Cx31 is assembled and trafficked to cell surface by ER-Golgi pathway and degraded by proteasomal or lysosomal pathways

Gap junctions, consisting of connexins, allow the exchange of small molecules (less than 1 KD) between adjacent cells, thus providing a mechanism for synchronizing the responses of groups of cells to environmental stimuli. Connexin 31 is a member of the connexin family. Mutations on connexin 31 are associated with erythrokeratodermia variabilis, hearing impairment and peripheral neuropathy. However, the pathological mechanism for connexin 31 mutants in these diseases are still unknown. In this study, we analyzed the assembly, trafficking and metabolism of connexin 31 in HeLa cells stably expressing connexin 31. Calcein transfer assay showed that calcein transfer was inhibited when cells were treated with Brefeldin A or cytochalasin D, but not when treated with nocodazole or a-glycyrrhetinic acid, suggesting that Golgi apparatus and actin filaments, but not microtubules, are crucial to the trafficking and assembly of connexin 31, as well as the formation of gap junction intercellular communication by connexin 31. Additionally, a-glycyrrhetinic acid did not effectively inhibit gap junctional intercellular communication formed by connexin 31. Pulse-chase assay revealed that connexin 31 had a half-life of about 6 h. Moreover, Western blotting and fluorescent staining demonstrated that in HeLa cells stably expressing connexin 31, the amount of connexin 31 was significantly increased after these cells were treated with proteasomal or lysosomal inhibitors. These findings indicate that connexin 31 was rapidly renewed, and possibly degraded by both proteasomal and lysosomal pathways.

Recent findings on the genetic basis of bipolar disorder

What began as a search for a specific gene for bipolar disorder has now become a search for multiple susceptibility genes as it has be-come clear that the genetic basis of bipolar disorder probably involves multiple genes interacting with each other and with environmental components in as-yet mysterious ways. This article reviews the most recent findings and the emerging picture in the genetics of bipolar disorder.

A missense mutation in the previously undescribed gene Tmhs underlies deafness in hurry-scurry (hscy) mice

Mouse deafness mutations provide valuable models of human hearing disorders and entry points into molecular pathways important to the hearing process. A newly discovered mouse mutation named hurry-scurry (hscy) causes deafness and vestibular dysfunction. Scanning electron microscopy of cochleae from 8-day-old mutants revealed disorganized hair bundles, and by 50 days of age, many hair cells are missing. To positionally clone hscy, 1,160 F(2) mice were produced from an intercross of (C57BL/6-hscy x CAST/EiJ) F(1) hybrids, and the mutation was localized to a 182-kb region of chromosome 17. A missense mutation causing a critical cysteine to phenylalanine codon change was discovered in a previously undescribed gene within this candidate interval. The gene is predicted to encode an integral membrane protein with four transmembrane helices. A synthetic peptide designed from the predicted protein was used to produce specific polyclonal antibodies, and strong immunoreactivity was observed on hair bundles of both inner and outer hair cells in cochleae of newborn +/+ controls and +/hscy heterozygotes but was absent in hscy/hscy mutants. Accordingly, the gene was given the name "tetraspan membrane protein of hair cell stereocilia," symbol Tmhs. Two related proteins (>60% amino acid identity) are encoded by genes on mouse chromosomes 5 and 6 and, together with the Tmhs-encoded protein (TMHS), comprise a distinct tetraspan subfamily. Our localization of TMHS to the apical membrane of inner ear hair cells during the period of stereocilia formation suggests a function in hair bundle morphogenesis.

GJB2 mutations in keratitis-ichthyosis-deafness syndrome including its fatal form

Keratitis-ichthyosis-deafness syndrome (KID; MIM 148210) is a rare congenital disorder characterized by vascularizing keratitis, sensorineural hearing loss (HL), and progressive erythrokeratoderma. Clinical variability including a fatal course of KID in the first year of life has been reported. Germline missense mutations in GJB2, encoding connexin-26, were recently found to cause KID in 14 unrelated juvenile and adult patients. We identified a de novo GJB2 mutation G45E in a patient displaying the fatal form of the disease. No mutations were detected in five other connexin and mitochondrial genes. The G45E mutation was not reported previously in Caucasian patients but was the third most common GJB2 mutation (16% of disease alleles) in Japanese patients with autosomal recessive non-syndromic HL. This finding suggests different modes of action of the same GJB2 mutation depending on the genetic background. This hypothesis was further substantiated by our observation of a variable clinical course in unrelated KID patients from Austria harboring the common D50N mutation in GJB2.

Nuclear and mitochondrial genes mutated in nonsyndromic impaired hearing

Half of the cases with congenital impaired hearing are hereditary (HIH). HIH may occur as part of a multisystem disease (syndromic HIH) or as disorder restricted to the ear and vestibular system (nonsyndromic HIH). Since nonsyndromic HIH is almost exclusively caused by cochlear defects, affected patients suffer from sensorineural hearing loss. One percent of the total human genes, i.e. 300-500, are estimated to cause syndromic and nonsyndromic HIH. Of these, approximately 120 genes have been cloned thus far, approximately 80 for syndromic HIH and 42 for nonsyndromic HIH. In the majority of the cases, HIH manifests before (prelingual), and rarely after (postlingual) development of speech. Prelingual, nonsyndromic HIH follows an autosomal recessive trait (75-80%), an autosomal dominant trait (10-20%), an X-chromosomal, recessive trait (1-5%), or is maternally inherited (0-20%). Postlingual nonsyndromic HIH usually follows an autosomal dominant trait. Of the 41 mutated genes that cause nonsyndromic HIH, 15 cause autosomal dominant HIH, 15 autosomal recessive HIH, 6 both autosomal dominant and recessive HIH, 2 X-linked HIH, and 3 maternally inherited HIH. Mutations in a single gene may not only cause autosomal dominant, nonsyndromic HIH, but also autosomal recessive, nonsyndromic HIH (GJB2, GJB6, MYO6, MYO7A, TECTA, TMC1), and even syndromic HIH (CDH23, COL11A2, DPP1, DSPP, GJB2, GJB3, GJB6, MYO7A, MYH9, PCDH15, POU3F4, SLC26A4, USH1C, WFS1). Different mutations in the same gene may cause variable phenotypes within a family and between families. Most cases of recessive HIH result from mutations in a single locus, but an increasing number of disorders is recognized, in which mutations in two different genes (GJB2/GJB6, TECTA/KCNQ4), or two different mutations in a single allele (GJB2) are involved. This overview focuses on recent advances in the genetic background of nonsyndromic HIH.

Meta-analysis in psychiatric genetics

The article reviews literature on methods for meta-analysis of genetic linkage and association studies, and summarizes and comments on specific meta-analysis findings for psychiatric disorders. The Genome Scan Meta-Analysis and Multiple Scan Probability methods assess the evidence for linkage across studies. Multiple Scan Probability analysis suggested linkage of two chromosomal regions (13q and 22q) to schizophrenia and bipolar disorder, whereas Genome Scan Meta-Analysis on a larger sample identified at least 10 schizophrenia linkage regions, but none for bipolar disorder. Meta-analyses of pooled ORs support association of schizophrenia to the Ser311Cys polymorphism in DRD2 and the T102C polymorphism in HTR2A, and of attention deficit hyperactivity disorder to the 48-bp repeat in DRD4. The 5-HTTLPR polymorphism in the serotonin transporter gene (SLC6A4) may contribute to the risk of bipolar disorder, suicidal behavior, and neuroticism, but association to the lifetime risk of major depression has not been shown. Meta-analyses support linkage of schizophrenia to regions where replicable associations to candidate genes have been identified through positional cloning methods. There are additional supported regions where susceptibility genes are likely to be identified. Linkage meta-analysis has had less clear success for bipolar disorder based on a smaller dataset. Meta-analysis can guide the prioritization of regions for study, but proof of association requires biological confirmation of hypotheses about gene actions. Elucidation of causal mechanisms will require more comprehensive study of sequence variation in candidate genes, better statistical and meta-analytic methods to take all variation into account, and biological strategies for testing etiologic hypotheses.

Bipolar disorder and polymorphisms in the dysbindin gene (DTNBP1)

BACKGROUND

Several studies support the dysbindin (dystrobrevin binding protein 1) gene (DTNBP1) as a susceptibility gene for schizophrenia. We previously reported that variation at a specific 3-locus haplotype influences susceptibility to schizophrenia in a large United Kingdom (UK) Caucasian case-control sample.

METHODS

Using similar methodology to our schizophrenia study, we have investigated this same 3-locus haplotype in a large, well-characterized bipolar sample (726 Caucasian UK DSM-IV bipolar I patients; 1407 ethnically matched controls).

RESULTS

No significant differences were found in the distribution of the 3-locus haplotype in the full sample. Within the subset of bipolar I cases with predominantly psychotic episodes of mood disturbance (n = 133) we found nominally significant support for association at this haploptype (p < .042) and at SNP rs2619538 (p = .003), with a pattern of findings similar to that in our schizophrenia sample. This finding was not significant after correction for multiple testing.

CONCLUSIONS

Our data suggest that variation at the polymorphisms examined does not make a major contribution to susceptibility to bipolar disorder in general. They are consistent with the possibility that DTNBP1 influences susceptibility to a subset of bipolar disorder cases with psychosis. However, our subset sample is small and the hypothesis requires testing in independent, adequately powered samples.

SNPNB: analyzing neighboring-nucleotide biases on single nucleotide polymorphisms (SNPs)

SNPNB is a user-friendly and platform-independent application for analyzing Single Nucleotide Polymorphism NeighBoring sequence context and nucleotide bias patterns, and subsequently evaluating the effective SNP size for the bias patterns observed from the whole data. It was implemented by Java and Perl. SNPNB can efficiently handle genome-wide or chromosome-wide SNP data analysis in a PC or a workstation. It provides visualizations of the bias patterns for SNPs or each type of SNPs.

AVAILABILITY

SNPNB and its full description are freely available at http://bioinfo.vipbg.vcu.edu/SNPNB/

Patterns of CAG repeat interruptions in SCA1 and SCA2 genes in relation to repeat instability

About 3% of the human genome is composed of simple sequence repeats and many of these sequences occur within genes. These repeats are often polymorphic in a normal population and their expansion in specific genes leads to a number of hereditary neurological diseases. Normal variants of disease-related genes contain either pure or interrupted repeats, and the postulated function of the interruptions is to prevent repeat expansions. Their structural role in the repeat tracts of genes and transcripts awaits detailed characterization. In this study, we have determined the SCA1 and SCA2 genotypes in a Polish population and found significant differences in allele spectra and frequencies from those reported for other populations. They are discussed in relation to the repeat expansion mechanism and disease incidence. We postulate that the dynamic mutation of the genes SCA1 (also ATX1 or ataxin 1) and SCA2 (also ATX2 or ataxin 2) may begin from the expansion of long pure repeat tracts without the prior loss of interruptions. A simple way of cost-effective allelotyping of CAG repeat regions in the SCA1 and SCA2genes is also shown. The reliable SSCP/duplex analysis presented here may be the method of choice for the systematic searching of genes for known and novel interrupted repeats.

A family-based study of the association between the G72/G30 genes and schizophrenia in the Chinese population

Studies have shown a strong positive association between schizophrenia and G72/G30, demonstrated by both individual markers and haplotypes. A further functional study also supports the role of G72 in the etiology of schizophrenia. In this study, we have replicated these results of transmission/disequilibrium testing (TDT) and haplotype analysis in the Han Chinese population, showing P values of 0.0018 and 0.00007 for individual markers and haplotypes, respectively. Hence, our data supports the hypothesis that G72/G30 are important candidate genes for explaining schizophrenia in the Han Chinese population.

The occurrence of dominant spinocerebellar ataxias among 251 Finnish ataxia patients and the role of predisposing large normal alleles in a genetically isolated population

OBJECTIVES

Frequency and distribution of dominant ataxias caused by dynamic mutations may vary in different populations, which has been explained on the basis of relative frequency of predisposing normal alleles. The aim of the study was to evaluate the occurrence of spinocerebellar ataxias (SCAs) and dentatorubral-pallidoluysian atrophy (DRPLA) in Finland, and to investigate the role of predisposing normal alleles in a genetically homogenous population.

MATERIAL AND METHODS

Mutation analyses for SCA1, 2, 3, 6, 7, 8, 10, 12, 17, and DRPLA and frataxin genes were performed for 251 unrelated Finnish patients who presented with progressive ataxia disorder.

RESULTS

Expansions of SCA1, SCA2, SCA6, SCA7, SCA8, and SCA17 genes were detected in 2, 1, 1, 7, 22, and 1 patients, respectively. Altogether, 39 and 7% of dominant and sporadic SCA patients, respectively, harboured expansions at some of the investigated loci. Normal variation, collected from 477 to 502 chromosomes at each disease loci, revealed that Finns were different from the Japanese but largely similar to other Caucasians.

CONCLUSIONS

Lack of SCA3 and excess of SCA8 are characteristic to the Finnish population. Homozygosity for the SCA8 expansion increases penetrance. Frequencies of large normal alleles at the SCA loci predict poorly prevalence of the respective diseases in Finland. Prioritization in DNA testing, based on ethnic origin and geographical location, is recommendable in Finland, and analogous approach may be applied to other countries as well.

Linkage disequilibrium analysis in the LOC93081-KDELC1-BIVM region on 13q in bipolar disorder

Genome-wide scans in bipolar disorder and a meta analysis on published data have provided evidence for linkage to chromosome 13q, although the reported peaks from various studies have not converged in a narrow region. Recently, single nucleotide polymorphisms (SNPs) at the G72/G30 locus have been shown to be associated with bipolar disorder suggesting its potential role in increasing disease risk. The proposed linkage region on 13q extends over a wide span, and could provide a clue to the existence of other susceptibility variants. In the present study, SNPs in the LOC93081-KDELC1-BIVM, a region proximal to G72, were interrogated in two bipolar family series. KDELC1 has a predicted filamin domain and BIVM contains an immunoglobulin-like motif. The small pedigree series yielded a nominally significant global P-value due to under-transmission of a rare haplotype but this finding was not supported by results from the larger series and in the case-control study that compared 278 cases and 277 controls.

Expression of the carrier protein apolipoprotein D in the mouse inner ear

The cochlear portion of the inner ear converts movements produced by sound waves into electrical impulses. Transcripts enriched in the cochlea are likely to have an important role in hearing. In this paper, we report that microarray analyses of the Soares NMIE inner ear library revealed cochlear enriched expression of apolipoprotein D (apoD), a glycoprotein and member of the lipocalin family that transport small hydrophobic ligands. The cochlear enriched expression of Apod was validated by quantitative real time PCR analysis. To investigate the function of apoD in the inner ear the transcript and protein were localised in the cochlea. Apod messenger RNA (mRNA) expression was localised to the spiral ligament and spiral limbus, particularly in the suprastrial and supralimbral regions. The apoD protein was detected in the spiral ligament, spiral limbus and also in the outer hair cells of the organ of Corti. Investigation of cell lines exhibiting characteristics of hair and supporting cells revealed no Apod mRNA expression in these cells. This suggests transport of the protein within the cochlea, followed by internalisation into outer hair cells. The spiral limbus and ligament contain subpopulations of fibrocytes that are intimately involved in regulation of ion balance in the cochlear fluids and type I, II and III fibrocytes of the spiral ligament were all shown to be positive for apoD protein. On the basis of these results it was hypothesised that apoD could be involved in maintaining cochlear fluid homeostasis. To determine whether the apoD gene product was important for normal auditory function the hearing ability of an apoD knockout mouse was tested. The mouse was found to have a hearing threshold that was not significantly different to the control strain.

Mood disorder with psychotic features, schizoaffective disorder, and schizophrenia with mood features: trouble at the borders

Psychiatry has long struggled with the problem of how to understand the relationship between psychotic symptoms and mood symptoms. In the past, these debates were over conceptualizations of categories based on syndromal definitions of mental illnesses. Ample data now exists that provide insight into the biologic basis for syndromal distinctions. We examine the syndromes of mood disorder with psychotic features, schizoaffective disorder, and schizophrenia with mood features, reviewing their classification, clinical features, course, and treatment. We provide evidence that, clinically, mood disorders and schizophrenia do not separate neatly. We will also review data arising from studies in brain imaging, molecular neurobiology, and genetics. Evidence is accumulating that overlap across diagnostic boundaries for both pathologic and etiologic factors exist, along with disorder-specific factors. The nosology that will carve the reality of psychotic illness at the joints awaits further advances in genetics and neurobiology. Or, alternatively, carving out categories may turn out to be less useful for some purposes than considering dimensions.

Neurodevelopment, neuroplasticity, and new genes for schizophrenia

Schizophrenia is a complex, debilitating neuropsychiatric disorder. Epidemiological, clinical, neuropsychological, and neurophysiological studies have provided substantial evidence that abnormalities in brain development and ongoing neuroplasticity play important roles in the pathogenesis of the disorder. Complementing these clinical studies, a range of cytoarchitectural, morphometric, ultrastructural, immunochemical, and gene expression methods have been applied in investigations of postmortem brain tissues to characterize the cellular and molecular profile of putative developmental and plastic abnormalities in schizophrenia. While findings have been diverse and many are in need of replication, investigations focusing on higher cortical and limbic brain regions are increasingly demonstrating abnormalities in the structural and molecular integrity of the synaptic complex as well as glutamate-related receptors and signal transduction pathways that play critical roles in brain development, synaptogenesis, and synaptic plasticity. Most exciting have been recent associations of schizophrenia with specific genes, such as neuregulin-1, dysbindin-1, and AKT-1, which are vital to synaptic development, neurotransmission, and plasticity.

Schizophrenia genes, gene expression, and neuropathology: on the matter of their convergence

This review critically summarizes the neuropathology and genetics of schizophrenia, the relationship between them, and speculates on their functional convergence. The morphological correlates of schizophrenia are subtle, and range from a slight reduction in brain size to localized alterations in the morphology and molecular composition of specific neuronal, synaptic, and glial populations in the hippocampus, dorsolateral prefrontal cortex, and dorsal thalamus. These findings have fostered the view of schizophrenia as a disorder of connectivity and of the synapse. Although attractive, such concepts are vague, and differentiating primary events from epiphenomena has been difficult. A way forward is provided by the recent identification of several putative susceptibility genes (including neuregulin, dysbindin, COMT, DISC1, RGS4, GRM3, and G72). We discuss the evidence for these and other genes, along with what is known of their expression profiles and biological roles in brain and how these may be altered in schizophrenia. The evidence for several of the genes is now strong. However, for none, with the likely exception of COMT, has a causative allele or the mechanism by which it predisposes to schizophrenia been identified. Nevertheless, we speculate that the genes may all converge functionally upon schizophrenia risk via an influence upon synaptic plasticity and the development and stabilization of cortical microcircuitry. NMDA receptor-mediated glutamate transmission may be especially implicated, though there are also direct and indirect links to dopamine and GABA signalling. Hence, there is a correspondence between the putative roles of the genes at the molecular and synaptic levels and the existing understanding of the disorder at the neural systems level. Characterization of a core molecular pathway and a 'genetic cytoarchitecture' would be a profound advance in understanding schizophrenia, and may have equally significant therapeutic implications.

A developmental model for similarities and dissimilarities between schizophrenia and bipolar disorder

Schizophrenia and mania have a number of symptoms and epidemiological characteristics in common, and both respond to dopamine blockade. Family, twin and molecular genetic studies suggest that the reason for these similarities may be that the two conditions share certain susceptibility genes. On the other hand, individuals with schizophrenia have more obvious brain structural and neuropsychological abnormalities than those with bipolar disorder; and pre-schizophrenic children are characterised by cognitive and neuromotor impairments, which are not shared by children who later develop bipolar disorder. Furthermore, the risk-increasing effect of obstetric complications has been demonstrated for schizophrenia but not for bipolar disorder. Perinatal complications such as hypoxia are known to result in smaller volume of the amygdala and hippocampus, which have been frequently reported to be reduced in schizophrenia; familial predisposition to schizophrenia is also associated with decreased volume of these structures. We suggest a model to explain the similarities and differences between the disorders and propose that, on a background of shared genetic predisposition to psychosis, schizophrenia, but not bipolar disorder, is subject to additional genes or early insults, which impair neurodevelopment, especially of the medial temporal lobe.

Coding sequences of functioning human genes derived entirely from mobile element sequences

Among all of the many examples of mobile elements or "parasitic sequences" that affect the function of the human genome, this paper describes several examples of functioning genes whose sequences have been almost completely derived from mobile elements. There are many examples where the synthetic coding sequences of observed mRNA sequences are made up of mobile element sequences, to an extent of 80% or more of the length of the coding sequences. In the examples described here, the genes have named functions, and some of these functions have been studied. It appears that each of the functioning genes was originally formed from mobile elements and that in some process of molecular evolution a coding sequence was derived that could be translated into a protein that is of some importance to human biology. In one case (AD7C), the coding sequence is 99% made up of a cluster of Alu sequences. In another example, the gene BNIP3 coding sequence is 97% made up of sequences from an apparent human endogenous retrovirus. The Syncytin gene coding sequence appears to be made from an endogenous retrovirus envelope gene.

Disrupted in schizophrenia 1 (DISC1): association with schizophrenia, schizoaffective disorder, and bipolar disorder

Schizophrenia, schizoaffective disorder, and bipolar disorder are common psychiatric disorders with high heritabilities and variable phenotypes. The Disrupted in Schizophrenia 1 (DISC1) gene, on chromosome 1q42, was originally discovered and linked to schizophrenia in a Scottish kindred carrying a balanced translocation that disrupts DISC1 and DISC2. More recently, DISC1 was linked to schizophrenia, broadly defined, in the general Finnish population, through the undertransmission to affected women of a common haplotype from the region of intron 1/exon 2. We present data from a case-control study of a North American white population, confirming the underrepresentation of a common haplotype of the intron 1/exon 2 region in individuals with schizoaffective disorder. Multiple haplotypes contained within four haplotype blocks extending between exon 1 and exon 9 are associated with schizophrenia, schizoaffective disorder, and bipolar disorder. We also find overrepresentation of the exon 9 missense allele Phe607 in schizoaffective disorder. These data support the idea that these apparently distinct disorders have at least a partially convergent etiology and that variation at the DISC1 locus predisposes individuals to a variety of psychiatric disorders.

Regional features of autosomal-dominant cerebellar ataxia in Nagano: clinical and molecular genetic analysis of 86 families

The frequency of autosomal-dominant cerebellar ataxia (ADCA) subtypes was examined in 86 unrelated families originating from Nagano prefecture. In Nagano, the prevalence of spinocerebellar degeneration (SCD) was approximately 22 per 100,000 population. Among ADCA families, SCA6 was the most prevalent subtype (16 families, 19%), followed by DRPLA (nine families, 10%), SCA3/MJD (three families, 3%), SCA1 (two families, 2%), and SCA2 (one family, 1%). No families with SCA7, SCA12, or SCA17 were detected. Compared with other districts in Japan, the prevalence of SCA3/MJD was very low in Nagano. More interestingly, the ratio of genetically undetermined ADCA families was much higher in Nagano (55 families, 65%) than in other districts in Japan. These families tended to accumulate in geographically restricted areas such as Kiso, Saku, and Ina, indicating that the founder effect might be responsible for the high frequency of ADCA in these areas. Most patients clinically showed slowly progressive pure cerebellar ataxia of late-onset (ADCA III). In the case of 36 patients from 36 genetically undetermined ADCA III families, however, no one was completely consistent with the founder allele proposed for 16q-ADCA. These results indicate that there might be genetically distinct ADCA subtypes in Nagano.

The contribution of three strong candidate schizophrenia susceptibility genes in demographically distinct populations

Here we characterize and compare the contribution of three recently identified strong candidate schizophrenia susceptibility genes; G72, neuregulin 1 (NRG1) and dystrobrevin-binding protein 1 (DTNBP1) in two independent datasets of patients with distinct genetic backgrounds. On the basis of corrected P-values from single- and multilocus transmission distortion tests our analysis provides no support for a contribution of G72, NRG1 or DTNBP1 in the tested samples. When transmission of individual haplotypes was considered, a picture more consistent with the original studies emerged, where transmission distortions in the same direction as the original samples and involving the same core haplotypes were observed for G72 and NRG1. Interestingly, whereas the NRG1 gene analysis was dominated by the presence of over-transmitted haplotypes, the G72 gene analysis was consistently dominated in both datasets by under-transmissions. Negative transmissions involved a core haplotype complementary to the originally detected over-transmitted haplotype, suggesting the presence of a protective variant within the G72 locus.

Polymorphisms in the trace amine receptor 4 (TRAR4) gene on chromosome 6q23.2 are associated with susceptibility to schizophrenia

Several linkage studies across multiple population groups provide convergent support for a susceptibility locus for schizophrenia--and, more recently, for bipolar disorder--on chromosome 6q13-q26. We genotyped 192 European-ancestry and African American (AA) pedigrees with schizophrenia from samples that previously showed linkage evidence to 6q13-q26, focusing on the MOXD1-STX7-TRARs gene cluster at 6q23.2, which contains a number of prime candidate genes for schizophrenia. Thirty-one screening single-nucleotide polymorphisms (SNPs) were selected, providing a minimum coverage of at least 1 SNP/20 kb. The association observed with rs4305745 (P=.0014) within the TRAR4 (trace amine receptor 4) gene remained significant after correction for multiple testing. Evidence for association was proportionally stronger in the smaller AA sample. We performed database searches and sequenced genomic DNA in a 30-proband subsample to obtain a high-density map of 23 SNPs spanning 21.6 kb of this gene. Single-SNP analyses and also haplotype analyses revealed that rs4305745 and/or two other polymorphisms in perfect linkage disequilibrium (LD) with rs4305745 appear to be the most likely variants underlying the association of the TRAR4 region with schizophrenia. Comparative genomic analyses further revealed that rs4305745 and/or the associated polymorphisms in complete LD with rs4305745 could potentially affect gene expression. Moreover, RT-PCR studies of various human tissues, including brain, confirm that TRAR4 is preferentially expressed in those brain regions that have been implicated in the pathophysiology of schizophrenia. These data provide strong preliminary evidence that TRAR4 is a candidate gene for schizophrenia; replication is currently being attempted in additional clinical samples.

The N-methyl D-aspartate receptor glycine site and D-serine metabolism: an evolutionary perspective

The N-methyl D-aspartate (NMDA) type of glutamate receptor requires two distinct agonists to operate. Glycine is assumed to be the endogenous ligand for the NMDA receptor glycine site, but this notion has been challenged by the discovery of high levels of endogenous d-serine in the mammalian forebrain. I have outlined an evolutionary framework for the appearance of a glycine site in animals and the metabolic events leading to high levels of D-serine in brain. Sequence alignments of the glycine-binding regions, along with the scant experimental data available, suggest that the properties of invertebrate NMDA receptor glycine sites are probably different from those in vertebrates. The synthesis of D-serine in brain is due to a pyridoxal-5'-phosphate (B(6))-requiring serine racemase in glia. Although it remains unknown when serine racemase first evolved, data concerning the evolution of B(6) enzymes, along with the known occurrences of serine racemases in animals, point to D-serine synthesis arising around the divergence time of arthropods. D-Serine catabolism occurs via the ancient peroxisomal enzyme d-amino acid oxidase (DAO), whose ontogenetic expression in the hindbrain of mammals is delayed until the postnatal period and absent from the forebrain. The phylogeny of D-serine metabolism has relevance to our understanding of brain ontogeny, schizophrenia and neurotransmitter dynamics.

Spinocerebellar ataxia type 2 (SCA2) presenting with ophthalmoplegia and developmental delay in infancy

An 11-year-old boy was evaluated for progressive ataxia, cognitive deterioration, and ophthalmoplegia. The child initially presented with abnormal eye movements at the age of 2 months and was noted to have developmental delay at 6 months. At the age of 7 years, he developed ataxia and cognitive impairment, and subsequently manifested dysphagia and incontinence. The pertinent family history included gait difficulty in the paternal grandmother. At the age of 11, his general physical examination was normal. On neurological examination, he had bilateral external ophthalmoplegia, ataxic dysarthria, dysmetria and tremor in the upper extremities, and marked gait ataxia. An ophthalmological evaluation showed no evidence of pigmentary retinopathy. Brain MRI demonstrated cerebellar, brainstem, and cerebral atrophy. An ataxia panel showed 62 repeats in one allele of the SCA2 gene. Most cases of spinocerebellar ataxia type 2 (SCA2) present between 20 years and 40 years, and affected individuals typically have between 34 and 57 CAG repeats. Neonatal cases of SCA2 have been reported in individuals with over 200 CAG repeats. Childhood SCA2 has been reported previously in two patients but not described clinically. This case broadens the spectrum of the clinical features of infantile-onset SCA2 and highlights the importance of considering this diagnosis in infants and children.

Genetics of major mood disorders

The results presented in recent research suggest that nosology must be changed to reflect the genetic origins of the multiple disorders that are collectively described by the term bipolar disorder.

High prevalence of V37I genetic variant in the connexin-26 (GJB2) gene among non-syndromic hearing-impaired and control Thai individuals

Hearing loss is highly prevalent with a worldwide incidence of 1-2 per 1000 newborns. Several previous studies have demonstrated that mutations of connexin 26 (Cx26 or GJB2) are responsible for most cases of the recessive non-syndromic sensorineural hearing loss (NSSHL). Certain mutations have been described frequently among various populations, which include 35delG, 167delT, and 235delC. Recently, a missense mutation, V37I, was reported as a pathogenic change in East Asian affected individuals. To identify genetic variants associated with NSSHL in Thai population, we performed mutation analysis of Cx26 in 166 unrelated probands with NSSHL and 205 controls. We identified seven novel genetic variants in Cx26. We also identified a high prevalence of the V37I mutation among both affected probands (11.1%) and control subjects (8.5%), which suggests that the pathologic role of V37I may be modified by other genes. Our data support previous studies that show heterogeneity in the frequencies and types of mutations in Cx26 within populations and among ethnicities and that before clinical significance and causality can be attributed to a genetic variant, functional characterization is necessary.

Association of G72/G30 with schizophrenia in the Chinese population

Recently, the G72 gene was reported to be associated with schizophrenia in the French Canadian and Russian populations. Here, we report the results obtained from the study of six single-nucleotide polymorphisms (SNPs: rs3916965, rs3916967, rs2391191, rs1935062, rs778293, and rs3918342), which span an 82-kb region covering the complementary DNA sequences of G72 and G30, in 537 schizophrenia cases and 538 controls of the Han Chinese. In this work, we have identified statistically significant differences in allele distributions of two markers rs3916965 (P = 0.019) and rs2391191 (P = 0.0010), and a highly significant association between haplotype AGAC of the G72/G30 locus (P = 1.7 x 10(-4)) and schizophrenia. Our data provide further evidence that markers of the G72/G30 genes are associated with schizophrenia in a non-Caucasian population.

Molecular genetics of affective disorders

Evidence for familial aggregation in Affective Disorders (AD) has been provided in classical studies. Linkage and association genetic studies have been proposed to detect genetic factors implicated in AD. However, findings from molecular genetic studies remain inconclusive. Nevertheless, current research is focusing on the phenotypes, both sub- and endophenotypes. In addition, recent advances in technology, such as microarrays, provide new tools in psychiatric genetics. These different approaches offer a new optimism era in the search of genetic factors in AD.

Is the G72/G30 locus associated with schizophrenia? single nucleotide polymorphisms, haplotypes, and gene expression analysis

BACKGROUND

The genes G72/G30 were recently implicated in schizophrenia in both Canadian and Russian populations. We hypothesized that 1) polymorphic changes in this gene region might be associated with schizophrenia in the Ashkenazi Jewish population and that 2) changes in G72/G30 gene expression might be expected in schizophrenic patients compared with control subjects.

METHODS

Eleven single nucleotide polymorphisms (SNPs) encompassing the G72/G30 genes were typed in the genomic deoxyribonucleic acid (DNA) from 60 schizophrenic patients and 130 matched control subjects of Ashkenazi ethnic origin. Case-control comparisons were based on linkage disequilibrium (LD) and haplotype frequency estimations. Gene expression analysis of G72 and G30 was performed on 88 postmortem dorsolateral prefrontal cortex samples.

RESULTS

Linkage disequilibrium analysis revealed two main SNP blocks. Haplotype analysis on block II, containing three SNPs external to the genes, demonstrated an association with schizophrenia. Gene expression analysis exhibited correlations between expression levels of the G72 and G30 genes, as well as a tendency toward overexpression of the G72 gene in schizophrenic brain samples of 44 schizophrenic patients compared with 44 control subjects.

CONCLUSIONS

It is likely that the G72/G30 region is involved in susceptibility to schizophrenia in the Ashkenazi population. The elevation in expression of the G72 gene coincides with the glutamatergic theory of schizophrenia.

Lack of association between Connexin 31 (GJB3) alterations and sensorineural deafness in Austria

Mutations in the gap junction protein beta 3 (GJB3) gene encoding Connexin 31 (Cx31) are known to cause autosomal inherited sensorineural deafness, erythrokeratodermia and neuropathy. The role of Cx31 mutations has not been described in familial cases of non-syndromic hearing impairment (NSHI) in central European populations. To identify mutations in the Austrian population, highly selected familial (n=24) and sporadic (n=21) cases of isolated NSHI were screened by analysis of the complete coding sequence of Cx31, after exclusion of a common Cx26 causing deafness. Three different variations occurring in a total of 37% of all cases were identified. A C94T (R32W) missense mutation was seen in 4.4% of cases and two silent alterations C357T and C798T were detected in 8.9% and 24.4% of cases exclusively in a heterozygous pattern. No correlation between Cx31 alterations and deafness was found. To investigate the role of heterozygous Cx31 variations for a possibly combination allelic disease inheritance with Cx26 mutations as shown for Connexin 30 and Connexin 26, patients with Cx26 variations were tested. Our data suggest that Cx31 alterations are common but have no or a low genetic relevance in the Austrian hearing impaired population with or without Cx26 alterations.

A case-control study provides evidence of association for a functional polymorphism -197C/G in XBP1 to schizophrenia and suggests a sex-dependent effect

Schizophrenia and bipolar disorder are two major psychiatric illnesses that may share specific genetic risk factors to a certain extent. Increasing evidence suggests that the two disorders might be more closely related than previously considered. In order to test this hypothesis, we investigated a functional polymorphism -197C/G in XBP1, which was reported to increase the risk of bipolar disorder, in a case-control study (374 cases vs. 371 controls) to evaluate its genetic role in the pathogenesis of schizophrenia. In the present study, this polymorphism was found to be associated with schizophrenia both at allele (P=0.034; OR=1.26, 95% CI 1.02-1.55) and genotype levels (GG vs. CG+CC, 47.59% vs. 38.81%; P=0.016, df=1; OR=1.43, 95% CI 1.07-1.92). Our current data suggest that -197C/G in XBP1 is also a genetic risk factor for schizophrenia. In addition, it presents a sex-dependent genetic effect for the disorder.

The genetics of schizophrenia

Schizophrenia is a complex biological disorder with multifactorial mode of transmission where non-genetic determinants are also play important role. It is now clear that it involves combined effect of many genes, each conferring a small increase in liability to the illness. Thus no causal disease genes or single gene of major effects, only susceptible genes are operating. Given this complexity, it comes as no surprise of the difficulty to find susceptible genes. However, schizophrenia genes have been found at last. Recent studies on molecular genetics of schizophrenia which focused on positional and functional candidate genes postulated to be associated with schizophrenia are beginning to produce findings of great interest. These include neuregulin (NRG-1, 8p12-21), dysbindin, (DTNBP1,6p22.3), G72 (13q34) / D-amino acid oxidase (DAAO,12q24), proline dehydrogenase (PRODH-2, 22q11.21), catechol-O-methyltransferase (COMT, 22q11.21), regulator of G protein signaling (RGS-4), 5HT2A and dopamine D3 receptor (DRD3). Applications of microarrays methods were able to locate positional candidate genes related to dopaminergic, serotonergic and glutamatergic neurotransmission. New genome scan project, seen in the light of previous scans, provide support for schizophrenia candidate region on chromosome 1q, 2q, 5q, 6p, 8p, 10p, 13q,15q and 22q. Other reports described including the application of LD mapping and positional cloning technique, microarray technology and efforts to develop quantitative phenotype. More exciting finding is expected in near future with the completion of Hap Map project.

Linkage disequlibrium in the DTNBP1 (dysbindin) gene region and on chromosome 1p36 among psychotic patients from a genetic isolate in Israel: findings from identity by descent haplotype sharing analysis

Several genes have been reported recently to be associated with schizophrenia and bipolar disorder. Because of the complexity of the inheritance of these disorders, there is an urgent need to replicate these findings and to search for additional candidate genes. The study of genetic isolates is a powerful technique that may overcome some of the obstacles caused by genetic heterogeneity and ambiguity of phenotype definition. Identity by descent (IBD) haplotype sharing analysis in these populations may be used to detect mutations within shared haplotypes in smaller samples of affected individuals. In this study, we used IBD haplotype sharing analysis to replicate positive linkage and association findings in psychotic disorders, and to identify other regions of interest. Fifty-two patients with major psychiatric disorders from a genetically isolated village in Israel were studied. By studying eight Y chromosome markers, we were able to confirm the oral tradition of members of this isolate regarding a common paternal origin. Three hundred fifty nine microsatellite markers on 9 candidate chromosomes were genotyped, and haplotypes were reconstructed using information from family members. Two highly significant (P < 0.0001) peaks of haplotype sharing were found. One was for psychotic patients with any diagnosis at the location of dysbindin, a gene previously associated with schizophrenia. The other peak was for patients with schizophrenia on chromosome 1p36. Thus, this study both replicates an earlier finding and points to a novel region of interest, which might be unique to this population.

Evidence for shared susceptibility in bipolar disorder and schizophrenia

This article reviews evidence that bipolar disorder (BPD) and schizophrenia (SZ) share familial risk characteristics. The topic is introduced with a brief discussion of various shared epidemiologic characteristics of SZ and BPD. Family studies of BPD and SZ, conducted by multiple independent groups of investigators, are consistent with partial overlap in familial susceptibility. Given that the family study data suggest overlap in familial susceptibility for BPD and SZ, several confirmed linkages of BPD or SZ are reviewed, with the conclusion that there are five genomic regions for which evidence suggests shared genetic susceptibility of BPD and SZ. It is suggested that nosology must be changed to reflect the genetic origins of the multiple disorders that are collectively described by the terms BPD and SZ.

Autosomal dominant cerebellar ataxias: clinical features, genetics, and pathogenesis

Autosomal dominant cerebellar ataxias are hereditary neurodegenerative disorders that are known as spinocerebellar ataxias (SCA) in genetic nomenclature. In the pregenomic era, ataxias were some of the most poorly understood neurological disorders; the unravelling of their molecular basis enabled precise diagnosis in vivo and explained many clinical phenomena such as anticipation and variable phenotypes even within one family. However, the discovery of many ataxia genes and loci in the past decade threatens to cause more confusion than optimism among clinicians. Therefore, the provision of guidance for genetic testing according to clinical findings and frequencies of SCA subtypes in different ethnic groups is a major challenge. The identification of ataxia genes raises hope that essential pathogenetic mechanisms causing SCA will become more and more apparent. Elucidation of the pathogenesis of SCA hopefully will enable the development of rational therapies for this group of disorders, which currently can only be treated symptomatically.

Polymorphisms in the 13q33.2 gene G72/G30 are associated with childhood-onset schizophrenia and psychosis not otherwise specified

BACKGROUND

Childhood-onset schizophrenia (COS), defined as onset of psychotic symptoms by age 12 years, is a rare and severe form of the disorder that seems to be clinically and neurobiologically continuous with the adult disorder.

METHODS

We studied a rare cohort consisting of 98 probands; 71 of these probands received a DSM-defined diagnosis of schizophrenia, and the remaining 27 were diagnosed as psychosis not otherwise specified (NOS) (upon 2-6 year follow-up, 13 have subsequently developed bipolar disorder). Two overlapping genes, G72 and G30 on 13q33.2, were identified through linkage-disequilibrium-based positional cloning. Single nucleotide polymorphisms (SNPs) at the G72/G30 locus were independently associated with both bipolar illness and schizophrenia. We analyzed SNPs at this locus with a family-based transmission disequilibrium test (TDT) and haplotype analyses for the discrete trait, as well as quantitative TDT for intermediate phenotypes, using the 88 probands (including COS and psychosis-NOS) with parental participation.

RESULTS

We observed significant pairwise and haplotype associations between SNPs at the G72/G30 locus and psychotic illness. Furthermore, these markers showed associations with scores on a premorbid phenotype measured by the Autism Screening Questionnaire, and with age of onset.

CONCLUSIONS

These findings, although limited by potential referral bias, confirm and strengthen previous reports that G72/G30 is a susceptibility locus both for schizophrenia and bipolar disorder.

Degeneration of the central vestibular system in spinocerebellar ataxia type 3 (SCA3) patients and its possible clinical significance

Although the vestibular complex represents an important component of the neural circuits crucial for the maintenance of truncal and postural stability, and it is integrated into specialized oculomotor circuits, knowledge regarding the extent of the involvement of its nuclei and associated fibre tracts in cases with spinocerebellar ataxia type 3 (SCA3) is incomplete. Accordingly, we performed a pathoanatomical analysis of the vestibular complex and its associated fibre tracts in four clinically diagnosed and genetically confirmed SCA3 patients with the aim of providing more exact information as to the involvement of the vestibular system in this disorder. By means of unconventionally thick serial sections through the vestibular nuclei stained for lipofuscin pigment and Nissl material, we could show that all five nuclei of this complex (interstitial, lateral, medial, spinal, and superior vestibular nuclei) are subject to neurodegenerative processes in SCA3, whereby examination of thick serial sections stained for myelin revealed that all associated fibre tracts (ascending tract of Deiters, juxtarestiform body, lateral and medial vestibulospinal tracts, medial longitudinal fascicle, vestibular portion of the eighth cranial nerve) underwent atrophy and demyelinization in all four of the patients studied. The reported lesions can help to explain the truncal and postural instability as well as the impaired optokinetic nystagmus, vestibulo-ocular reaction, and horizontal gaze-holding present in SCA3 cases.

Analysis of trinucleotide repeats in different SCA loci in spinocerebellar ataxia patients and in normal population of Taiwan

OBJECTIVE

To identify various subtypes of spinocerebellar ataxias (SCAs) among autosomal dominant cerebellar ataxia (ADCA) patients referred to our research center, SCA1, SCA2, SCA3/MJD (Machado-Joseph disease), SCA6, SCA7, SCA8 and SCA12 loci were assessed for expansion of trinucleotide repeats.

PATIENTS AND METHODS

A total of 211 ADCA patients, including 202 patients with dominantly inherited ataxia from 81 Taiwanese families and nine patients with sporadic ataxia, were included in this study and subjected to polymerase chain reaction (PCR) analysis. The amplified products of all loci were analyzed on both 3% agarose gels and 6% denaturing urea-polyacrylamide gels. PCR-based Southern blots were also applied for the detection of SCA7 locus.

RESULTS

The SCA1 mutation was detected in six affected individuals from one family (1.2%) with expanded alleles of 50-53 CAG repeats. Fourteen individuals from nine families (11%) had a CAG trinucleotide repeat expansion at the SCA2 locus, while affected SCA2 alleles have 34-49 CAG repeats. The SCA3/MJD CAG trinucleotide repeat expansion in 60 affected individuals from 26 families (32%) was expanded to 71-85 CAG repeats. As for the SCA7 locus, there were two affected individuals from one family (1.2%) possessed 41 and 100 CAG repeats, respectively. However, we did not detect expansion in the SCA6, SCA8 and SCA12 loci in any patient.

CONCLUSIONS

The SCA3/MJD CAG expansion was the most frequent mutation among the SCA patients. The relative prevalence of SCA3/MJD in Taiwan was higher than that of SCA2, SCA1 and SCA7.

Human genome research in China

Significant progress in human genome research has been made in China since 1994. This review aims to give a brief and incomplete introduction to the major research institutions and their achievements in human genome sequencing and functional genomics in medicine, with emphasis on the "1% Sequencing Project", the generation of single nucleotide polymorphism and haplotype maps of the human genome, disease gene identification, and the molecular characterization of leukemia and other diseases. Chinese efforts towards the sequencing of pathogenic microbial genomes and of the rice (Oryza sativa ssp. Indica) genome are also described.

Exchange of serine residues 263 and 266 reduces the function of mouse gap junction protein connexin31 and exhibits a dominant-negative effect on the wild-type protein in HeLa cells

To characterize the role of Cx31 phosphorylation, serine residues 263 and 266 (Cx31Delta263,266) or 266 (Cx31Delta266) alone were exchanged for amino acids that cannot be phosphorylated. HeLa cells, which were stably transfected with wild type and the two different mutant Cx31-cDNA constructs, were analyzed for expression, phosphorylation, localization, formation of functional gap junction channels, and degradation of mutant Cx31 protein. Both mutant proteins showed similar reduced phosphorylation levels compared to Cx31 wild type, indicating a pivotal role of serine residue 266 for Cx31 phosphorylation. None of these mutations did interfere with correct intracellular trafficking of gap junction proteins. Pulse chase experiments with the different transfectants revealed an increased turnover of both mutated Cx31 proteins. They showed decreased intercellular communication as shown by dye transfer to neighboring cells and measurement of total conductance (mutant Cx31Delta263,266). Mutated Cx31 protein (Cx31Delta263,266) diminished the function of the Cx31 wild-type protein dependent on the amount of the mutated protein, indicating a dominant-negative effect of the mutated protein in HeLa cells.

The DNA sequence and analysis of human chromosome 13

Chromosome 13 is the largest acrocentric human chromosome. It carries genes involved in cancer including the breast cancer type 2 (BRCA2) and retinoblastoma (RB1) genes, is frequently rearranged in B-cell chronic lymphocytic leukaemia, and contains the DAOA locus associated with bipolar disorder and schizophrenia. We describe completion and analysis of 95.5 megabases (Mb) of sequence from chromosome 13, which contains 633 genes and 296 pseudogenes. We estimate that more than 95.4% of the protein-coding genes of this chromosome have been identified, on the basis of comparison with other vertebrate genome sequences. Additionally, 105 putative non-coding RNA genes were found. Chromosome 13 has one of the lowest gene densities (6.5 genes per Mb) among human chromosomes, and contains a central region of 38 Mb where the gene density drops to only 3.1 genes per Mb.

Genomewide scan in families with schizophrenia from the founder population of Afrikaners reveals evidence for linkage and uniparental disomy on chromosome 1

We report on our initial genetic linkage studies of schizophrenia in the genetically isolated population of the Afrikaners from South Africa. A 10-cM genomewide scan was performed on 143 small families, 34 of which were informative for linkage. Using both nonparametric and parametric linkage analyses, we obtained evidence for a small number of disease loci on chromosomes 1, 9, and 13. These results suggest that few genes of substantial effect exist for schizophrenia in the Afrikaner population, consistent with our previous genealogical tracing studies. The locus on chromosome 1 reached genomewide significance levels (nonparametric LOD score of 3.30 at marker D1S1612, corresponding to an empirical P value of.012) and represents a novel susceptibility locus for schizophrenia. In addition to providing evidence for linkage for chromosome 1, we also identified a proband with a uniparental disomy (UPD) of the entire chromosome 1. This is the first time a UPD has been described in a patient with schizophrenia, lending further support to involvement of chromosome 1 in schizophrenia susceptibility in the Afrikaners.

The hereditary adult-onset ataxias in South Africa

There is little data on the spectrum and frequencies of the autosomal dominant spinocerebellar ataxias (SCAs) from the African continent. We undertook a large prospective population-based study over a 10-year period in South Africa (SA). Affected persons were clinically evaluated, and the molecular analysis for the SCA1, 2, 3, 6 and 7 expansions was undertaken. Of the 54 SA families with dominant ataxia, SCA1 accounted for 40.7%, SCA2 for 13%, SCA3 for 3.7%, SCA6 for 1.9%, SCA7 for 22.2% and 18.5% were negative for all these mutations. The frequency of the SCA1 and SCA7 expansions in SA represents one of the highest frequencies for these expansions reported in any country. In this study, the SCA7 mutations have only been found in SA families of Black ethnic origin.