Ian P. Hughes

The DRD2 gene 957C>T polymorphism is associated with Posttraumatic Stress Disorder in war veterans

Background: Variations in genes related to the dopaminergic pathway have been implicated in neuropsychiatric disorders such as schizophrenia, substance misuse, Alzheimers disease and Post Traumatic Stress Disorder (PTSD). A single nucleotide polymorphism (SNP) (957C>T) and a deletion polymorphism (‐141delC) in the DRD2 gene and a SNP (Taq1A) in a gene directly downstream of DRD2 have all been implicated in dopamine functioning in the brain. Methods: To test the importance of these three polymorphisms in PTSD susceptibility, a genetic screen was performed in 127 war veterans diagnosed with PTSD and 228 control individuals without a history of PTSD. Results: No significant association was found between PTSD and the Taq1A or ‐141delC polymorphisms. However, a significant association was observed with PTSD and the 957C>T polymorphism. PTSD individuals were more likely to carry the C allele compared to the controls (P=0.021). Conclusions: Our findings suggest that the 957C>T polymorphism in the DRD2 gene is one of the genetic factors for susceptibility to PTSD. Depression Anxiety, 2009.

Unravelling the molecular control of calvarial suture fusion in children with craniosynostosis

BackgroundCraniosynostosis, the premature fusion of calvarial sutures, is a common craniofacial abnormality. Causative mutations in more than 10 genes have been identified, involving fibroblast growth factor, transforming growth factor beta, and Eph/ephrin signalling pathways. Mutations affect each human calvarial suture (coronal, sagittal, metopic, and lambdoid) differently, suggesting different gene expression patterns exist in each human suture. To better understand the molecular control of human suture morphogenesis we used microarray analysis to identify genes differentially expressed during suture fusion in children with craniosynostosis. Expression differences were also analysed between each unfused suture type, between sutures from syndromic and non-syndromic craniosynostosis patients, and between unfused sutures from individuals with and without craniosynostosis.ResultsWe identified genes with increased expression in unfused sutures compared to fusing/fused sutures that may be pivotal to the maintenance of suture patency or in controlling early osteoblast differentiation (i.e. RBP4, GPC3, C1QTNF3, IL11RA, PTN, POSTN). In addition, we have identified genes with increased expression in fusing/fused suture tissue that we suggest could have a role in premature suture fusion (i.e. WIF1, ANXA3, CYFIP2). Proteins of two of these genes, glypican 3 and retinol binding protein 4, were investigated by immunohistochemistry and localised to the suture mesenchyme and osteogenic fronts of developing human calvaria, respectively, suggesting novel roles for these proteins in the maintenance of suture patency or in controlling early osteoblast differentiation. We show that there is limited difference in whole genome expression between sutures isolated from patients with syndromic and non-syndromic craniosynostosis and confirmed this by quantitative RT-PCR. Furthermore, distinct expression profiles for each unfused suture type were noted, with the metopic suture being most disparate. Finally, although calvarial bones are generally thought to grow without a cartilage precursor, we show histologically and by identification of cartilage-specific gene expression that cartilage may be involved in the morphogenesis of lambdoid and posterior sagittal sutures.ConclusionThis study has provided further insight into the complex signalling network which controls human calvarial suture morphogenesis and craniosynostosis. Identified genes are candidates for targeted therapeutic development and to screen for craniosynostosis-causing mutations.

Developing waist-to-height ratio cut-offs to define overweight and obesity in children and adolescents.

OBJECTIVE The waist-to-height ratio (WHtR) assesses abdominal adiposity and has been proposed to be of greater value in predicting obesity-related cardiovascular health risks in children than BMI. The present study aims to develop WHtR cut-offs for overweight and obesity based on the 85th and 95th percentiles for the percentage body fat (%BF) in a cohort of children and adolescents. DESIGN Waist circumference (WC), height, triceps and subscapular skinfolds were used to calculate WHtR and %BF. Correlations between WHtR and %BF and WHtR/mid-abdominal skinfold were made. Receiver-operating characteristic (ROC) curve analysis was used to select WHtR cut-offs to define overweight and obesity. Subjects were grouped by WHtR cut-offs, and mean values for anthropometry, blood lipids and blood pressure (BP) variables were compared. SETTING Australian primary and secondary schools. SUBJECTS A total of 2773 male (M) and female (F) subjects of the 1985 Australian Health and Fitness Survey, aged 8-16 years. RESULTS Correlation coefficients between WHtR and %BF were M: r = 0.73, F: r = 0.60, P < 0.01 and WHtR/mid-abdominal skinfold were M: r = 0.78, F: r = 0.65, P < 0.01. WHtR of 0.46(M) and 0.45(F) best identified subjects with > or = 85th percentile for %BF and 0.48(M) and 0.47(F) identified subjects with > or = 95th percentile for %BF. When comparing the highest WHtR group to the lowest, both sexes had significantly higher means for weight, WC, %BF, TG (male subjects only), systolic BP (female subjects only) and lower means for HDL cholesterol (P < 0.05). CONCLUSIONS WHtR is useful in clinical and population health as it identifies children with higher %BF at greater risk of developing weight-related CVD at an earlier age.

A polymorphism in the dysbindin gene (DTNBP1) associated with multiple psychiatric disorders including schizophrenia

BackgroundA number of studies have found associations between dysbindin (DTNBP1) polymorphisms and schizophrenia. Recently we identified a DTNBP1 SNP (rs9370822) that is strongly associated with schizophrenia. Individuals diagnosed with schizophrenia were nearly three times as likely to carry the CC genotype compared to the AA genotype.MethodsTo investigate the importance of this SNP in the function of DTNBP1, a number of psychiatric conditions including addictive behaviours and anxiety disorders were analysed for association with rs9370822.ResultsThe DTNBP1 polymorphism was significantly associated with post-traumatic stress disorder (PTSD) as well as nicotine and opiate dependence but not alcohol dependence. Individuals suffering PTSD were more than three times as likely to carry the CC genotype compared to the AA genotype. Individuals with nicotine or opiate dependence were more than twice as likely to carry the CC genotype compared to the AA genotype.ConclusionsThis study provides further support for the importance of DTNBP1 in psychiatric conditions and suggests that there is a common underlying molecular defect involving DTNBP1 that contributes to the development of several anxiety and addictive disorders that are generally recognised as separate clinical conditions. These disorders may actually be different expressions of a single metabolic pathway perturbation. As our participant numbers are limited our observations should be viewed with caution until they are independently replicated.

DRD2 C957T and TaqIA Genotyping Reveals Gender Effects and Unique Low-Risk and High-Risk Genotypes in Alcohol Dependence

AIMS As recent conflicting reports describe a genetic association between both the C- and the T-alleles of the dopamine D2 receptor (DRD2) C957T polymorphism (rs6277) in alcohol-dependent subjects, our aim was to examine this polymorphism and TaqIA (rs1800497) in Australian alcohol-dependent subjects. METHODS The C957T polymorphism was genotyped in 228 patients with alcohol dependence (72 females and 156 males) and 228 healthy controls. RESULTS The C-allele and C/C genotype of C957T was associated with alcohol dependence, whereas the TaqIA polymorphism was not. When analysed separately for C957T, males showed an even stronger association with the C-allele and females showed no association. The C957T and TaqIA haplotyping revealed a strong association with alcohol dependence and a double-genotype analysis (combining C957T and TaqIA genotypes) revealed that the relative risk of different genotypes varied by up to 27-fold with the TT/A1A2 having an 8.5-fold lower risk of alcohol dependence than other genotypes. CONCLUSION Decreased DRD2 binding associated with the C-allele of the DRD2 C957T polymorphism is likely to be important in the underlying pathophysiology of at least some forms of alcohol dependence, and this effect appears to be limited to males only.

A novel SNP in COMT is associated with alcohol dependence but not opiate or nicotine dependence: a case control study

BackgroundIt is well established that COMT is a strong candidate gene for substance use disorder and schizophrenia. Recently we identified two SNPs in COMT (rs4680 and rs165774) that are associated with schizophrenia in an Australian cohort. Individuals with schizophrenia were more than twice as likely to carry the GG genotype compared to the AA genotype for both the rs165774 and rs4680 SNPs. Association of both rs4680 and rs165774 with substance dependence, a common comorbidity of schizophrenia has not been investigated.MethodsTo determine whether COMT is important in substance dependence, rs165774 and rs4680 were genotyped and haplotyped in patients with nicotine, alcohol and opiate dependence.ResultsThe rs165774 SNP was associated with alcohol dependence. However, it was not associated with nicotine or opiate dependence. Individuals with alcohol dependence were more than twice as likely to carry the GG or AG genotypes compared to the AA genotype, indicating a dominant mode of inheritance. The rs4680 SNP showed a weak association with alcohol dependence at the allele level that did not reach significance at the genotype level but it was not associated with nicotine or opiate dependence. Analysis of rs165774/rs4680 haplotypes also revealed association with alcohol dependence with the G/G haplotype being almost 1.5 times more common in alcohol-dependent cases.ConclusionsOur study provides further support for the importance of the COMT in alcohol dependence in addition to schizophrenia. It is possible that the rs165774 SNP, in combination with rs4680, results in a common molecular variant of COMT that contributes to schizophrenia and alcohol dependence susceptibility. This is potentially important for future studies of comorbidity. As our participant numbers are limited our observations should be viewed with caution until they are independently replicated.

Gender Bias in Children Receiving Growth Hormone Treatment

BACKGROUND About twice as many boys than girls are treated with GH. Ascertainment bias is a possible explanation. HYPOTHESES For ascertainment bias, the gender least frequently treated should be relatively shorter, and in an unbiased population sample, equal numbers of boys and girls should be eligible for GH treatment. SUBJECTS AND SETTING In 2007 a total of 1485 Australian children received GH (OZGROW database). Heights were also obtained from two recent unbiased surveys consisting of 3596 and 4794 Australian children. METHODS Numbers of boys and girls treated with GH were determined for each treatment indication. Height sd scores (SDS) at first presentation for GH-treated boys and girls were assessed. Frequency of boys and girls from two unbiased populations with height SDS less than -2.326 were recorded. OUTCOMES OUTCOMES included gender frequencies and height SDSs. HYPOTHESES were formed before interrogation of preexisting databases. RESULTS More boys than girls received GH (P = 3.68 x 10(-20)). By indication: biochemical GH deficiency (P = 0.001), cranial irradiation (P = 0.002), slow growing (P = 2.09 x 10(-16)), and chronic renal failure (P = 0.061). Approximately equal numbers of girls and boys were treated for hypoglycemia (P = 0.543). Slow-growing girls were relatively shorter than boys for ages spanning 4.50-8.49 yr (P = 3.80 x 10(-4)), but boys were relatively shorter in the 6.00- to 17.99-month age group (P = 0.011). Biochemical boys were relatively shorter than girls (P = 0.023). In the two unbiased surveys, boys outnumbered girls 11 to six and 16 to eight for height SDS less than -2.326. CONCLUSIONS There is a gender bias in this GH-treated population. Ascertainment bias does not appear to be the major cause.

In vitro differentiation of human calvarial suture derived cells with and without dexamethasone does not induce in vivo‐like expression

Osteogenic supplements are a requirement for osteoblastic cell differentiation during in vitro culture of human calvarial suture‐derived cell populations. We investigated the ability of ascorbic acid and β‐glycerophosphate with and without the addition of dexamethasone to stimulate in vivo‐like osteoblastic differentiation. Cells were isolated from unfused and prematurely fused suture tissue from patients with syndromic and non‐syndromic craniosynostosis and cultured in each osteogenic medium for varying lengths of time. The effect of media supplementation was investigated with respect to the ability of cells to form mineralised bone nodules and the expression of five osteodifferentiation marker genes (COL1A1, ALP, BSP, OC and RUNX2), and five genes that are differentially expressed during human premature suture fusion (GPC3, RBP4, C1QTNF3, WIF1 and FGF2). Cells from unfused sutures responded more slowly to osteogenic media but formed comparable bone nodules to fused suture‐derived cells after 16 days of culture in either osteogenic media. However, gene expression differed between unfused and fused suture‐derived cells, as did expression in each osteogenic medium. When compared to expression in the explant tissue of origin, neither medium induced a level or profile of gene expression similar to that seen in vivo. Overall, our results demonstrate that cells from the same suture that are isolated during different stages of morphogenesis in vivo, despite being de‐differentiated to a similar level in vitro, respond uniquely and differently to each osteogenic medium. Further, we suggest that neither cell culture medium recapitulates differentiation via activation of the same genetic cascades as occurs in vivo. J. Cell. Physiol. 218: 183–191, 2009.

Growth hormone regimens in Australia: analysis of the first 3 years of treatment for idiopathic growth hormone deficiency and idiopathic short stature

Objective  To investigate response to growth hormone (GH) in the first, second and third years of treatment for all idiopathic GH‐deficient (GHD) and idiopathic short stature (ISS) patients in Australia.

A novel DRD2 single-nucleotide polymorphism associated with schizophrenia predicts age of onset : HapMap tag-single-nucleotide polymorphism analysis

BACKGROUND Dopamine D2 receptor (DRD2) is thought to be critical in regulating the dopaminergic pathway in the brain, which is known to be important in the etiology of schizophrenia. It is, therefore, not surprising that most antipsychotic medication acts on DRD2. DRD2 is widely expressed in the brain; levels are reduced in the brains of patients with schizophrenia, and DRD2 polymorphisms have been associated with reduced brain expression. We have previously identified a genetic variant in DRD2, rs6277 to be strongly implicated in schizophrenia susceptibility. METHODS To identity new associations in the DRD2 gene with disease status and clinical severity, we genotyped seven single-nucleotide polymorphisms (SNPs) in DRD2 by using a multiplex mass spectrometry method. SNPs were chosen by using a haplotype block-based gene-tagging approach; so, the entire DRD2 gene was represented. RESULTS One polymorphism, rs2734839 was found to be significantly associated with schizophrenia as well as late onset age. Individuals carrying the genetic variation were more than twice as likely to have schizophrenia compared with controls. CONCLUSIONS Our results suggest that DRD2 genetic variation is a good indicator for schizophrenia risk and may also be used as a predictor of age of onset.