Evidence for genetic heterogeneity between clinical subtypes of bipolar disorder

We performed a genome-wide association study of 6447 bipolar disorder (BD) cases and 12 639 controls from the International Cohort Collection for Bipolar Disorder (ICCBD). Meta-analysis was performed with prior results from the Psychiatric Genomics Consortium Bipolar Disorder Working Group for a combined sample of 13 902 cases and 19 279 controls. We identified eight genome-wide significant, associated regions, including a novel associated region on chromosome 10 (rs10884920; P=3.28 × 10-8) that includes the brain-enriched cytoskeleton protein adducin 3 (ADD3), a non-coding RNA, and a neuropeptide-specific aminopeptidase P (XPNPEP1). Our large sample size allowed us to test the heritability and genetic correlation of BD subtypes and investigate their genetic overlap with schizophrenia and major depressive disorder. We found a significant difference in heritability of the two most common forms of BD (BD I SNP-h2=0.35; BD II SNP-h2=0.25; P=0.02). The genetic correlation between BD I and BD II was 0.78, whereas the genetic correlation was 0.97 when BD cohorts containing both types were compared. In addition, we demonstrated a significantly greater load of polygenic risk alleles for schizophrenia and BD in patients with BD I compared with patients with BD II, and a greater load of schizophrenia risk alleles in patients with the bipolar type of schizoaffective disorder compared with patients with either BD I or BD II. These results point to a partial difference in the genetic architecture of BD subtypes as currently defined.

A genome-wide association study of kynurenic acid in cerebrospinal fluid: implications for psychosis and cognitive impairment in bipolar disorder

Elevated cerebrospinal fluid (CSF) levels of the glia-derived N-methyl-D-aspartic acid receptor antagonist kynurenic acid (KYNA) have consistently been implicated in schizophrenia and bipolar disorder. Here, we conducted a genome-wide association study based on CSF KYNA in bipolar disorder and found support for an association with a common variant within 1p21.3. After replication in an independent cohort, we linked this genetic variant-associated with reduced SNX7 expression-to positive psychotic symptoms and executive function deficits in bipolar disorder. A series of post-mortem brain tissue and in vitro experiments suggested SNX7 downregulation to result in a caspase-8-driven activation of interleukin-1β and a subsequent induction of the brain kynurenine pathway. The current study demonstrates the potential of using biomarkers in genetic studies of psychiatric disorders, and may help to identify novel drug targets in bipolar disorder.

The KMO allele encoding Arg452 is associated with psychotic features in bipolar disorder type 1, and with increased CSF KYNA level and reduced KMO expression

The kynurenine pathway metabolite kynurenic acid (KYNA), modulating glutamatergic and cholinergic neurotransmission, is increased in cerebrospinal fluid (CSF) of patients with schizophrenia or bipolar disorder type 1 with psychotic features. KYNA production is critically dependent on kynurenine 3-monooxygenase (KMO). KMO mRNA levels and activity in prefrontal cortex (PFC) are reduced in schizophrenia. We hypothesized that KMO expression in PFC would be reduced in bipolar disorder with psychotic features and that a functional genetic variant of KMO would associate with this disease, CSF KYNA level and KMO expression. KMO mRNA levels were reduced in PFC of bipolar disorder patients with lifetime psychotic features (P=0.005, n=19) or schizophrenia (P=0.02, n=36) compared with nonpsychotic patients and controls. KMO genetic association to psychotic features in bipolar disorder type 1 was studied in 493 patients and 1044 controls from Sweden. The KMO Arg(452) allele was associated with psychotic features during manic episodes (P=0.003). KMO Arg(452) was studied for association to CSF KYNA levels in an independent sample of 55 Swedish patients, and to KMO expression in 717 lymphoblastoid cell lines and 138 hippocampal biopsies. KMO Arg(452) associated with increased levels of CSF KYNA (P=0.03) and reduced lymphoblastoid and hippocampal KMO expression (P≤0.05). Thus, findings from five independent cohorts suggest that genetic variation in KMO influences the risk for psychotic features in mania of bipolar disorder patients. This provides a possible mechanism for the previous findings of elevated CSF KYNA levels in those bipolar patients with lifetime psychotic features and positive association between KYNA levels and number of manic episodes.

Long-term lithium treatment in bipolar disorder is associated with longer leukocyte telomeres

Telomere shortening is a hallmark of aging and has been associated with oxidative stress, inflammation and chronic somatic, as well as psychiatric disorders, including schizophrenia and depression. Additionally, antidepressants have been found to protect against telomere shortening. However, pharmacological telomere studies are lacking in bipolar disorder (BD). Therefore, the objective of this study was to explore telomere length (TL) in patients with BD in the context of lithium treatment. We determined TL by quantitative real-time PCR using peripheral blood leukocytes. Participants were outpatients diagnosed with BD type 1 or 2 (n=256) and healthy controls (n=139). Retrospective case-control and case-case study designs were applied. Lithium response (LiR) was scored using the Alda-Scale. Lithium-treated BD patients overall, as well as those on lithium monotherapy, had 35% longer telomeres compared with controls (P<0.0005, partial η(2)=0.13). TL correlated positively with lithium treatment duration of >30 months (P=0.031, R(2)=0.13) and was negatively associated with increasing number of depressive episodes (P<0.007). BD patients responding well to lithium treatment had longer telomeres than those not responding well. This is the first study to report a positive effect of long-term lithium treatment on TL. Importantly, longer TL was also associated with a better LiR in BD patients. These data suggest that lithium exerts a protective effect against telomere shortening especially when therapeutically efficacious. We hypothesize that induction of telomerase activity may be involved in LiR in BD.

Clinical and genetic outcome determinants of Internet- and group-based cognitive behavior therapy for social anxiety disorder

OBJECTIVE

No study has investigated clinical or genetic predictors and moderators of Internet-based cognitive behavior therapy (ICBT) compared with cognitive behavioral group therapy for (CBGT) for SAD. Identification of predictors and moderators is essential to the clinician in deciding which treatment to recommend for whom. We aimed to identify clinical and genetic (5-HTTLPR, COMTval158met, and BDNFval66met) predictors and moderators of ICBT and CBGT.

METHOD

We performed three types of analyses on data from a sample comprising participants (N = 126) who had undergone ICBT or CBGT in a randomized controlled trial. Outcomes were i) end state symptom severity, ii) SAD diagnosis, and iii) clinically significant improvement.

RESULTS

The most stable predictors of better treatment response were working full time, having children, less depressive symptoms, higher expectancy of treatment effectiveness, and adhering to treatment. None of the tested gene polymorphisms were associated with treatment outcome. Comorbid general anxiety and depression were moderators meaning that lower levels were associated with a better treatment response in ICBT but not in CBGT.

CONCLUSION

We conclude that demographic factors, symptom burden, adherence, and expectations may play an important role as predictors of treatment outcome. The investigated gene polymorphisms do not appear to make a difference.

Impact of inflammation on epigenetic DNA methylation - a novel risk factor for cardiovascular disease?

OBJECTIVE

The lifespan of dialysis patients is as short as in patients with metastatic cancer disease, mainly due to cardiovascular disease (CVD). DNA methylation is an important cellular mechanism modulating gene expression associated with ageing, inflammation and atherosclerotic processes.

DESIGN

DNA methylation was analysed in peripheral blood leucocytes from three different groups of chronic kidney disease (CKD) populations (37 CKD stages 3 and 4 patients, 98 CKD stage 5 patients and 20 prevalent haemodialysis patients). Thirty-six healthy subjects served as controls. Clinical characteristics (diabetes mellitus, nutritional status and presence of clinical CVD), inflammation and oxidative stress biomarkers, homocysteine and global DNA methylation in peripheral blood leucocytes (defined as HpaII/MspI ratio by the Luminometric Methylation Assay method) were evaluated. CKD stage 5 patients (n=98) starting dialysis treatment were followed for a period of 36 +/- 2 months.

RESULTS

Inflamed patients had lower ratios of HpaII/MspI, indicating global DNA hypermethylation. Analysis by the Cox regression model demonstrated that DNA hypermethylation (HpaII/MspI ratio <median) was significantly associated with both all-cause (RR 5.0; 95% CI: 1.7-14.8; P<0.01) and cardiovascular (RR 13.9; 95% CI: 1.8-109.3; P<0.05) mortality, even following the adjustment for age, CVD, diabetes mellitus and inflammation.

CONCLUSION

The present study demonstrates that global DNA hypermethylation is associated with inflammation and increased mortality in CKD.

Peroxisome proliferator-activated receptor γ polymorphisms affect systemic inflammation and survival in end-stage renal disease patients starting renal replacement therapy

BACKGROUND

Inflammation may contribute to the markedly increased cardiovascular morbidity and mortality in end-stage renal disease (ESRD). However, the prevalence of inflammation varies in different ESRD populations. Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) is an important nuclear signaling protein that may regulate inflammatory response, and recent studies have revealed genetic polymorphisms that have significant effect on PPAR-gamma signaling. The aim of this study was to clarify whether the PPAR-gamma 161C/T and PPAR-gamma2 Pro12Ala single-nucleotide polymorphisms (SNPs) influence the inter-individual variance of inflammation and mortality in ESRD patients.

METHODS

The present prospective study included 229 incident Caucasian ESRD patients (62% males) just prior to starting renal replacement therapy and 207 healthy controls (62% males). Blood samples were taken for measuring systemic inflammatory (CRP, TNF-alpha, IL-6) and nutritional (S-albumin) parameters. The presence of diabetes mellitus, malnutrition (subjective global assessment (SGA)) and cardiovascular disease (CVD) were also assessed. Genotyping of the two PPAR-gamma SNPs was performed using Pyrosequencing. During follow-up (1621+/-63 days), both all-cause and CVD-mortality were investigated.

RESULTS

ESRD patients had a higher prevalence of both the PPAR-gamma 161 CC and PPAR-gamma2 Pro12Pro genotypes than the general population (p<0.01). Whereas the Pro12Pro genotype was associated with higher median serum levels of both hs-CRP (p<0.05) and TNF-alpha (p<0.01) the 161CC genotype was associated with a significantly higher (6.6 mg/L versus 3.3 mg/L; p<0.01) median hs-CRP level. Following adjustment for age, gender, SGA and CVD a significantly higher mortality rate was observed in patients with the Pro12Pro genotype.

CONCLUSION

This study demonstrates significant differences in PPAR-gamma genotype distribution between ESRD patients and healthy controls. Furthermore, as the PPAR-gamma2 Pro12Pro genotype was associated with both higher levels of biomarkers of inflammation as well as shorter survival, genetic polymorphisms seem to play a role in determining systemic inflammatory status and outcome in this patient group.

Association study between chromosome 10q26.11 and obesity among Swedish men

OBJECTIVE

Proximal chromosome 10q26 was recently linked to waist/hip ratio in European and African-American families. The objective was to investigate whether genomic variation in chromosome 10q26.11 reflects variation in obesity-related clinical parameters in a Swedish population.

DESIGN

Genetic association study of single-nucleotide polymorphisms (SNPs) in chromosome 10q26.11 and obesity-related clinical parameters was performed. Obesity was defined as body mass index (BMI) > or = 30 kg/m2.

SUBJECTS

Swedish Caucasians comprising 276 obese and 480 nonobese men, 313 obese and 494 nonobese women, 177 obese and 163 nonobese patients with type 2 diabetes mellitus (T2DM), and 106 obese and 201 nonobese subjects with impaired glucose tolerance (IGT) patients.

MEASUREMENTS

Genotypes of 11 SNPs at chromosome 10q26.11, and various obesity-related clinical parameters.

RESULTS

Homozygosity of a common haplotype constructed by three SNPs, rs2185937, rs1797 and hCV1402327, covering an interval of 2.7 kb, was suggested to confer an increased risk for obesity of 1.5 among men (P = 0.043). The C allele frequency and homozygous genotype frequency of the rs1797 tended to be higher among obese compared to among nonobese men (P = 0.017 and 0.020, respectively). The distribution of BMI and diastolic blood pressure was higher among those with the C/C genotype (P = 0.022 and 0.0061, respectively). The obese and the nonobese groups were homogeneous over BMI subgroups with regard to rs1797 risk genotype distribution. There was no tendency for association between rs1797 and obesity among neither women nor T2DM nor IGT patients.

CONCLUSION

We show support for association between proximal chromosome 10q26.11 and obesity among Swedish men but not women through the analysis of a haplotype encompassing 2.7 kb.

Possible pathologic involvement of receptor for advanced glycation end products (RAGE) for development of encapsulating peritoneal sclerosis in Japanese CAPD patients

Encapsulating peritoneal sclerosis (EPS) is a serious complication of PD. The cause(s) of EPS are unknown but may include peritonitis and long duration of PD treatment. However, EPS may also develop in some patients without a history of peritonitis or with rather short duration of PD therapy. It has been suggested that an increasing peritoneal solute transport rate (PSTR) as a function of time on PD treatment is a risk factor for EPS development after transfer to hemodialysis, and that high PSTR is associated with an increased peritoneal microvessels surface area. Other putative mechanisms might include advanced glycated end products (AGE) and their receptors, RAGE. The purpose of this study was to investigate genetic variations in PD patients developing EPS in comparison to PD patients without EPS. SNPs in genes related to angiogenesis as well as RAGE were analyzed. Twenty patients (M/F: 12/8, mean age at start of PD 42.2 years, mean duration of PD 8.4 years) who were diagnosed as EPS during the period 1982 - 2002 at Jikei University Hospital and a matched control group (n = 20) of nonEPS PD patients were studied. The following 5 SNPs were analyzed: VEGF 936 C/T, ecNOS -786 T/C, 298 Glu/Asp, and RAGE -374 T/A, and -429 T/C. The SNPs were analyzed by the pyrosequencing method. The C allele (T/C and C/C) in the RAGE -429T/C genotype was not found in any of the EPS patients (EPS, T/T: 20/20 (100%), nonEPS, T/T: 15/20 (75%), T/C: 4/20 (20%), C/C: 1/2 0(5%), nonC allele vs C allele, p = 0.013), although every allele was found in other SNPs. We conclude that these preliminary data show that whereas genotypes directly related to angiogenesis did not differ between EPS and nonEPS patients, it is noteworthy that no patients in the EPS group had a C allele in the RAGE -429T/C genotype. This might indicate a possible genetic contribution to the development of EPS that is related to RAGE.

Gender differences in heritability of depressive symptoms in the elderly

BACKGROUND

The present study aimed to investigate the relative importance of genetic and environmental influences on depressive symptoms in the elderly.

METHOD

Depressive symptoms were assessed through the Center for Epidemiological Studies-Depression (CES-D) scale. The CES-D scale was administered to 959 twin pairs (123 female MZs, 90 male MZs, 207 same-sex female DZs, 109 same-sex male DZs and 430 opposite-sex DZs) aged 50 years or older (mean age 72 years). A dichotomous depressed state variable was constructed based on CES-D cut-offs and self-reported use of antidepressant medication. Structural equation models were fitted to the data to dissect genetic and environmental variance components.

RESULTS

The sex-specific heritability estimates for depressive symptoms were 14% for males and 29% for females and 23% when constrained to be equal for men and women. The prevalence of clinically significant depressive symptoms was 16% for men and 24% for women. Heritability estimates for the dichotomous depressed state measure were 7% for males and 49% for females in the full model and 33% when constrained to be equal.

CONCLUSION

Our results suggest that depressive symptoms in the elderly are moderately heritable, with a higher heritability for women than men, although differences in heritability estimates were not statistically significant.

Selective noradrenaline reuptake inhibition enhances serotonergic neuronal activity and transmitter release in the rat forebrain

Present pharmacotherapy of major depression is, in principle, based on enhancement of central monoaminergic neurotransmission. Clinical studies utilizing depletion experiments indicate that antidepressants which primarily enhance serotonergic or noradrenergic central activity, i.e. serotonin or nor-adrenaline reuptake inhibitors, largely work by two separate neuronal pathways. However, experimental studies have shown that noradrenaline may regulate serotonergic neurotransmission both at the serotonin cell body and nerve-terminal level. We therefore investigated the effects of the selective NRI reboxetine on serotonergic neuronal activity and extracellular levels of transmitter in the nerve-terminal area. In vivo electrophysiological experiments showed that low doses of reboxetine significantly enhance the firing rate of serotonergic neurons in the dorsal raphe nucleus of anaesthetized rats. Also, in the medial prefrontal cortex reboxetine (3 mg/kg s.c.) enhanced, whereas citalopram (3 mg/kg s.c.) reduced, extracellular concentrations of serotonin measured by means of microdialysis in awake rats, using a low dose of citalopram (0,5 micro M) in the perfusion solution. Local administration of reboxetine only induced an increase in cortical serotonin levels at very high concentrations (1000 micro M). Hence, NRIs may cause a secondary enhancement of central serotonergic activity by a mechanism separate from 5-HT reuptake inhibition; an effect that may contribute to their clinical antidepressant efficacy.

Association between depressed mood in the elderly and a 5-HTR2A gene variant

The aim of this study was to investigate any possible association between depressed mood in the elderly and two candidate SNPs in the serotonin system: one in the 5-HTR2A gene promotor (-1438 G/A) and one in the 5-HT transporter gene (-925 C/A). DNA from a population-based Swedish twin sample (N = 1,592; mean age = 73) was genotyped using Pryosequencing trade mark. An association was found between the 5-HTR2A gene promotor polymorphism and depressed mood (OR: 1.5, CI: 1.1-2.1) for the A/A genotype in the total sample. When the sample was analyzed by gender, a significant association (OR: 2.4, CI: 1.4-4.4) was found for males and the A/A genotype, but not for females. The 5-HT transporter gene was not associated with depressed mood in this elderly population. These results suggest that there might be different genetic mechanisms for males and females contributing to the development of depressed mood in the elderly.

The serotonin transporter promoter repeat length polymorphism, seasonal affective disorder and seasonality

BACKGROUND

Conflicting results have been reported in previous association studies of the serotonin transporter promoter repeat length polymorphism (5-HTTLPR), seasonal affective disorder (SAD) and seasonality (seasonal variations in mood and behaviour). The aim of this study was to test for association in new case-control and population-based materials, and to perform a combined analysis of all published studies of 5-HTTLPR and SAD.

METHOD

One hundred and forty-seven new SAD cases and 115 controls were genotyped for 5-HTTLPR and in total 464 patients and 414 controls were included in the pooled analysis. In addition, 226 individuals selected for unusually high or low seasonality scores from a population based material and 46 patients with non-seasonal depression were analysed. Different genetic models were tested and seasonality was analysed both as a qualitative (high v. low) and as a quantitative trait in the different sample sets.

RESULTS

No association between 5-HTTLPR and SAD was found in the new case-control material, in the combined analysis of all samples, or when only including 316 patients with controls (N = 298) selected for low seasonality. A difference was detected between the population based high and low seasonality groups, when assuming a recessive effect of the short allele (20% and 10% short allele homozygotes, respectively, OR (95% CI): 2.24 (1.03-4.91)). Quantitative analysis of seasonality revealed no association with 5-HTTLPR in any sample set.

CONCLUSIONS

These results do not suggest a major role of the short variant of 5-HTTLPR in susceptibility to SAD, but provide modest evidence for an effect on seasonality.

Physical map of the chromosome 6q22 region containing the oculodentodigital dysplasia locus: analysis of thirteen candidate genes and identification of novel ESTs and DNA polymorphisms

Oculodentodigital dysplasia (ODDD) is an autosomal dominant condition with congenital anomalies of the craniofacial and limb regions and neurodegeneration. Genetic anticipation for the dysmorphic and neurologic features has been inferred in a few families. Our previous linkage studies have refined the ODDD candidate region to chromosome 6q22-->q23. In an attempt to clone the ODDD gene, we created a yeast artificial chromosome contig with 31 redundant clones spanning the region and identified and ordered candidate genes and markers. Fluorescent IN SITU hybridization mapped two of these YAC clones to chromosome 6q22.2 telomeric to a known 6q21 fragile site, excluding it as a possible cause of the suggested anticipation. We performed mutation analysis on thirteen candidate genes - GRIK2, HDAC2, COL10A1, PTD013, KPNA5, PIST, ROS1, BRD7, PLN, HSF2, PKIB, FABP7, and HEY2. Although no mutations were found, we identified 44 polymorphisms, including 28 single nucleotide polymorphisms. Direct cDNA selection was performed and fifty-five clones were found to contain sequences that were not previously reported as known genes or ESTs. These clones and polymorphisms will assist in the further characterization of this region and identification of disease genes.

The hormone-sensitive lipase i6 gene polymorphism and body fat accumulation

BACKGROUND

The hormone sensitive lipase (HSL) catalyses the breakdown of adipose tissue triglycerides into free fatty acids. The objective of this study was to determine whether HSLi6 microsatellite allele 5 (A5) and/or homozygosity for this allele is associated with body fat in Swedes.

DESIGN

A large case-control study on gender-specific association for several body fat-related clinical parameters to HSLi6 A5, and to HSLi6 A5 homozygosity, comparing A5 with the other alleles in group. The subjects were 323 obese patients (85 males, 238 females) without other metabolic complication, and 301 nonobese healthy individuals (134 males, 167 females). They were analyzed for various body fat-related clinical parameters, and HSLi6 genotype.

RESULTS

Homozygosity for HSLi6 A5 was a risk factor for obesity, BMI > or = 30 kg m-2 (Odds ratio = 1.75, 95% CI 1.58-1.93) and body fat mass > 39.6% (Odds ratio = 1.89, 95% CI 1.60-2.23) in women. This genotype was also associated with increased diastolic blood pressure and triglyceride level among nonobese women, and with increased body fat mass and waist/hip ratio among nonobese men.

CONCLUSION

HSLi6 A5 homozygosity is a risk factor for body fat accumulation.

Expanded repeat sequences and disease

The clinical phenomenon of an earlier age of onset or a more severe phenotype in later generations of a family has been termed anticipation. In a number of neurological and neuropsychiatric disorders, the anticipation has been linked to expanded repeat sequences that increase in size upon transmission. This novel mutational mechanism has been demonstrated in more than 15 disorders today. The repeat sequence motif (base composition), size, and localization of expanded repeats within the respective disease genes vary between disorders and influence the way the repeat causes disease. Here, we review the occurrence and properties of repeats in the genome. The different groups of disorders and possible pathogenic mechanisms are summarized. In addition, methods used for detection and identification of expanded repeats and the related disorders are discussed.

Spastic paraplegia, ataxia, mental retardation (SPAR): a novel genetic disorder

OBJECTIVE

To describe a kindred with a dominantly inherited neurologic disorder manifested either as uncomplicated spastic paraplegia or ataxia, spastic paraplegia, and mental retardation.

METHODS

Neurologic examinations and molecular genetic analysis (exclusion of known SCA and HSP genes and loci; and trinucleotide repeat expansion detection [RED]) were performed in six affected and four unaffected subjects in this family. MRI, electromyography (EMG), and nerve conduction studies were performed in three affected subjects.

RESULTS

The phenotype of this dominantly inherited syndrome varied in succeeding generations. Pure spastic paraplegia was present in the earliest generation; subsequent generations had ataxia and mental retardation. MRI showed marked atrophy of the spinal cord in all patients and cerebellar atrophy in those with ataxia. Laboratory analysis showed that the disorder was not caused by mutations in genes that cause SCA-1, SCA-2, SCA-3, SCA-6, SCA-7, SCA-8, and SCA-12; not linked to other known loci for autosomal dominant ataxia (SCA-4, SCA-5, SCA-10, SCA-11, SCA-13, SCA-14, and SCA-16); and not linked to known loci for autosomal dominant hereditary spastic paraplegia (HSP) (SPG-3, SPG-4, SPG-6, SPG-8, SPG-9, SPG-10, SPG-12, and SPG-13) or autosomal recessive HSP SPG-7. Analysis of intergenerational differences in age at onset of symptoms suggests genetic anticipation. Using RED, the authors did not detect expanded CAG, CCT, TGG, or CGT repeats that segregate with the disease.

CONCLUSIONS

The authors describe an unusual, dominantly inherited neurologic disorder in which the phenotype (pure spastic paraplegia or spastic ataxia with variable mental retardation) differed in subsequent generations. The molecular explanation for apparent genetic anticipation does not appear to involve trinucleotide repeat expansion.

Genetics of affective disorders

Despite substantial evidence for heritability in affective disorders the contributing genes have proven elusive. Here we discuss the genetic epidemiology of depression, as well as methodological issues and results from molecular genetic studies. There has been rapid advances in genetics, genomics and statistical modelling, facilitating the search for molecular mechanisms underlying affective disorders and several strategies reviewed in this paper hold promise to provide progress in the field. Considering the poorly understood biological basis of vulnerability to affective disorders, the identification of genes involved in the pathophysiology will unravel mechanisms and pathways that could permit more personalized therapeutic strategies and result in new targets for pharmacological intervention.

A common hormone-sensitive lipase i6 gene polymorphism is associated with decreased human adipocyte lipolytic function

Hereditary factors may be involved in the pathogenesis of type 2 diabetes. A polymorphism in the hormone-sensitive lipase (HSL) gene (HSLi6) is associated with obesity and diabetes, although it is unknown whether the polymorphism is functional and thereby influences lipolysis. We genotyped 355 apparently healthy nonobese male and female subjects for the HSLi6 polymorphism. Allele 5 was found to be the most common allele (allele frequency 0.57). In 117 of the subjects, we measured abdominal subcutaneous fat cell lipolysis induced by drugs acting at various steps in the lipolytic cascade. The lipolysis rate induced by norepinephrine isoprenaline (acting on beta-adrenoceptors), forskolin (acting on adenylyl cyclase), and dibutyryl cyclic AMP (acting on HSL) were all decreased by approximately 50% in allele 5 homozygotes, as compared with noncarriers. Heterozygotes showed an intermediate lipolytic rate. The difference in lipolysis rate between genotypes was more pronounced in men than in women. We conclude that allele 5 of the HSLi6 polymorphism is associated with a marked decrease in the lipolytic rate of abdominal fat cells. This may in turn contribute to the development of obesity.

A cloning strategy for identification of genes containing trinucleotide repeat expansions

Until today, nineteen trinucleotide repeat expansions larger than forty repeat copies have been found in the human genome. Of these, the CAG/CTG repeat is predominant motif with twelve loci identified, ten of which have been associated with the development of neurodegenerative diseases. We have developed a cloning approach which isolates disease genes containing trinucleotide repeat expansions. The method is based on size separation of genomic fragments, followed by subcloning and library hybridization with an oligonucleotide probe. Fractions and clones containing expanded repeats are identified by the repeat expansion detection (RED) method throughout the cloning procedure. Large family materials are not required and as little as 10 microg genomic DNA from a single individual is sufficient for this method. Using this strategy we have cloned two DNA fragments containing expanded repeats from two unrelated patients with a clinical diagnosis of cerebellar ataxia. Sequencing of the two fragments showed sequence identities with two disease genes, the Huntington gene and the ataxin 3 gene, respectively. The method should be adaptable to the cloning of any long repeat motif in any species. Furthermore the experimental steps can be performed in less than a month, making it very effective and time efficient to disease gene identification.

Muscleblind localizes to nuclear foci of aberrant RNA in myotonic dystrophy types 1 and 2

The phenotypes in myotonic dystrophy types 1 and 2 (DM1 and DM2) are similar, suggesting a shared pathophysiologic mechanism. DM1 is caused by expansion of a CTG repeat in the DMPK gene. Pathogenic effects of this mutation are likely to be mediated, at least in part, by the expanded CUG repeat in mutant mRNA. The mutant transcripts are retained in the nucleus in multiple discrete foci. We investigated the possibility that DM2 is also caused by expansion of a CTG repeat or related sequence. Analysis of DNA by repeat expansion detection methods, and RNA by ribonuclease protection, did not show an expanded CTG or CUG repeat in DM2. However, hybridization of muscle sections with fluorescence-labeled CAG-repeat oligonucleotides showed nuclear foci in DM2 similar to those seen in DM1. Nuclear foci were present in all patients with symptomatic DM1 (n = 9) or DM2 (n = 9) but not in any disease controls or healthy subjects (n = 23). The foci were not seen with CUG- or GUC-repeat probes. Foci in DM2 were distinguished from DM1 by lower stability of the probe-target duplex, suggesting that a sequence related to the DM1 CUG expansion accumulates in the DM2 nucleus. Muscleblind proteins, which interact with expanded CUG repeats in vitro, localized to the nuclear foci in both DM1 and DM2. These results support the idea that nuclear accumulation of mutant RNA is pathogenic in DM1, suggest that a similar disease process occurs in DM2, and point to a role for muscleblind in the pathogenesis of both disorders.

Genetic survival analysis of age-at-onset of bipolar disorder: evidence for anticipation or cohort effect in families

Age-at-onset (AAO) in a number of extended families ascertained for bipolar disorder was analysed using survival analysis techniques, fitting proportional hazards models to estimate the fixed effects of sex, year of birth, and generation, and a random polygenic genetic effect. Data comprised the AAO (for 171 affecteds) or age when last seen (ALS) for 327 unaffecteds, on 498 individuals in 27 families. ALS was treated as the censored time in the statistical analyses. The majority of individuals classified as affected were diagnosed with bipolar I and II (n = 103) or recurrent major depressive disorder (n = 68). In addition to the significant effects of sex and year of birth, a fitted 'generation' effect was highly significant, which could be interpreted as evidence for an anticipation effect. The risk of developing bipolar or unipolar disorder increased twofold with each generation descended from the oldest founder. However, although information from both affected and unaffected individuals was used to estimate the relative risk of subsequent generations, it is possible that the results are biased because of the 'Penrose effect'. Females had a twofold increased risk in developing depressive disorder relative to males. The risk of developing bipolar or unipolar disorder increased by approximately 4% per year of birth. A polygenic component of variance was estimated, resulting in a 'heritability' of AAO of approximately 0.52. In a family showing strong evidence of linkage to chromosome 4p (family 22), the 'affected haplotype' increased the relative risk of being affected by a factor of 46. In this family, there was strong evidence of a time trend in the AAO. When either year of birth or generation was fitted in the model, these effects were highly significant, but neither was significant in the presence of the other. For this family, there was no increase in trinucleotide repeats measured by the repeat expansion detection method in affected individuals compared with control subjects. Proportional hazard models appear appropriate to analyse AAO data, and the methodology will be extended to map quantitative trait loci (QTL) for AAO.

Altered dopaminergic transmission in the anorexic anx/anx mouse striatum

We demonstrate abnormal dopaminergic neurotransmission in anorexic mice, homozygous for a recessive mutation (anx) causing starvation and motor disturbances. Isolated neurons from anx/anx striatum displayed a markedly increased activity of the Na+,K+-ATPase compared with normal littermates. Dopamine down-regulates Na+,K+-ATPase activity in striatal medium spiny neurons in rat, mouse and guinea pig. However, addition of dopamine in vitro failed to suppress the increased activity in anx/anx striatal neurons. Striatal dopamine and its metabolites, but not norepinephrine, were slightly but significantly lower in anx/anx mice than in normal littermates. We suggest that abnormal dopaminergic transmission may contribute to the anx phenotype.

Expression of alpha-synuclein in the human brain: relation to Lewy body disease

Alpha-synuclein is mutated in some hereditary cases of Parkinson's disease and the protein precipitates in Lewy bodies, the pathological hallmark of both Parkinson's disease and Lewy body disease. Transgenic mice overexpressing human wild-type alpha-synuclein develop alpha-synuclein-immunoreactive inclusions in brain regions typically affected with Lewy body disease. We used in situ hybridization to characterize alpha-synuclein expression and examine mRNA levels in patients affected with Lewy body disease and controls. Substantia nigra was avoided because of the extensive neuronal loss and cingulate gyrus was chosen as it is one of the diagnostic regions in Lewy body disease where Lewy bodies most frequently are demonstrated. beta-tubulin was used to control for neuronal degeneration. The alpha-synuclein probe showed intense labeling of pyramidal cells in lamina III and V in both patients and controls. We found no difference in alpha-synuclein mRNA levels and beta-tubulin mRNA was not significantly altered (P=0.06) in patient brains. There was no difference in the ratio of alpha-synuclein and beta-tubulin mRNA levels between patients and controls. Further, we found no relationship between alpha-synuclein mRNA levels and Lewy bodies. Great variability in alpha-synuclein mRNA levels among patients indicates that Lewy body disease may be a heterogeneous disorder with regard to alpha-synuclein involvement.

Reboxetine modulates the firing pattern of dopamine cells in the ventral tegmental area and selectively increases dopamine availability in the prefrontal cortex

Central dopaminergic neurons have been suggested to be involved in the pathophysiology of several psychiatric disorders, including depression, and appear to be modulated by noradrenergic activity both at the nerve terminal level and at the somatodendritic level. In recent years reboxetine, a selective noradrenaline reuptake inhibitor that differs from tricyclic antidepressants by its low affinity for muscarinic, cholinergic and alpha(1)-adrenergic receptors, has been introduced clinically. In the present study the effect of reboxetine on the function of the mesolimbocortical dopamine system was investigated by means of single cell recording and microdialysis in rats following administration of reboxetine in doses that appear to yield clinically relevant plasma concentrations. Reboxetine (0.625--20 mg/kg intravenously) induced an increase in burst firing, but not in average firing frequency of dopamine (DA) cells in the ventral tegmental area (VTA). Moreover, reboxetine (0.15--13.5 mg/kg intraperitoneally) caused a significantly enhanced DA output in the medial prefrontal cortex, whereas no effect was observed in the nucleus accumbens. Local administration of reboxetine (333 microM, 60 min), by means of reversed microdialysis into these brain regions, caused a significant increase in DA output in both brain regions. However, local administration of reboxetine into the VTA (333 microM, 60 min) did not affect DA availability in these terminal areas. Our results imply that clinical treatment with reboxetine may result in facilitation of both prefrontal DA output and the excitability of VTA DA neurons, effects that may contribute to its antidepressant action, especially on drive and motivation.

Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) blockade enhances incidence and severity of experimental autoimmune neuritis in resistant mice

Experimental autoimmune neuritis (EAN), an autoimmune inflammatory demyelinating disease of the peripheral nervous system, represents an animal model of the human Guillain-Barré syndrome. EAN can be induced by active immunization in several animals, including Lewis rats. In contrast, most strains of mice including the widely used C57BL/6 (B6) strain are reputedly resistant to the induction of EAN. In the present study, we demonstrate that in B6 mice, anti-CTLA-4 monoclonal antibody administration in conjunction with immunization with the P0 protein derived peptide 180-199 can induce clinical and pathological definite EAN. Upregulating effects of CTLA-4 blockade on initial and ongoing EAN are demonstrated. CTLA-4 blockade augmented cellular infiltration and enhanced demyelination in the target organ sciatic nerves as well as increased T cell proliferation in lymph node cells. Moreover, serum levels of IFN-gamma and IL-4 were increased. Thus, manipulation of CTLA-4/B7 costimulatory pathway by CTLA-4 blockade can promote autoreactivity and break the relative tolerance to peripheral autoantigen P0 in resistant B6 mice.

Seasonal affective disorder and serotonin-related polymorphisms

Disturbances in central serotonergic systems have been hypothesized to be involved in seasonal affective disorder (SAD). Association between SAD and the shorter allele of the serotonin transporter promoter repeat length polymorphism (5-HTTLPR) has been reported in an American sample. We have genotyped 82 SAD patients and 82 healthy controls from Sweden, Finland, and Germany for this and five other polymorphisms in the genes coding for serotonin receptors 5-HT2A and 5-HT2C, tryptophan hydroxylase and white. No associations with SAD or seasonality (seasonal variations in mood and behavior) were detected. Although minor effects cannot be excluded, our results suggest that these polymorphisms do not play a major role in the pathogenesis of SAD in the northern European population.

Androgen receptor trinucleotide repeat polymorphism and personality traits

Human family and twin studies have established considerable heritable components influencing individual differences in personality traits as assessed by self-report questionnaires. We have investigated a trinucleotide repeat polymorphism in the androgen receptor gene and personality traits. Healthy Swedish subjects (n = 335) were assessed with the Karolinska Scales of Personality inventory. There were tendencies (P > or = 0.006) in some scales indicating possible relationships between the androgen receptor allele length and personality traits related to dominance and aggression. However, after correction for multiple testing, no significant differences were found. We conclude that no significant association could be found between the androgen receptor polymorphism investigated and any personality trait, although the tendencies found are worthwhile subjects for replication attempts.

Dominantly inherited familial myasthenia gravis as a separate genetic entity without involvement of defined candidate gene loci

Myasthenia gravis (MG) is a sporadic autoimmune disorder affecting neuromuscular transmission. Very rarely autoimmune myasthenia gravis may be inherited within a family. We present here the genetic analysis of a Hungarian family where nine members from two generations are affected by myasthenia gravis. Genetic characterisation of this unique Hungarian family using linkage analysis and mutation screening excludes the involvement of defined candidate gene loci. These findings point to familial MG as a separate genetic entity. Identification of the underlying genetic defect in this family may greatly enhance our understanding of the pathogenesis of myasthenia gravis.

Expression of cholecystokinin, enkephalin, galanin and neuropeptide Y is markedly changed in the brain of the megencephaly mouse

Megencephaly, enlarged brain, is a major sign in several human neurological diseases. The mouse model for megencephaly (mceph/mceph) has an enlarged brain, presumably due to brain cell hypertrophy, and exhibits neurological and motor disturbances with seizure-like activity, as well as disturbances in the insulin-like growth factor system. Here, we report that expression of the neuropeptides cholecystokinin, enkephalin, galanin and neuropeptide Y is dramatically changed in mceph/mceph brains compared to wild type, as revealed by in situ hybridization and immunohistochemistry. The changes were confined to discrete brain regions and occurred in a parallel fashion for peptides and their transcripts. For cholecystokinin, mceph/mceph brains had region-specific up- and down-regulations in several layers of the hippocampal formation and increased levels in, especially ventral, cortical regions. Enkephalin messenger RNA expression was up-regulated in the dentate gyrus granular layer and in ventral cortices, but down-regulated in the CA1 pyramidal layer. Enkephalin-like immunoreactivity was elevated in mossy fibers of the hippocampus and the ventral cortices. Galanin expression was increased in several layers and interneurons of the hippocampal formation, as well as in ventral cortices. Galanin-like immunoreactivity was reduced in nerve terminals in the forebrain. Neuropeptide Y expression was increased in the hippocampal formation and ventral cortices. Whether the mainly increased peptide levels contribute to the excessive growth of the brain or represent a consequence of this growth and/or of the neurological and motor disturbances remains to be elucidated.

Insulin-like growth factor-II in endocrine pancreatic tumours. Immunohistochemical, biochemical and in situ hybridization findings

In earlier studies a high-molecular-weight (HMW) insulin-like growth factor-II (IGF-II) peptide was identified in adult human pancreas and localized to the insulin-producing B-cells. This peptide has now been investigated in neoplastic insulin cells. Forty endocrine pancreatic tumours and 17 pancreatic adenocarcinomas of ductal type were included in the study. All cases were investigated with immunohistochemical techniques using antibodies to IGF-II, insulin, pro-insulin, glucagon, somatostatin, pancreatic polypeptide, gastrin and vasoactive intestinal peptide (VIP). Frozen tissue from nine tumours and two normal pancreatic glands was extracted, gel separated, and quantified using radioimmunoassay. The tumours were also investigated by in situ hybridization. IGF-II-immunoreactive cells were found in nearly all the 18 insulin-producing tumours (16/18), in a minority of the other endocrine tumours, but not in pancreatic adenocarcinomas. All extracts from the endocrine tumours showed varying amounts of IGF-II and had different molecular-weight forms. The immunohistochemical and radioimmunoassay findings are both based on immunological binding and were further confirmed by Northern blot and in situ hybridization. These results show that IGF-II is expressed in insulin-producing tumours as well as in pancreatic tumours producing other peptides, in contrast to normal pancreatic islets where IGF-II is found exclusively in insulin-producing cells.

Hypothalamic CART and serum leptin levels are reduced in the anorectic (anx/anx) mouse

Cocaine- and amphetamine-regulated transcript (CART) is expressed in the hypothalamus, and putative peptides encoded by CART potently inhibit feeding when administered centrally. CART is strongly down-regulated in the lateral hypothalamic area and the arcuate nucleus in animal models of obesity with disrupted leptin signaling. Here we have used in situ hybridization and immunohistochemistry to study CART expression in mice homozygous for the anorexia (anx) mutation which are characterized by a much reduced food intake and premature death. anx/anx mice had significantly decreased levels of CART mRNA label and peptide-immunoreactive cell bodies and fibers in the arcuate nucleus and a lower number of detectable CART-expressing cells in the dorsomedial hypothalamic nucleus/lateral hypothalamic area. Moreover, serum leptin levels were significantly lower in anx/anx mice compared to normal littermates, most likely due to the prominent depletion of body fat in these animals. The decrease in the anorexigenic agents leptin and CART, may reflect a compensatory down-regulation in response to the energy-deprived state of anx/anx mice. Alternatively, the reduced arcuate CART expression may be a consequence of a molecular defect in the arcuate nucleus of these animals.

Long repeat tracts at SCA8 in major psychosis

Expansion at a recently identified unstable trinucleotide repeat on chromosome 13q21 has been reported as the molecular cause for spinocerebellar ataxia type 8 (SCA8). The trinucleotide repeat, which consists of a [CTA]n repeat and adjacent [CTG]n repeat, was reported to have a pathogenic range of 107-127 CTG repeats (or 110-130 combined CTA and CTG repeats) in a large ataxia kindred. This repeat region was also cloned by our group from a bipolar affective disorder (BPAD) patient, who has approximately 600 combined repeats, and large alleles (>100 repeats) were reported to be present in 0.7% of controls and 1.5% of major psychosis patients (n = 710 and n = 1,120, respectively). We have followed up these findings by screening three new samples of BPAD and schizophrenia (SCZ) patients and controls, including 272 individuals from 14 BPAD families from Sweden, 130 individuals from 32 SCZ and BPAD families/trios from the Azores Islands, and 206 SCZ individuals from the United Kingdom and Ireland, and 219 matched controls. We found large repeat alleles above the SCA8 pathogenic range in individuals from 3 of 32 Azorean pedigrees and in 1 of 206 SCZ individuals from the United Kingdom, and repeat alleles within the SCA8 pathogenic range in 1 of 14 Swedish families. Although the rarity of major psychosis patients carrying the SCA8 expansion mutation would require a much larger sample size to reach statistical significance, these results support the previously reported observation of increased occurrence of large repeats at SCA8 in major psychosis. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:873-876, 2000.

P0 protein peptide 180-199 together with pertussis toxin induces experimental autoimmune neuritis in resistant C57BL/6 mice

The C57BL/6 mice strain is known to be reputedly resistant to induction of experimental autoimmune neuritis (EAN), an animal model of Guillain-Barré syndrome in human by bovine peripheral myelin (BPM), and P2 protein or the P2 protein peptide 57-81. The P0 peptide 180-199 is a stronger neuritogenic antigen than the P2 peptide 57-81. We found that this synthetic peptide induced both clinical and pathological characteristics of an acute monophasic EAN in C57BL/6 mice. Only male mice were more sensitive to EAN induction with the P0 peptide 180-199. Intravenously administrated pertussis toxin (PT) had an adjuvant effect that increased the incidence of P0 peptide 180-199-induced EAN as well as the inflammation and demyelination in the peripheral nerves. Spontaneous and P0 peptide 180-199 stimulated proliferation of peripheral T-cells were enhanced by PT-treatment as well. The enhancing effect was lower before onset of the disease (Day 6 post immunization) (p.i.) as compared to the early phase of the disease (Day 22 p.i.). Thus, P0 peptides together with PT are able to break tolerance to myelin in C57BL/6 mice.

Fat tissue accumulation during peritoneal dialysis is associated with a polymorphism in uncoupling protein 2

BACKGROUND

Chronic treatment with peritoneal dialysis (PD) is a unique long-term metabolic procedure entailing a continuous 24-hour supply of glucose absorbed from the dialysis fluid. One common and important side effect of this treatment is weight gain and accumulation of body fat stores. However, not all patients accumulate body fat mass during PD, and the reason for this is not clear. Recently, two new mitochondrial uncoupling proteins (UCP2 and UCP3) have been found to have thermogenic properties that suggest involvement in the control of metabolic efficiency in humans. Moreover, recent results suggest that a polymorphism in the UCP2 gene may contribute to adipose tissue accumulation through its effects on energy metabolism. It could therefore be speculated that genetic differences in the metabolic rate might contribute to the differences in the accumulation of fat tissue during PD.

METHODS

Genotyping of a polymorphism in the 3' untranslated region of exon 8 of UCP2 was performed in 41 patients (53 +/- 2 years) with chronic renal failure for whom we had prospective data on body composition (as estimated by dual-energy x-ray absorptiometry) following PD. In addition, indices of dialysis adequacy, peritoneal glucose absorption, and urea kinetics were followed (3 to 6 times per year in each patient) during treatment with PD. The degree of physical activity was assessed before the start of PD.

RESULTS

Twenty patients with the deletion/deletion UCP2 genotype had a significant increase in body weight (3.0 +/- 0.8 vs. -1.0 +/- 1.1 kg, P < 0.01) and body fat mass (3.8 +/- 0.9 vs. 0.8 +/- 1.0 kg, P < 0.05) during PD, compared with 19 patients with an insertion/deletion UCP2 genotype. On the other hand, no significant differences in indices of dialysis adequacy, peritoneal glucose absorption, urea kinetic parameters, or degree of physical activity were observed when comparing patients who accumulated or lost fat tissue during PD.

CONCLUSIONS

As most patients with the deletion/deletion UCP2 genotype acquired fat tissue during PD, the present results suggest that the UCP2 polymorphism contributes to variations in body composition. Thus, variations in UCP2 production or activity may be factors contributing to adipose tissue accumulation in a subgroup of patients treated with PD. It is possible that the polymorphism has a similar effect in the general population.

ARSACS, a spastic ataxia common in northeastern Québec, is caused by mutations in a new gene encoding an 11.5-kb ORF

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS or SACS) is an early onset neurodegenerative disease with high prevalence (carrier frequency 1/22) in the Charlevoix-Saguenay-Lac-Saint-Jean (CSLSJ) region of Quebec. We previously mapped the gene responsible for ARSACS to chromosome 13q11 and identified two ancestral haplotypes. Here we report the cloning of this gene, SACS, which encodes the protein sacsin. The ORF of SACS is 11,487 bp and is encoded by a single gigantic exon spanning 12,794 bp. This exon is the largest to be identified in any vertebrate organism. The ORF is conserved in human and mouse. The putative protein contains three large segments with sequence similarity to each other and to the predicted protein of an Arabidopsis thaliana ORF. The presence of heat-shock domains suggests a function for sacsin in chaperone-mediated protein folding. SACS is expressed in a variety of tissues, including the central nervous system. We identified two SACSmutations in ARSACS families that lead to protein truncation, consistent with haplotype analysis.

No evidence for long CAG/CTG repeats in families with spastic paraplegia linked to chromosome 2p21-24

Autosomal dominant familial spastic paraplegia (AD-FSP) is a genetically heterogeneous, neurodegenerative disorder characterized by spasticity and progressive weakness in the lower limbs. Anticipation has been suggested to occur and an association between expanded CAG/CTG repeats and AD-FSP linked to the SPG4 locus (2p21-p24) has been described. In this study, 42 affected individuals from six SPG4 families were screened for expanded CAG/CTG repeats using the repeat expansion detection (RED) method. Large RED products (range 180-240 nucleotides) corresponding in size to repeats at the ERDA1 locus were detected in eight patients and at the CTG 18.1 locus in one patient. The large ERDA1 repeats did not segregate with the disorder within families. Mean age at onset and index of severity were not significantly different between patients with or without expanded RED products. Furthermore, no abnormal proteins were found by Western blot in 15 selected patient samples as compared with controls, using the 1C2 antibody, which detects long polyglutamine stretches. Thus, in contrast to previous reports, our study provides evidence against the hypothesis that a large translated CAG repeat expansion is the basis of SPG4. We propose that mechanisms other than large pathogenic CAG/CTG repeats may account for the disease in the SPG4 families tested here.

Primary megalencephaly at birth and low intelligence level

OBJECTIVES

To evaluate the association between primary megalencephaly (PMG) at birth and psychosensory conditions and to determine mother-child similarity for PMG at birth.

BACKGROUND

PMG is defined as a head circumference (HC) above the 98th percentile that most likely is due to brain enlargement and is not secondary to disease. Previously, PMG in children was reported to be associated with learning disabilities. Contradictory results regarding an association between PMG and intelligence in children exist. Many believe PMG expressed in childhood and adulthood may be inherited.

METHODS

Birth records on HC from 144,273 boys, of whom 732 had PMG, were linked to data concerning intelligence level, mental retardation, and impairment of vision and hearing. A potential association between PMG at birth and mental retardation was also examined in 3,204 mentally retarded boys and girls. Parent-offspring similarity for PMG at birth was determined in 13,585 mother-child pairs.

RESULTS

PMG was significantly associated with low intelligence level (odds ratio, 1.32; 95% confidence interval [CI], 1.11 to 1.38). The estimated odds ratio for mental retardation in PMG cases versus controls was 1.31 (95% CI, 0.80 to 2.02). There were no differences in frequencies of vision and hearing impairments between PMG cases and controls. Associations between mother's and child's birth weight-normalized HC (r = 0.14; p<0.0001) and PMG (odds ratio, 2.55; CI, 2.00 to 3.25) were found, supporting a multifactorial inheritance of PMG.

CONCLUSIONS

PMG at birth is a risk factor for low intelligence level but not for vision and hearing impairments. The heritability of HC and PMG is moderate.

Molecular interpretation of expanded RED products in bipolar disorder by CAG/CTG repeats located at chromosomes 17q and 18q

Previously we provided evidence that the anticipation observed in bipolar (BP) disorder may be explained by expanded CAG/CTG triplet repeats. Data were generated with the repeat expansion detection (RED) method in a BP case-control sample showing a significant association of BP disorder with expanded CAG/CTG repeats (RED products of 120 bp). In this study we demonstrated that 86% of the RED expansions could be accounted for by the ERDA1 and CTG18.1 CAG/CTG repeats located respectively on chromosomes 17 and 18. Further, significantly different allele distributions were observed for ERDA1, with a larger proportion of BP patients (34.7%) carrying one or two expanded ERDA1 alleles (CAG/CTG repeats >40) than controls (19.2%) (P = 0.032). Also, a negative correlation was observed for ERDA1 between CAG/CTG length and age at onset in affected offspring of eight BP families. Although interesting, these data should be interpreted with caution since the ERDA1 association did not remain significant after correcting for multiple testing. Also, no linkage was observed between BP disorder and expanded ERDA1 alleles in the families.

Exclusion of dominant mutations within the FTDP-17 locus on chromosome 17 for Parkinson's disease

Parkinson's disease (PD) is a prevalent movement disorder, and 10-30% of PD is familial. Several neurodegenerative disorders which are collectively called frontotemporal dementia and parkinsonism have been mapped to chromosome 17q and mutations in tau have been identified. The clinical and pathological overlap suggests that these related conditions may be due to mutations in tau. We examined linkage to the candidate region on chromosome 17 including and surrounding tau in eight familial PD kindreds. We found no evidence for linkage and excluded the 6cM candidate region which suggest that in our families, PD is not caused by dominant mutations within tau.

The megencephaly mouse has disturbances in the insulin-like growth factor (IGF) system

Megencephaly, enlarged brain, is a major sign in several human neurological diseases. The mouse model for megencephaly, mceph/mceph, has an enlarged brain and a lowered body weight. In addition, it displays several neurological and motoric disturbances. Previous studies suggest that the brain enlargement results from hypertrophy of the brain cells, rather than hyperplasia. No structural abnormalities, edema or increased myelination have been found. In this study, a major imbalance in the mRNA expression of molecules in the insulin-like growth factor (IGF) system was found in brains of 9-10 weeks old mceph/mceph mice compared to +/+ wild-type mice. In mceph/mceph brains, we found upregulation of IGF binding proteins (BP)-2, -4, -5, and -6 mRNA, the regulating hormone transforming growth factor (TGF)beta1 mRNA and also a local downregulation of IGFBP-5 mRNA compared to wild-type brains by in situ hybridization. The altered expression of these mRNA species is colocalized in cerebral cortex, hippocampus, amygdala and piriform/entorhinal cortex. The mceph/mceph mice express less of the myelin component proteolipid protein (PLP) mRNA in corpus callosum. No expression difference of the housekeeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in brain or IGF system components in liver was found between mceph/mceph and wild-type mice. These data suggest that the IGF system has an important role in the excessive growth of the mceph/mceph brains.

Changes in neuropeptide Y receptors and pro-opiomelanocortin in the anorexia (anx/anx) mouse hypothalamus

The pro-opiomelanocortinergic (POMCergic) system originating in the hypothalamic arcuate nucleus extends projections widely over the brain and has been shown to be intricately linked and parallel to the arcuate neuropeptide Y (NPY) system. Both NPY and POMC-derived peptides (melanocortins) have been strongly implicated in the control of feeding behavior, with the former exerting orexigenic effects and the latter having anorexigenic properties. Mice homozygous for the lethal anorexia (anx) mutation are hypophagic, emaciated, and exhibit anomalous processing of NPY exclusively in the arcuate nucleus, providing an interesting model to study NPY-POMC interactions. In the present study, several morphological markers were used to investigate the histochemistry and morphology of the POMC system in anx/anx mice. In situ hybridization demonstrated decreased numbers of POMC mRNA-expressing neurons in the anx/anx arcuate nucleus. In parallel, mRNA levels for both the NPY Y1 and Y5 receptors, which are expressed in POMC neurons, were decreased. Also, expression of the NPY Y2 autoreceptor was attenuated. Immunohistochemistry using antibodies against adrenocorticotropic hormone to demonstrate POMC cell bodies, against alpha-melanocyte-stimulating hormone to demonstrate axonal projections and against the NPY Y1 receptor to demonstrate dendritic arborizations, showed strikingly decreased immunoreactivities for all these markers. The present data suggest that degeneration of the arcuate POMC system is a feature characteristic of the anx/anx mouse. The possible relationship to the NPYergic phenotype of this animal is discussed.