CAG repeat expansions and schizophrenia: association with disease in females and with early age-at-onset

An increase in the severity of schizophrenia through consecutivegenerations (anticipation) has been found in some studies offamilies with affected members. Anticipation in five neurologlcaidisorders is known to arise from the expansion of CAG repeatsbetween generations of affected individuais. The ‘repeatexpansion detection’ method was used to screen indlviduaigenomes for the size of such expansions in a sampie of schizophrenicand normai sub jects. Comparison of the frequency distributionof CAG expansions observed in schizophrenic patients to thatfor normal subjects, showed that there are significantly moreexpansions in patients (p = 0.048). When male and female subjectsare considered separateiy, there is a highly significant differencein the distribution of repeat sizes found between affected andnormal females (p = 0.0023) but no significant difference betweenaffected and normal males. Over all there is a 28% excess ofexpansions observed in affected versus normal females, and theirpresence confers a relative risk of 4.12 (p <0.005). in contrast,the frequency distribution of age-at-onset with respect to repeatsize is nearly the same in male and female patients and, whenthe sexes are combined, the larger (CAG)^69–136 expansionsare associated with a younger age-at-onset (p = 0.02).     

伴发与非伴发迟发性运动障碍的慢性精神分裂症患者血清尿酸浓度

迟发性运动障碍(tardive dyskinesia,TD)是由于长期运用神经阻制剂而产生的一种较为常见的运动系统副作用.有研究提示,基底节神经元变性可能是TD发生的病理基础,自由基代谢异常可能在TD的病理生理过程中作用关键[1].     

Schizophrenia and tardive dyskinesia: Is schizophrenia also a “denervation hypersensitivity”?

In human beings, amphetamine can induce both schizophreniform psychosis and oral-facial dyskinesia resembling tardive dyskinesia, while neuroleptic agents reduce the manifestations of both conditions. This suggests that such psychosis and movement disorder may occur by the same or very similar mechanisms. It is thought that tardive dyskinesia may result from neuroleptic-induced denervation hypersensitivity to dopamine. The author cites evidence suggesting that amphetamine may act on dopaminergic pathways in the CNS to produce a denervation hypersensitivity like that caused by neuroleptic agents. Clinical evedence compatible with a denervation hypersensitivity hypothesis of schizophrenia is then discussed.     

hSKCa3: no association of the polymorphic CAG repeat with bipolar affective disorder and schizophrenia

hSKCa3 is a neuronal small conductance calcium-activated potassium channel, which contains a polyglutamine tract, encoded by a polymorphic CAG repeat in the gene. Since an association between longer alleles of this CAG repeat and bipolar disorder or schizophrenia has been reported, we genotyped the polymorphic CAG repeat in 91 German family trios of patients with bipolar disorder I and used the transmission disequilibrium test (TDT) to test for association. Applying a dichotomized model (< or = 19 or > 19 CAG triplets), we found no evidence for an association of longer alleles with bipolar disorder (TDT = 0.75, P = 0.386). Regarding the whole range of alleles, there was no preference in transmitting the larger of the two observed alleles from parents to the affected offspring. In parallel we performed an independent case-control study on German patients with bipolar disorder and schizophrenia. Again we did not detect an overrepresentation of longer CAG repeats in patients. Thus, our data do not support the hypothesis that longer CAG repeats in the hSkCa3 gene contribute to the susceptibility for bipolar disorder and schizophrenia.     

Association between three functional polymorphisms of dopamine D2 receptor gene and tardive dyskinesia in schizophrenia.

The dopamine D2 receptor (DRD2) gene is considered one of the candidate genes contributing to the development of tardive dyskinesia (TD). In the present study, we investigated the genetic association between three functional polymorphisms (Ser311Cys, -141C Ins/Del and TaqI A) in the DRD2 gene and TD (200 patients with schizophrenia: 44 with TD and 156 without TD). No significant difference in the allelic and genotypic distribution between patients with TD and those without TD was observed. However, we found a slightly significant association between the -141C Ins/Del polymorphism and the total Abnormal Involuntary Movement Scale (AIMS) score (P = 0.037). The significant association between the -141C Ins/Del polymorphism and the total AIMS score did not remain after the regression analysis was taken into account (P = 0.14). Our results suggest that that three functional polymorphisms in DRD2 may not play a major role in the occurrence of TD.     

CAG repeat instability at SCA2 locus: anchoring CAA interruptions and linked single nucleotide polymorphisms.

Spinocerebellar ataxia 2 (SCA2) is an autosomal dominant neurodegenerative disorder that results from the expansion of a cryptic CAG repeat within the exon 1 of the SCA2 gene. The CAG repeat in normal individuals varies in length from 14 to 31 repeats and is frequently interrupted by one or more CAA triplets, whereas the expanded alleles contain a pure uninterrupted stretch of 34 to 59 CAG repeats. We have previously reported the presence of a limited pool of 'ancestral' or 'at risk' haplotypes for the expanded SCA2 alleles in the Indian population. We now report the identification of two novel single nucleotide polymorphisms (SNPs) in exon 1 of the SCA2 gene and their characterization in 215 normal and 64 expanded chromosomes. The two biallelic SNPs distinguished two haplotypes, GT and CC, each of which formed a predominant haplotype associated with normal and expanded SCA2 alleles. All the expanded alleles segregated with CC haplotype, which otherwise was associated with only 29.3% of the normal chromosomes. CAA interspersion analysis revealed that majority of the normal alleles with CC haplotype were either pure or lacked the most proximal 5' CAA interruption. The repeat length variation at SCA2 locus also appeared to be polar with changes occurring mostly at the 5' end of the repeat. Our results demonstrate that CAA interruptions play an important role in conferring stability to SCA2 repeat and their absence predisposes alleles towards instability and pathological expansion. Our study also provides new haplotypes associated with SCA2 that should prove useful in further understanding the mutational history and mechanism of repeat instability at the SCA2 locus.     

Anticipation is not associated with CAG repeat expansion in parent-offspring pairs of patients affected with schizophrenia

With the rationale that a disease that presents with anticipation could be associated with expansion of trinucleotide repeats, we selected parent-offspring pairs of schizophrenia patients with earlier age at onset in the filial generation to measure the expansion of CAG repeats using the repeat expansion detection (RED) method. Intergenerational comparisons were made for age at onset, length of CAG repeats, and clinical variables. Although the patients from the filial generation became affected 13 years earlier than the parents (P < 0.0005), we did not find larger CAG repeats in the offspring. No association was found between size of CAG repeat and age at onset or with any other clinical variable. Overall, the frequency of patients with CAG repeats longer than 40 was 32%, which was similar to that observed in control subjects (27%). It is particularly noteworthy that in 86% of the pairs, the mother was the affected parent. In this Spanish sample with parent-offspring pairs presenting schizophrenia with clinical anticipation and apparent female bias of transmission, neither the phenomenon of anticipation nor disease status was associated with the expansion of CAG repeats.     

Intergenerational CAG repeat expansion at ERDA1 in a family with childhood-onset depression, schizoaffective disorder, and recurrent major depression

Reported evidence of anticipation for schizophrenia and bipolar disorder has recently precipitated a search for unstable trinucleotide repeats for these diseases. Several initial studies suggested an increase in the frequency of large CAG/CTG repeats in the genomes of schizophrenic and bipolar individuals. Published reports do not demonstrate expansion per se, and may be suggestive of allelic association with the disease rather than actual dynamic DNA mutations. This report documents evidence of a significant expansion of CAG/CTG repeats from one generation to the next in a family demonstrating evidence of anticipation for psychiatric disorders. Using the repeat expansion detection (RED) technique, we observed that a proband with multiple psychiatric diagnoses, including childhood-onset depression, inherited a larger CAG/CTG repeat than either parent. Analysis of the ERDA1 locus on 17q21.3 revealed that the proband inherited a very large allele from the father which increased in repeat number through transmission. The mother was diagnosed with schizoaffective disorder and the father with depression. While this DNA mutation may be a stochastic event unconnected with the disease, it could represent DNA instability as an etiologic factor in psychiatric diseases.     

Effect of therapy with atypical antipsychotic drugs on prolactin concentration in patients with schizophrenia and schizoaffective disorders

Plasma prolactin concentration was measured in patients with schizophrenia and schizoaffective disorders receiving therapy with risperidone, olanzapine, and quetiapine and compared with the corresponding parameter in patient receiving typical neuroleptic drug haloperidol. We evaluated the specific effects of the test drugs on prolactin concentration in men and women. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 140, No. 12, pp. 667–669, December, 2005     

Familial aggregation of schizophrenia-spectrum disorders and obsessive-compulsive associated disorders in schizophrenia probands with and without OCD.

A substantial proportion of schizophrenia patients also has obsessive-compulsive disorder (OCD). To further validate the clinical validity of a schizo-obsessive diagnostic entity, we assessed morbid risks for schizophrenia-spectrum disorders and OC-associated disorders in first-degree relatives of schizophrenia probands with and without OCD. Two groups of schizophrenia probands [with OCD (n = 57) and without OCD (n = 60)] and community-based controls (n = 50) were recruited. One hundred eighty two first-degree relatives of probands with OCD-schizophrenia, 210 relatives of non-OCD schizophrenia probands, and 165 relatives of community subjects were interviewed directly [59.3% (108/182), 51.9% (109/210), and 54.5% (90/165), respectively], using the Structured Clinical Interview for Axis-I DSM-IV Disorders and Axis II DSM-III-R Personality Disorders and the remaining relatives were interviewed indirectly, using the Family History Research Diagnostic Criteria. Relatives of OCD-schizophrenia probands had significantly higher morbid risks for OCD-schizophrenia (2.2% vs. 0%; P = 0.033) and OCPD (7.14% vs. 1.90%; P = 0.014), and a trend towards higher morbid risk for OCD (4.41% vs. 1.43%; P = 0.08) compared to relatives of non-OCD schizophrenia probands. When morbid risks for OCD, OCPD, and OCD-schizophrenia were pooled together, the significant between-group difference became robust (13.74% vs. 3.33%; P = 0.0002). In contrast, relatives of the two schizophrenia groups did not differ significantly in morbid risks for schizophrenia-spectrum disorders, mood disorders, or substance abuse disorders. A differential aggregation of OC-associated disorders in relatives of OCD-schizophrenia versus non-OCD schizophrenia probands, provides further support for the validity of a putative OCD-schizophrenia ("schizo-obsessive") diagnostic entity.     

Association between three functional polymorphisms of dopamine D2 receptor gene and tardive dyskinesia in schizophrenia

The dopamine D2 receptor (DRD2) gene is considered one of the candidate genes contributing to the development of tardive dyskinesia (TD). In the present study, we investigated the genetic association between three functional polymorphisms (Ser311Cys, ?141C Ins/Del and TaqI A) in the DRD2 gene and TD (200 patients with schizophrenia: 44 with TD and 156 without TD). No significant difference in the allelic and genotypic distribution between patients with TD and those without TD was observed. However, we found a slightly significant association between the ?141C Ins/Del polymorphism and the total Abnormal Involuntary Movement Scale (AIMS) score (P = 0.037). The significant association between the ?141C Ins/Del polymorphism and the total AIMS score did not remain after the regression analysis was taken into account (P = 0.14). Our results suggest that that three functional polymorphisms in DRD2 may not play a major role in the occurrence of TD. © 2001 Wiley‐Liss, Inc.     

Angiotensin converting enzyme gene insertion/deletion polymorphism: case-control association studies in schizophrenia, major affective disorder, and tardive dyskinesia and a family-based association study in schizophrenia

Angiotensin converting enzyme (ACE) is a candidate gene for psychiatric disorders. We examined the frequency of a functional insertion/deletion (I/D) polymorphism in the 16th intron of the ACE gene (located on chromosome 17q23) in groups of patients with schizophrenia (n = 104 and 113), major depression (n = 55), and bipolar disorder (n = 87) compared to healthy control subjects (n = 87). There was no evidence for allelic or genotypic association of the polymorphism with any of the disorders or with tardive dyskinesia (TD) in patients with schizophrenia. In a sample of nuclear families (n = 61) made up of one or more patients with schizophrenia recruited with their parents, there was no evidence for biased transmission of ACE I/D alleles. Particularly in the case of schizophrenia, these findings do not support an association of the ACE I/D polymorphism with the phenotypes examined.     

Analysis of CAG repeat of the Machado-Joseph gene in human, chimpanzee and monkey populations: a variant nucleotide is associated with the number of CAG repeats

Machado-Joseph disease (MJD) is an autosomal dominant neurodegenerative disorder associated with an unstable and expanded CAG repeat. We analyzed this locus from various sources including MJD families, Acadian, African American, Caucasian, Greenland Inuit and Thai populations. The range of the CAG repeat size was 14-40 in the normal alleles while the MJD alleles contained 73-78 repeats in our studies. We found 25 different alleles on normal chromosomes with a heterozygosity of 0.86 in combined populations. The most common alleles were 23 (22.9%) and 14 (25.5%) repeats. We also examined 16 chimpanzees and various Old World monkeys: a pigtail macaque, a mangabey and 12 rhesus macaques. The DNA sequences surrounding the CAG repeat did not vary among species. The range of the number of the CAG repeats is 13-14 in macaques, 16 in mangabey and 14-20 in chimpanzees. Variant CAA or AAG triplets in the CAG repeat tracts were found in all 268 human, 28 monkey and 32 chimpanzee chromosomes. As reported in a previous study [Kawaguchi et al. (1994) Nature Genet. 8, 221-228] the common variant positions were the third (CAA), fourth (AAG) and sixth (CAA) positions. However, we found three human chromosomes containing CAG at the sixth position and the mangabey had AAG at the ninth position. In addition, we found CAG at the fourth position and AAG at the sixth position in all macaque chromosomes. The nucleotide following the CAG repeat tract was usually G in all species studied. However, we sometimes found C at this position in human and chimpanzee chromosomes. Interestingly, this variant C was found in all expanded chromosomes and in 54.5% of chromosomes with 27-40 CAG repeats but it was not found in any chromosomes with less than 20 CAG repeats. We hypothesize that the variant C may be associated with CAG repeat instability.      

The significance of subtyping tardive dyskinesia: a study of prevalence and associated factors

The prevalence of tardive dyskinesia (TD) in 137 Nigerian psychiatric patients was 27%. There were no differences in the prevalence rate between patients with affective disorder and those with schizophrenia. There were also no significant differences between the sexes but a trend for the more severe forms of dyskinesia to be commoner in females was noticed. Demographic, clinical and treatment variables were investigated for association with TD and each of its two putative subsyndromes: orofacial and appendicular dyskinesias. Two cases of severe and persistent tardive dystonia, associated with orofacial TD, were seen in two young adults, one with relatively short exposure to neuroleptics. After initial univariate screening, multivariate statistical methods revealed that different factors were associated with each of the two subsyndromes. While length of hospitalization correlated significantly with orofacial dyskinesia, cumulative duration of exposure to high-potency neuroleptics and number of ECTs received were significantly associated with appendicular TD. Neither age nor sex correlated with either of the subsyndromes. The findings confirm and extend previous observations suggesting that these dyskinesias may involve different pathophysiological mechanisms.     

Anticipation in schizophrenia: No evidence of expanded CAG/CTG repeat sequences in French families and sporadic cases

A decrease in age of onset of schizophrenia through consecutive family generations (anticipation) has been found in several studies. Anticipation is known to result from expansion of CAG repeats in genes that determine several neurodegenerative disorders. In a previous study we analysed 26 unilineal two-generation French pedigrees and found clinical evidence of anticipation. A 10-year mean reduction in age of onset of schizophrenia was found in the second generation compared with the parental generation. The repeat expansion detection method was used to screen for CAG expansion in 21 of the 26 families with evidence of anticipation for the disease and in 59 sporadic schizophrenics and 59 controls. Comparison of the frequency distributions of CAG/CTG repeat size observed in schizophrenics and controls showed no significant difference, even when we considered familial (P = 0.23) and sporadic (P = 0.25) affected individuals separately. These results do not support the association between long CAG repeats and schizophrenia. However, the possibility that expansions with fewer than 40 repeats are involved in schizophrenia cannot be excluded. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 81:342–346, 1998. © 1998 Wiley-Liss, Inc.     

Bromocriptine in affective disorders. A pilot study.

The authors present the results of a pilot study of the use of bromocriptine in affective disorders. Twelve inpatients suffering from endogenous depression (9 bipolar, 1 schizoaffective and 2 unipolar patients) and 3 excited inpatients (2 schizo-affective and one bipolar manic patient) were treated for 15 days with doses of bromocriptine that varied between 10–15 mg for depressed patients and 5–10 mg for excited patients. The limited improvement is discussed.     

Cognitive function in schizoaffective disorder and clinical subtypes of schizophrenia.

Cognitive studies of patients with Schizoaffective Disorder typically indicate that the cognitive function of these patients resembles that of patients with Schizophrenic Disorder more than it does patients with nonpsychotic Mood Disorder. In this study patients with Schizoaffective Disorder were compared with patients with Paranoid, Undifferentiated and Residual clinical subtypes on a number of measures of cognitive function. Multivariate analyses of variance indicated that the cognitive function of Schizoaffective and Paranoid patients had more intact cognitive function that did Undifferentiated and Residual patients. Application of cluster analysis indicated that there were relative high percentages of Schizoaffective and Paranoid patients in a "Neuropsychologically Normal" cluster. It was concluded that Schizoaffective Disorder as well as other clinical subtypes of schizophrenia are cognitively heterogeneous, and it was suggested that a subgroup of patients with Schizoaffective Disorder may not differ in cognitive ability from patients with nonpsychotic Mood Disorder.