Bipolar disorder (BP) is a severe psychiatric disease, with a strong genetic component, that affects 1% of the population worldwide and is characterized by recurrent episodes of mania and depression. Brain-derived neurotrophic factor (BDNF) has been implicated in the pathogenesis of mood disorders, and the aim of the present study was to test for the presence of linkage disequilibrium between two polymorphisms in the BDNF gene and BP in 283 nuclear families. Family-based association test (FBAT) results for the dinucleotide repeat (GT)(N) polymorphism at position -1040 bp showed that allele A3 was preferentially transmitted to the affected individuals (Z=2.035 and P=.042). FBAT results for the val66met SNP showed a significant association for allele G (Z=3.415 and P=.00064). Transmission/disequilibrium test (TDT) haplotype analysis showed a significant result for the 3-G allele combination (P=.000394), suggesting that a DNA variant in the vicinity of the BDNF locus confers susceptibility to BP. Given that there is no direct evidence that either of the polymorphisms we examined alters function, it is unlikely that the actual risk-conferring allele is from these two sites. Rather, the causative site is likely nearby and in linkage disequilibrium with the 3-G haplotype that we have identified.

Schizophrenia is a severe psychiatric disease with a strong genetic component. Brain-derived neurotrophic factor (BDNF) has been implicated in the pathogenesis of schizophrenia and bipolar (BP) disorders. The present study has examined two polymorphisms in linkage disequilibrium in the BDNF gene, which have been variously reported as associated with schizophrenia and BP. In our study, 321 probands with a primary diagnosis of schizophrenia or schizoaffective disorder, and 263 with a diagnosis of bipolar affective disorder, were examined together with 350 controls drawn from the same geographical region of Scotland. The val66met single-nucleotide polymorphism (SNP) showed significant (P ¼ 0.005) association for valine (allele G) with schizophrenia but not bipolar disorder. Haplotype analysis of val/ met SNP and a dinucleotide repeat polymorphism in the putative promoter region revealed highly significant (Po1 Â 10 À8 ) under-representation of the methionine or met-1 haplotype in the schizophrenic but not the BP population. We conclude that, although the val66met polymorphism has been reported to alter gene function, the risk may depend upon the haplotypic background on which the val/met variant is carried.

These observations implicate EIF4E, and more specifically control of EIF4E activity, directly in autism. The findings raise the exciting possibility that pharmacological manipulation of EIF4E may provide therapeutic benefit for those with autism caused by disturbance of the converging pathways controlling EIF4E activity.

Larger CAG/CTG trinucleotide-repeat tracts in individuals affected with schizophrenia (SCZ) and bipolar affective disorder (BPAD) in comparison with control individuals have previously been reported, implying a possible etiological role for trinucleotide repeats in these diseases. Two unstable CAG/CTG repeats, SEF2-1B and ERDA1, have recently been cloned, and studies indicate that the majority of individuals with large repeats as detected by repeat-expansion detection (RED) have large repeat alleles at these loci. These repeats do not show association of large alleles with either BPAD or SCZ. Using RED, we have identified a BPAD individual with a very large CAG/CTG repeat that is not due to expansion at SEF2-1B or ERDA1. From this individual's DNA, we have cloned a highly polymorphic trinucleotide repeat consisting of (CTA)n (CTG)n, which is very long ( approximately 1,800 bp) in this patient. The repeat region localizes to chromosome 13q21, within 1.2 cM of fragile site FRA13C. Repeat alleles in our sample were unstable in 13 (5.6%) of 231 meioses. Large alleles (>100 repeats) were observed in 14 (1. 25%) of 1,120 patients with psychosis, borderline personality disorder, or juvenile-onset depression and in 5 (.7%) of 710 healthy controls. Very large alleles were also detected for Centre d'Etude Polymorphisme Humaine (CEPH) reference family 1334. This triplet expansion has recently been reported to be the cause of spinocerebellar ataxia type 8 (SCA8); however, none of our large alleles above the disease threshold occurred in individuals either affected by SCA or with known family history of SCA. The high frequency of large alleles at this locus is inconsistent with the much rarer occurrence of SCA8. Thus, it seems unlikely that expansion alone causes SCA8; other genetic mechanisms may be necessary to explain SCA8 etiology.

No abstract

Schizophrenia patients demonstrate a deficiency in the filtering of sensory information, and one specific measure involves a response to the second of a pair of auditory stimuli. A neurophysiological measure of this consists of the electroencephalographic response to pairs of auditory signals, emitted fractions of a second apart. Schizophrenic patients and some of their unaffected relatives show a failure of inhibition of a second tone if it occurs 50 msec after the first. A recent genome scan indicated that the gating defect is linked to the alpha 7 neuronal nicotinic acetyl choline receptor gene on chromosome 15. We genotyped 5 schizophrenia families with a total of 96 subjects with a dinucleotide polymorphic marker located less than 120 kb from the first exon of the alpha 7 neuronal nicotinic acetylcholine receptor gene. Linkage analysis was undertaken using parametric and nonparametric statistical methods. The results of the parametric analysis showed negative lod scores under both narrow and broad diagnosis (lod = -3.6 and -4.8, respectively, at theta = 0), and dominant and recessive modes of transmission of the disease. Nonparametric analysis using GENEHUNTER produced nonsignificant NPL scores (NPL = -0.4 and -0.3 for broad and narrow diagnoses, respectively). In summary, we did not find any evidence that the alpha 7 neuronal nicotinic acetylcholine receptor gene (CHRNA7) is linked to schizophrenia. However, we have not been able to assess the P50 measures in these families.

No abstract

Social phobia, particularly in its generalized form, has a genetic component in its etiology as suggested by positive twin studies and child temperament studies of social anxiety. Observations from functional imaging research suggest that dopamine function may be abnormal in the brains of patients with social phobia. Our investigation examined polymorphisms in the dopamine D2, D3 and D4 receptor genes, plus the dopamine transporter gene in a sample consisting of 17 multiplex social phobia families. We employed both parametric and non-parametric methods to test for linkage. Linkage was excluded for all loci under the broad diagnostic category. In the medium diagnostic category, the D3 receptor gene showed non-significant positive LOD scores (LOD = 0.62). We are able to clearly exclude a major effect for each of the four dopamine gene markers under the broad diagnosis of social phobia. Additional studies of dopamine system genes will be necessary to define clearly their role in social phobia.