Transcription factor AP-2beta genotype, striatal dopamine D2 receptor density and cerebrospinal fluid monoamine metabolite concentrations in humans.

Transcription factor AP-2beta has been suggested to influence brain monoaminergic systems by regulating target genes. In order to explore a possible functional role, AP-2beta genotype was analysed in relation to striatal dopamine D2 receptor density determined in vivo by positron emission tomography in human subjects (n = 52). The AP-2beta genotype was also analysed in relation to cerebrospinal fluid (CSF) concentrations of homovanillic acid (HVA), 3-methoxy-4-hydroxy-phenylglycol (MHPG) and 5-hydroxyindoleacetic acid (5-HIAA) in healthy human subjects (n = 90). There was no association between the AP-2beta genotype and measures of dopamine receptor density, or CSF 5-HIAA concentrations. However, AP-2beta genotype was associated with CSF-levels of HVA (in women) and MHPG. These data may suggest a functional involvement of AP-2beta in the dopaminergic system, but should be interpreted with caution until replicated.

A systematic genomewide linkage study in 353 sib pairs with schizophrenia.

We undertook a genomewide linkage study in a total of 353 affected sib pairs (ASPs) with schizophrenia. Our sample consisted of 179 ASPs from the United Kingdom, 134 from Sweden, and 40 from the United States. We typed 372 microsatellite markers at approximately 10-cM intervals. Our strongest finding was a LOD score of 3.87 on chromosome 10q25.3-q26.3, with positive results being contributed by all three samples and a LOD-1 interval of 15 cM. This finding achieved genomewide significance (P<.05), on the basis of simulation studies. We also found two regions, 17p11.2-q25.1 (maximum LOD score [MLS] = 3.35) and 22q11 (MLS = 2.29), in which the evidence for linkage was highly suggestive. Linkage to all of these regions has been supported by other studies. Moreover, we found strong evidence for linkage (genomewide P<.02) to 17p11.2-q25.1 in a single pedigree with schizophrenia. In our view, the evidence is now sufficiently compelling to undertake detailed mapping studies of these three regions.

Autoradiographic mapping of 5-HT(1B) and 5-HT(1D) receptors in the post mortem human brain using [(3)H]GR 125743.

The distribution of 5-HT(1B) and 5-HT(1D) receptors in the human post mortem brain was examined using whole hemisphere autoradiography and the radioligand [(3)H]GR 125743. [(3)H]GR 125743 binding was highest in the substantia nigra and the globus pallidus. Lower levels were detected in the striatum, with the highest densities in the ventromedial parts. In the amygdala, the hippocampus, the septal region and the hypothalamus, lower [(3)H]GR 125743 binding was observed, reflecting low densities of 5-HT(1B/1D) receptors. In the cerebral cortex, binding was similar in most regions, although restricted parts of the medial occipital cortex were markedly more densely labeled. Binding densities were very low in the cerebellar cortex and in the thalamus. Two methods were used to distinguish between the two receptor subtypes, the first using ketanserin to block 5-HT(1D) receptors and the second using SB 224289 to inhibit 5-HT(1B) receptor binding. The autoradiograms indicated that in the human brain, the 5-HT(1B) receptor is much more abundant than the 5-HT(1D) receptor, which seemed to occur only in low amounts mainly in the ventral pallidum. Although [(3)H]GR 125743 is a suitable radioligand to examine the distribution of 5-HT(1B) receptors in the human brain in vitro, the selectivities of ketanserin and SB 224289 are not sufficiently high to give definite evidence for the occurrence of the 5-HT(1D) receptor in the human brain.

Characterization of human cleaved N-CAM and association with schizophrenia.

The neural cell adhesion molecule (N-CAM) is a cell recognition molecule involved in cellular migration, synaptic plasticity, and CNS development. A 105- to 115-kDa isoform of N-CAM (cleaved N-CAM or cN-CAM) is increased in schizophrenia in hippocampus, prefrontal cortex, and CSF. We purified and partially characterized cN-CAM, a putative novel isoform, and confirmed that the first 9 amino acids were identical to exon 1 of N-CAM, without the signal sequence. Analysis of trypsin-digested cN-CAM fragments by matrix-assisted laser desorption ionization on a time-of-flight mass spectrometer (MALDI-TOF) yielded peptides that could be identified as being derived from the first 548 amino acid residues of the expected N-CAM amino acid sequence. Immunological identification with four specific N-CAM antisera directed toward cytoplasmic, secreted, variable alternative spliced exon, or GPI epitopes failed to indicate other known splice variants. Neuraminidase treatment of cN-CAM produced a minor alteration resulting in a faster migrating immunoreactive band, indicating partial glycosylation of cN-CAM. Membranous particles from cytosolic brain extract containing cN-CAM were obtained by ultracentrifugation; however, CSF contained few such particles. cN-CAM and synaptophysin were colocalized on these particles. Both cN-CAM and N-CAM 180 were present in synaptosomal preparations of human brain. Following incubation of synaptosomes or brain tissue without protease inhibitors, N-CAM 180 was degraded and cN-CAM was increased. A cN-CAM-like band was present in human fetal neuronal cultures, but not in fetal astrocyte cultures. Thus, cN-CAM represents a protease- and neuraminidase-susceptible fragment possibly derived by proteolytic cleavage of N-CAM 180. An enlargement in ventricular volume in a group of adult patients with schizophrenia over a 2-year interval was found to be correlated with CSF cN-CAM levels as measured at the time of the initial MRI scan (r = 0.53, P = 0.01). cN-CAM is associated with ventricular enlargement; thus, the release of N-CAM fragments may be part of the pathogenic mechanism of schizophrenia in vulnerable brain regions such as the hippocampus and prefrontal cortex. Alternatively, the increases in cN-CAM in schizophrenia may be a reflection of a more general abnormality in the regulation of proteolysis or of extracellular matrix stability.

No association between a promoter dopamine D(4) receptor gene variant and schizophrenia.

The dopamine D(4) receptor has been implicated in the pathogenesis of schizophrenia. An association between a putative functional promoter polymorphism (-521C/T) in the dopamine D(4) receptor gene (DRD4) and schizophrenia was recently reported. In the present study, patients with schizophrenia (n = 132) and control subjects (n = 388) were analyzed with respect to the DRD4 - 521C/T polymorphism. No significant case control differences emerged. The present results do not support a major role for DRD4 in the etiology of schizophrenia among Caucasians from Sweden.

D1 and D2 dopamine receptor mRNA expression in whole hemisphere sections of the human brain.

Understanding dopamine signaling in human behavior requires knowledge of the distribution of all molecular components involved in dopamine pathways throughout the human brain. In the present study, the relative distributions of D1 and D2 dopamine receptor mRNAs were determined by in situ hybridization histochemistry in whole hemisphere sections from normal human post mortem brains. The findings confirmed information documented from single structure examination that the highest expression of both the D1 and D2 mRNAs were localized to the striatum. The cerebral cortex expressed moderate D1 mRNA in all regions with the highest signal in the medial orbital frontal area (Brodmann areas 11, 14), the paraterminal gyrus (Brodmann area 32) and the insular cortex (Brodmann areas 13-16), whereas the D2 mRNA expression had very low cortical expression. The bed nucleus of the stria terminalis and islands of Calleja had high expression of the D1 mRNA and moderate D2 mRNA levels. Moderate to high expression of the D2 mRNA was evident in the hippocampal formation, parafascicular and paraventricular thalamic nuclei, geniculate bodies, subthalamic nucleus, and pineal gland, all of which were devoid of, or showed only faint, D1 mRNA expression. Brainstem regions, e.g. substantia nigra, red nucleus, inferior colliculus, medial lemniscus, and pontine nuclei expressed D2, but not D1, mRNA. These results emphasize the differential anatomical localization of D1 and D2 dopamine receptor mRNA neuronal populations in the human brain. The restricted expression of the D1 mRNA to the cortical mantle and to a few forebrain structures indicates a strong involvement of the D1 system in cognitive function.

No association between serotonin 2A receptor gene variants and personality traits.

Among theories of biological underpinnings to personality traits, different mechanisms of the serotonergic system are perhaps the most common factors suggested to influence individual differences in personality traits. We have investigated two frequent variants in the serotonin 2A receptor gene (5-HT2A) and personality traits. Healthy Swedish subjects (n = 304) were assessed with the Karolinska Scales of Personality (KSP) inventory. After correction for multiple testing, no significant differences were found. We conclude that the investigated 5-HT2A gene variants do not significantly influence personality as assessed by the KSP in the present population.

Identification of four novel polymorphisms in the calcitonin/alpha-CGRP (CALCA) gene and an investigation of their possible associations with Parkinson disease, schizophrenia, and manic depression.

We identified novel polymorphisms in the calcitonin/CGRPalpha (CALCA) gene by direct sequencing of genomic DNA and subsequent genotyping by RFLP (restriction fragment length polymorphism) detection and investigated association with neurological or psychiatric disease. Four novel polymorphic alleles were found: two (g.979G>A and g.4218T>C) represented single nucleotide polymorphisms (SNPs), one consisted of two coupled SNPs in close vicinity to each other (g.1210T>C and g.1214C>G), and one was an intronic 16-bp microdeletion (2919-2934del16). One of the SNPs (g.4218T>C) causes a non-synonymous amino acid change (Leu66Pro) in the third exon, an exon common to both procalcitonin and pro-alpha-CGRP. In a subsequent association study, frequencies of the identified polymorphisms in Parkinson and schizophrenia patients were compared with frequencies in the normal population. No statistically significant association was found in our material. The 16-bp microdeletion polymorphism was present in a family with multiple cases of unipolar or bipolar depressive disorder. Using this polymorphism as marker, cosegregation with the phenotype was observed in the majority of individuals.

SPET imaging of central muscarinic acetylcholine receptors with iodine-123 labelled E-IQNP and Z-IQNP.

1-Azabicyclo[2.2.2]oct-3-yl alpha-hydroxy-alpha-(1-iodo-1-propen-3-yl)-alpha-phenylacetate (IQNP) is a muscarinic acetylcholine receptor (mAChR) antagonist and the racemic ligand contains eight stereoisomers. In a single-photon emission tomography (SPET) study in monkeys we recently confirmed that [123I]E-(R,R)-IQNP ([123I]E-IQNP) is a radioligand with modest selectivity for the M1 and M4 subtypes, whereas [123I]Z-(R,R)-IQNP ([123I]Z-IQNP) is non-subtype selective. In the present SPET study, E- and Z-IQNP were examined in human subjects. SPET examination was performed on three male subjects after i.v. injection of [123I]E-IQNP and in another three after i.v. injection of [123I]Z-IQNP. The binding potential (BP) for [123I]E-IQNP was calculated using several quantitative approaches with the cerebellum as a reference region. High-performance liquid chromatography was used to measure radioligand metabolism in plasma. Following [123I]E-IQNP, the radioactivity was high in the neocortex and striatum, intermediate in the thalamus and low in the pons and cerebellum, which is consistent with the rank order for the regional density of M1 and M4 subtypes in vitro. For all regions, peak equilibrium was identified within the 48-h data acquisition. The simplified reference tissue approach using SPET data from 0 to 48 h was the most reliable in this limited series of subjects. Following injection of [123I]Z-IQNP, radioactivity was high in the neocortex and striatum, intermediate in the thalamus and pons and low in the cerebellum, which is in agreement with the density of M1, M2 and M4 subtypes as measured in vitro. Quantitative analyses provided indirect support for specific M2 binding of Z-IQNP in the cerebellum. The high selectivity of [123I]E-IQNP for M1 and M4 receptors allowed the use of cerebellum as a reference region devoid of specific binding, and may be advantageous for applied clinical studies of M1 and M4 receptors binding in man. [123I]Z-IQNP has potential for exploration of M2 receptor binding in the cerebellum.

Reliability and reproducibility of brain tissue volumetry from segmented MR scans.

Reliable measurement of different tissue volumes in the living brain is of great importance for human brain research. In this article, we report on the inter- and intraoperator reliability and scan-rescan reproducibility of segmented intracranial tissue volumes from MR images using the image analysis software suite BRAINS. The absolute data of tissue volume measurements are also presented. The reliability and consistency of the measurements of the segmented volumes were excellent. The segmentation is robust and rapid and the volume measurements are plausible and suitable for quantitative studies in clinical brain research.

NURR1 mutations in cases of schizophrenia and manic-depressive disorder.

Transgenic mice lacking the nuclear orphan transcription factor Nur-related receptor 1 (Nurr1) fail to develop mesencephalic dopamine neurons. There is a highly homologous NURR1 gene in humans (formerly known as NOT) which therefore constitutes a good candidate gene for neurologic and psychiatric disorders with an involvement of the dopamine neuron system, such as Parkinson's disease, schizophrenia, and manic-depression. By direct sequencing of genomic DNA, we found two different missense mutations in the third exon of NURR1 in two schizophrenic patients and another missense mutation in the same exon in an individual with manic-depressive disorder. All three mutations caused a similar reduction of in vitro transcriptional activity of NURR1 dimers of about 30-40%. Neither of these amino acid changes, nor any sequence changes whatsoever, were found in patients with Parkinson's disease or control DNA material of normal populations. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:808-813, 2000.

Autoradiographic localization of 5-HT(2A) receptors in the human brain using [(3)H]M100907 and [(11)C]M100907.

M100907 (MDL 100907, R-(+)-alpha-(2, 3-dimethoxyphenyl)-1-[2-(4-fluorophenyl)ethyl]-4-piperidinemethanol++ +) is a new selective antagonist of 5-HT(2A) receptors. The compound has been labeled with (11)C and proved useful for in vivo studies of 5-HT(2A) receptors using positron emission tomography (PET). In the present study the distribution of 5-HT(2A) receptors was examined in the postmortem human brain using whole hemisphere autoradiography and [(3)H]M100907 and [(11)C]M100907. The autoradiograms showed very dense binding to all neocortical regions, whereas the hippocampus was only weakly labeled with [(3)H]M100907. Other central brain regions, such as the basal ganglia and thalamus, showed low [(3)H]M100907 binding, reflecting low densities of 5-HT(2A) receptors. The cerebellum or structures of the brain stem were virtually devoid of 5-HT(2A) receptors. [(11)C]M100907 gave images qualitatively similar to those of [(3)H]M100907, although with lower spatial resolution. The labeling of human 5-HT(2A) receptors with [(3)H]M100907 was inhibited by the addition of the 5-HT(2A) receptor blockers ketanserin or SCH 23390 (10 microM), leaving a very low background of nonspecific binding. The 5-HT(1A) receptor antagonist WAY-100635 and the D(2)-dopamine receptor antagonist raclopride had no effect on the binding of [(3)H]M100907. The selective labeling of 5-HT(2A) receptors with [(3)H]M100907 clearly shows that this compound is suitable for further studies of the human 5-HT(2A) receptor subtype in vitro. The in vitro autoradiography of the distribution of 5-HT(2A) receptors obtained with radiolabeled M100907 provides detailed qualitative and quantitative information on the distribution of 5-HT(2A)-receptors in the human brain as well as reference information for the interpretation of previous initial results at much lower resolution in humans in vivo with PET and [(11)C]M100907.

A 39-year followup of the Genain quadruplets.

The Genains, a unique group of monozygotic female quadruplets, all developed a schizophrenic disorder by age 24. They have been studied since the 1950s, because of the rarity of this occurrence (estimated to be one in 1.5 billion) and because their illnesses varied in severity. The identical inheritance would tend to rule out genetic differences as the cause of the neuropsychological differences; however, we cannot disentangle the effects of early brain injury and harsh punitive treatment as factors accounting for the differences in the severity of their disorders. We conducted neuropsychological examinations of the Genains at age 66, compared their test profiles, and contrasted certain test scores at 66 with those at ages 27 and 51. Test results indicate generally stable (or even improved) performance over time and support the notion that cognitive decline is not a degenerative process in schizophrenia. The Genains remind us of the exquisite interaction among variables that must be understood before additional, satisfactory progress can be made in preventing the development and predicting the course of schizophrenia.

A promoter polymorphism in the monoamine oxidase A gene and its relationships to monoamine metabolite concentrations in CSF of healthy volunteers.

Concentrations of monoamine metabolites (MM) in lumbar cerebrospinal fluid (CSF) have been used extensively as indirect estimates of monoamine turnover in the brain. We investigated possible relationships between a putative functional promoter polymorphism in the monoamine oxidase A (MAOA) gene and CSF concentrations of homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA), and 3-methoxy-4-hydroxyphenylglycol (MHPG) in healthy volunteers (n=88). Among women (n=37), those carrying at least one copy of the alleles associated with more efficient transcription displayed higher concentrations of HVA (p=0.01) and 5-HIAA (p=0.01). In men (n=51), however, there was a tendency in the opposite direction. The results suggest that MAOA genotypes may participate differentially in the regulation of dopamine and serotonin turnover rates under presumed steady state in the central nervous system. The results should be interpreted with caution until replicated because of the limited sample size.

Z-IQNP: a potential radioligand for SPECT imaging of muscarinic acetylcholine receptors in Alzheimer's disease.

RATIONALE: The density of the M2 subtype of muscarinic acetylcholine receptors (mAChR) has been shown to be reduced in the brain of patients with Alzheimer's disease (AD). It is therefore of interest to develop a brain imaging method for diagnostic purposes. Z-(R,R)-1-azabicyclo[2.2.2]oct-3-yl alpha-hydroxy-alpha-(1-iodo1-propen-3-yl)-alpha-phenylacetat e (Z-IQNP) is a muscarinic antagonist with high affinity for the M2 subtype. OBJECTIVE: The pharmacological characteristics and topographic distribution of radiolabelled Z-IQNP as a radioligand for the M2 mAChR subtype were examined in vitro and in vivo. METHODS: Z-IQNP was labelled with 1251 and 123I. Autoradiography was performed on whole-hemisphere cryosections from human post mortem brains. SPECT was performed in a cynomolgus monkey. RESULTS: Autoradiography showed binding of [125I]Z-IQNP in all brain regions, which was inhibited by the non-selective muscarinic antagonist scopolamine. The addition of BIBN 99, a compound with high affinity for the M2 subtype, inhibited [125I]Z-IQNP binding particularly in the cerebellum, which has a high density of the M2 subtype. SPECT demonstrated high uptake of [123I]Z-IQNP in all brain regions. The binding was markedly reduced in all brain regions after pretreatment with the non-selective muscarinic antagonist dexetimide and also the M1 antagonist biperiden. Dexetimide markedly inhibited [123I]Z-IQNP binding in the cerebellum, which is consistent with a high density of M2-receptors in this region. The sigma receptor binding compound DuP 734 had no effect on Z-IQNP binding either in vitro or in vivo. CONCLUSIONS: This study indicates that radiolabelled Z-IQNP has high specificity for mAChR with higher affinity for the M2 than the M1 subtype and negligible affinity for sigma recognition sites both in vitro and in vivo. [123I]Z-IQNP should be useful for future SPECT studies in AD for examination of the density of M2 receptors particularly in the cerebellum.

Association between a promoter polymorphism in the dopamine D2 receptor gene and schizophrenia.

Genetic factors and dopamine receptor dysfunction have been implicated in the pathophysiology of schizophrenia. Recently, an association between a putative functional promoter polymorphism (-141C Ins/Del) in the dopamine D2 receptor gene and schizophrenia was reported. We investigated unrelated Swedish schizophrenic patients (n = 129) and control subjects (n = 179) for the same polymorphism. Similarly to a previous Japanese report, the - 141C Del allele frequency was significantly lower in patients than controls (chi2=4.4, 1 df, p<0.05; odds ratio 0.49, 95% confidence interval 0.26-0.91). The present and previous results may indicate that the -141C Ins/Del dopamine D2 receptor gene polymorphism affects susceptibility to schizophrenia.

Polymorphisms in the dopamine D2 receptor gene and their relationships to striatal dopamine receptor density of healthy volunteers.

The density of striatal dopamine D2 receptors has been shown to vary considerably among healthy subjects. This variability might be due to genetic or environmental factors. In the present analysis we searched for relationships between dopamine D2 receptor gene (DRD2) polymorphisms and striatal dopamine D2 receptor density in vivo, as measured by positron emission tomography and [11C]raclopride in 56 healthy subjects. There was a significant association between presence of a putative functional DRD2 promoter allele (-141C Del) and high striatal dopamine receptor density (t= 2.32, P= 0.02). In agreement with some previous studies the presence of the DRD2 TaqIA1 allele was associated with measures of low dopamine receptor density (t=2.58, P=0.01). Also the DRD2 TaqIB1 allele was associated with low dopamine receptor density (t= 2.58, P= 0.01) wheras there was no significant relationship between another common silent intronic DRD2 short tandem repeat polymorphism (STRP) and striatal dopamine D2 receptor density. The results suggest that DRD2 genotypes may participate differentially in the regulation of striatal dopamine D2 receptor density in healthy human subjects. The results should be interpreted with caution because of the limited sample size.

Preprotachykinin-A mRNA expression in the human and monkey brain: An in situ hybridization study.

The mRNA expression for preprotachykinin-A (PPT-A) was studied throughout the human and cynomolgus monkey brain to assess the neuroanatomical expression pattern of the PPT-A gene in primates. In situ hybridization showed that the PPT-A mRNA is expressed highly in specific regions of the postmortem human brain, including the striatum, islands of Calleja, hypothalamus (posterior, premammillary, medial mammillary, and ventromedial nuclei), superior and inferior colliculi, periaqueductal gray, and oculomotor nuclear complex. PPT-A mRNA-expressing neurons also were present in the paranigralis (ventral tegmental area) and were scattered in the bed nucleus stria terminalis throughout the sublenticular substantia innominata region, including the diagonal band of Broca and the nucleus basalis of Meynert. In the hippocampus, high PPT-A mRNA expression was localized predominantly to the polymorphic layer of the dentate gyrus; no labeled cells were present in the granular layer. Positively labeled cells also were found scattered in the CA regions as well as in the amygdaloid complex. Neocortical expression of PPT-A mRNA was localized mainly to the deep laminae (layers V/VI), except for the striate cortex (labeling was seen also in superficial layers). The subiculum, thalamus, globus pallidus, ventral pallidum, substantia nigra pars compacta, red nucleus, pontine nuclei, and cerebellum were characterized by very weak to undetectable expression of PPT-A mRNA. An expression pattern was evident in the monkey forebrain similar to that observed in the human, except for the absence of PPT mRNA-expressing cells in the medial mammillary nucleus despite intense expression in supramammillary, lateral mammillary, and premammillary nuclei. Overall, more similarities than differences are apparent between primate species in the expression pattern of the PPT-A gene. J. Comp. Neurol. 411;56-72, 1999.

Trend for an association between schizophrenia and D3S1310, a marker in proximity to the dopamine D3 receptor gene.

There is considerable controversy regarding a putative association between schizophrenia and a biallelic BalI polymorphism in the first exon of the dopamine D3 receptor gene (DRD3), although meta-analyses of published data suggest an association. If such an association exists, it may be detectable at markers physically close to DRD3. Accordingly, we conducted a case-control association study using D3S1310, a short tandem repeat polymorphism located approximately 700 kb telomeric to DRD3 on chromosome 3q13.3. The subjects were Swedish patients with schizophrenia (DSM III-R criteria, n = 110) and screened adult controls (n = 83). A trend for a negative association with the 141 bp allele was detected (chi2 = 7.6, d.f. = 1, P = 0.006; odds ratio 0.46, 95% confidence intervals 0.26, 0.81). However, following corrections for multiple comparisons using subgroups (n = 15) the difference was not significant. Also, due to the risk for population stratification in case-control association studies the results must be treated as tentative. If replicated the results may lend further support for the proposition of an association between schizophrenia and DRD3 or a gene in close proximity to DRD3 on chromosome 3q.

No association between serotonin transporter gene polymorphisms and personality traits.

Human family and twin studies have established considerable heritable components in personality traits as assessed by self-report questionnaires. Recently, an association between a functional polymorphism in the upstream regulatory region of the serotonin transporter gene and neuroticism-related personality traits was reported. Two different serotonin transporter polymorphisms including the previously associated variant were genotyped in two samples of healthy Swedish subjects (n = 127 and n = 178, respectively) assessed with the Karolinska Scales of Personality (KSP) inventory. No statistically significant association between serotonin transporter polymorphisms and any of the eight neuroticism-related KSP scales was found. Thus, the previously reported association between serotonin transporter alleles and neuroticism-related personality traits could not be replicated in the present study.