Genome-wide study of association and interaction with maternal cytomegalovirus infection suggests new schizophrenia loci

Genetic and environmental components as well as their interaction contribute to the risk of schizophrenia, making it highly relevant to include environmental factors in genetic studies of schizophrenia. This study comprises genome-wide association (GWA) and follow-up analyses of all individuals born in Denmark since 1981 and diagnosed with schizophrenia as well as controls from the same birth cohort. Furthermore, we present the first genome-wide interaction survey of single nucleotide polymorphisms (SNPs) and maternal cytomegalovirus (CMV) infection. The GWA analysis included 888 cases and 882 controls, and the follow-up investigation of the top GWA results was performed in independent Danish (1396 cases and 1803 controls) and German-Dutch (1169 cases, 3714 controls) samples. The SNPs most strongly associated in the single-marker analysis of the combined Danish samples were rs4757144 in ARNTL (P=3.78 × 10(-6)) and rs8057927 in CDH13 (P=1.39 × 10(-5)). Both genes have previously been linked to schizophrenia or other psychiatric disorders. The strongest associated SNP in the combined analysis, including Danish and German-Dutch samples, was rs12922317 in RUNDC2A (P=9.04 × 10(-7)). A region-based analysis summarizing independent signals in segments of 100 kb identified a new region-based genome-wide significant locus overlapping the gene ZEB1 (P=7.0 × 10(-7)). This signal was replicated in the follow-up analysis (P=2.3 × 10(-2)). Significant interaction with maternal CMV infection was found for rs7902091 (P(SNP × CMV)=7.3 × 10(-7)) in CTNNA3, a gene not previously implicated in schizophrenia, stressing the importance of including environmental factors in genetic studies.

GAGE cancer-germline antigens are recruited to the nuclear envelope by germ cell-less (GCL)

GAGE proteins are highly similar, primate-specific molecules with unique primary structure and undefined cellular roles. They are restricted to cells of the germ line in adult healthy individuals, but are broadly expressed in a wide range of cancers. In a yeast two-hybrid screen we identified the metazoan transcriptional regulator, Germ cell-less (GCL), as an interaction partner of GAGE12I. GCL directly binds LEM-domain proteins (LAP2β, emerin, MAN1) at the nuclear envelope, and we found that GAGE proteins were recruited to the nuclear envelope inner membrane by GCL. Based on yeast two-hybrid analysis and pull-down experiments of GCL polypeptides, GCL residues 209–320 (which includes the BACK domain) were deduced sufficient for association with GAGE proteins. GAGE mRNAs and GCL mRNA were demonstrated in human testis and most types of cancers, and at the protein level GAGE members and GCL were co-expressed in cancer cell lines. Structural studies of GAGE proteins revealed no distinct secondary or tertiary structure, suggesting they are intrinsically disordered. Interestingly GAGE proteins formed stable complexes with dsDNA in vitro at physiological concentrations, and GAGE12I bound several different dsDNA fragments, suggesting sequence-nonspecific binding. Dual association of GAGE family members with GCL at the nuclear envelope inner membrane in cells, and with dsDNA in vitro, implicate GAGE proteins in chromatin regulation in germ cells and cancer cells.

Risk of schizophrenia in relation to parental origin and genome-wide divergence

BACKGROUND

Second-generation immigrants have an increased risk of schizophrenia, a finding that still lacks a satisfactory explanation. Various operational definitions of second-generation immigrants have been used, including foreign parental country of birth. However, with increasing global migration, it is not clear that parental country of birth necessarily is informative with regard to ethnicity. We compare two independently collected measures of parental foreign ethnicity, parental foreign country of birth versus genetic divergence, based on genome-wide genotypic data, to access which measure most efficiently captures the increased risk of schizophrenia among second-generation immigrants residing in Denmark.

METHOD

A case-control study covering all children born in Denmark since 1981 included 892 cases of schizophrenia and 883 matched controls. Genetic divergence was assessed using principal component analyses of the genotypic data. Independently, parental foreign country of birth was assessed using information recorded prospectively in the Danish Civil Registration System. We compared incidence rate ratios of schizophrenia associated with these two independently collected measures of parental foreign ethnicity.

RESULTS

People with foreign-born parents had a significantly increased risk of schizophrenia [relative risk (RR) 1.94 (95% confidence intervals (CI) 1.41-2.65)]. Genetically divergent persons also had a significant increased risk [RR 2.43 (95% CI 1.55-3.82)]. Mutual adjustment of parental foreign country of birth and genetic divergence showed no difference between these measures with regard to their potential impact on the results.

CONCLUSIONS

In terms of RR of schizophrenia, genetic divergence and parental foreign country of birth are interchangeable entities, and both entities have validity with regard to identifying second-generation immigrants.

Myoblasts generated by lentiviral mediated MyoD transduction of myotonic dystrophy type 1 (DM1) fibroblasts can be used for assays of therapeutic molecules

Background

Myotonic dystrophy type 1 (DM1) is the most common muscle dystrophy in adults. The disease is caused by a triplet expansion in the 3'end of the myotonic dystrophy protein kinase (DMPK) gene. In order to develop a human cell model for investigation of possible effects of antisense and RNAi effector molecules we have used lentiviral mediated myoD-forced myogenesis of DM1 patient fibroblasts.

Findings

Transduced fibroblasts show a multinuclear phenotype and express the differentiation marker myogenin. Furthermore, fluorescence in situ hybridization (FISH) analysis revealed a statistical significant increase in the amount of nuclear foci in DM1 patient fibroblasts after myogenesis. Finally, no nuclear foci were found after treatment with oligonucleotides targeting the repeat expansions.

Conclusions

The abundance of nuclear foci in DM1 patient fibroblasts increase following myogenesis, as visualized by FISH analysis. Foci were eradicated after treatment with antisense oligonucleotides. Thus, we propose that the current cell model is suitable for testing of novel treatment modalities.

Vulnerability to oxidative stress in vitro in pathophysiology of mitochondrial short-chain acyl-CoA dehydrogenase deficiency: response to antioxidants

Objective

To elucidate the pathophysiology of SCAD deficient patients who have a unique neurological phenotype, among fatty acid oxidation disorders, with early developmental delay, CNS malformations, intractable seizures, myopathy and clinical signs suggesting oxidative stress.

Methods

We studied skin fibroblast cultures from patients homozygous for ACADS common variant c.625G>A (n = 10), compound heterozygous for c.625G>A/c.319C>T (n = 3) or homozygous for pathogenic c.319C>T (n = 2) and c.1138C>T (n = 2) mutations compared to fibroblasts from patients with carnitine palmitoyltransferase 2 (CPT2) (n = 5), mitochondrial trifunctional protein (MTP)/long-chain L-3-hydroxyacyl-CoA dehydrogenase (LCHAD) (n = 7), and medium-chain acyl-CoA dehydrogenase (MCAD) deficiencies (n = 4) and normal controls (n = 9). All were exposed to 50 µM menadione at 37°C. Additonal conditions included exposure to 39°C and/or hypoglycemia. Time to 100% cell death was confirmed with trypan blue dye exclusion. Experiments were repeated with antioxidants (Vitamins C and E or N-acetylcysteine), Bezafibrate or glucose and temperature rescue.

Results

The most significant risk factor for vulnerability to menadione-induced oxidative stress was the presence of a FAO defect. SCADD fibroblasts were the most vulnerable compared to other FAO disorders and controls, and were similarly affected, independent of genotype. Cell death was exacerbated by hyperthermia and/or hypoglycemia. Hyperthermia was a more significant independent risk factor than hypoglycemia. Rescue significantly prolonged survival. Incubation with antioxidants and Bezafibrate significantly increased viability of SCADD fibroblasts.

Interpretation

Vulnerability to oxidative stress likely contributes to neurotoxicity of SCADD regardless of ACADS genotype and is significantly exacerbated by hyperthermia. We recommend rigorous temperature control in SCADD patients during acute illness. Antioxidants and Bezafibrate may also prove instrumental in their management.

Toxic response caused by a misfolding variant of the mitochondrial protein short-chain acyl-CoA dehydrogenase

BACKGROUND

Variations in the gene ACADS, encoding the mitochondrial protein short-chain acyl CoA-dehydrogenase (SCAD), have been observed in individuals with clinical symptoms. The phenotype of SCAD deficiency (SCADD) is very heterogeneous, ranging from asymptomatic to severe, without a clear genotype-phenotype correlation, which suggests a multifactorial disorder. The pathophysiological relevance of the genetic variations in the SCAD gene is therefore disputed, and has not yet been elucidated, which is an important step in the investigation of SCADD etiology.

AIM

To determine whether the disease-associated misfolding variant of SCAD protein, p.Arg107Cys, disturbs mitochondrial function.

METHODS

We have developed a cell model system, stably expressing either the SCAD wild-type protein or the misfolding SCAD variant protein, p.Arg107Cys (c.319 C > T). The model system was used for investigation of SCAD with respect to expression, degree of misfolding, and enzymatic SCAD activity. Furthermore, cell proliferation and expression of selected stress response genes were investigated as well as proteomic analysis of mitochondria-enriched extracts in order to study the consequences of p.Arg107Cys protein expression using a global approach.

CONCLUSIONS

We found that expression of the p.Arg107Cys variant SCAD protein gives rise to inactive misfolded protein species, eliciting a mild toxic response manifested though a decreased proliferation rate and oxidative stress, as shown by an increased demand for the mitochondrial antioxidant SOD2. In addition, we found markers of apoptotic activity in the p.Arg107Cys expressing cells, which points to a possible pathophysiological role of this variant protein.

Antioxidant dysfunction: potential risk for neurotoxicity in ethylmalonic aciduria

Mitochondrial dysfunction and oxidative stress are central to the molecular basis of several human diseases associated with neuromuscular disabilities. We hypothesize that mitochondrial dysfunction also contributes to the neuromuscular symptoms observed in patients with ethylmalonic aciduria and homozygosity for ACADS c.625G>A-a common variant of the short-chain acyl-coenzyme A (CoA) dehydrogenase (SCAD) enzyme in the mitochondrial fatty acid oxidation pathway. This study sought to identify the specific factors that initiate cell dysfunction in these patients. We investigated fibroblast cultures from 10 patients with neuromuscular disabilities, elevated levels of ethylmalonic acid (EMA) (>50 mmol/mol creatinine), and ACADS c.625G>A homozygosity. Functional analyses, i.e., ACADS gene and protein expression as well as SCAD enzyme activity measurements, were performed together with a global nano liquid chromatography tandem mass spectroscopy (nano-LC-MS/MS)-based screening of the mitochondrial proteome in patient fibroblasts. Moreover, cell viability of patient fibroblasts exposed to menadione-induced oxidative stress was evaluated. Loss of SCAD function was detected in the patient group, most likely due to decreased ACADS gene expression and/or elimination of misfolded SCAD protein. Analysis of the mitochondrial proteome in patient fibroblasts identified a number of differentially expressed protein candidates, including reduced expression of the antioxidant superoxide dismutase 2 (SOD2). Additionally, patient fibroblasts demonstrated significantly higher sensitivity to oxidative stress than control fibroblasts. We propose that reduced mitochondrial antioxidant capacity is a potential risk factor for ACADS c.625G>A-associated ethylmalonic aciduria and that mitochondrial dysfunction contributes to the neurotoxicity observed in patients.

Misfolding of short-chain acyl-CoA dehydrogenase leads to mitochondrial fission and oxidative stress

Short-chain acyl-CoA dehydrogenase deficiency (SCADD) is a rare inherited disorder of the mitochondrial beta-oxidation of fatty acids. Patients with SCADD present mainly with symptoms of neuromuscular character. In order to investigate factors involved in the pathogenesis, we studied a disease-associated variant of the SCAD protein (p.Arg83Cys, c.319C>T), which is known to compromise SCAD protein folding. We investigated the consequences of overexpressing the misfolded mitochondrial protein, and thus determined whether the misfolded p.Arg83Cys SCAD proteins can elicit a toxic reaction. Human astrocytes were transiently transfected with either wild-type or p.Arg83Cys encoding cDNA, and analyzed for insoluble proteins/aggregate-formation, alterations in mitochondrial morphology, and for the presence of reactive oxygen species (ROS) in the mitochondria. The majority of cells overexpressing the p.Arg83Cys SCAD variant protein presented with an altered mitochondrial morphology of a grain-like structure, whereas the majority of the cells overexpressing wild-type SCAD presented with a normal thread-like mitochondrial reticulum. We found this grain-like structure to be associated with an increased amount of ROS. The mitochondrial morphology change was partly alleviated by addition of the mitochondrial targeted antioxidant MitoQ, indicating a ROS-induced mitochondrial fission. We therefore propose that SCAD misfolding leads to production of ROS, which in turn leads to fission and a grain-like structure of the mitochondrial reticulum. This finding indicates a toxic response elicited by misfolded p.Arg83Cys SCAD proteins.

Psychiatric family history and schizophrenia risk in Denmark: which mental disorders are relevant?

BACKGROUND

A family history of schizophrenia is the strongest single indicator of individual schizophrenia risk. Bipolar affective disorder and schizo-affective disorders have been documented to occur more frequently in parents and siblings of schizophrenia patients, but the familial occurrence of the broader range of mental illnesses and their role as confounders have not been studied in large population-based samples.

METHOD

All people born in Denmark between 1955 and 1991 (1.74 million) were followed for the development of schizophrenia (9324 cases) during 28 million person-years at risk. Information of schizophrenia in cohort members and psychiatric history in parents and siblings was established through linkage with the Danish Psychiatric Central Register. Data were analysed using log-linear Poisson regression.

RESULTS

Schizophrenia was, as expected, strongly associated with schizophrenia and related disorders among first-degree relatives. However, almost any other psychiatric disorder among first-degree relatives increased the individual's risk of schizophrenia. The population attributable risk associated with psychiatric family history in general was 27.1% whereas family histories including schizophrenia only accounted for 6.0%. The general psychiatric family history was a confounder of the association between schizophrenia and urbanization of place of birth.

CONCLUSIONS

Clinically diagnosed schizophrenia is associated with a much broader range of mental disorders in first-degree relatives than previously reported. This may suggest risk haplotypes shared across many disorders and/or shared environmental factors clustering in families. Failure to take the broad range of psychiatric family history into account may bias results of all risk-factor studies of schizophrenia.

Mitochondrial proteomics on human fibroblasts for identification of metabolic imbalance and cellular stress

Background

Mitochondrial proteins are central to various metabolic activities and are key regulators of apoptosis. Disturbance of mitochondrial proteins is therefore often associated with disease. Large scale protein data are required to capture the mitochondrial protein levels and mass spectrometry based proteomics is suitable for generating such data. To study the relative quantities of mitochondrial proteins in cells from cultivated human skin fibroblasts we applied a proteomic method based on nanoLC-MS/MS analysis of iTRAQ-labeled peptides.

Results

When fibroblast cultures were exposed to mild metabolic stress – by cultivation in galactose medium- the amount of mitochondria appeared to be maintained whereas the levels of individual proteins were altered. Proteins of respiratory chain complex I and IV were increased together with NAD⁺-dependent isocitrate dehydrogenase of the citric acid cycle illustrating cellular strategies to cope with altered energy metabolism. Furthermore, quantitative protein data, with a median standard error below 6%, were obtained for the following mitochondrial pathways: fatty acid oxidation, citric acid cycle, respiratory chain, antioxidant systems, amino acid metabolism, mitochondrial translation, protein quality control, mitochondrial morphology and apoptosis.

Conclusion

The robust analytical platform in combination with a well-defined compendium of mitochondrial proteins allowed quantification of single proteins as well as mapping of entire pathways. This enabled characterization of the interplay between metabolism and stress response in human cells exposed to mild stress.

Mitochondrial fatty acid oxidation defects--remaining challenges

Mitochondrial fatty acid oxidation defects have been recognized since the early 1970s. The discovery rate has been rather constant, with 3-4 'new' disorders identified every decade and with the most recent example, ACAD9 deficiency, reported in 2007. In this presentation we will focus on three of the 'old' defects: medium-chain acyl-CoA dehydrogenase (MCAD) deficiency, riboflavin responsive multiple acyl-CoA dehydrogenation (RR-MAD) deficiency, and short-chain acyl-CoA dehydrogenase (SCAD) deficiency. These disorders have been discussed in many publications and at countless conference presentations, and many questions relating to them have been answered. However, continuing clinical and pathophysiological research has raised many further questions, and new ideas and methodologies may be required to answer these. We will discuss these challenges. For MCAD deficiency the key question is why 80% of symptomatic patients are homozygous for the prevalent ACADM gene variation c.985A > G whereas this is found in only approximately 50% of newborns with a positive screen. For RR-MAD deficiency, the challenge is to find the connection between variations in the ETFDH gene and the observed deficiency of a number of different mitochondrial dehydrogenases as well as deficiency of FAD and coenzyme Q(10). With SCAD deficiency, the challenge is to elucidate whether ACADS gene variations are disease-associated, especially when combined with other genetic/cellular/environmental factors, which may act synergistically.

The ACADS gene variation spectrum in 114 patients with short-chain acyl-CoA dehydrogenase (SCAD) deficiency is dominated by missense variations leading to protein misfolding at the cellular level

Short-chain acyl-CoA dehydrogenase (SCAD) deficiency is an inherited disorder of mitochondrial fatty acid oxidation associated with variations in the ACADS gene and variable clinical symptoms. In addition to rare ACADS inactivating variations, two common variations, c.511C > T (p.Arg171Trp) and c.625G > A (p.Gly209Ser), have been identified in patients, but these are also present in up to 14% of normal populations leading to questions of their clinical relevance. The common variant alleles encode proteins with nearly normal enzymatic activity at physiological conditions in vitro. SCAD enzyme function, however, is impaired at increased temperature and the tendency to misfold increases under conditions of cellular stress. The present study examines misfolding of variant SCAD proteins identified in patients with SCAD deficiency. Analysis of the ACADS gene in 114 patients revealed 29 variations, 26 missense, one start codon, and two stop codon variations. In vitro import studies of variant SCAD proteins in isolated mitochondria from SCAD deficient (SCAD-/-) mice demonstrated an increased tendency of the abnormal proteins to misfold and aggregate compared to the wild-type, a phenomenon that often leads to gain-of-function cellular phenotypes. However, no correlation was found between the clinical phenotype and the degree of SCAD dysfunction. We propose that SCAD deficiency should be considered as a disorder of protein folding that can lead to clinical disease in combination with other genetic and environmental factors.

Handling of human short-chain acyl-CoA dehydrogenase (SCAD) variant proteins in transgenic mice

To investigate the in vivo handling of human short-chain acyl-CoA dehydrogenase (SCAD) variant proteins, three transgenic mouse lines were produced by pronuclear injection of cDNA encoding the wild-type, hSCAD-wt, and two disease causing folding variants hSCAD-319C>T and hSCAD-625G>A. The transgenic mice were mated with an SCAD-deficient mouse strain (BALB/cByJ) and, in the second generation, three mouse lines were obtained without endogenous SCAD expression but harboring hSCAD-wt, hSCAD-319C>T, and hSCAD-625G>A transgenes, respectively. All three lines had expression of the transgene at the RNA level in liver, muscle or brain tissues. Expression at the protein level was detected only in the brain tissue of hSCAD-wt mice, but here it was significantly higher than the level of endogenous SCAD protein in control mouse brains--in correlation with expression at the RNA level. The results may indicate that the two hSCAD folding variants are degraded by the mouse mitochondrial protein quality control system. Indeed, pulse-chase studies with isolated mitochondria revealed that soluble variant hSCAD protein was rapidly eliminated. This is in agreement with the fact that no disease phenotype developed for any of the lines transgenic for the hSCAD folding variants. The indicated remarkable efficiency of the mouse protein quality control system in the degradation of SCAD folding variants should be further substantiated and investigated, since it might indicate ways to prevent disease-causing effects.

Variations in IBD (ACAD8) in children with elevated C4-carnitine detected by tandem mass spectrometry newborn screening

The isobutyryl-CoA dehydrogenase (IBD) enzyme is involved in the degradation of valine. IBD deficiency was first reported in 1998 and subsequent genetic investigations identified acyl-CoA dehydrogenase (ACAD) 8, now IBD, as the gene responsible for IBD deficiency. Only three individuals homozygous or compound heterozygous for variations in the IBD gene have been reported. We present IBD deficiency in an additional four newborns with elevated C(4)-carnitine identified by tandem mass spectrometry (MS/MS) screening in Denmark and the United States. Three showed urinary excretions of isobutyryl-glycine, and in vitro probe analysis of fibroblasts from two newborns indicated enzymatic IBD defect. Molecular genetic analysis revealed seven new rare variations in the IBD gene (c.348C>A, c.400G>T, c.409G>A, c.455T>C, c.958G>A, c.1000C>T and c.1154G>A). Furthermore, sequence analysis of the short-chain acyl-CoA dehydrogenase (SCAD) gene revealed heterozygosity for the prevalent c.625G>A susceptibility variation in all newborns and in the first reported IBD patient. Functional studies in isolated mitochondria demonstrated that the IBD variations present in the Danish newborn (c.409G>A and c.958G>A) together with a previously published IBD variation (c.905G>A) disturbed protein folding and reduced the levels of correctly folded IBD tetramers. Accordingly, low/no IBD residual enzyme activity was detectable when the variant IBD proteins were overexpressed in Chang cells.

Sibship characteristics during upbringing and schizophrenia risk

The potential association between sibship characteristics and the risk of schizophrenia has been investigated previously. However, methods have differed and results have been conflicting. The authors explored the association between birth order, sibship size, and birth interval to siblings and schizophrenia while accounting for potential confounders. Using Danish Civil Registration System data, the authors established a cohort of 763,000 people. Schizophrenia was identified by linkage with the Danish Psychiatric Central Register. Overall, 2,536 people developed schizophrenia from 1986 to 2001. Children with no siblings and children with three or more siblings had significantly increased risks (relative risk = 1.22 and 1.27, respectively). This association was explained by change of residence and urbanization during upbringing. Children with half siblings had a significantly increased risk (relative risk = 1.20). The authors found a significantly increased risk associated with siblings 7-8 and 11-14 years younger (relative risk = 1.30 and 1.22, respectively) combined with a significantly decreased risk associated with siblings 2-10 and 12 or more years older (relative risk = 0.92 and 0.82, respectively). There was no consistent pattern between the birth interval to siblings and schizophrenia risk. Results of the association between sibship characteristics and schizophrenia from a single country may not be comparable with results from other countries, and sibship characteristics are minor determinants of schizophrenia risk.

The incidence and prevalence of pervasive developmental disorders: a Danish population-based study

BACKGROUND

Based on prevalence studies and the few incidence studies of pervasive developmental disorders (PDDs) the prevalence and incidence of these disorders have been claimed to be increasing.

METHOD

The annual and age-specific prevalence and incidence rates of childhood autism, atypical autism, Asperger's disorder, and pervasive developmental disorder not otherwise specified (PDD-NOS) in Denmark during the period 1971--2000 in children younger than 10 years were estimated using data from the Danish Psychiatric Central Register.

RESULTS

A total of 2.4 million children younger than 10 years were followed and 2061 cases with the PDDs studied were identified. Generally, the prevalence and incidence rates of the PDDs studied were stable until the early 1990s after which an increase in the occurrence of all disorders was seen, until 2000. The annual incidence rate per 10000 children younger than 10 years was 2.0 for childhood autism, 0.7 for atypical autism, 1.4 for Asperger's disorder, and 3.0 for PDD-NOS in 2000. We calculated a 'corrected' prevalence of childhood autism at 11.8, atypical autism at 3.3, Asperger's disorder at 4.7, and PDD-NOS at 14.6 per 10,000 children younger than 10 years on 1 January 2001.

CONCLUSIONS

We found that the estimated prevalences of the PDDs studied were probably underestimated. Furthermore, the increasing prevalence and incidence rates during the 1990s may well be explained by changes in the registration procedures and more awareness of the disorders, although a true increase in the incidence cannot be ruled out.

Individual and familial risk factors for bipolar affective disorders in Denmark

BACKGROUND

Few population-based studies have addressed risk factors for bipolar affective disorder.

OBJECTIVE

To study the possible association between bipolar affective disorder and history of mental illness in a parent or sibling; urbanicity of birth place; season of birth; sibship characteristics, including birth order; influenza epidemics during pregnancy; and early parental loss.

DESIGN

We used a population-based cohort of 2.1 million individuals based on data from the Danish Civil Registration System linked with the Danish Psychiatric Central Register.

SETTING

Nationwide population-based sample of all individuals hospitalized or in outpatient clinic contact for the first time with bipolar affective disorder. Patients Overall, 2299 individuals were first diagnosed with bipolar affective disorder during the 31.8 million person-years of follow-up.

RESULTS

Risk of bipolar affective disorder was associated with a history of bipolar affective disorder as well as other psychiatric disorders, including schizophrenia and schizoaffective disorder, in parents or siblings. People with a first-degree relative with bipolar affective disorder had a 13.63-fold (95% confidence interval, 11.81-15.71) increased risk of bipolar affective disorder. No other consistent associations were found with the exception of an association between early parental loss, in particular maternal, and bipolar affective disorder. Children who experienced maternal loss before their fifth birthday had a 4.05 (95% confidence interval, 1.68-9.77) increased risk of bipolar affective disorder.

CONCLUSIONS

Early parental loss may represent both environmental and genetic risk factors for bipolar affective disorder. Most of the risk factors included in our study that previously have been associated with schizophrenia were not associated with bipolar affective disorder, supporting that the 2 disorders may be at least partially separate etiological entities.

ICP is lower during propofol anaesthesia compared to isoflurane and sevoflurane

OBJECTIVES

Propofol is a cerebral vasoconstrictor while inhalation anaesthetics like isoflurane and sevoflurane act as cerebral vasodilators in both animal and human studies. This difference of action upon cerebral vessels might implicate a lower ICP during propofol anaesthesia. Cerebral metabolism is decreased by all three anaesthetics. In a prospective, randomised multicenter study ICP was compared during anaesthesia with propofol, isoflurane and sevoflurane.

METHODS

117 patients subjected to elective craniotomy for supratentorial tumour. Propofol: N = 41; isoflurane: N = 38; sevoflurane: N = 38. Nitrous oxide was omitted and all anaesthetics were supplemented with a continuous infusion of fentanyl. ICP was measured subdurally after removal of the bone flap. MABP, CPP, PCO2, AVDO2, rectal temperature, tumour size and midline shift were registered too.

STATISTICS

Kruskal-Wallis Variance on Ranks. All values in medians with range. P < 0.05 was considered significant.

RESULTS

ICP (mmHg): propofol 7 (-1-20), isoflurane 12 (1-29), sevoflurane 11 (2-32). ICP was significantly lower in the propofol group compared to the isofluane and sevoflurane groups. CPP (mmHg): propofol 80 (45-104), isoflurane 60 (32-84), sevoflurane 63 (44-77). CPP was significantly higher in the propofol group compared to the isoflurane and sevoflurane groups. AVDO2 (mmol/l): propofol 3.1 (0.9-5.1), isoflurane 2.5 (1.1-4.5), sevoflurane 2.6 (0.8-4.1). AVDO2 was significantly higher in the propofol group compared to the isoflurane and sevoflurane groups. No significant differences in PCO2, rectal temperature, tumour size and midline shift were found.

CONCLUSIONS

Subdural ICP is significantly lower during propofol anaesthesia compared to isoflurane and sevoflurane anaesthesia. CPP and AVDO2 are significantly higher during propofol anaesthesia compared to isoflurane and sevoflurane anaesthesia.

Recurrent vomiting and ethylmalonic aciduria associated with rare mutations of the short-chain acyl-CoA dehydrogenase gene

We report identification of short-chain acyl-CoA dehydrogenase (SCAD) deficiency in a 12-year-old boy who suffered from recurrent attacks of vomiting once or twice a year from infancy. Growth and development were normal and there were no muscular symptoms. Metabolic screening was performed during a hospitalization at 8 years of age and revealed an increased excretion of ethylmalonic acid (EMA; 45-80 mmol/mol creatinine, normal 0.2-6.6), suggesting a degradation defect of short-chain fatty acids. An increased n-butyrylcarnitine was found in freshly collected serum (0.9 micromol/L; normal <0.4) but not in dry blood spots. Neither of the frequent SCAD gene variants 625G>A and 511C>T was present, but direct sequencing of the promoter and coding regions of the SCAD gene revealed that the patient had mutations on both alleles: 417G>C (Trpl15Cys) and 1095G>T (Gln341His). Neither mutation has been described before in compound heterozygosity or homozygosity. Enzymatic investigations subsequently confirmed a defect of SCAD in both fibroblasts and muscle extracts. Furthermore, expression studies of both mutations demonstrated impaired enzyme function or structure. To our knowledge, this case is the first description of a patient with proven SCAD deficiency presenting with recurrent emesis but without other symptoms, and emphasizes the wide clinical phenotype of this disorder.

Evidence of a dose-response relationship between urbanicity during upbringing and schizophrenia risk

BACKGROUND

Many studies have demonstrated that an urban birth or upbringing increases schizophrenia risk, but no studies have been able to distinguish between these effects. The objectives of this study were to discriminate the effect of urbanicity at birth from an effect of urbanicity during upbringing, and to identify particularly vulnerable age periods and a possible dose-response relationship between urbanicity during upbringing and schizophrenia risk.

METHODS

Using data from the Danish Civil Registration System, we established a population-based cohort of 1.89 million people, which included information on place of birth, place of residence during upbringing, and the accumulated number of years lived in each category of the 5-level degree of urbanization during upbringing. Schizophrenia in cohort members and mental illness in a parent or sibling were identified by linkage with the Danish Psychiatric Central Register.

RESULTS

Individuals living in a higher degree of urbanization than 5 years earlier had a 1.40-fold (95% confidence interval, 1.28-1.51) increased risk, while individuals living in a lower degree of urbanization than 5 years earlier had a 0.82-fold (95% confidence interval, 0.77-0.88) decreased risk of schizophrenia. For fixed urbanicity at the 15th birthday, risk increased with increasing degree of urbanization at birth. Furthermore, the more years lived in the higher the degree of urbanization, the greater the risk. Individuals who lived their first 15 years in the highest category of the 5-level urbanicity had a 2.75-fold (95% confidence interval, 2.31-3.28) increased risk of schizophrenia.

CONCLUSION

Continuous, or repeated, exposures during upbringing that occur more frequently in urbanized areas may be responsible for the association between urbanization and schizophrenia risk.

[Sibships characteristics, influenza and risk of schizophrenia. A population-based cohort study]

INTRODUCTION

To address the hypothesis that infections, perhaps prenatal exposure to influenza virus, might increase the risk of schizophrenia we studied the possible association between schizophrenia risk and birth order, sibship size, interval between siblings, and influenza prevalence.

MATERIAL AND METHODS

We established a population-based cohort of 1,746,366 persons born to Danish woman who themselves were born since 1935 using data from the Civil Registration System. Schizophrenia in cohort members (n = 2669) and their parents was identified by linkage with the Danish Psychiatric Case Register. Influenza notifications per month in Denmark were obtained from the National Board of Health and Statens Serum Institut.

RESULTS

We found no association between birth order and schizophrenia risk or between schizophrenia risk and influenza prevalence during any month of prenatal life. Coming from a large sibship and having a short interval to the nearest older or younger sibling was associated with an increased risk of schizophrenia.

DISCUSSION

Our findings do not add support to the hypothesis that schizophrenia is associated with prenatal exposure to influenza virus or other common infections, but are compatible with the hypothesis that environmental exposure, perhaps to common infections in childhood, may be a risk factor.

Family history, place and season of birth as risk factors for schizophrenia in Denmark: a replication and reanalysis

BACKGROUND

Although a family history of schizophrenia is the strongest individual risk factor for schizophrenia, environmental factors related to urbanicity may contribute to a substantial proportion of the population occurrence of the disease.

AIMS

This study replicates previous findings in four mutually exclusive Danish study populations, including out-patient information, ICD-10 diagnoses of schizophrenia, and a broader adjustment for mental illness in family members.

METHOD

We established a population-based cohort of 2.66 million Danish people using data from the Civil Registration System linked with the Psychiatric Case Register.

RESULTS

Overall, 10 264 persons developed schizophrenia during the 50.7 million person-years of follow-up. The risk of schizophrenia was increased by urbanicity of place of birth and by family history of schizophrenia or other mental disorders.

CONCLUSIONS

Urban-rural differences of schizophrenia risk were replicated and could not be associated with the potential sources of bias we assessed. Environmental factors underlying the effect of place of birth are major determinants of schizophrenia occurrence at the population level, although the effect of family history is the strongest at the individual level.

[The Cusum score. A tool for evaluation of clinical competence]

INTRODUCTION

The cusum analysis (cummulative summation) is a statistical technique used to assess the competence of medical trainees. We wanted to re-examine the validity of the test as a technique for qualitative assessment of competence, as well as a technique for monitoring the level of specialists' competence.

METHODS

Doctors in two anaesthetic departments were asked to plot the cusum as they performed the following procedures: epidural and spinal analgesia, insertion of central venous and arterial cannulae.

RESULTS

Data were collected over a year. Thirty-five doctors were asked to plot the cusum. The plots were returned by 75% (9/12) of the first year trainees, 50% (4/8) of the second- and third-year trainees, and 20% (1/5) of the four- and five-year trainees. From the specialists and consultants on the staff, we received 66% (4/6) and 50% (2/4). The correlation, according to the level of competence respecting spinal and epidural techniques, is shown in Figures 1 and 2.

DISCUSSION

We found, that the cusum analysis is a valid and practical technique for the qualitative assessment of clinical competence as well as a tool for monitoring continuous professional development. The technique can be used in a number of settings. With the increasing demand in health care for continuous quality assurance, the analysis can be used both in personal professional monitoring and in monitoring of performance during training.