8. Genetics, Basic GENETIC VARIATION IN THE ALPHA-2A ADRENERGIC RECEPTOR MAY PLAY A ROLE IN THE AETIOLOGY OF SCHIZOPHRENIA M.J. Arranz, R. Murray,
A. Bolonna, R. Ketwin
Department of Psychological London SE5. UK
A BRAIN-SPECIFIC 14-3-3 PROTEIN GENE, YWHAH, IS MUTATION SCREENED IN TWO SCHIZOPHRENIC FAMILIES FORM THE INTERMOUNTAIN WEST Bennett,
Department Utah 84132
AN INVESTIGATION OF A STRUCTURAL POLYMORPHISM IN THE mGLuR7 GENE IN ASSOCIATION
Evidence, including altered levels, increased affinity and abnormal function of alpha-2A (aZA) adrenergic receptors in schizophrenic patients (Hayashi et al., 1997; Meana et al., 1992; Rice et al., 1994) suggest that these neuroreceptors may be related to the aetiology of the illness. In addition, antiadrenergicand adrenergic-blocking drugs are used for the treatment of disorders of thought, mood, anxiety, and movement. Therefore, variation in the genes coding for these neuroreceptors could play a role in the illness or in the individual’s response to psychiatric treatment. Two polymorphisms in the promoter region of the receptor gene (-1291-C/G and -261-G/A) have been identified (Bono et al., 1996; Lario et al., 1997) which could be related to the altered levels of expression observed in schizophrenic patients and may influence treatment response. In a preliminary study, no relation was observed between these polymorphisms and clinical response in a sample of clozapine-treated patients (125). However, comparisons of a larger sample (261 patients) versus controls (89) revealed that individuals homozygous for the -1291-G allele were more frequent in the schizophrenic group ( x2p = 0.04). This finding supports the hypothesis that alterations in cc,,-adrenergic genes may contribute to the aetiology of the disease.
activation of tyrosine and tryptophan hydroxylases, among other functions. The 14-3-3 eta chain gene has two exons, totalling approximately 2 kb. The 5’ flanking region contains numerous regulatory elements, including GC and CAAT boxes. Mutation screening of the two exons and 5’ flanking region was carried out in two affected members of each family and two Caucasian controls. Polymorphisms have been identified and are being analyzed to test for an association with the inhibitory phenotype in these families.
A.A. Bolonna, A.J. Markoff, J. Munro, G. Kirov, R.W. Kerwin Section of Clinical Neuropharmacology, Department Psychological Medicine, Institute of Psychiatry, London SE5 8AF, UK
In addition to the serotonergic and dopaminergic systems, a dysfunctional glutamatergic system has been implicated in the aetiology of schizophrenia. Although observations from binding and messenger RNA-expressions studies of the NMDA and non-NMDA receptors provide evidence for abnormal functioning of glutamate receptors, the precise role of glutamate in the disorder remains unclear. Taking into account these studies and the hypothesis that schizophrenia is a multifactorial illness, the genes encoding the glutamate-receptor family are candidate genes in its aetiology. We have analysed a structural polymorphism (Phe433Tyr) in the gene encoding the metabotropic glutamate-receptor type 7(mGluR7) for association with schizophrenia. The same population was composed of 181 patients of W. European origin with a DSMIII/IVR classification and 95 ethnically-matched controls. No significant association was observed in the genotype or allele frequencies of the Phe433Tyr polymorphism. In conclusion, the mGlur7 gene does not appear to play a role in the aetiology of schizophrenia.
LINKAGE OF FAMILIAL TO CHROMOSOME 134
W. Byerley of Utah, Sait Lake
Schizophrenia is a complex, multi-factorial syndrome that affects 1% of the world’s population, with devastating results. Twin and adoption studies have indicated that a substantial amount of liability to the disease is inherited. Linkage analysis, using a composite inhibitory phenotype (antisaccade and P50 sensory gating) and genotypes along chromosome 22 in two Utah multiplex families, has resulted in a lod score of 3.55 which maximizes at D22S315 (22q11.2-12.1). This region includes a brain-specific 14-3-3 protein that is involved in the
L.M. Brzustowicz, W.G. Honer, E.W.C. Chow, S.A. Roberts, D. Little, J. Hayter, M. Kahn, L.E. Scutt, J. Hogan, K. Hodgkinson, A.S. Bassett Center for University, USA
Molecular and Behavioral Neuroscience, Rutgers 197 University Avenue, Newark, New Jersey 07102,
Recent studies have suggested that an autosomal recessive schizophrenia susceptibility locus is located at chromosome 13q32. We evaluated 11 genetic markers spanning chromosome 13 for evidence of linkage to schizophrenia in 21 Canadian families (n = 261 subjects). Markers were from the Cooperative
Human Linkage Center linkage mapping screening set, with average spacing of 10 CM and average heterozygosity of 0.76. Families were analyzed using FASTLINK under both autosoma1 dominant and recessive models, using broad and narrow definitions of schizophrenia. Maximum 2-point LOD scores under the hypothesis of genetic homogeneity were: dominant, narrow model: 0.74 at theta=0.2 with Dl3S317; dominant, broad model: 0.17 at theta =0.3 with Dl38796; recessive, narrow model: 0.82 at theta =0.2 with Dl3S793; recessive, broad model: 1.92 at theta = 0.1 with Dl33793. Three-point analysis using broad disease definitions under the recessive model and with the assumption of genetic homogeneity produced a maximal LOD score of 3.51 within the 14 CM interval between the markers Dl3S317 and Dl3S793. Under the hypothesis of heterogeneity, the maximum 3-point LOD score under this model was 3.78 at Dl3S317 with alpha=0.65, although the hypothesis of heterogeneity was not significantly supported. These results replicate linkage of a schizophrenia susceptibility locus at 13q32. Further refining of the genetic localization of this locus may lead to the isolation of the involved schizophrenia susceptibility gene.
THE HISTAMINERGIC SYSTEM, SCHIZOPHRENIA, AND ANTIPSYCHOTIC DRUG RESPONSE D. Mancama, J. Munro, M.J. Arranz, A. Makoff, R. Kenvin Section of Clinical Neuropharmacology, Department of Psychological Medicine, Institute of Psychiatry, De Crespigny Park, London SE5 SAF, UK
Histamine 1 (Hl), histamine 2 (H2) and histamine 3 (H3) receptors mediate the effects of the histaminergic signalling system. Reduced Hl-receptor densities have been found in the brain of some schizophrenic individuals, which an association has been reported between the H2-receptor 649-G allele and schizophrenia. We are investigating the potential role of the histaminergic system in schizophrenia and in patient response to clozapine treatment. Mutation screening of the Hl-receptor promoter and coding regions revealed five novel polymorphisms: -11-C/T, Lysl9Asp, Asp349Glu, 1067-A/G, and Leu449Ser, while similar work on the H2 receptor identified four novel changes: -1077-G/A, -1018-G/A, -592-A/G, and 542-G/A. The coding polymorphisms were found to be relatively rare (all less than 7%) in both the control and schizophrenic individuals studied. Mutations within the promoter regions of the two receptors were found to be more frequent in the same group of individuals. The most frequent mutantpromoter allele (H 1 -17-T allele) was detected in 33% and 28% of the control and schizophrenics respectively. No association, however, could be found between the nine Hl- and HZ-receptor polymorphisms and schizophrenia, nor with patient response to clozapine treatment.
ROLE OF A POLYMORPHIC SEQUENCE ASSOCIATED WITH PSYCHIATRIC DISEASES IN TYROSINE HYDROXYLASE GENE REGULATION R. Meloni, V. Alban&se, J. Voisin, F. Treilhou, N. Faucon-Biguet, J. Mallet L.G.N.-C. France
N. R.S., H6pital
de la Piti&Salpt?tri.?re,
The tyrosine hydroxylase (TH) gene is pivotal in the synthesis of catecholamines and is thus a candidate gene for neuropsychiatric diseases. We have previously shown positive association between TH and bipolar disorder, as well as schizophrenia, using a polymorphic tetranucleotide repeat (HIJMTHOl) localized in the first intron of the TH gene. Moreover, a rare allele associated with schizophrenia is also associated with variations of the catecholamine metabolism in schizophrenic patients, Subsequently we showed that this tetranucleotide repeat is a powerful enhancer of transcription. In order to establish the role of the HUMTHOl in TH gene regulation, we have made several new constructions with the TH proximal 5’ regulatory region and the three first exons and introns fused to the luciferase reporter gene. We have also evaluated methylation profiles of the HUMTHOl and its flanking regions in TH expressing and nonexpressing cells. Our preliminary data indicate that the HUMTHOl sequence is relevant in TH gene expression. Thus, these tetrarepeated motifs may represent a new regulatory element and may have important implications in the expression of the TH gene in normal and pathological states.
DNA METHYLATION ANALYSIS OF THE PUTATIVE PROMOTER REGION OF THE DOPAMINE D2 RECEPTOR GENE IN POSTMORTEM BRAINS OF SCHIZOPHRENIA PATIENTS AND CONTROLS A. Petronis, V. Popendikyte, J.L. Kennedy, A. Laurinavicius Neurogenetics 250 College
Section, Centre of Addiction and Mental Street, Toronto Ontario MSTIR8 Canada
Developments in molecular biology over the last few decades have led to an increasing awareness of the importance of epigenetic phenomena in a variety of genome functions. Epigenetics pertains to a set of mechanisms that determine the phenotypic expression of genetic information and deal with potentially reversible modification of DNA mediated by DNA methylation and/or chromation conformation. Various aspects of epigenetic DNA methylation have recently been re-evaluated through their putative relevance to the main etiological theories of schizophrenia (SCA). It has been hypothesized that, in addition to pathological effects of DNA, structural mutations, and environmental factors, inherited and acquired epigenetic
defects may be of etiopathogenic importance in SCZ. For our studies, we selected the dopamine D2 receptor gene (DRD2). In our preliminary analysis, 23 DNA samples extracted from brain tissue (striatum) were analyzed, 7 of which were from SCZ patients. Methylated cytosines (““‘C) were mapped in the putative DRD2 promoter region using the bisulfite modification technique. The SCZ sample exhibited several differences in DRD2 methylation pattern in comparison to control individuals: (1) the 10 most common positions of ““‘C in controls were hypomethylated in SCZ patients (p
EVIDENCE FOR INVOLVEMENT OF THE x7-NICOTINIC CHOLINERGIC RECEPTOR GENE ON CHROMOSOME 15q13-q14 IN SCHIZOPHRENIA IN SOUTH AFRICAN BANTU-SPEAKING FAMILIES B.P. Riley, M. Mogudi-Carter, T.J. Jenkins, R. Williamson, D.A. Collier, R.M. Murray Department of Psychological London SE5 8AF. UK
Recent reports have strongly linked the ~(-7 nicotinic cholinergic receptor gene on chromosome 15q13-q14 to a sensory gating deficit common in schizophrenics and have shown positive although nonsignificant results linking this receptor gene to the primary phenotype of schizophrenia in a sample of North American families. We, therefore, tested for linkage between markers in this region of chromosome 15q and schizophrenia in a sample of 16 families multiply affected with schizophrenia drawn from the Bantu-speaking black population of South Africa. The map of markers used was D15S167-4cMD15S1360-2cM-D15S144-6cM-D15S118-7cM-D15S641. We find an affected-only LOD score maximum of 1.08 at 0 = 0.00 for D15S1360, a dinucleotide polymorphism found on the same YAC as the x-7 receptor gene, when analysing affected individuals only under a recessive transmission model with penetrance = 0.5. Nonparametric affected-only multipoint analysis yields a z-score of 1.29, p = 0.98, for D15S1360, and z = 1.45, p = 0.075 for D 15s 118. Transmission disequilibrium testing was not possible with D15S1360 alone due to large numbers of parents homozygous at this marker. However, haplotype data from D15S1360 and D15S144 were analysed for transmission disequilibrium. Allele-wise testing yields a chi-square of
19.74, 12 df, p = 0.073. Analyses of an extended map of marker data at 1 CM intervals and genomic clones of CHRNA7 and its partial duplication are in progress currently.
WHAT DOES DISCORDANCE MONOZYGOTIC TWINS?
CL. Smith, G. Nyugen, N. Storm, C. Foulon, J. Bouchard Center for Advanced Biotechnology and Departments of Biomedical Engineering, Biology, and Pharmacology, 36 Cummington Street, Boston University, Boston, Massachusetts 02215, USA Concordance studies in monozygotic and dizygotic twins are used to determine genetic and environmental contributors to disease phenotypes. These studies assume that monozygotic twins have identical genomes. These assumptions fail to take into account epigenetic and somatic DNA changes due to development, aging, or random changes in DNA. For instance, there are several well-documented cases of monozygotic twins where discordance in a disease phenotype can be traced to a specific difference in a DNA sequence. Our research is assessing the level of DNA identity of monozygotic twins on a genomewide scale. The results show that the genome identity is very high (>90%) but significant differences exist and the amount depends on which sequences are examined. Furthermore, some of the differences are tissue specific. These results question the meaning of disease discordance in monozygotic twins and results of current zygosity testing methods. Several differences between monozygotic twins discordant for schizophrenia were characterized in detail. One difference represents a series of multiple single base changes while another represents a de novo recombination event. These and other genomic changes are being characterized in schizophrenic and normal twins and other samples of ill and well individuals.
REPORT OF A GENOME SCAN FOR LINKAGE WITH SCHIZOPHRENIA IN 72 FAMILIES FROM GERMANY AND ISRAEL WITH 2 AND MORE AFFECTED SIBLINGS D.B. Wildenauer, S.G. Schwab, J. Hallmayer, B. Lerer, M. Albus, M. Borrman, D. Lichtermann, B. Dreikorn, C. Hanses, G.N. Eckstein, P. Zill, S. Hbnig, K. Kanya, R. Segman, R.E. Ebstein, M. Trixler, M. Rietschel, W. Maier Department Germany
Classic lod score analysis, which has been extremely successful in mapping monogenic diseases may not work for complex genetic disorders like schizophrenia because parameters like mode of inheritance, gene frequencies, penetrance, etc. are hard
to define. We collected a family sample with affected siblings which enabled us to carry out nonparametric methods like affected sib-pair analysis. Seventy-two families (470 individuals) were ascertained through a schizophrenic or chronic schizoaffective (RDC) index patient, each family having at least 2 affected siblings and parental information (67 families with both parents, 5 families with 1 parent, but additional nonaffected siblings). Thirteen families were from Israel (mainly non-Ashkenazi), 59 families from Germany. The sample comprises a total of 87 (n- 1) and 107 (n[n- 1]1/2) sib-pair
combinations for affected sib-pair analysis, identity by descent. Using fluorescence-based technology, about 300 microsatellite markers in an average distance of lo-20 cMorgans were used for first analysis. Regions of interest (i.e., regions for which a priori evidence for susceptibility genes exists) were analysed with additional markers in a distance of 2 cMorgans and less. Evidence for 5 potential susceptibility loci has been obtained in the sample mapping to 5q31, 6p22,23, 10~14-11, 18~11.2, 22ql2,13 each locus supported by additional evidence from other groups in independent samples.