Post-zygotic genomic changes in glutamate and dopamine pathway genes may explain discordance of monozygotic twins for schizophrenia

Background

Monozygotic twins are valuable in assessing the genetic vs environmental contribution to diseases. In the era of complete genome sequences, they allow identification of mutational mechanisms and specific genes and pathways that offer predisposition to the development of complex diseases including schizophrenia.

Methods

We sequenced the complete genomes of two pairs of monozygotic twins discordant for schizophrenia (MZD), including one representing a family tetrad. The family specific complete sequences have allowed identification of post zygotic mutations between MZD genomes. It allows identification of affected genes including relevant network and pathways that may account for the diseased state in pair specific patient.

Results

We found multiple twin specific sequence differences between co-twins that included small nucleotides [single nucleotide variants (SNV), small indels and block substitutions], copy number variations (CNVs) and structural variations. The genes affected by these changes belonged to a number of canonical pathways, the most prominent ones are implicated in schizophrenia and related disorders. Although these changes were found in both twins, they were more frequent in the affected twin in both pairs. Two specific pathway defects, glutamate receptor signaling and dopamine feedback in cAMP signaling pathways, were uniquely affected in the two patients representing two unrelated families.

Conclusions

We have identified genome-wide post zygotic mutations in two MZD pairs affected with schizophrenia. It has allowed us to use the threshold model and propose the most likely cause of this disease in the two patients studied. The results support the proposition that each schizophrenia patient may be unique and heterogeneous somatic de novo events may contribute to schizophrenia threshold and discordance of the disease in monozygotic twins.

Electronic supplementary material

The online version of this article (10.1186/s40169-017-0174-1) contains supplementary material, which is available to authorized users.

Integration of DNA sequence and DNA methylation changes in monozygotic twin pairs discordant for schizophrenia

Schizophrenia is a complex mental disorder with high heritability (80%), extensive genetic heterogeneity, environmental contributions and only 50% concordance in discordant monozygotic (MZ) twins. Discordant MZ twins provide an exceptional opportunity to assess patient specific genome-wide genetic and epigenetic changes that may account for the disease phenotype. A combined analysis of genetic and epigenetic changes on the same twin pairs is expected to provide a more effective approach for two reasons. First, it is now possible to generate relatively reliable complete genome sequences as well as promoter methylation states on an individual level and second, the unaffected twin that originated from the same zygote provides a near perfect genetic match for contrast and comparison. This report deals with the combined analysis of DNA sequence data and methylation data on two pairs of discordant MZ twins that have been clinically followed for over 20 years. Results on Family 1 show that 58 genes differ in DNA sequence as well as promoter methylation in a schizophrenia-affected twin as compared to her healthy co-twin. The corresponding number for family 2 was 13. The two lists are over represented by neuronal genes and include a number of known schizophrenia candidate genes and drug targets. The results argue that changes in multiple genes via co-localized genetic and epigenetic alteration contribute to a liability threshold that is necessary for development of schizophrenia. This novel hypothesis, although logical, remains to be validated.

Copy number variation showers in schizophrenia: an emerging hypothesis

Genetic discoveries on Schizophrenia remain challenging. Traditional approaches have provided clues, but no genes. Novel theories that must account for extensive heterogeneity, including high discordance of monozygotic (MZD) twins, are needed. To this end, the extensive repeats of the human genome may provide the predisposition for DNA replication errors operational at every cell cycle during meiosis and mitosis. These errors will shower the genome with replication errors including copy number variations. Depending on the timing and the genes involved, this will contribute to the mutational load and disease. The evidence for such a mechanism in schizophrenia is emerging.

Is mandatory outpatient treatment effective?

This paper reviews the major studies of mandatory outpatient treatment (MOT) and examines why there has been inconsistency in some of the findings. Attempts to answer the question "is mandatory treatment effective?" must first clarify the type of mandatory treatment being examined, the type of patient being treated, and the outcome by which effectiveness is measured. There is consistent evidence that various forms of MOT increase follow-up with psychiatric services and that court-ordered outpatient committal decreases victimization of patients in the community. It also appears likely that MOT reduces the use of hospitalization; but, due to methodological problems associated with the research, this conclusion remains controversial.

Involvement of gene-diet/drug interaction in DNA methylation and its contribution to complex diseases: from cancer to schizophrenia

Most biological processes, including diseases, involve genetic and non-genetic factors. Also, the realization of a genetic potential may depend on environmental factors by directly affecting the expression of gene(s). Exactly how different environmental factors affect gene expression is not well understood. One of the mechanisms may involve DNA methylation and thereby gene expression. Diet, chemicals, and metals are known to affect DNA methylation and other epigenetic processes but are just beginning to be elucidated. For example, methylation of cytosine(s) in the promoter region could prevent the binding of transcription factors or create binding sites for complexes that deacetylate neighboring histones that in turn compact the chromatin, encouraging a gene to become silent. This article will discuss DNA methylation as an epigenetic mechanism of gene regulation and examine how factors like diet, chemicals, and metals may affect DNA methylation. The effect of alterations in DNA methylation may include aberrant expression of genes or genomes and chromosomal instability, which in turn may contribute to the etiology of complex multifactorial diseases. A similar mechanism is now recognized in a number of cancers. There is also indirect evidence to suggest that methylation could apply to a number of complex diseases, including schizophrenia.

Client satisfaction in a feasibility study comparing face-to-face interviews with telepsychiatry

We carried out a pilot study comparing satisfaction levels between psychiatric patients seen face to face (FTF) and those seen via videoconference. Patients who consented were randomly assigned to one of two groups. One group received services in person (FTF from the visiting psychiatrist) while the other was seen using videoconferencing at 128 kbit/s. One psychiatrist provided all the FTF and videoconferencing assessment and follow-up visits. A total of 24 subjects were recruited. Three of the subjects (13%) did not attend their appointments and two subjects in each group were lost to follow-up. Thus there were nine in the FTF group and eight in the videoconferencing group. The two groups were similar in most respects. Patient satisfaction with the services was assessed using the Client Satisfaction Questionnaire (CSQ-8), completed four months after the initial consultation. The mean scores were 25.3 in the FTF group and 21.6 in the videoconferencing group. Although there was a trend in favour of the FTF service, the difference was not significant. Patient satisfaction is only one component of evaluation. The efficacy of telepsychiatry must also be measured relative to that of conventional, FTF care before policy makers can decide how extensively telepsychiatry should be implemented.

Clinically significant differences among Canadian mental health acts

OBJECTIVES

First, to highlight the major differences among mental health acts in different Canadian jurisdictions as they relate to involuntary admission criteria, treatment authorization, review and appeal procedures, and conditional leave and community treatment orders. Second, to analyze the impact of these differences on the care that individuals with mental illness receive.

METHOD

We examined the mental health act provisions of all Canadian jurisdictions to determine how the clinical management of a typical case would differ among jurisdictions. We used a statement of principles for mental health legislation endorsed by the Canadian Psychiatric Association to guide the analysis. We confirmed interpretation of each act and its implementation through key informant contact in each province and territory.

RESULTS

We found clinically significant differences among the provinces and territories on all major components of their mental health acts.

CONCLUSION

Provisions that prevent patients receiving appropriate clinical care can be found in some Canadian mental health acts. Alternate provisions that support appropriate clinical care, that respect the human rights and personal dignity of patients, and that are consistent with the Canadian Charter of Rights and Freedoms can be found in the legislation of other jurisdictions.

A survey of the use of community treatment orders by psychiatrists in Saskatchewan

OBJECTIVE

To determine the pattern of use and satisfaction with community treatment orders (CTOs) by psychiatrists in Saskatchewan.

METHOD

All psychiatrists who were licensed to practise by the College of Physicians and Surgeons of Saskatchewan were surveyed by mail in July 1998.

RESULTS

The response rate was 72%. The responding psychiatrists were treating 14 patients on CTOs at the time of the survey. Psychiatrists were generally satisfied with the operation of CTOs, though many felt that commitment of only of 3 months before mandatory renewal was too short a period. Almost one-half expected their use of treatment orders to increase.

CONCLUSION

While CTOs are used for only a small number of patients in Saskatchewan, they are a clinically useful tool for dealing with a group of otherwise difficult-to-treat patients.

Molecular characterization of a MSRV-like sequence identified by RDA from monozygotic twin pairs discordant for schizophrenia

Retroviral-related amplicons were used in modified RDA to identify four sequences from affected members of three pairs of monozygotic twins discordant for schizophrenia. One sequence (schizophrenia associated retrovirus, SZRV-1, GenBank Accession No. AF135487) is characterized here. It is similar to two known sequences of retroviral origin: multiple sclerosis-associated retrovirus, MSRV (GenBank Accession No. AF009668), and ERV-9 (GenBank Accession No. S77575). It is present in multiple copies in the human genome and has been localized to six different chromosomal sites. A zooblot shows that this multicopy sequence is predominant in the primate lineage and present in rhesus monkeys and humans. SZRV-1 is expressed as a 9-kb RNA band in the placenta. This could offer support to the hypothesis that retroviral sequences transposing during fetal growth may alter neurodevelopmental genes and cause diseases, although its direct involvement in the causation of schizophrenia remains to be established.

Review board outcomes for involuntary patients in provincial psychiatric hospitals

OBJECTIVE

To identify long-term trends and compare different psychiatric hospitals with regard to outcomes of involuntary certification.

METHOD

Data on outcomes of involuntary certification were obtained from the London and St Thomas Psychiatric Hospitals for 1987 to 1997, from the Psychiatric Patient Advocate Office pertaining to 10 psychiatric hospitals for 1987 to 1993, and from published data from the North Bay Psychiatric Hospital for 1992 to 1994. Data were compared regarding outcome variables.

RESULTS

There are variable rates and proportions among the psychiatric hospitals for outcomes of involuntary certification, including patients choosing to withdraw their applications to Review Boards, physicians cancelling involuntary certificates by completing Form 5s, and Review Boards rescinding certificates. Overall, few certificates were rescinded by the Boards, a trend that was even more pronounced in recent years.

CONCLUSIONS

Patients who are in psychiatric hospitals on an involuntary basis are infrequently released from hospital as a result of a Review Board rescinding their certificate.

Why are patients discharged by review boards?

OBJECTIVE

To identify why Review Boards revoked certificates for involuntary hospitalization.

METHOD

The outcome of all applications for a Review Board hearing at 2 psychiatric hospitals in Ontario were recorded from the beginning of 1987 to the end of 1996. All cases where a certificate of involuntary hospitalization was revoked were identified. For each of these cases, the clinical record, including the Review Board's written reasons for its decision, was reviewed.

RESULTS

During the study period, 2644 patients applied for a review of their involuntary hospitalization. Only 42% of applications reached a hearing. Of these, 9% were revoked. Several recurring reasons for overturning certificates were identified. These included the physician relying too much on hearsay evidence, relatives supporting discharge at the hearings, and the patient clearly having recovered by the time the hearing took place.

CONCLUSIONS

Relatives or staff who observe dangerous behaviour should be encouraged to give evidence at hearings. The treatment team should take careful note of the views of patients' families and friends and review the patients' progress before hearings.

Search for retroviral related DNA polymorphisms using RAPD PCR in schizophrenia

Random amplification of polymorphic DNA (RAPD) is widely used to detect polymorphisms in many organisms. Individual (or strain) specific amplified bands are generated with single or pairs of primers in PCR reactions and can serve as genetic markers. We have used this method to generate a large number of reproducible bands with single primers, random and retroviral related, on 92 human DNA samples. Theoretically, RAPD PCR presents a logical approach for assessing variability among individuals. We used ten retroviral related primers (12, 20 and 22 bp) and eight random primers (10 bp) to assess individual differences in the context of testing the retroviral hypothesis for schizophrenia. Three pairs of discordant monozygotic twins, four pairs of discordant full sibs and 53 schizophrenic individuals with 25 of their unrelated matched controls were analyzed. Ten of these primers resulted in a total of approx. 850 amplified bands (65-110 bands per primer). Almost all of these bands were identical among each individual analyzed. However, the results are inconclusive with respect to the retroviral hypothesis for schizophrenia. The general lack of RAPD polymorphism in this study may argue for mechanisms other than rearrangements such as inversions, associated with the evolution of the human genome.

The relationship of catatonia symptoms to symptoms of schizophrenia

OBJECTIVE

To evaluate the relationships of symptoms of catatonic schizophrenia to 77 symptoms relevant for diagnosing schizophrenia and to socioanamnestic variables.

METHOD

Data from a sample of 112 Canadian patients diagnosed with schizophrenia according to the Diagnostic and Statistical Manual of Mental Disorders (DSM-III) were evaluated via phi correlation coefficients.

RESULTS

Forty-five (40.2%) of our 112 patients had catatonic symptoms, either at the time of this study or in the past. However, only weak correlations (phi < 0.31) to other symptoms relevant for diagnosing schizophrenia were found, and no significant correlations to socioanamnestic variables were found.

CONCLUSION

Symptoms of catatonia appear to be independent of the key symptoms of schizophrenia.

Mental health legislation and the right to appropriate treatment

OBJECTIVE

To demonstrate how mental health legislation and its implementation can detract from a patient's "right to health."

METHOD

The author surveyed colleagues working at the London and St Thomas Psychiatric Hospitals about cases where the structure or implementation of the Mental Health Act in Ontario impeded the provision of good psychiatric care.

RESULTS

Four clinical vignettes illustrate specific problems; possible solutions to these difficulties are suggested.

CONCLUSION

Physicians must remain vigilant in their role as advocates for patients' right to appropriate treatment.

A single-primer PCR-based retroviral-related DNA polymorphism shared by two distinct human populations

Almost 10% of the human genome consists of DNA sequences that share homology with retroviruses. These sequences, which represent a stable component of the human genome (although some may retain the ability to transpose), remain poorly understood. We used degenerate primers specific to the two conserved regions (boxes 4 and 5) of the retroviral pol gene, common to all retroviruses, and PCR-amplified related sequences from individuals representing two distinct populations: Caucasians and Dogrib Indians. The large number of sequences that are reproducibly amplified represent numerous sites of retroviral integration in the human genome. In both populations studied, one of the two primers yielded a polymorphic band, present in approximately 30% of the samples, that has probably been present in the human genome since before the divergence of the two populations approximately 10,000 years ago. It was established that this polymorphism was due to priming-site differences and not to deletions. Further, this priming site is duplicated at two genomic sites (representing 341- and 343-bp fragments) with at least two alleles each. Such novel polymorphisms should provide useful markers and permit assessment of evolutionary mechanisms associated with retroviral-related genomic evolution.

Sensation Seeking Scales and consumer satisfaction with a substance abuse treatment program

Satisfaction of 119 addicts with an addiction treatment program was measured by an 11 item satisfaction scale. The scale's internal consistency was acceptable (Cronbach's alpha = .75). The total satisfaction score was weakly but significantly correlated with Zuckerman's Sensation Seeking scales: Those with higher scores on the Boredom Susceptibility scale (i.e., those easily bored) reported less satisfaction, whereas those with higher scores on Thrill and Adventure Seeking scale (i.e., risk, adventure, and thrill seekers) reported higher levels of treatment satisfaction. Older patients were more satisfied with the feedback they received from their psychological tests and also with staff's respect for their rights.

Symptom patterns in schizophrenia for men and women

Differences on symptoms and anamnestic variables were studied in a sample of 112 Canadian patients (42 men and 70 women) who met DSM-III criteria for schizophrenia. Men were more often rated as providing unreliable information than were women. A smaller proportion of men than women showed spontaneous remissions (a return to premorbid level), and fewer men also displayed phasic changes in appetite, weight, or sexual activity. It is noteworthy that men and women did not differ on general indices of severity of illness such as the number of past hospitalizations or length of hospital stay. In contrast to numerous past studies, an earlier age of onset of the illness for men was nonsignificant.

Antisocial personality traits and patients' satisfaction with treatment for addiction

The over-all satisfaction with treatment for addiction (sum of scores on 11 items of a questionnaire) by 50 addicts and their self-reported confidence in remaining abstinent were unrelated to scores on MMPI-2 scales (all classical clinical and validity scales, 15 content scales and 7 research scales) except to reports of shyness on the Social Discomfort Scale: patients characterizing themselves as shy gave the higher ratings of satisfaction with treatment (r = .33). We note that our previous finding using the MMPI-2, i.e., that less.socially responsible and more rebellious patients provided lower satisfaction ratings, was not replicated for this sample of addicts.

Retroviruses and schizophrenia revisited

Both genetic and environmental factors appear to contribute to the causation of schizophrenia. Evidence indicating that fetal development is disrupted in schizophrenia and the finding of an excess of winter births among schizophrenic patients have led to continued speculation that an intrauterine viral infection may cause developmental lesions, genetic mutations, or persistent infections that lead to schizophrenia. Certain unique characteristics of the retroviruses render them plausible as candidate "schizoviruses" and the involvement of an endogenous retrovirus would be compatible with some of the puzzling epidemiological findings in schizophrenia. Reverse transcriptase (RT) is a retrovirally encoded enzyme essential for retroviral integration into host DNA. While attempts to detect retroviral infections by measuring RT activity in the peripheral lymphocytes and serum of schizophrenic patients have been unsuccessful, such negative findings may simply mean that the virus is not active in peripheral lymphocytes. A more sensitive and comprehensive approach to detect a retrovirus is to search the genomes of schizophrenic patients directly for the presence of retroviral DNA sequences encoding RT and one possible approach is described.

Pharmacogenetic response to antidepressants in a multicase family with affective disorder

Eight members from two generations of a family met the DSM-III-R criteria for major depression. Four individuals had severe prolonged depressive disorders that did not respond to standard therapeutic doses of tricyclic and new generation antidepressants, but subsequently responded to the monoamine oxidase inhibitor, tranylcypromine. The literature on pharmacogenetics of the antidepressants is sparse. The pattern of selective response to tranylcypromine in this family supports the view that there is a familial tendency to respond to specific antidepressants or antidepressant groups. A history of response to a specific antidepressant in a relative may be helpful when selecting an antidepressant. Families demonstrating preferential response to specific psychotropics may be suitable pedigrees in which to perform linkage analysis using candidate genes related to the site of action of that psychotropic drug.

Viruses and schizophrenia

A viral hypothesis for the pathogenesis of schizophrenia has been under serious consideration for more than 70 years. To date, attempts have failed to identify a specific virus which contributes to the aetiology of the disorder. There has, however, been a recent resurgence of interest in a possible relationship between viral illness and schizophrenia. This renewed attention is the result of epidemiological evidence suggesting an excess of winter births in patients with schizophrenia, indications of foetal insults in persons who develop schizophrenia and an association between foetal exposure to the influenza virus and the subsequent development of schizophrenia. Advances in our understanding of the pathophysiology of viral diseases and the development of sophisticated techniques to study them have resulted in more complex viral hypotheses of schizophrenic aetiology, such as viral disruption of normal neurodevelopment, viral induced autoimmunity and retroviral integration. These hypotheses are now beginning to be tested experimentally.

Phenylethylamine and schizophrenia

1. The evidence that phenylethylamine (PEA) plays a role in the etiology of schizophrenia is reviewed. 2. PEA shares structural and physiological similarities with the amphetamines, the administration of which can induce a schizophrenia-like psychosis. 3. While there are a number of reports of high urinary PEA excretion in schizophrenic patients, the measurement of PEA in other body fluids and the measurement of phenylacetic acid (the major metabolite of PEA) has resulted in inconsistent findings. 4. The use of neuroleptic medication is a major confounding variable in most of the clinical studies. If PEA does have a role in the etiology of schizophrenia, the mechanism may involve PEAs ability to amplify dopamine responses.

Benzodiazepines and Confusion in Medically Ill Alcoholics: Balancimg safety against toxicity

It is generally believed that benzodiazepines are effective and safe drugs for use in alcohol withdrawal states. The authors describe three cases in which benzodiazepines aggravated or caused confusion in alcoholic patients admitted to a general hospital for emergency medical treatment. Strategies to avoid this problem are discussed.

Orthodontic abnormalities in patients with eating disorders

Many anorexic and bulimic patients induce vomiting by inserting their fingers in the oral cavity. We hypothesized that finger pressure could lead to tooth movement, eventually resulting in the development of orthodontic abnormalities, particularly open-bite. Twenty-four females with eating disorders and 24 matched controls underwent orthodontic examination and completed a dental questionnaire. Orthodontic abnormalities were more commonly found in the eating disorder group and open-bite was the most common abnormality seen. The presence of open-bite or other orthodontic abnormality was not associated with patient reports of self-induced vomiting, which would suggest that digital pressure was not the causative factor. The dental appearances indicated that the skeletal base pattern was abnormal in many cases. The findings could, in part, be accounted for by the fact that patients with eating disorders were less likely than controls to have completed courses of orthodontic treatment. Alternatively, the orthodontic abnormality may have contributed to the development of an eating disorder. Further study of this area is proposed.

Are the monamine oxidase inhibitors facing extinction?

The use of monoamine oxidase inhibitors (MAOIs) in the province of Saskatchewan was compared for two years, 1978 and 1986, using the Saskatchewan Prescription Drug Plan data base. The percentage of the adult population receiving an MAOI decreased from 0.17% in 1978 to 0.07% in 1986. The use of both tricyclic antidepressants and the new generation antidepressants increased during the same period. Physicians appear to have selectively avoided using MAOIs for the elderly. Physicians who are not psychiatrists showed the greatest reduction in their use of the MAOIs. The data indicate an increasing reluctance to prescribe the MAOIs despite the recent resurgence of interest in these agents and the positive literature concerning their safety and efficacy.

The effect of age, sex, weight and height on the plasma concentrations in healthy subjects of the acidic metabolites of some biogenic monoamines involved in psychiatric and neurological disorders

1. The plasma concentrations of unconjugated phenylacetic acid and m-hydroxyphenylacetic acid are lower in male than in female subjects. 2. The plasma concentrations of unconjugated phenylacetic acid and mandelic acid decrease with increasing weight and height for all subjects combined. The same relationships apply for both males and females but are significant only for males. 3. Homovanillic and vanillylmandelic acid concentrations in plasma increase with age. 4. The importance of using age, sex, weight and height matched groups in studies involving the plasma concentrations of some of the trace amine metabolites in psychiatric disorders has been demonstrated. This is particularly the case for phenylacetic acid, the major metabolite of phenylethylamine which is now thought to be a neuromodulator of catecholaminergic neurotransmission.

Effect of dietary phenylalanine on the plasma concentrations of phenylalanine, phenylethylamine and phenylacetic acid in healthy volunteers

1. Phenylethylamine has been proposed as a neuromodulator in several psychiatric and other brain disorders, and its concentration and that of its major metabolite, phenylacetic acid, in plasma may prove useful as state or trait markers in diagnosis, treatment or in the elucidation of biochemical mechanisms of these disorders. 2. The effect of dietary phenylalanine intake and changes in dietary phenylalanine intake on the plasma concentrations and changes in plasma concentrations, respectively, of phenylalanine, phenylethylamine and unconjugated and conjugated phenylacetic acid have been investigated. 3. Dietary phenylalanine affects the concentration of plasma phenylalanine on the following day, but has no effect on phenylethylamine or phenylacetic acid concentrations. Thus single measurements per subject of phenylethylamine or phenylacetic acid do not need to take dietary factors into account. 4. Changes in dietary phenylalanine (whether in absolute amount or in the proportion of phenylalanine in the diet) are significantly correlated with changes in unconjugated phenylacetic acid. Therefore, in longitudinal studies, dietary factors should be taken into account.

Psychiatrists' experience of suicide in their patients

Ninety-nine psychiatrists from a defined geographical area were sent a questionnaire asking them to report on clinical, social and demographic characteristics of patients who suicided while under their care. Seventy-three psychiatrists returned the questionnaire and reported having seen a total of 122 suicides. This resulted in a mean of 0.12 suicides per psychiatrist per year of practice. Twenty-four percent of the patients were reported to have had a diagnosis of schizophrenia which is significantly higher than in studies based on coroner's cases. Evidence of withdrawal, considering oneself a burden to others and help negation are factors that had frequently been present in the month prior to the suicide. The authors recommend that these three factors should be examined further by using a prospective strategy.

Resolving the conflict of training and therapy in psychiatry

This paper poses the question of whether psychiatric patients are disadvantaged by their exposure to psychiatric residents. The advantages and disadvantages of short residency rotations both for patient treatment and resident education are examined. Recommendations are suggested for alternative models of supervision which may reduce the negative effects of short-term rotations on therapeutic outcome and result in improved educational opportunities for psychiatric residents, especially in the area of chronic care.