Unravelling the Genetic Landscape of Hemiplegic Migraine: Exploring Innovative Strategies and Emerging Approaches

Migraine is a severe, debilitating neurovascular disorder. Hemiplegic migraine (HM) is a rare and debilitating neurological condition with a strong genetic basis. Sequencing technologies have improved the diagnosis and our understanding of the molecular pathophysiology of HM. Linkage analysis and sequencing studies in HM families have identified pathogenic variants in ion channels and related genes, including CACNA1A, ATP1A2, and SCN1A, that cause HM. However, approximately 75% of HM patients are negative for these mutations, indicating there are other genes involved in disease causation. In this review, we explored our current understanding of the genetics of HM. The evidence presented herein summarises the current knowledge of the genetics of HM, which can be expanded further to explain the remaining heritability of this debilitating condition. Innovative bioinformatics and computational strategies to cover the entire genetic spectrum of HM are also discussed in this review.

Association Study of a Comprehensive Panel of Neuropeptide-Related Polymorphisms Suggest Potential Roles in Verbal Learning and Memory

Neuropeptides are mostly expressed in regions of the brain responsible for learning and memory and are centrally involved in cognitive pathways. The majority of neuropeptide research has been performed in animal models; with acknowledged differences between species, more research into the role of neuropeptides in humans is necessary to understand their contribution to higher cognitive function. In this study, we investigated the influence of genetic polymorphisms in neuropeptide genes on verbal learning and memory. Variants in genes encoding neuropeptides and neuropeptide receptors were tested for association with learning and memory measures using the Hopkins Verbal Learning Test-Revised (HVLT-R) in a healthy cohort of individuals (n = 597). The HVLT-R is a widely used task for verbal learning and memory assessment and provides five sub-scores: recall, delay, learning, retention, and discrimination. To determine the effect of candidate variants on learning and memory performance, genetic association analyses were performed for each HVLT-R sub-score with over 1300 genetic variants from 124 neuropeptide and neuropeptide receptor genes, genotyped on Illumina OmniExpress BeadChip arrays. This targeted analysis revealed numerous suggestive associations between HVLT-R test scores and neuropeptide and neuropeptide receptor gene variants; candidates include the SCG5, IGFR1, GALR1, OXTR, CCK, and VIPR1 genes. Further characterization of these genes and their variants will improve our understanding of the genetic contribution to learning and memory and provide insight into the importance of the neuropeptide network in humans.

Investigation of CACNA1I Cav3.3 Dysfunction in Hemiplegic Migraine

Familial hemiplegic migraine (FHM) is a severe neurogenetic disorder for which three causal genes, CACNA1A, SCN1A, and ATP1A2, have been implicated. However, more than 80% of referred diagnostic cases of hemiplegic migraine (HM) are negative for exonic mutations in these known FHM genes, suggesting the involvement of other genes. Using whole-exome sequencing data from 187 mutation-negative HM cases, we identified rare variants in the CACNA1I gene encoding the T-type calcium channel Cav3.3. Burden testing of CACNA1I variants showed a statistically significant increase in allelic burden in the HM case group compared to gnomAD (OR = 2.30, P = 0.00005) and the UK Biobank (OR = 2.32, P = 0.0004) databases. Dysfunction in T-type calcium channels, including Cav3.3, has been implicated in a range of neurological conditions, suggesting a potential role in HM. Using patch-clamp electrophysiology, we compared the biophysical properties of five Cav3.3 variants (p.R111G, p.M128L, p.D302G, p.R307H, and p.Q1158H) to wild-type (WT) channels expressed in HEK293T cells. We observed numerous functional alterations across the channels with Cav3.3-Q1158H showing the greatest differences compared to WT channels, including reduced current density, right-shifted voltage dependence of activation and inactivation, and slower current kinetics. Interestingly, we also found significant differences in the conductance properties exhibited by the Cav3.3-R307H and -Q1158H variants compared to WT channels under conditions of acidosis and alkalosis. In light of these data, we suggest that rare variants in CACNA1I may contribute to HM etiology.

Comprehensive Exonic Sequencing of Hemiplegic Migraine-Related Genes in a Cohort of Suspected Probands Identifies Known and Potential Pathogenic Variants

Hemiplegic migraine (HM) is a rare migraine disorder with aura subtype including temporary weakness and visual, sensory, and/or speech symptoms. To date, three main genes—CACNA1A, ATP1A2, and SCN1A—have been found to cause HM. These encode ion channels or transporters, important for regulating neuronal ion balance and synaptic transmission, leading to HM being described as a channelopathy. However, <20% of HM cases referred for genetic testing have mutations in these genes and other genes with roles in ion and solute transport, and neurotransmission has also been implicated in some HM cases. In this study, we performed whole exome sequencing for 187 suspected HM probands referred for genetic testing, but found to be negative for CACNA1A, ATP1A2, and SCN1A mutations, and applied targeted analysis of whole exome sequencing data for rare missense or potential protein-altering variants in the PRRT2, PNKD, SLC1A3, SLC2A1, SLC4A4, ATP1A3, and ATP1A4 genes. We identified known mutations and some potentially pathogenic variants in each of these genes in specific cases, suggesting that their screening improves molecular diagnosis for the disorder. However, the majority of HM patients were found not to have candidate mutations in any of the previously reported HM genes, suggesting that additional genetic factors contributing to the disorder are yet to be identified.

Investigating the influence of mtDNA and nuclear encoded mitochondrial variants on high intensity interval training outcomes

Mitochondria supply intracellular energy requirements during exercise. Specific mitochondrial haplogroups and mitochondrial genetic variants have been associated with athletic performance, and exercise responses. However, these associations were discovered using underpowered, candidate gene approaches, and consequently have not been replicated. Here, we used whole-mitochondrial genome sequencing, in conjunction with high-throughput genotyping arrays, to discover novel genetic variants associated with exercise responses in the Gene SMART (Skeletal Muscle Adaptive Response to Training) cohort (n = 62 completed). We performed a Principal Component Analysis of cohort aerobic fitness measures to build composite traits and test for variants associated with exercise outcomes. None of the mitochondrial genetic variants but eight nuclear encoded variants in seven separate genes were found to be associated with exercise responses (FDR < 0.05) (rs11061368: DIABLO, rs113400963: FAM185A, rs6062129 and rs6121949: MTG2, rs7231304: AFG3L2, rs2041840: NDUFAF7, rs7085433: TIMM23, rs1063271: SPTLC2). Additionally, we outline potential mechanisms by which these variants may be contributing to exercise phenotypes. Our data suggest novel nuclear-encoded SNPs and mitochondrial pathways associated with exercise response phenotypes. Future studies should focus on validating these variants across different cohorts and ethnicities.

Targeted next generation sequencing identifies a genetic spectrum of DNA variants in patients with hemiplegic migraine

Objective:

Hemiplegic migraine in both familial (FHM) and sporadic (SHM) forms is a rare subtype of migraine with aura that can be traced to mutations in the CACNA1A, ATP1A2 and SCN1A genes. It is characterised by severe attacks of typical migraine accompanied by hemiparesis, as well as episodes of complex aura that vary significantly between individuals.

Methods:

Using a targeted next generation sequencing (NGS) multigene panel, we have sequenced the genomic DNA of 172 suspected hemiplegic migraine cases, in whom no mutation had previously been found by Sanger sequencing (SS) of a limited number of exons with high mutation frequency in FHM genes.

Results:

Genetic screening identified 29 variants, 10 of which were novel, in 35 cases in the three FHM genes ( CACNA1A, ATP1A2 and SCN1A). Interestingly, in this suspected HM cohort, the ATP1A2 gene harboured the highest number of variants with 24/35 cases (68.6%), while CACNA1A ranked the second gene, with 5 variants identified in 7/35 cases (20%). All detected variants were confirmed by SS and were absent in 100 non-migraine healthy control individuals. Assessment of variants with the American College of Medical Genetics and Genomics guidelines classified 8 variants as pathogenic, 3 as likely pathogenic and 18 as variants of unknown significance. Targeted NGS gene panel increased the diagnostic yield by fourfold over iterative SS in our diagnostics facility.

Conclusion:

We have identified 29 potentially causative variants in an Australian and New Zealand cohort of suspected HM cases and found that the ATP1A2 gene was the most commonly mutated gene. Our results suggest that screening using NGS multigene panels to investigate ATP1A2 alongside CACNA1A and SCN1A is a clinically useful and efficient method.

Exome Sequencing Diagnoses X-Linked Moesin-Associated Immunodeficiency in a Primary Immunodeficiency Case

Background

We investigated the molecular etiology of a young male proband with confirmed immunodeficiency of unknown cause, presenting with recurrent bacterial and Varicella zoster viral infections in childhood and persistent lymphopenia into early adulthood.

Aim

To identify causative functional genetic variants related to an undiagnosed primary immunodeficiency.

Method

Whole genome microarray copy number variant (CNV) analysis was performed on the proband followed by whole exome sequencing (WES) and trio analysis of the proband and family members. A >4 kbp deletion identified by repeated CNV analysis of exome sequencing data along with three damaging missense single nucleotide variants were validated by Sanger sequencing in all family members. Confirmation of the causative role of the candidate gene was performed by qPCR and Western Blot analyses on the proband, family members and a healthy control.

Results

CNV identified our previously reported interleukin 25 amplification in the proband; however, the variant was not validated to be a candidate gene for immunodeficiency. WES trio analysis, data filtering and in silico prediction identified a novel, damaging (SIFT: 0; Polyphen 1; Grantham score: 101) and disease-causing (MutationTaster) single base mutation in the X chromosome (c.511C > T p.Arg171Trp) MSN gene not identified in the UCSC Genome Browser database. The mutation was validated by Sanger sequencing, confirming the proband was hemizygous X-linked recessive (–/T) at this locus and inherited the affected T allele from his non-symptomatic carrier mother (C/T), with other family members (father, sister) confirmed to be wild type (C/C). Western Blot analysis demonstrated an absence of moesin protein in lymphocytes derived from the proband, compared with normal expression in lymphocytes derived from the healthy control, father and mother. qPCR identified significantly lower MSN mRNA transcript expression in the proband compared to an age- and sex-matched healthy control subject in whole blood (p = 0.02), and lymphocytes (p = 0.01). These results confirmed moesin deficiency in the proband, directly causative of his immunodeficient phenotype.

Conclusion

These findings confirm X-linked moesin-associated immunodeficiency in a proband previously undiagnosed up to 24 years of age. This study also highlights the utility of WES for the diagnosis of rare or novel forms of primary immunodeficiency disease.

An Analysis of Clinical Characteristics in Genetically Linked Migraine-Affected Pedigrees

Migraine is a common complex disorder characterized by severe recurrent headache and usually accompanied by nausea and vomiting. Previous studies in our laboratory have utilized three large multigenerational Australian pedigrees affected with migraine to indicate that the disease is genetically heterogeneous, with linkage results implicating genomic susceptibility regions on both chromosomes 19p and Xq. The present study explores the possibility of a correlation between genetic and clinical heterogeneity in these affected pedigrees. Specifically, the clinical characteristics of migraine including subtype, age of onset, frequency, duration, and disease symptoms were compared between the migraine pedigrees, and gender differences were also assessed. Our exploratory analyses revealed no significant differences in any of the clinical characteristics tested between the chromosome 19-linked family and the two X-linked families. Also, we did not detect any differences in male vs. female clinical features for these pedigrees. In conclusion, migraine is considered to be a clinically and genetically heterogeneous disorder; however, our study provided no conclusive evidence that variation in genomic susceptibility region is related to heterogeneity at the clinical level in these migraine-affected pedigrees.

Next-generation sequencing reveals broad down-regulation of microRNAs in secondary progressive multiple sclerosis CD4+ T cells

Background

Immunoactivation is less evident in secondary progressive MS (SPMS) compared to relapsing-remitting disease. MicroRNA (miRNA) expression is integral to the regulation of gene expression; determining their impact on immune-related cell functions, especially CD4+ T cells, during disease progression will advance our understanding of MS pathophysiology. This study aimed to compare miRNA profiles of CD4+ T cells from SPMS patients to healthy controls (HC) using whole miRNA transcriptome next-generation sequencing (NGS). Total RNA was extracted from CD4+ T cells and miRNA expression patterns analyzed using Illumina-based small-RNA NGS in 12 SPMS and 12 HC samples. Results were validated in a further cohort of 12 SPMS and 10 HC by reverse transcription quantitative polymerase chain reaction (RT-qPCR).

Results

The ten most dysregulated miRNAs identified by NGS were selected for qPCR confirmation; five (miR-21-5p, miR-26b-5p, miR-29b-3p, miR-142-3p, and miR-155-5p) were confirmed to be down-regulated in SPMS (p < 0.05). SOCS6 is targeted by eight of these ten miRNAs. Consistent with this, SOCS6 expression is up-regulated in SPMS CD4+ T cells (p < 0.05). This is of particular interest as SOCS6 has previously been shown to act as a negative regulator of T cell activation.

Conclusions

Ninety-seven percent of miRNA candidates identified by NGS were down-regulated in SPMS. The down-regulation of miRNAs and increased expression of SOCS6 in SPMS CD4+ T cells may contribute to reduced immune system activity in progressive MS.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-016-0253-y) contains supplementary material, which is available to authorized users.

Serum bilirubin concentration is modified by UGT1A1 haplotypes and influences risk of type-2 diabetes in the Norfolk Island genetic isolate

Background

Located in the Pacific Ocean between Australia and New Zealand, the unique population isolate of Norfolk Island has been shown to exhibit increased prevalence of metabolic disorders (type-2 diabetes, cardiovascular disease) compared to mainland Australia. We investigated this well-established genetic isolate, utilising its unique genomic structure to increase the ability to detect related genetic markers. A pedigree-based genome-wide association study of 16 routinely collected blood-based clinical traits in 382 Norfolk Island individuals was performed.

Results

A striking association peak was located at chromosome 2q37.1 for both total bilirubin and direct bilirubin, with 29 SNPs reaching statistical significance (P < 1.84 × 10⁻⁷). Strong linkage disequilibrium was observed across a 200 kb region spanning the UDP-glucuronosyltransferase family, including UGT1A1, an enzyme known to metabolise bilirubin. Given the epidemiological literature suggesting negative association between CVD-risk and serum bilirubin we further explored potential associations using stepwise multivariate regression, revealing significant association between direct bilirubin concentration and type-2 diabetes risk. In the Norfolk Island cohort increased direct bilirubin was associated with a 28 % reduction in type-2 diabetes risk (OR: 0.72, 95 % CI: 0.57-0.91, P = 0.005). When adjusted for genotypic effects the overall model was validated, with the adjusted model predicting a 30 % reduction in type-2 diabetes risk with increasing direct bilirubin concentrations (OR: 0.70, 95 % CI: 0.53-0.89, P = 0.0001).

Conclusions

In summary, a pedigree-based GWAS of blood-based clinical traits in the Norfolk Island population has identified variants within the UDPGT family directly associated with serum bilirubin levels, which is in turn implicated with reduced risk of developing type-2 diabetes within this population.

Electronic supplementary material

The online version of this article (doi:10.1186/s12863-015-0291-z) contains supplementary material, which is available to authorized users.

'Mutiny on the Bounty': the genetic history of Norfolk Island reveals extreme gender-biased admixture

Background

The Pacific Oceania region was one of the last regions of the world to be settled via human migration. Here we outline a settlement of this region that has given rise to a uniquely admixed population. The current Norfolk Island population has arisen from a small number of founders with mixed Caucasian and Polynesian ancestry, descendants of a famous historical event. The ‘Mutiny on the Bounty’ has been told in history books, songs and the big screen, but recently this story can be portrayed through comprehensive molecular genetics. Written history details betrayal and murder leading to the founding of Pitcairn Island by European mutineers and the Polynesian women who left Tahiti with them. Investigation of detailed genealogical records supports historical accounts.

Findings

Using genetics, we show distinct maternal Polynesian mitochondrial lineages in the present day population, as well as a European centric Y-chromosome phylogeny. These results comprehensively characterise the unique gender-biased admixture of this genetic isolate and further support the historical records relating to Norfolk Island.

Conclusions

Our results significantly refine previous population genetic studies investigating Polynesian versus Caucasian diversity in the Norfolk Island population and add information that is beneficial to future disease and gene mapping studies.

Electronic supplementary material

The online version of this article (doi:10.1186/s13323-015-0028-9) contains supplementary material, which is available to authorized users.

An analysis of DNA methylation in human adipose tissue reveals differential modification of obesity genes before and after gastric bypass and weight loss

Background

Environmental factors can influence obesity by epigenetic mechanisms. Adipose tissue plays a key role in obesity-related metabolic dysfunction, and gastric bypass provides a model to investigate obesity and weight loss in humans.

Results

Here, we investigate DNA methylation in adipose tissue from obese women before and after gastric bypass and significant weight loss. In total, 485,577 CpG sites were profiled in matched, before and after weight loss, subcutaneous and omental adipose tissue. A paired analysis revealed significant differential methylation in omental and subcutaneous adipose tissue. A greater proportion of CpGs are hypermethylated before weight loss and increased methylation is observed in the 3′ untranslated region and gene bodies relative to promoter regions. Differential methylation is found within genes associated with obesity, epigenetic regulation and development, such as CETP, FOXP2, HDAC4, DNMT3B, KCNQ1 and HOX clusters. We identify robust correlations between changes in methylation and clinical trait, including associations between fasting glucose and HDAC4, SLC37A3 and DENND1C in subcutaneous adipose. Genes investigated with differential promoter methylation all show significantly different levels of mRNA before and after gastric bypass.

Conclusions

This is the first study reporting global DNA methylation profiling of adipose tissue before and after gastric bypass and associated weight loss. It provides a strong basis for future work and offers additional evidence for the role of DNA methylation of adipose tissue in obesity.

Electronic supplementary material

The online version of this article (doi:10.1186/s13059-014-0569-x) contains supplementary material, which is available to authorized users.

Genetic association and gene expression studies suggest that genetic variants in the SYNE1 and TNF genes are related to menstrual migraine

BACKGROUND

Menstrual migraine (MM) encompasses pure menstrual migraine (PMM) and menstrually-related migraine (MRM). This study was aimed at investigating genetic variants that are potentially related to MM, specifically undertaking genotyping and mRNA expression analysis of the ESR1, PGR, SYNE1 and TNF genes in MM cases and non-migraine controls.

METHODS

A total of 37 variants distributed across 14 genes were genotyped in 437 DNA samples (282 cases and 155 controls). In addition levels of gene expression were determined in 74 cDNA samples (41 cases and 33 controls). Association and correlation analysis were performed using Plink and RStudio.

RESULTS

SNPs rs3093664 and rs9371601 in TNF and SYNE1 genes respectively, were significantly associated with migraine in the MM population (p = 0.008; p = 0.009 respectively). Analysis of qPCR results found no significant difference in levels of gene expression between cases and controls. However, we found a significant correlation between the expression of ESR1 and SYNE1, ESR1 and PGR and TNF and SYNE1 in samples taken during the follicular phase of the menstrual cycle.

CONCLUSIONS

Our results show that SNPs rs9371601 and rs3093664 in the SYNE1 and TNF genes respectively, are associated with MM. The present study also provides strong evidence to support the correlation of ESR1, PGR, SYNE1 and TNF gene expression in MM.

Association study of MTHFD1 coding polymorphisms R134K and R653Q with migraine susceptibility

OBJECTIVE

There is evidence that folate metabolism has a role in migraine pathophysiology, particularly in the migraine with aura (MA) subtype. In this study, we investigate whether two non-synonymous single nucleotide polymorphisms (SNPs), rs1950902 (C401T; R134K) and rs2236225 (G1958A; R653Q), in MTHF dehydrogenase (MTHFD1) are associated with migraine in an Australian case-control population.

BACKGROUND

Increased plasma levels of homocysteine, one of the metabolites produced in the folate pathway, has been found to be a risk factor for migraine. There is also a genetic link: a common polymorphism (rs1801133, C667T) that reduces the catalytic activity of the enzyme that catalyzes the formation of homocysteine, methylenetetrahydrofolate reductase (MTHFR), is associated with an increase in risk of MA. MTHFD1 is a crucial multifunctional enzyme that catalyzes three separate reactions of the folate pathway and therefore variants in MTHFD1 may also influence migraine susceptibility.

METHODS

The R134K and R653Q variants in MTHFD1 were genotyped in an Australian cohort of 520 unrelated migraineurs (162 were diagnosed with migraine without aura [MO] and 358 with MA) and 520 matched controls. Data were analyzed for association with migraine and for interaction with the MTHFR C667T polymorphism.

RESULTS

We find no significant differences in genotype or allele frequencies for either SNP between migraineurs and controls, or when either MO or MA cases were compared with controls. In addition, these MTHFD1 polymorphisms did not appear to influence the risk of MA conferred by the MTHFR 667T allele.

CONCLUSIONS

We find no evidence for association of the MTHFD1 R134K and R653Q polymorphisms with migraine in our Australian case-control population. However, as folate metabolism appears to be important in migraine, particularly with respect to the aura component, future studies using high throughput methods to expand the number of SNPs in folate-related genes genotyped and investigation of interactions between SNPs may be justified.

Epigenetics and migraine; complex mitochondrial interactions contributing to disease susceptibility

Migraine is a common neurological disorder classified by the World Health Organisation (WHO) as one of the top twenty most debilitating diseases in the developed world. Current therapies are only effective for a proportion of sufferers and new therapeutic targets are desperately needed to alleviate this burden. Recently the role of epigenetics in the development of many complex diseases including migraine has become an emerging topic. By understanding the importance of acetylation, methylation and other epigenetic modifications, it then follows that this modification process is a potential target to manipulate epigenetic status with the goal of treating disease. Bisulphite sequencing and methylated DNA immunoprecipitation have been used to demonstrate the presence of methylated cytosines in the human D-loop of mitochondrial DNA (mtDNA), proving that the mitochondrial genome is methylated. For the first time, it has been shown that there is a difference in mtDNA epigenetic status between healthy controls and those with disease, especially for neurodegenerative and age related conditions. Given co-morbidities with migraine and the suggestive link between mitochondrial dysfunction and the lowered threshold for triggering a migraine attack, mitochondrial methylation may be a new avenue to pursue. Creative thinking and new approaches are needed to solve complex problems and a systems biology approach, where multiple layers of information are integrated is becoming more important in complex disease modelling.

Methylation differences at the HLA-DRB1 locus in CD4+ T-Cells are associated with multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) is thought to be caused by T-cell mediated autoimmune dysfunction. Risk of developing MS is influenced by environmental and genetic factors. Modifiable differences in DNA methylation are recognized as epigenetic contributors to MS risk and may provide a valuable link between environmental exposure and inherited genetic systems.

OBJECTIVES AND METHODS

To identify methylation changes associated with MS, we performed a genome-wide DNA methylation analysis of CD4+ T cells from 30 patients with relapsing-remitting MS and 28 healthy controls using Illumina 450K methylation arrays.

RESULTS

A striking differential methylation signal was observed at chr. 6p21, with a peak signal at HLA-DRB1. After prioritisation, we identified a panel of 74 CpGs associated with MS in this cohort. Most notably we found evidence of a major effect CpG island in DRB1 in MS cases (pFDR < 3 × 10(-3)). In addition, we found 55 non-HLA CpGs that exhibited differential methylation, many of which localise to genes previously linked to MS.

CONCLUSIONS

Our findings provide the first evidence for association of DNA methylation at HLA-DRB1 in relation to MS risk. Further studies are now warranted to validate and understand how these findings are involved in MS pathology.

Mapping eQTLs in the Norfolk Island genetic isolate identifies candidate genes for CVD risk traits

Cardiovascular disease (CVD) affects millions of people worldwide and is influenced by numerous factors, including lifestyle and genetics. Expression quantitative trait loci (eQTLs) influence gene expression and are good candidates for CVD risk. Founder-effect pedigrees can provide additional power to map genes associated with disease risk. Therefore, we identified eQTLs in the genetic isolate of Norfolk Island (NI) and tested for associations between these and CVD risk factors. We measured genome-wide transcript levels of blood lymphocytes in 330 individuals and used pedigree-based heritability analysis to identify heritable transcripts. eQTLs were identified by genome-wide association testing of these transcripts. Testing for association between CVD risk factors (i.e., blood lipids, blood pressure, and body fat indices) and eQTLs revealed 1,712 heritable transcripts (p < 0.05) with heritability values ranging from 0.18 to 0.84. From these, we identified 200 cis-acting and 70 trans-acting eQTLs (p < 1.84 × 10(-7)) An eQTL-centric analysis of CVD risk traits revealed multiple associations, including 12 previously associated with CVD-related traits. Trait versus eQTL regression modeling identified four CVD risk candidates (NAAA, PAPSS1, NME1, and PRDX1), all of which have known biological roles in disease. In addition, we implicated several genes previously associated with CVD risk traits, including MTHFR and FN3KRP. We have successfully identified a panel of eQTLs in the NI pedigree and used this to implicate several genes in CVD risk. Future studies are required for further assessing the functional importance of these eQTLs and whether the findings here also relate to outbred populations.

Molecular approaches to transfusion medicine in Polynesians and Maori in New Zealand

In recent years, with the application of genotyping technology, there has been a substantial increase in the number of reported blood group alleles. This survey was designed to evaluate new molecular blood group genotyping methods and compile reference blood group data sets for Polynesian and Maori subjects. Subsequent analyses of these results were used to calculate probability of random match, to trace Polynesian ancestry and migration patterns and to reveal past and present episodes of genetic admixture. Genomic DNA samples from Maori and Polynesian subjects were drawn from the Victoria University of Wellington DNA Bank and genotyped using combination of commercial PCR-SSP kits, hybridization SNP assay services or sequence-based typing. This survey also involves compilation of serological ABO and Rhesus blood group data from RakaiPaaka Iwi tribal members for comparison with those generated during our molecular blood group study. We observed perfect consistency between results obtained from all molecular methods for blood group genotyping. The A, O, DCcEe, DCCee, MNs, K-k+, Jk(a+b-), Jk(a+b+), Fy(a+b-), Fy(a+b+), Di(a+b-), Co(a+b-) and Do(a-b+) were predominant blood group phenotypes in both Polynesians and Maori. Overall, our survey data show only small differences in distributions of blood group phenotypes between Polynesian and Maori groups and their subgroups. These differences might be associated with selection, population history and gene flow from Europeans. In each case, we estimate that patients with certain blood groups have a very low probability of an exact phenotypic match, even if the patients were randomly transfused with blood from donors of their own ethnicity. The best way to avoid haemolytic transfusion reaction in such cases is to perform a pretransfusion cross-match and recruit increased numbers of donors with rare phenotype profiles. The conclusion of this study is that application of molecular method covering as many known variants as possible may help to improve the accuracy blood group genotyping and potentially conserve the routine requirements of transfusion centres.

Analysis of chromosome 1 microsatellite markers and the FHM2-ATP1A2gene mutations in migraine pedigrees

OBJECTIVES

The aims of the study were: (i) to extend our linkage analysis of chromosome 1q microsatellite markers in predominantly migraine with aura pedigrees and (ii) to test the novel FHM-2 ATP1A2 gene for involvement in these migraine affected pedigrees and a previous pedigree (MF14) showing evidence of linkage of markers to C1q31.

METHODS

A chromosome 1 scan (31 markers) was performed in 21 multiplex pedigrees affected predominantly with migraine with aura (MA). The known FHM-2 ATP1A2 gene mutations were tested, by sequencing, for the involvement in MA and migraine without aura (MO) in these pedigrees. Sequencing was performed in the coding areas of the ATP1A2 gene through three MA individuals from MF14.

RESULTS

Evidence for linkage was obtained at C1q23 to markers spanning the ATP1A2 gene. However, testing of the known ATP1A2 gene mutations (for FHM) in common migraine probands of pedigrees showing excess allele sharing was negative. Sequencing of the entire coding areas of the gene through all the three MA affected from MF14 was also negative for mutations.

DISCUSSION

Microsatellite markers on chromosome 1q23 show evidence of excess allele sharing in MA and some MO pedigrees, suggesting linkage to the common forms of migraine and the presence of a susceptibility gene in this region. The FHM-2 (ATP1A2 gene) does not seem to be involved in the common types of migraine. Despite certain clinical characteristics, the genetic correlation between FHM and familial typical migraine remains unclear. Several candidate genes lie within the C1q23 and C1q31 cytogenetic regions; therefore, further studies are needed.

Human platelet antigens frequencies in Maori and Polynesian populations

BACKGROUND

Allele frequencies of human platelet antigens (HPA) reflect population history and possibility of platelet-specific alloimmunization. Here, we report on screening of variants at HPA loci for Polynesian and Maori subjects.

OBJECTIVES

Our aims are to evaluate new HPA genotyping methods, compile and analyse new HPA datasets for these subjects, use HPA data for tracing ancestry, migration patterns, genetic admixture and its potential influence on health.

MATERIALS AND METHODS

A total of 75 Maori and 25 Polynesian DNA samples were genotyped using commercial BAGene HPA-TYPE DNA-SSP kits, BLOODchip hybridization SNP assays and DNA sequence based typing.

RESULTS

Genotyping was successful and cross validation of PCR-SSP and BLOODchip gave 100% agreement. Among the HPA loci tested, only six are dimorphic (HPA-1 to -3, -5, -6 and -15) and all others are monomorphic. The Polynesians and Maori have the 'a' allele form as the most common for all loci except HPA-15.

CONCLUSIONS

The newly observed HPA data as well as principal coordinate analysis clearly indicate genetic contributions from both, Asia and Australasia in Maori and Polynesian populations together with recent admixture with Europeans. In addition, different prevalences of HPA alleles among Polynesian, Maori and European populations contribute towards different risk profiles for platelet-specific alloimmunization. This is the first report for these populations and our findings are of direct practical relevance for blood transfusion centres, the management of pregnancies, assessment of neonatal alloimmune thrombocytopenia and management of multi-transfused patients.

Unique X-linked familial FSGS with co-segregating heart block disorder is associated with a mutation in the NXF5 gene

Focal segmental glomerulosclerosis (FSGS) is the consequence of a disease process that attacks the kidney's filtering system, causing serious scarring. More than half of FSGS patients develop chronic kidney failure within 10 years, ultimately requiring dialysis or renal transplantation. There are currently several genes known to cause the hereditary forms of FSGS (ACTN4, TRPC6, CD2AP, INF2, MYO1E and NPHS2). This study involves a large, unique, multigenerational Australian pedigree in which FSGS co-segregates with progressive heart block with apparent X-linked recessive inheritance. Through a classical combined approach of linkage and haplotype analysis, we identified a 21.19 cM interval implicated on the X chromosome. We then used a whole exome sequencing approach to identify two mutated genes, NXF5 and ALG13, which are located within this linkage interval. The two mutations NXF5-R113W and ALG13-T141L segregated perfectly with the disease phenotype in the pedigree and were not found in a large healthy control cohort. Analysis using bioinformatics tools predicted the R113W mutation in the NXF5 gene to be deleterious and cellular studies support a role in the stability and localization of the protein suggesting a causative role of this mutation in these co-morbid disorders. Further studies are now required to determine the functional consequence of these novel mutations to development of FSGS and heart block in this pedigree and to determine whether these mutations have implications for more common forms of these diseases in the general population.

Investigation of lymphotoxin α genetic variants in migraine

Migraine is a common neurological disease with a genetic basis affecting approximately 12% of the population. Pain during a migraine attack is associated with activation of the trigeminal nerve system, which carries pain signals from the meninges and the blood vessels infusing the meninges to the trigeminal nucleus in the brain stem. The release of inflammatory mediators following cortical spreading depression (CSD) may further promote and sustain the activation and sensitization of meningeal nociceptors, inducing the persistent throbbing headache characterised in migraine. Lymphotoxin α (LTA) is a cytokine secreted by lymphocytes and is a member of the tumour necrosis factor (TNF) family. Genetic variation with the TNF and LTA genes may contribute to threshold brain excitability, propagation of neuronal hyperexcitability and thus initiation and maintenance of a migraine attack. Three LTA variants rs2009658, rs2844482 and rs2229094 were identified in a recent pGWAS study conducted in the Norfolk Island population as being potentially implicated in migraine with nominally significant p values of p=0.0093, p=0.0088 and p=0.033 respectively. To determine whether these SNPs played a role in migraine in a general outbred population these SNPs were gentoyped in a large case control Australian Caucasian population and tested for association with migraine. All three SNPs showed no association in our cohort (p>0.05). Validation of GWAS data in independent case-controls cohorts is essential to establish risk validity within specific population groups. The importance of cytokines in modulating neural inflammation and pain threshold in addition to other studies showing associations between TNF-α and SNPs in the LTA gene with migraine, suggests that LTA could be an important factor contributing to migraine. Although the present study did not support a role for the tested LTA variants in migraine, investigation of other variants within the LTA gene is still warranted.

An X chromosome association scan of the Norfolk Island genetic isolate provides evidence for a novel migraine susceptibility locus at Xq12

Migraine is a common and debilitating neurovascular disorder with a complex envirogenomic aetiology. Numerous studies have demonstrated a preponderance of women affected with migraine and previous pedigree linkage studies in our laboratory have identified susceptibility loci on chromosome Xq24-Xq28. In this study we have used the genetic isolate of Norfolk Island to further analyse the X chromosome for migraine susceptibility loci.An association approach was employed to analyse 14,124 SNPs spanning the entire X chromosome. Genotype data from 288 individuals comprising a large core-pedigree, of which 76 were affected with migraine, were analysed. Although no SNP reached chromosome-wide significance (empirical α = 1 × 10(-5)) ranking by P-value revealed two primary clusters of SNPs in the top 25. A 10 SNP cluster represents a novel migraine susceptibility locus at Xq12 whilst a 11 SNP cluster represents a previously identified migraine susceptibility locus at Xq27. The strongest association at Xq12 was seen for rs599958 (OR = 1.75, P = 8.92 × 10(-4)), whilst at Xq27 the strongest association was for rs6525667 (OR = 1.53, P = 1.65 × 10(-4)). Further analysis of SNPs at these loci was performed in 5,122 migraineurs from the Women's Genome Health Study and provided additional evidence for association at the novel Xq12 locus (P<0.05).Overall, this study provides evidence for a novel migraine susceptibility locus on Xq12. The strongest effect SNP (rs102834, joint P = 1.63 × 10(-5)) is located within the 5'UTR of the HEPH gene, which is involved in iron homeostasis in the brain and may represent a novel pathway for involvement in migraine pathogenesis.

Heritability and genome-wide linkage analysis of migraine in the genetic isolate of Norfolk Island

Migraine is a common neurovascular disorder with a complex envirogenomic aetiology. In an effort to identify migraine susceptibility genes, we conducted a study of the isolated population of Norfolk Island, Australia. A large portion of the permanent inhabitants of Norfolk Island are descended from 18th Century English sailors involved in the infamous mutiny on the Bounty and their Polynesian consorts. In total, 600 subjects were recruited including a large pedigree of 377 individuals with lineage to the founders. All individuals were phenotyped for migraine using International Classification of Headache Disorders-II criterion. All subjects were genotyped for a genome-wide panel of microsatellite markers. Genotype and phenotype data for the pedigree were analysed using heritability and linkage methods implemented in the programme SOLAR. Follow-up association analysis was performed using the CLUMP programme. A total of 154 migraine cases (25%) were identified indicating the Norfolk Island population is high-risk for migraine. Heritability estimation of the 377-member pedigree indicated a significant genetic component for migraine (h(2)=0.53, P=0.016). Linkage analysis showed peaks on chromosome 13q33.1 (P=0.003) and chromosome 9q22.32 (P=0.008). Association analysis of the key microsatellites in the remaining 223 unrelated Norfolk Island individuals showed evidence of association, which strengthen support for the linkage findings (P≤0.05). In conclusion, a genome-wide linkage analysis and follow-up association analysis of migraine in the genetic isolate of Norfolk Island provided evidence for migraine susceptibility loci on chromosomes 9q22.22 and 13q33.1.

Variants in the human potassium channel gene (KCNN3) are associated with migraine in a high risk genetic isolate

The calcium-activated potassium ion channel gene (KCNN3) is located in the vicinity of the familial hemiplegic migraine type 2 locus on chromosome 1q21.3. This gene is expressed in the central nervous system and plays a role in neural excitability. Previous association studies have provided some, although not conclusive, evidence for involvement of this gene in migraine susceptibility. To elucidate KCNN3 involvement in migraine, we performed gene-wide SNP genotyping in a high-risk genetic isolate from Norfolk Island, a population descended from a small number of eighteenth century Isle of Man ‘Bounty Mutineer’ and Tahitian founders. Phenotype information was available for 377 individuals who are related through the single, well-defined Norfolk pedigree (96 were affected: 64 MA, 32 MO). A total of 85 SNPs spanning the KCNN3 gene were genotyped in a sub-sample of 285 related individuals (76 affected), all core members of the extensive Norfolk Island ‘Bounty Mutineer’ genealogy. All genotyping was performed using the Illumina BeadArray platform. The analysis was performed using the statistical program SOLAR v4.0.6 assuming an additive model of allelic effect adjusted for the effects of age and sex. Haplotype analysis was undertaken using the program HAPLOVIEW v4.0. A total of four intronic SNPs in the KCNN3 gene displayed significant association (P < 0.05) with migraine. Two SNPs, rs73532286 and rs6426929, separated by approximately 0.1 kb, displayed complete LD (r² = 1.00, D′ = 1.00, D′ 95% CI = 0.96–1.00). In all cases, the minor allele led to a decrease in migraine risk (beta coefficient = 0.286–0.315), suggesting that common gene variants confer an increased risk of migraine in the Norfolk pedigree. This effect may be explained by founder effect in this genetic isolate. This study provides evidence for association of variants in the KCNN3 ion channel gene with migraine susceptibility in the Norfolk genetic isolate with the rarer allelic variants conferring a possible protective role. This the first comprehensive analysis of this potential candidate gene in migraine and also the first study that has utilised the unique Norfolk Island large pedigree isolate to implicate a specific migraine gene. Studies of additional variants in KCNN3 in the Norfolk pedigree are now required (e.g. polyglutamine variants) and further analyses in other population data sets are required to clarify the association of the KCNN3 gene and migraine risk in the general outbred population.

The Norfolk Island Eye Study (NIES): rationale, methodology and distribution of ocular biometry (biometry of the bounty)

AIM

To describe the recruitment, ophthalmic examination methods and distribution of ocular biometry of participants in the Norfolk Island Eye Study, who were individuals descended from the English Bounty mutineers and their Polynesian wives.

METHODS

All 1,275 permanent residents of Norfolk Island aged over 15 years were invited to participate, including 602 individuals involved in a 2001 cardiovascular disease study. Participants completed a detailed questionnaire and underwent a comprehensive eye assessment including stereo disc and retinal photography, ocular coherence topography and conjunctival autofluorescence assessment. Additionally, blood or saliva was taken for DNA testing.

RESULTS

781 participants aged over 15 years were seen (54% female), comprising 61% of the permanent Island population. 343 people (43.9%) could trace their family history to the Pitcairn Islanders (Norfolk Island Pitcairn Pedigree). Mean anterior chamber depth was 3.32mm, mean axial length (AL) was 23.5mm, and mean central corneal thickness was 546 microns. There were no statistically significant differences in these characteristics between persons with and without Pitcairn Island ancestry. Mean intra-ocular pressure was lower in people with Pitcairn Island ancestry: 15.89mmHg compared to those without Pitcairn Island ancestry 16.49mmHg (P = .007). The mean keratometry value was lower in people with Pitcairn Island ancestry (43.22 vs. 43.52, P = .007). The corneas were flatter in people of Pitcairn ancestry but there was no corresponding difference in AL or refraction.

CONCLUSION

Our study population is highly representative of the permanent population of Norfolk Island. Ocular biometry was similar to that of other white populations. Heritability estimates, linkage analysis and genome-wide studies will further elucidate the genetic determinants of chronic ocular diseases in this genetic isolate.

Testing the thrifty gene hypothesis: the Gly482Ser variant in PPARGC1A is associated with BMI in Tongans

Background

The thrifty gene hypothesis posits that, in populations that experienced periods of feast and famine, natural selection favoured individuals carrying thrifty alleles that promote the storage of fat and energy. Polynesians likely experienced long periods of cold stress and starvation during their settlement of the Pacific and today have high rates of obesity and type 2 diabetes (T2DM), possibly due to past positive selection for thrifty alleles. Alternatively, T2DM risk alleles may simply have drifted to high frequency in Polynesians. To identify thrifty alleles in Polynesians, we previously examined evidence of positive selection on T2DM-associated SNPs and identified a T2DM risk allele at unusually high frequency in Polynesians. We suggested that the risk allele of the Gly482Ser variant in the PPARGC1A gene was driven to high frequency in Polynesians by positive selection and therefore possibly represented a thrifty allele in the Pacific.

Methods

Here we examine whether PPARGC1A is a thrifty gene in Pacific populations by testing for an association between Gly482Ser genotypes and BMI in two Pacific populations (Maori and Tongans) and by evaluating the frequency of the risk allele of the Gly482Ser variant in a sample of worldwide populations.

Results

We find that the Gly482Ser variant is associated with BMI in Tongans but not in Maori. In a sample of 58 populations worldwide, we also show that the 482Ser risk allele reaches its highest frequency in the Pacific.

Conclusion

The association between Gly482Ser genotypes and BMI in Tongans together with the worldwide frequency distribution of the Gly482Ser risk allele suggests that PPARGC1A remains a candidate thrifty gene in Pacific populations.

Association study of calcitonin gene-related polypeptide-alpha (CALCA) gene polymorphism with migraine

Migraine is a neurological disorder that is associated with increased levels of calcitonin gene-related peptide (CGRP) in plasma. CGRP, being one of the mediators of neurogenic inflammation and a phenomenon implicated in the pathogenesis of migraine headache, is thus suggested to have an important role in migraine pathophysiology. Polymorphisms of the CALCA gene have been linked to Parkinson's disease, ovarian cancer and essential hypertension, suggesting a functional role for these polymorphisms. Given the strong evidence linking CGRP and migraine, it is hypothesised that polymorphisms in the CALCA gene may play a role in migraine pathogenesis. Seemingly non functional intronic polymorphisms are capable of disrupting normal RNA processing or introducing a splice site in the transcript. A 16bp deletion in the first intron of the CALCA gene has been reported to be a good match for the binding site for a transcription factor expressed strongly in neural crest derived cells, AP-2. This deletion also eliminates an intron splicing enhancer (ISE) that may potentially cause exon skipping. This study investigated the role of the 16bp intronic deletion in the CALCA gene in migraineurs and matched control individuals. Six hundred individuals were genotyped for the deletion by polymerase chain reaction followed by fragment analysis on the 3130 Genetic Analyser. The results of this study showed no significant association between the intronic 16bp deletion in the CALCA gene and migraine in the tested Australian Caucasian population. However, given the evidence linking CGRP and migraine, further investigation of variants with this gene may be warranted.

Effect of D1-like and D2-like receptor antagonists on methamphetamine and 3,4-methylenedioxymethamphetamine self-administration in rats

It has been suggested that activation of dopamine D1-like and D2-like receptors contribute equally to the maintenance of drug self-administration. This study compared the contribution of these receptor subtypes to 3,4-methylenedioxymethamphetamine (MDMA) and methamphetamine (MA) self-administration. Effects of pretreatment with the D2-like receptor antagonist, eticlopride (0.0, 0.0125, 0.025 or 0.05 mg/kg, intraperitoneal), on responding maintained by several doses of MDMA (0.5, 1.0 and 2.0 mg/kg/infusion) and MA (0.05, 0.1 and 0.2 mg/kg/infusion) were determined. As we have published data showing the effects of the D1-like receptor antagonist, SCH23390 (0.0, 0.01 or 0.02 mg/kg, subcutaneous), on MDMA self-administration, effects of this dose range on the MA dose-response curve were determined. In our previous study, 0.02 mg/kg SCH23390 produced a rightward shift in the MDMA dose response curve, whereas in the present results, this dose decreased responding maintained by most doses of MA. Eticlopride increased the responding maintained by most doses of MDMA but failed to alter MA self-administration. The present results suggest that both D1-like and D2-like receptors contribute to the maintenance of MDMA self-administration, whereas MA self-administration was more sensitive to D1-like receptor blockade.

Association of a Notch 3 gene polymorphism with migraine susceptibility

Introduction: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL) shares common symptoms with migraine. Most CADASIL causative mutations occur in exons 3 and 4 of the Notch 3 gene. This study investigated the role of C381T (rs 3815188) and G684A (rs 1043994) single nucleotide polymorphisms (SNP) in exons 3 and 4, respectively, of the Notch 3 gene in migraine.

Results: The first part of the study, in a population of 275 migraineurs and 275 control individuals, found a significant association between the C381T variant and migraine, specifically in migraine without aura (MO) sufferers. The G684A variant was also found to be significantly associated with migraine, specifically in migraine with aura (MA) sufferers. A follow-up study in 300 migraineurs and 300 control individuals did not show replicated association of the C381T variant with migraineurs. However, the G684A variant was again shown to be significantly associated with migraine, specifically with MA.

Conclusion: Further investigation of the G684A variant and the Notch 3 gene is warranted to understand their role in migraine.

Analysis of the MTHFR C677T variant with migraine phenotypes

BACKGROUND

The methylenetetrahydrofolate reductase (MTHFR) gene variant C677T has been implicated as a genetic risk factor in migraine susceptibility, particularly in Migraine with Aura. Migraine, with and without aura (MA and MO) have many diagnostic characteristics in common. It is postulated that migraine symptomatic characteristics might themselves be influenced by MTHFR. Here we analysed the clinical profile, migraine symptoms, triggers and treatments of 267 migraineurs previously genotyped for the MTHFR C677T variant. The chi-square test was used to analyse all potential relationships between genotype and migraine clinical variables. Regression analyses were performed to assess the association of C677T with all migraine clinical variables after adjusting for gender.

FINDINGS

The homozygous TT genotype was significantly associated with MA (P < 0.0001) and unilateral head pain (P = 0.002). While the CT genotype was significantly associated with physical activity discomfort (P < 0.001) and stress as a migraine trigger (P = 0.002). Females with the TT genotype were significantly associated with unilateral head pain (P < 0.001) and females with the CT genotype were significantly associated with nausea (P < 0.001), osmophobia (P = 0.002), and the use of natural remedy for migraine treatment (P = 0.003). Conversely, male migraineurs with the TT genotype experienced higher incidences of bilateral head pain (63% vs 34%) and were less likely to use a natural remedy as a migraine treatment compared to female migraineurs (5% vs 20%).

CONCLUSIONS

MTHFR genotype is associated with specific clinical variables of migraine including unilateral head pain, physical activity discomfort and stress.

Nicotinic receptors and stages of nicotine dependence

Smoking is one of the leading causes of preventable death, where nicotine has been identified as the primary addictive constituent of tobacco. Consequently, there have been extensive investigations into the neuroadaptations that occur as nicotine dependence develops, where numerous neurological systems have been implicated. The focus of this review was on nicotinic acetylcholine receptor neuroadaptations that occur during the development of nicotine dependence. This focus was selected because (1) the nicotinic receptors are the primary binding sites for both nicotine and the most efficacious pharmacological smoking cessation treatments and (2) the receptors are located throughout the brain with considerable neuromodulatory ability. However, there was difficulty associated in outlining the role of nicotinic receptors in the development of nicotine dependence because it comprises a series of stages involving different neurological systems rather than a single state. To address this issue, the review adopts a novel approach and considers the role of nicotinic receptor subtypes at separate stages of the nicotine dependence cycle. This information was then used to examine the nicotinic receptor-related therapeutic mechanisms of three main pharmacological smoking cessation treatments.

Legacy of mutiny on the Bounty: founder effect and admixture on Norfolk Island

The population of Norfolk Island, located off the eastern coast of Australia, possesses an unusual and fascinating history. Most present-day islanders are related to a small number of the 'Bounty' mutineer founders. These founders consisted of Caucasian males and Polynesian females and led to an admixed present-day population. By examining a single large pedigree of 5742 individuals, spanning >200 years, we analyzed the influence of admixture and founder effect on various cardiovascular disease (CVD)-related traits. On account of the relative isolation of the population, on average one-third of the genomes of present-day islanders (single large pedigree individuals) is derived from 17 initial founders. The proportion of Polynesian ancestry in the present-day individuals was found to significantly influence total triglycerides, body mass index, systolic blood pressure and diastolic blood pressure. For various cholesterol traits, the influence of ancestry was less marked but overall the direction of effect for all CVD-related traits was consistent with Polynesian ancestry conferring greater CVD risk. Marker-derived homozygosity was computed and agreed with measures of inbreeding derived from pedigree information. Founder effect (inbreeding and marker-derived homozygosity) significantly influenced height. In conclusion, both founder effect and extreme admixture have substantially influenced the genetic architecture of a variety of CVD-related traits in this population.

Methamphetamine self-administration and the effect of contingency on monoamine and metabolite tissue levels in the rat

A number of studies have shown that exposure to high doses of methamphetamine (MA) is toxic to central dopamine (DA) and serotonin (5-HT) neurons. In most of those studies, however, high doses of MA were experimenter-administered during a short exposure time. Because contingency is a determinant for many effects of drug exposure, the present objective was to investigate the effects of self-administered MA on tissue monoamine levels following a short (24 hours) or longer (7 days) withdrawal period. As previously reported, a noncontingent "binge" high-dose treatment regimen (4 injections of 10 mg/kg MA administered every 2 hours) produced persistent depletion of cortical 5-HT and striatal DA. Effects of self-administered MA (0.1 mg/kg/infusion) were then determined following a 20-day duration where a yoked design was employed such that some rats received MA contingent on an operant lever press and others received either MA or saline dependent on the responses of the contingent rat. Self-administered MA produced a transient striatal DA depletion with a more persistent increase in DA turnover, indicating the presence of some lasting adaptations. Furthermore, the yoked design revealed that there was no effect of contingency on these parameters.

Hand-rolled cigarette smoking patterns compared with factory-made cigarette smoking in New Zealand men

BACKGROUND

Roll-your-own (RYO) cigarettes have increased in popularity, yet their comparative potential toxicity is uncertain. This study compares smoking of RYO and factory-made (FM) cigarettes on smoking pattern and immediate potential toxicity.

METHODS

At a research clinic, 26 RYO and 22 FM volunteer male cigarette smokers, (addicted and overnight-tobacco-abstinent) each smoked 4 filter cigarettes, one half-hourly over 2 hours, either RYO or FM according to usual habit, using the CReSSMicro flowmeter. First cigarette smoked was their own brand. Subsequent cigarettes, all Holiday regular brand, were RYOs (0.5 g tobacco with filter), or FM with filter. Cravings on 100 mm visual analogue scale, and exhaled carbon monoxide (CO) were measured before and after each cigarette smoked.

RESULTS

Smokers reported similar daily cigarette consumption (RYO 19.0, FM 17.4, p = 0.45), and similar time after waking to first cigarette. (RYO 6.1 minutes, FM 8.6 minutes, p = 0.113). First cigarette's RYO tobacco (0.45 g) weighed less than for FM (0.7 g, p < 0.001); less tobacco was burnt (0.36 g, FM 0.55 g, p < 0.001) but smoking patterns were no different. RYO smokers smoked subsequent cigarettes more intensively; inhaled 28% more smoke per cigarette (RYO 952 mL, FM 743 mL, p = 0.025); took 25% more puffs (RYO 16.9, FM 13.6, p = 0.035); puffed longer (RYO 28 seconds, FM 22 seconds, p = 0.012), taking similar puffs (RYO 57 mL, FM 59 mL). Over four cigarettes, RYOs boosted alveolar CO (RYO 13.8 ppm, FM 13.8 ppm), and reduced cravings (RYO 53%, FM 52%) no differently from FM cigarettes.

CONCLUSION

In these smokers, RYO smoking was associated with increased smoke exposure per cigarette, and similar CO breath levels, and even with filters is apparently no less and possibly more dangerous than FM smoking. Specific package warnings should warn of RYO smoking's true risk. RYOs are currently taxed much less than FM cigarettes in most countries; similar harm merits similar excise per cigarette.

Principal component and linkage analysis of cardiovascular risk traits in the Norfolk isolate

OBJECTIVE(S)

An individual's risk of developing cardiovascular disease (CVD) is influenced by genetic factors. This study focussed on mapping genetic loci for CVD-risk traits in a unique population isolate derived from Norfolk Island.

METHODS

This investigation focussed on 377 individuals descended from the population founders. Principal component analysis was used to extract orthogonal components from 11 cardiovascular risk traits. Multipoint variance component methods were used to assess genome-wide linkage using SOLAR to the derived factors. A total of 285 of the 377 related individuals were informative for linkage analysis.

RESULTS

A total of 4 principal components accounting for 83% of the total variance were derived. Principal component 1 was loaded with body size indicators; principal component 2 with body size, cholesterol and triglyceride levels; principal component 3 with the blood pressures; and principal component 4 with LDL-cholesterol and total cholesterol levels. Suggestive evidence of linkage for principal component 2 (h(2) = 0.35) was observed on chromosome 5q35 (LOD = 1.85; p = 0.0008). While peak regions on chromosome 10p11.2 (LOD = 1.27; p = 0.005) and 12q13 (LOD = 1.63; p = 0.003) were observed to segregate with principal components 1 (h(2) = 0.33) and 4 (h(2) = 0.42), respectively.

CONCLUSION(S)

This study investigated a number of CVD risk traits in a unique isolated population. Findings support the clustering of CVD risk traits and provide interesting evidence of a region on chromosome 5q35 segregating with weight, waist circumference, HDL-c and total triglyceride levels.

Association between migraine and a functional polymorphism at the dopamine beta-hydroxylase locus

Migraine is a common neurological disorder with a significant genetic component. Although a number of linkage and association studies have been undertaken, the number and identity of all migraine susceptibility genes has yet to be defined. The existence of dopaminergic hypersensitivity in migraine has been recognised on a pharmacological basis and some studies have reported genetic association between migraine and dopamine-related gene variants. Our laboratory has previously reported association of migraine with a promoter STR marker in the dopamine beta hydroxylase (DBH) gene. In the present study, we analysed two additional DBH markers in two independent migraine case-control cohorts. These two markers are putative functional SNPs, one within the promoter (-1021C-->T) and another SNP (+1603C-->T) in exon 11 of the DBH gene. The results showed a significant association for allelic and genotypic frequency distribution between the DBH marker in the promoter and migraine in the first (P = 0.004 and P = 0.012, respectively) and the second (P = 0.013 and P = 0.031, respectively) tested cohorts. There was no association observed between either genotype and/or allelic frequencies for the DBH marker located in exon 11 and migraine (P > or = 0.05). The promoter DBH marker, reported associated with migraine in this study, has been shown to affect up to 52% of plasma DBH activity. Varying DBH activity levels have been postulated to be involved in migraine process with an increase of dopamine, resulting from a lower DBH activity shown positively correlated with migraine severity. It is plausible that the functional promoter variant of DBH may play a role in the migraine disorder.

Investigation of gamma-aminobutyric acid (GABA) A receptors genes and migraine susceptibility

BACKGROUND

Migraine is a neurological disorder characterized by recurrent attacks of severe headache, affecting around 12% of Caucasian populations. It is well known that migraine has a strong genetic component, although the number and type of genes involved is still unclear. Prior linkage studies have reported mapping of a migraine gene to chromosome Xq 24-28, a region containing a cluster of genes for GABA A receptors (GABRE, GABRA3, GABRQ), which are potential candidate genes for migraine. The GABA neurotransmitter has been implicated in migraine pathophysiology previously; however its exact role has not yet been established, although GABA receptors agonists have been the target of therapeutic developments. The aim of the present research is to investigate the role of the potential candidate genes reported on chromosome Xq 24-28 region in migraine susceptibility. In this study, we have focused on the subunit GABA A receptors type epsilon (GABRE) and type theta (GABRQ) genes and their involvement in migraine.

METHODS

We have performed an association analysis in a large population of case-controls (275 unrelated Caucasian migraineurs versus 275 controls) examining a set of 3 single nucleotide polymorphisms (SNPs) in the coding region (exons 3, 5 and 9) of the GABRE gene and also the I478F coding variant of the GABRQ gene.

RESULTS

Our study did not show any association between the examined SNPs in our test population (P>0.05).

CONCLUSION

Although these particular GABA receptor genes did not show positive association, further studies are necessary to consider the role of other GABA receptor genes in migraine susceptibility.

Linkage mapping of CVD risk traits in the isolated Norfolk Island population

To understand the underlying genetic architecture of cardiovascular disease (CVD) risk traits, we undertook a genome-wide linkage scan to identify CVD quantitative trait loci (QTLs) in 377 individuals from the Norfolk Island population. The central aim of this research focused on the utilization of a genetically and geographically isolated population of individuals from Norfolk Island for the purposes of variance component linkage analysis to identify QTLs involved in CVD risk traits. Substantial evidence supports the involvement of traits such as systolic and diastolic blood pressures, high-density lipoprotein-cholesterol, low-density lipoprotein-cholesterol, body mass index and triglycerides as important risk factors for CVD pathogenesis. In addition to the environmental influences of poor diet, reduced physical activity, increasing age, cigarette smoking and alcohol consumption, many studies have illustrated a strong involvement of genetic components in the CVD phenotype through family and twin studies. We undertook a genome scan using 400 markers spaced approximately 10 cM in 600 individuals from Norfolk Island. Genotype data was analyzed using the variance components methods of SOLAR. Our results gave a peak LOD score of 2.01 localizing to chromosome 1p36 for systolic blood pressure and replicated previously implicated loci for other CVD relevant QTLs.

Metastatic susceptibility locus, an 8p hot-spot for tumour progression disrupted in colorectal liver metastases: 13 candidate genes examined at the DNA, mRNA and protein level

Background

Mortality from colorectal cancer is mainly due to metastatic liver disease. Improved understanding of the molecular events underlying metastasis is crucial for the development of new methods for early detection and treatment of colorectal cancer. Loss of chromosome 8p is frequently seen in colorectal cancer and implicated in later stage disease and metastasis, although a single metastasis suppressor gene has yet to be identified. We therefore examined 8p for genes involved in colorectal cancer progression.

Methods

Loss of heterozygosity analyses were used to map genetic loss in colorectal liver metastases. Candidate genes in the region of loss were investigated in clinical samples from 44 patients, including 6 with matched colon normal, colon tumour and liver metastasis. We investigated gene disruption at the level of DNA, mRNA and protein using a combination of mutation, semi-quantitative real-time PCR, western blotting and immunohistochemical analyses.

Results

We mapped a 2 Mb region of 8p21-22 with loss of heterozygosity in 73% of samples; 8/11 liver metastasis samples had loss which was not present in the corresponding matched primary colon tumour. 13 candidate genes were identified for further analysis. Both up and down-regulation of 8p21-22 gene expression was associated with metastasis. ADAMDEC1 mRNA and protein expression decreased during both tumourigenesis and tumour progression. Increased STC1 and LOXL2 mRNA expression occurred during tumourigenesis. Liver metastases with low DcR1/TNFRSF10C mRNA expression were more likely to present with extrahepatic metastases (p = 0.005). A novel germline truncating mutation of DR5/TNFRSF10B was identified, and DR4/TNFRSF10A SNP rs4872077 was associated with the development of liver metastases (p = 0.02).

Conclusion

Our data confirm that genes on 8p21-22 are dysregulated during colorectal cancer progression. Interestingly, however, instead of harbouring a single candidate colorectal metastasis suppressor 8p21-22 appears to be a hot-spot for tumour progression, encoding at least 13 genes with a putative role in carcinoma development. Thus, we propose that this region of 8p comprises a metastatic susceptibility locus involved in tumour progression whose disruption increases metastatic potential.

Allele frequency differences of cytochrome P450 polymorphisms in a sample of New Zealand Māori

AIMS

To determine the prevalence of functional alleles for drug metabolising genes in a sample of Maori and compare allele frequencies with Caucasians estimates.

PROCEDURES

DNA from 60 Maori volunteers was genotyped for cytochrome P450 polymorphisms--CYP2A6, CYP2C9, CYP2C19, and CYP2D6--and allele frequencies calculated and compared with Caucasian estimates.

RESULTS

Absolute allele frequency differences between Maori and Caucasian groups ranged from 1% to 16% for the polymorphisms tested.

CONCLUSIONS

Functional allele frequencies of drug metabolising genes differed between Maori and European groups warranting larger general population surveys. These findings may also bear thinking about when conducting pharmacogenetic studies or clinical trials in New Zealand cohorts because patients with Maori ancestry may respond differently to certain medicines based on genotype.

Legislation reduces exposure to second-hand tobacco smoke in New Zealand bars by about 90%

AIM

To measure exposure to second-hand smoke (SHS) in New Zealand bars before and after comprehensive smoke-free legislation enacted on 10 December 2004.

METHODS

Cotinine is the main specific metabolite of nicotine and a well-established biomarker for SHS exposure. We measured cotinine levels in saliva of non-smoking volunteers before and after a 3 h visit to 30 randomly selected bars in 3 cities across the country. Two measures of cotinine before the smoke-free law change during winter and spring 2004, and two follow-up measurements in the same volunteers and venues during winter and spring 2005, were included.

RESULTS

Before the smoke-free law change, in all bars and in all volunteers, exposure to SHS was evident with an average increase in saliva cotinine of 0.66 ng/ml (SE 0.03 ng/ml). Increases in cotinine correlated strongly with the volunteers' subjective observation of ventilation, air quality and counts of lit cigarettes. However, even venues that were judged to be "seemingly smoke free" with "good ventilation" produced discernable levels of SHS exposure. After the law change, there remained some exposure to SHS, but at much lower levels (mean saliva cotinine increase of 0.08 ng/ml, SE 0.01 ng/ml). Smoking indoors in bars was almost totally eliminated: in 2005 only one lit cigarette was observed in 30 visits.

CONCLUSIONS

Comprehensive smoke-free legislation in New Zealand seems to have reduced exposure of bar patrons to SHS by about 90%. Residual exposures to SHS in bars do not result from illicit smoking indoors.

Linkage disequilibrium analysis in the genetically isolated Norfolk Island population

Norfolk Island is a human genetic isolate, possessing unique population characteristics that could be utilized for complex disease gene localization. Our intention was to evaluate the extent and strength of linkage disequilibrium (LD) in the Norfolk isolate by investigating markers within Xq13.3 and the NOS2A gene encoding the inducible nitric oxide synthase. A total of six microsatellite markers spanning approximately 11 Mb were assessed on chromosome Xq13.3 in a group of 56 men from Norfolk Island. Additionally, three single nucleotide polymorphisms (SNPs) localizing to the NOS2A gene were analyzed in a subset of the complex Norfolk pedigree. With the exception of two of the marker pairs, one of which is the most distantly spaced marker, all the Xq13.3 marker pairs were found to be in significant LD indicating that LD extends up to 9.5-11.5 Mb in the Norfolk Island population. Also, all SNPs studied showed significant LD in both Norfolk Islanders and Australian Caucasians, with two of the marker pairs in complete LD in the Norfolk population only. The Norfolk Island study population possesses a unique set of characteristics including founder effect, geographical isolation, exhaustive genealogical information and phenotypic data of use to cardiovascular disease risk traits. With LD extending up to 9.5-11 Mb, the Norfolk isolate should be a powerful resource for the localization of complex disease genes.

Benzylpiperazine: a drug of abuse?

N-benzylpiperazine (BZP) is the active ingredient in recreational 'party' or 'p.e.p.' pills, which are used to provide a stimulant, euphoric effect akin to that of methylenedioxymethamphetamine (MDMA, 'ecstasy'). BZP predominantly affects dopamine neurotransmission in a similar fashion to known 'drugs of abuse', such as methamphetamine and cocaine, which strongly suggests BZP has abuse liability. BZP is illegal in many countries including the United States of America and Australia, yet it remains legal in the United Kingdom, Canada and New Zealand. There has been little research, to date, on the neurological consequences of high dose or chronic exposure of BZP. Here we provide a comprehensive review of the information currently available on BZP and suggest a need for further research into the mechanisms of action, long-term effects and potentially addictive properties of BZP.

Association study of a functional variant in intron 8 of the dopamine transporter gene and migraine susceptibility

Migraine is a common, genetically influenced neurovascular disorder. The dopamine transporter gene is a candidate for migraine association studies. This study tested a functionally linked variable number tandem repeat (VNTR) in intron 8 of the dopamine transporter gene (DAT(Int8)) in 550 migraine cases (401 with aura, 149 without aura) and 550 non-migraine controls. Chi-squared analysis of the DAT(Int8) revealed that the allele and genotype frequency distributions for migraine cases (including subtype analysis) and controls were not different (P > 0.1). These findings offer no evidence for an association of the DAT(Int8) with migraine with and without aura and therefore do not implicate the dopamine transporter gene as a modifier of migraine risk.

Progesterone, glucocorticoid, but not estrogen receptor mRNA is altered in breast cancer stroma

Our laboratory has previously found that anti-mitogenic nuclear receptor mRNA is elevated in late stage tumours and this study was performed to scrutinize the possibility of cancer-stroma crosstalk using hormone signaling in these tissues. RNA levels in stromal tissue were examined for the estrogen alpha, estrogen beta, androgen, progesterone and glucocorticoid nuclear receptors by a semi-quantitative PCR. Significant differences in expression between the cancer stroma and control tissue were seen, analyzing for both cancer grade and estrogen receptor status. Stroma and control tissue were significantly different for the progesterone and glucocorticoid nuclear receptors (p=5.908 x 10(-7) and 2.761 x 10(-5), respectively). Glucocorticoid receptor also showed a significant increase to mRNA levels in the stroma of estrogen receptor negative tumours (p=5.85 x 10(-5)). By contrast, the estrogen receptors alpha and beta, those most closely associated with breast tissue growth, showed no significant change in mRNA (p=0.372 and 0.655, respectively). Androgen receptor mRNA also remained unaffected (p=0.174).

The search for migraine genes: an overview of current knowledge

Migraine is a complex familial condition that imparts a significant burden on society. There is evidence for a role of genetic factors in migraine, and elucidating the genetic basis of this disabling condition remains the focus of much research. In this review we discuss results of genetic studies to date, from the discovery of the role of neural ion channel gene mutations in familial hemiplegic migraine (FHM) to linkage analyses and candidate gene studies in the more common forms of migraine. The success of FHM regarding discovery of genetic defects associated with the disorder remains elusive in common migraine, and causative genes have not yet been identified. Thus we suggest additional approaches for analysing the genetic basis of this disorder. The continuing search for migraine genes may aid in a greater understanding of the mechanisms that underlie the disorder and potentially lead to significant diagnostic and therapeutic applications.