poorer outcome, more thought disorder, and fewer depressive symptoms than affected individuals from the other families in the study. CONCLUSIONS: These results raise the possibility that the putative susceptibility gene for schizophrenia localized in the 8p22-8p21 region may predispose individuals to the core dementia-praecox syndrome described by Kraepelin more than 100 years ago.

Chromosomes, Human, Pair 10↗
PubMed2000

Sibling correlation of deficit syndrome in the Irish study of high-density schizophrenia families.

OBJECTIVE: The deficit syndrome is a subtype of schizophrenia characterized by primary and enduring negative features of psychopathology. It appears to reflect a distinct subtype within the syndrome of schizophrenia. Little is known about the familial or genetic aspects of the deficit syndrome. The purpose of this study was to determine whether deficit versus nondeficit subtypes are correlated in sibling pairs affected with schizophrenia. METHOD: The present study was based on the Irish Study of High-Density Schizophrenia Families. From the earlier study the authors selected a subset of patients who were members of sibling pairs in which both siblings had been diagnosed with "core" schizophrenia, which included schizophrenia, simple schizophrenia, and schizoaffective disorder with poor outcome. The Schedule for the Deficit Syndrome was used to make deficit versus nondeficit diagnoses, which were based on chart examinations by reviewers blind to sibling status. This method resulted in 65 patients being diagnosed with the deficit syndrome and 401 patients diagnosed as nondeficit (prevalence=13.9%). This group included 347 full sibling pairs, which were analyzed for resemblance with respect to deficit versus nondeficit subtype by means of logistic regression. RESULTS: Deficit versus nondeficit subtypes were significantly correlated in sibling pairs concordant for core schizophrenia. CONCLUSIONS: Familial factors contribute significantly to whether a person has the deficit subtype of schizophrenia. This familial contribution could be genetic or environmental.

Adult↗
PubMed1999

Marker-to-marker linkage disequilibrium on chromosomes 5q, 6p, and 8p in Irish high-density schizophrenia pedigrees.

Linkage disequilibrium (LD) is a potentially powerful tool for the localization of disease genes for complex disorders. Most prior studies of the relationship between genetic distance and LD have examined only very short distances, focusing on the role of LD in fine-mapping and positional cloning. We examine here the relationship between marker-to-marker (M-M) LD and somewhat greater genetic distances. We analyzed 622 M-M pairings on chromosomes 6p, 8p, and 5q in 265 native Irish pedigrees ascertained for a high density of schizophrenia. LD, significant at the 5% level, was found for 96% of all M-M pairings within 0.5 cM, for 67% within 0.5-1 cM, for 35% within 1-2 cM, for 15% within 2-4 cM, for 8% within 5-10 cM, and for 7% above 10 cM. Thus, in Irish families selected for a high density of schizophrenia, M-M LD may be very common within 0.5 cM and frequent up to distances of 2 cM.

Chromosomes, Human, Pair 5↗
PubMed1999

Replication of linkage studies of complex traits: an examination of variation in location estimates.

In linkage studies, independent replication of positive findings is crucial in order to distinguish between true positives and false positives. Recently, the following question has arisen in linkage studies of complex traits: at what distance do we reject the hypothesis that two location estimates in a genomic region represent the same gene? Here we attempt to address this question. Sampling distributions for location estimates were constructed by computer simulation. The conditions for simulation were chosen to reflect features of "typical" complex traits, including incomplete penetrance, phenocopies, and genetic heterogeneity. Our findings, which bear on what is considered a replication in linkage studies of complex traits, suggest that, even with relatively large numbers of multiplex families, chance variation in the location estimate is substantial. In addition, we report evidence that, for the conditions studied here, the standard error of a location estimate is a function of the magnitude of the expected LOD score.

Chromosome Mapping↗
PubMed1998

A schizophrenia locus may be located in region 10p15-p11.

In our genomic scan of 265 Irish families with schizophrenia, we have thus far generated modest evidence for the presence of vulnerability genes in three chromosomal regions, i.e., 5q21-q31, 6p24-p22, and 8p22-p21. Outside of those regions, of all markers tested to date, D10S674 produced one of the highest pairwise heterogeneity lod (H-LOD) scores, 3.2 (P = 0.0004), when initially tested on a subset of 88 families. We then tested a total of 12 markers across a region of 32 centimorgans in region 10p15-p11 of all 265 families. The strongest evidence for linkage occurred assuming an intermediate phenotypic definition, and a recessive genetic model. The largest pairwise H-LOD score was found with marker D10S2443 (maximum 1.95, P = 0.005). Using multipoint H-LODs, we found a broad peak (maximum 1.91, P = 0.006) extending over the 11 centimorgans from marker D10S674 to marker D10S1426. Multipoint nonparametric linkage analysis produced a much broader peak, but with the maximum in the same location near D10S2443 (maximum z = 1.88, P = 0.03). Based on estimates from the multipoint analysis, this putative vulnerability locus appears to be segregating in 5-15% of the families studied, but this estimate should be viewed with caution. When evaluated in the context of our genome scan results, the evidence suggests the possibility of a fourth vulnerability locus for schizophrenia in these Irish families, in region 10p15-p11.

Chromosome Mapping↗
PubMed1998

Parental genotype reconstruction: applications of haplotype relative risk to incomplete parental data.

Intended to resolve the problem of constructing a matched population-based control sample, haplotype relative risk techniques frequently suffer from loss of power for late-onset diseases due to unavailability of parental genotypes that are required to form parent-offspring pairs. However, much of this missing information can be reconstructed using the genotypes of the affected individual's siblings. For some cases, an estimate of the marker-allele frequencies for controls is needed. We have developed a technique based upon this idea and call it PGR (Parental Genotype Reconstruction). PGR represents a combination of the internal controls used by haplotype relative risk and controls based upon estimated allele frequencies. Although the latter is just what haplotype relative risk was designed to avoid, PGR has the potential to substantially boost power to detect linkage disequilibrium, for a relatively small increase in type I error. This performance is reasonably robust with respect to errors in the estimated allele frequencies, as we demonstrate by numerical simulation. A PGR software package has been written in FORTRAN and is available from Dr. Martin's web site at http://electro.psi.vcu.edu/rmartin/.

Alleles↗
PubMed1997

The determinants of parenting: an epidemiological, multi-informant, retrospective study.

BACKGROUND: To understand the relationship between parenting and psychopathology in offspring, it is critical to clarify the determinants of parenting behaviour itself. METHODS: A 16-item version of the Parental Bonding Instrument (PBI) was administered to parents of epidemiologically sampled adult female-female twin pairs, who reported on the parenting they provided to their twins, and to the twins themselves who reported on the parenting they and their co-twin had received (N = 828 twin families). Using a mixed-model regression, we examined the impact on parenting, as retrospectively reported by parents and twins, of six variable domains: demographic factors, family characteristics, parental symptoms and personality, parental psychopathology, child vulnerability and childhood temperament. RESULTS: The PBI yielded three factors: warmth (W), protectiveness (P) and authoritarianism (A). W was most strongly predicted by parental personality and psychopathology, parental marital quality, and child temperament. P and A were both most strongly predicted by parental educational level and religious fundamentalism. In addition, P was predicted by neurotic/anxious traits in both parent and child. For a number of variables that predicted W, the strength of the association was stronger when twins were reporting than when parents were reporting. CONCLUSIONS: Parenting is a complex, multi-determined set of behaviours that is influenced by parental personality, psychopathology, values and marital quality and by a range of child characteristics. W appears to be strongly influenced by parental and childhood temperament and vulnerability to psychiatric illness while P and A are more strongly influenced by 'sociological' factors such as religious affiliation and educational status.

Adolescent↗
PubMed1997

Support for a possible schizophrenia vulnerability locus in region 5q22-31 in Irish families.

In our genome scan for schizophrenia genes in 265 Irish pedigrees, marker D5S818 in 5q22 produced the second best result of the first 223 markers tested (P = 0.002). We then tested an additional 13 markers and the evidence suggests the presence of a vulnerability locus for schizophrenia in region 5q22-31. This region appears to be distinct from those chromosome 5 regions studied in two prior reports, but the same as that producing positive results in the report by Wildenauer and colleagues found elsewhere in this issue. The largest pairwise heterogeneity LOD (H-LOD) score was found with marker D5S393 (max 3.04, P = 0.0005), assuming a narrow phenotypic category, and a genetic model with intermediate heterozygotic liability. In marked contrast to the H-LOD scores from our sample with markers from the regions of interest on chromosomes 6p and 8p, expanding the disease definition to include schizophrenia spectrum or nonspectrum disorders produced substantially smaller scores, with a number of markers failing to yield positive values at any recombination fraction. Using multipoint H-LODS, the strongest evidence for linkage occurs under the narrow phenotypic definition and recessive genetic model, with a peak at marker D5S804 (max 3.35, P = 0.0002). Multipoint nonparametric linkage analysis produced a peak in the same location (max z = 2.84, P = 0.002) with the narrow phenotypic definition. This putative vulnerability locus appears to be segregating in 10-25% of the families studied, but this estimate is tentative. Comparison of individual family multipoint H-LOD scores at the regions of interest on chromosomes 6p, 8p and 5q showed that only a minority of families yield high lod scores in two or three regions.

Chromosomes, Human, Pair 5↗
PubMed1997

Resemblance of psychotic symptoms and syndromes in affected sibling pairs from the Irish Study of High-Density Schizophrenia Families: evidence for possible etiologic heterogeneity.

OBJECTIVE: The authors sought to determine whether the clinical manifestations of schizophrenia and other psychotic disorders are correlated in affected sibling pairs. METHOD: They examined, in 256 sibling pairs concordant for DSM-III-R schizophrenia and 457 sibling pairs concordant for all nonaffective psychoses ascertained in the Irish Study of High-Density Schizophrenia Families, similarity for 1) symptoms, course, and outcome; 2) symptom factors; and 3) syndromes, defined by latent class analysis. RESULTS: Global course and outcome, as well as all major symptoms except hallucinations, were modestly but significantly correlated in sibling pairs concordant for schizophrenia. Three symptom factors-negative symptoms, positive symptoms, and affective symptoms-were all significantly correlated in concordant sib pairs. Latent class analysis suggested five schizophrenic syndromes. Class membership was significantly correlated in concordant sibling pairs. Similar results were found for sibling pairs concordant for nonaffective psychoses. CONCLUSIONS: The clinical manifestations of the schizophrenic syndrome (both narrowly and broadly defined) are moderately influenced by familial factors. From a familial/genetic perspective, schizophrenia as currently defined may be etiologically heterogeneous.

Adult↗
PubMed1996

Trials of the beta model for complex inheritance.

Theoretical advantages of nonparametric logarithm of odds to map polygenic diseases are supported by tests of the beta model that depends on a single logistic parameter and is the only model under which paternal and maternal transmissions to sibs of specified phenotypes are independent. Although it does not precisely describe recurrence risks in monozygous twins, the beta model has greater power to detect family resemblance or linkage than the more general delta model which describes the probability of 0, 1, or 2 alleles identical by descent (ibd) with two parameters. Available data on ibd in sibs are consistent with the beta model, but not with the equally parsimonious but less powerful gamma model that assumes a fixed probability of 1/2 for 1 allele ibd. Additivity of loci on the liability scale is not disproven. A simple equivalence extends the beta model to multipoint analysis.

Alleles↗
PubMed1996

Irish study on high-density schizophrenia families: field methods and power to detect linkage.

Large samples of multiplex pedigrees will probably be needed to detect susceptibility loci for schizophrenia by linkage analysis. Standardized ascertainment of such pedigrees from culturally and ethnically homogeneous populations may improve the probability of detection and replication of linkage. The Irish Study of High-Density Schizophrenia Families (ISHDSF) was formed from standardized ascertainment of multiplex schizophrenia families in 39 psychiatric facilities covering over 90% of the population in Ireland and Northern Ireland. We here describe a phenotypic sample and a subset thereof, the linkage sample. Individuals were included in the phenotypic sample if adequate diagnostic information, based on personal interview and/or hospital record, was available. Only individuals with available DNA were included in the linkage sample. Inclusion of a pedigree into the phenotypic sample required at least two first, second, or third degree relatives with non-affective psychosis (NAP), one whom had schizophrenia (S) or poor-outcome schizo-affective disorder (PO-SAD). Entry into the linkage sample required DNA samples on at least two individuals with NAP, of whom at least one had S or PO-SAD. Affection was defined by narrow, intermediate, and broad criteria. The phenotypic sample contained 277 pedigrees and 1,770 individuals and the linkage sample 265 pedigrees and 1,408 individuals. Using the intermediate definition of affection, the phenotypic sample contained 837 affected individuals and 526 affected sibling pairs. Parallel figures for the linkage sample were 700 and 420. Individuals with schizophrenia from these multiplex pedigrees resembled epidemiologically sampled cases with respect to age at onset, gender distribution, and most clinical symptoms, although they were more thought-disordered and had a poorer outcome. Power analyses based on the model of linkage heterogeneity indicated that the ISHDSF should be able to detect a major locus that influences susceptibility to schizophrenia in as few as 20% of families. Compared to first-degree relatives of epidemiologically sampled schizophrenic probands, first-degree relatives of schizophrenic members from the ISHDSF had a similar risk for schizotypal personality disorder, affective illness, alcoholism, and anxiety disorder. With sufficient resources, large-scale ascertainment of multiplex schizophrenia pedigrees is feasible, especially in countries with catchmented psychiatric care and stable populations. Although somewhat more severely ill, schizophrenic members of such pedigrees appear to clinically resemble typical schizophrenic patients. Our ascertainment process for multiplex schizophrenia families did not select for excess familial risk for affective illness or alcoholism. With its large sample ascertained in a standardized manner from a relatively homogeneous population, the ISHDSF provides considerable power to detect susceptibility loci for schizophrenia.

Adult↗
PubMed1996

A combined analysis of D22S278 marker alleles in affected sib-pairs: support for a susceptibility locus for schizophrenia at chromosome 22q12. Schizophrenia Collaborative Linkage Group (Chromosome 22).

Several groups have reported weak evidence for linkage between schizophrenia and genetic markers located on chromosome 22q using the lod score method of analysis. However these findings involved different genetic markers and methods of analysis, and so were not directly comparable. To resolve this issue we have performed a combined analysis of genotypic data from the marker D22S278 in multiply affected schizophrenic families derived from 11 independent research groups worldwide. This marker was chosen because it showed maximum evidence for linkage in three independent datasets (Vallada et al., Am J Med Genet 60:139-146, 1995; Polymeropoulos et al., Neuropsychiatr Genet 54:93-99, 1994; Lasseter et al., Am J Med Genet, 60:172-173, 1995. Using the affected sib-pair method as implemented by the program ESPA, the combined dataset showed 252 alleles shared compared with 188 alleles not share (chi-square 9.31, 1df, P = 0.001) where parental genotype data was completely known. When sib-pairs for whom parental data was assigned according to probability were included the number of alleles shared was 514.1 compared with 437.8 not shared (chi-square 6.12, 1df, P = 0.006). Similar results were obtained when a likelihood ratio method for sib-pair analysis was used. These results indicate that may be a susceptibility locus for schizophrenia at 22q12.

Alleles↗
PubMed1996

Age-related changes in stroke risk in men with hypertension and normal blood pressure.

BACKGROUND AND PURPOSE: Stroke is a major contributor to total morbidity and mortality in older individuals, and hypertension is an important risk factor for stroke. Relatively few data exist on whether this relationship changes with age. METHODS: To examine age-related changes in the relationships between risk of stroke and hypertension, we examined the 6-year incidence of stroke among men aged 45 to 81 years using updated blood pressure data from three examinations of Japanese-American men from the Honolulu Heart Program. RESULTS: Both the prevalence of hypertension (systolic blood pressure > or = 160 mm Hg or diastolic blood pressure > or = 95 mm Hg or the use of antihypertensive medication) and the 6-year incidence of stroke increased significantly with increasing age (P < .01). The increase in thromboembolic stroke incidence with age was more marked in those who were normotensive at baseline (2.7/1000 in those aged 45 to 54 years to 23.9/1000 in those > or = 65 years; P < .001) than in hypertensive men (20.6/1000 in those aged 45 to 54 years to 33.5/1000 in those > or = 65 years; P < .01). The age-related increase in risk of thromboembolic stroke among normotensive men resulted in a decrease in the percentage of strokes attributable to hypertension (50% in those aged 45 to 54 years to 18% in those > or = 65 years; P < .05). Similar trends were seen for hemorrhagic stroke. There were no age-related changes in the relationships of other major atherosclerotic risk factors with stroke. The hypertension/stroke relationships were present after multivariate adjustment for age, smoking, cholesterol, and other factors. CONCLUSIONS: In view of the greater prevalence of hypertension and the proven efficacy of treatment in the elderly, these findings do not negate the value of aggressive screening and treatment of hypertension in this age group. However, it appears that other unidentified factors have an increasing role in the causation of stroke with advancing age.

Age Factors↗
PubMed1996

Evidence for a schizophrenia vulnerability locus on chromosome 8p in the Irish Study of High-Density Schizophrenia Families.

OBJECTIVE: This study was an attempt to replicate evidence for a vulnerability locus for schizophrenia and associated disorders in the 8p22-21 region reported by Pulver and colleagues. METHOD: The linkage sample of the Irish Study of High-Density Schizophrenia Families consists of 265 multiplex families containing 1,408 individuals. Fifteen markers covering 30 centimorgans on chromosome 8p were tested. Three statistical methods were used: two-point and multipoint heterogeneity lod scores and a multipoint nonparametric test. RESULTS: According to two-point heterogeneity lod scores, the strongest evidence for linkage was found for markers D8S1731 (maximum lod score = 2.00), D8S1715 (maximum lod score = 2.52), and D8S133 (maximum lod score = 2.08) by assuming a phenotypic definition of all psychiatric illness and a range of genetic models. According to multipoint heterogeneity lod scores, the strongest evidence for linkage (maximum lod score = 2.34), found by using a dominant genetic model and a broad definition of the schizophrenia spectrum, extended over a 10-cM region between markers D8S1715 and D8S1739. Multipoint nonparametric linkage found the strongest evidence (maximum z = 2.51) over a broader region when either a diagnosis of core schizophrenia or a narrow definition of the schizophrenia spectrum was used. This putative vulnerability locus was segregating in 10%-25% of the families studied. CONCLUSIONS: This study supports the existence of a vulnerability locus for schizophrenia on chromosome 8p. In this sample, this locus appears to influence the risk of illness in only a modest proportion of families and predisposes to a range of schizophrenia spectrum and possibly nonspectrum disorders.

Chromosomes, Human, Pair 8↗