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We have previously reported a changed mitochondrial (mt) gene expression in brain from patients with schizophrenia [Schizophr. Res. 14 (1995) 203]; now, we describe the distribution in the mtDNA from lymphocytes of a heteroplasmic sequence variation that was originally found in the mtDNA from the postmortem brain of a patient with schizophrenia. The variant is m.12027T>C and results in the change from isoleucine to threonine at position 423 of the ND4 subunit of NADH-ubiquinone reductase. Using a PCR-RFLP method, we have determined the heteroplasmy as the ratio of variant to total (variant ratio) at m.12027 in 184 controls and 181 patients with schizophrenia as well as 24 postmortem brain samples. The distribution of variants is bimodal having peaks at variant ratios of 0.262 and 0.732. The variant-rich fraction is very significantly associated with schizophrenia in males (47%), while there is only 18% in control males. There are significantly more variant-rich control females (36%) than control males (18%), suggesting that the female population is less sensitive to the presence of a variant in terms of liability to schizophrenia. In variant-rich samples from postmortem brain originating from both sexes, there is an increased superoxide production, suggesting that the variation contributes to oxidative stress. Antioxidant glycosides, such as quercetin rutoside, quench the superoxide production without (in contrast to neuroleptic drugs) interfering with the electron transfer activity of the reductase.

The effects of the neuroleptic flupenthixol on the expression of the genes coding for the mitochondrial ubiquinone and cytochrome b5 reductases have been studied because of the importance of these enzymes in energy metabolism, oxidative stress and also because similar but oppositely directed changes have been previously observed in the cerebral cortex from schizophrenics. The neuroleptic flupenthixol reduces the expression in rats of the gene coding for NADH-cytochrome b5 reductase as measured by in situ hybridisation and its enzymic manifestation. Flupenthixol also reduces the enzymic activity of the mitochondrial NADH-ubiquinone reductase, and it has been previously shown that mRNA from the mitochondrially coded parts of the enzyme are reduced by the drug. Both the cis- and therapeutically less active trans-flupenthixol were found to produce these changes in rats. Post-mortem brain tissue from schizophrenics who have received neuroleptic medication have reduced levels of both reductases as measured enzymically, Lymphocyte samples from schizophrenics also have reduced levels of both reductases compared with normals. The superoxide anion O2- is the principle agent of oxidative stress and both the cytochrome b5 and the ubiquinone reductase enzymes were semi-purified from sheep liver and shown to produce appreciable amounts of superoxide. Superoxide production is reduced in brain homogenates from rats treated with flupenthixol. Its production is also reduced in brain tissue and lymphocytes from schizophrenics receiving neuroleptic medication. We conclude that neuroleptic medication reduces the expression of both the ubiquinone and cytochrome b5 reductase and among the effects of this reduction is a decrease in the production of neurotoxic superoxide.

Gene expression has been studied in post-mortem frontal cortex samples from patients who had suffered from schizophrenia and depressive illness. mRNA was extracted and characterised by translation and separation of the products by 2D gel electrophoresis. Post-mortem artefacts and the agonal experience did not affect the size distribution or amount of specific translation products. Four expression products were specifically reduced in samples from schizophrenics compared with normals. The expression of six products was altered in affective disorder, one in common with schizophrenia, two the same as in schizophrenia but increased. cDNA libraries were produced from the mRNA samples and 5 clones present at abnormal levels in schizophrenia identified by differential screening, isolated and sequenced. All the sequences encode mitochondrial transcripts; four encode mitochondrial rRNA and one the amino acid sequence of cytochrome oxidase sub-unit II. Increased cytochrome oxidase transcripts were found in a further set of mRNA extracts from schizophrenic patients including two who had not received neuroleptic medication. The effects of neuroleptic administration as exemplified by alpha-flupenthixol compared with the ineffective beta-flupenthixol were studied in experimental animals. It was found that 13 out of 28 clones whose levels were altered were mitochondrial in origin including rRNA, COX I & II and the NADH-Q reductase. Those encoding respiratory enzymes were at abnormally low levels as a result of alpha-flupenthixol administration. Measurements of the enzymic activity of cytochrome c oxidase in post-mortem frontal cortex of schizophrenics did not indicate any differences in overall activity but there was a decreased sensitivity to azide that was abolished by neuroleptics. Studies on NADH-cytochrome c reductase showed that schizophrenics whether medicated or not had a reduced rotenone sensitive activity that was compensated for by increased rotenone insensitive activity. We conclude that changes in mitochondrial gene expression are involved in schizophrenia and probably other functional psychoses.

In order to examine the molecular basis of schizophrenia we have employed a sequential differential hybridisation protocol to isolate mRNAs whose abundances are altered in schizophrenic compared to normal frontal cortex. Five cDNAs present at abnormal levels in the schizophrenic brain have been isolated by this method. The sequences were identified on the basis of homologies in the EMBL and Genbank databases. All the sequences encode mitochondrial transcripts; one encodes part of the 12s rRNA, three encode parts of the 16s rRNA region of the mitochondrial genome whilst the fourth encodes part of the amino acid sequence of cytochrome oxidase sub-unit II. It was established that mitochondrial sequences were not over-represented in the library and that this could therefore not account for the isolation of five mitochondrial transcripts by this procedure. Increased levels of cytochrome oxidase mRNA were detected in a further set of extracts from the frontal cortex of eight schizophrenic patients and five controls. The amount of mt-DNA was measured in these samples but there was no difference between schizophrenic and control. These results indicate a possible abnormality of mitochondrial function in the schizophrenic frontal cortex.

Poly(A+) mRNA was extracted from the post-mortem brain of schizophrenics (9 subjects), unipolar depressives (5 subjects) and controls (10 subjects) and used to direct the in vitro translation of radiolabelled protein in a cell-free reticulocyte-lysate system. Protein species were analysed on two-dimensional gels. Over 200 products were detected and, from these, 74 well-resolved species were chosen for further analysis. The optical density of each product was quantified by image analysis and normalised with respect to overall gel intensity. It was found that 7 novel, uncharacterised protein species, ranging from molecular weights (Mr) 17 kDa to 38 kDa and apparent isoelectric points (pI) 5.7-7.1, changed significantly in intensity in the psychotic groups compared to controls. One species changed only in the schizophrenia group (Mr = 26 kDa, pI = 5.8, 18% of control intensity) and 3 changed only in the depressive group (Mr = 38 kDa, pI = 6.2, 540% of control; Mr = 34 kDa, pI = 6.2, 6% of control; Mr = 17 kDa, pI = 5.7, 238% of control). Three further protein species were common to both psychotic groups (one species decreased in both schizophrenia and depression, Mr = 33 kDa, pI = 5.8; two species showed opposing intensity changes, decreasing in schizophrenia and increasing in depression, Mr = 35 kDa, pI = 7.1; Mr = 23 kDa, pI = 6.1). None of these changes was a function of post-mortem delay or mode of death. It is quite likely that such protein species reflect the abundance of specific mRNAs and target gene systems associated with the disease state.(ABSTRACT TRUNCATED AT 250 WORDS)

Total cellular polyadenylated RNA (poly(A)+ RNA, mRNA) was prepared after guanidinium thiocyanate extraction of frozen brain tissue from age-matched controls and patients suffering from schizophrenia and unipolar depression. These mRNA populations were analysed by in vitro translation followed by two-dimensional gel analysis. Data were obtained from fluorograms derived from 10 different schizophrenic patients, 10 different controls and 5 different depressive patients. The relative concentrations of mRNA species coding for 4 translation products (33 kDa, pI 5.8; 26 kDa, pI 5.8; 35 kDa, pI 7.1; 23 kDa, pI 6.1) were significantly reduced in schizophrenia compared to controls when determined by computerised image analysis of the fluorograms. In the case of depression, the relative concentrations of mRNA species coding for 6 translation products were significantly altered, 4 being increased (38 kDa, pI 6.2, 17 kDa, pI 5.7, 35 kDa, pI 7.1; 23 kDa, pI 6.1) and two decreased (34 kDa, pI 6.2; 33 kDa, pI 5.8). Three translation products were altered in both schizophrenia and depression, one (33 kDa, pI 5.8) being altered according to the same trend, a decrease relative to controls, but two (35 kDa, pI 7.1; 23 kDa, pI 6.1) being altered differently in schizophrenia (reduced) and depression (increased). The effects of post mortem delay, mode of death and drug treatment on mRNA composition were also examined and found not to affect the levels of these translation products significantly. The significance of these changes will be discussed in relation to their relevance of biological mechanisms in the psychoses.

The report of a putative schizophrenia susceptibility gene linked to markers in the chromosome 5q11-q13 region and subsequent failures of replication have provoked considerable controversy. We here report six Welsh families multiply affected with schizophrenia in which there is no evidence for linkage between a dominant-like schizophrenia gene and 5q11-q13 markers. It is argued that our new results together with a combined reanalysis of previous studies suggest that a schizophrenia susceptibility gene can be excluded from the 5q11-q13 region. The apparent disparities between published results are most likely to reflect a chance finding in the one positive study and probably should not be interpreted as resulting from true linkage heterogeneity.

Messenger RNA, obtained from post-mortem brain of 10 schizophrenics, five depressed patients and 10 control subjects, was characterised with respect to a number of parameters. It was found that post-mortem delay was not the major factor in determining RNA yield, size (as determined by cDNA synthesis) and biological activity. Biological activity, as determined by in vitro translation in a reticulocyte-lysate system, could be observed using messenger RNA from periods of 0 to 84 hours post-mortem. Two-dimensional gel analysis of the newly-synthesised radiolabelled products obtained from this material revealed several hundred individual species but no consistent degradation of any particular species with post-mortem delay. It is suggested, therefore, that premortem changes are as important as post-mortem changes in determining RNA yield, size and biological activity. Although no consistent difference could be found between patients and controls using any of these parameters, this study confirms that, by isolating messenger RNA from post-mortem human brain, valuable information can be gained on gene expression in psychiatric disorders.