Association of a GRIA3 gene polymorphism with migraine in an Australian case-control cohort

BACKGROUND: The excitatory neurotransmitter glutamate has been implicated in both the hyperexcitability required for cortical spreading depression as well as activation of the trigeminovascular system required for the allodynia associated with migraine. Polymorphisms in the glutamate receptor ionotropic amino-3-hydroxy-5-methyl-4-isoxazole-propionin acid 1 (GRIA1) and GRIA3 genes that code for 2 of 4 subunits of the glutamate receptor have been previously associated with migraine in an Italian population. In addition, the GRIA3 gene is coded within a previously identified migraine susceptibility locus at Xq24. This study investigated the previously associated polymorphisms in both genes in an Australian case-control population. METHODS: Variants in GRIA1 and GRIA3 were genotyped in 472 unrelated migraine cases and matched controls, and data were analyzed for association. RESULTS: Analysis showed no association between migraine and the GRIA1 gene. However, association was observed with the GRIA3 single nucleotide polymorphism (SNP) rs3761555 (P = .008). CONCLUSION: The results of this study confirmed the previous report of association at the rs3761555 SNP within the migraine with aura subgroup of migraineurs. However, the study identified association with the inverse allele suggesting that rs3761555 may not be the causative SNP but is more likely in linkage disequilibrium with another causal variant in both populations. This study supports the plethora of evidence suggesting that glutamate dysfunction may contribute to migraine susceptibility, warranting further investigation of the glutamatergic system and particularly of the GRIA3 gene.

An investigation of the C77G and C772T variations within the human protein tyrosine phosphatase receptor type C gene for association with multiple sclerosis in an Australian population

Multiple sclerosis (MS) is a common cause of neurological disability in young adults. The disease generally manifests in early to middle adulthood and causes various neurological deficits. Autoreactive T lymphocytes and their associated antigens have long been presumed important features of MS pathogenesis. The Protein tyrosine phosphatase receptor type C gene (PTPRC) encodes the T-cell receptor CD45. Variations within PTPRC have been previously associated with diseases of autoimmune origin such as type 1 diabetes mellitus and Graves' disease. We set out to investigate two variants within the PTPRC gene, C77G and C772T in subjects with MS and matched healthy controls to determine whether significant differences exist in these markers in an Australian population. We employed high resolution melt analysis (HRM) and restriction length polymorphism (RFLP) techniques to determine genotypic and allelic frequencies. Our study found no significant difference between frequencies for PTPRC C77G by either genotype (Χ2 = 0.65, P = 0.72) or allele (Χ2 = 0.48, P = 0.49). Similarly, we did not find evidence to suggest an association between PTPRC C772T by genotype (Χ2 = 1.06, P = 0.59) or allele (Χ2 = 0.20, P = 0.66). Linkage disequilibrium (LD) analysis showed strong linkage disequilibrium between the two tested markers (D' = 0.9970, SD = 0.0385). This study reveals no evidence to suggest that these markers are associated with MS in the tested Australian Caucasian population. Although the PTPRC gene has a significant role in regulating CD4+ and CD8+ autoreactive T-cells, interferon-beta responsiveness, and potentially other important processes, our study does not support a role for the two tested variants of this gene in MS susceptibility in the Australian population.

Allelic variation investigation of the estrogen receptor within an Australian multiple sclerosis population

Multiple Sclerosis (MS) is a central nervous system (CNS) chronic inflammatory demyelinating disease leading to various neurological disabilities. The disorder is more prevalent for women with a ratio of 3:2 female to male. Objectives: To investigate variation within the estrogen receptor 1 (ESR1) polymorphism gene in an Australian MS case-control population using two intragenic restriction fragment length polymorphisms; the G594A located in exon 8 detected with the BtgI restriction enzyme and T938C located in intron 1, detected with PvuII. One hundred and ten Australian MS patients were studied, with patients classified clinically as Relapsing Remitting MS (RR-MS), Secondary Progressive MS (SP-MS) or Primary Progressive MS (PP-MS). Also, 110 age, sex and ethnicity matched controls were investigated as a comparative group. No significant difference in the allelic distribution frequency was found between the case and control groups for the ESR1 PvuII (P = 0.50) and Btg1 (P = 0.45) marker. Our results do not support a role for these two ESR1 markers in multiple sclerosis susceptibility, however other markers within ESR1 should not be excluded for potential involvement in the disorder.

No role for estrogen receptor 1 gene intron 1 Pvu II and exon 4 C325G polymorphisms in migraine susceptibility

Background We have previously reported an association between the estrogen receptor 1 (ESR1) gene exon 8 G594A polymorphism and migraine susceptibility in two independent Australian cohorts. In this paper we report results of analysis of two further single nucleotide polymorphisms (SNPs) in the ESR1 gene in the same study group, the T/C Pvu II SNP in intron 1 and the C325G SNP in exon 4, as well as results of linkage disequilibrium (LD) analysis on these markers. Methods We investigated these variants by case-control association analysis in a cohort of 240 migraineurs and 240 matched controls. The SNPs were genotyped using specific restriction enzyme assays. Results were analysed using contingency table methods incorporating the chi-squared statistic. LD results are presented as D' statistics with associated P values. Results We found no evidence for association of the Pvu II T/C polymorphism and the C325G polymorphism and migraine susceptibility and no evidence for LD between these two SNPs and the previously implicated exon 8 G594A marker. Conclusion We have found no role for the polymorphisms in intron 1 and exon 4 with migraine susceptibility. To further investigate our previously implicated exon 8 marker, we suggest the need for studies with a high density of polymorphisms be undertaken, with particular focus on markers in LD with the exon 8 marker.

Investigation of the low-density lipoprotein receptor gene and cholesterol as a risk factor for migraine

The Low-Density Lipoprotein Receptor (LDLR) gene is a cell surface receptor that plays an important role in cholesterol homeostasis. We investigated the (TA)n polymorphism in exon 18 of the LDLR gene on chromosome 19p13.2 performing an association analysis in 244 typical migraine-affected patients, 151 suffering from migraine with aura (MA), 96 with migraine without aura (MO) and 244 unaffected controls. The populations consisted of Caucasians only, and controls were age- and sex-matched. The results showed no significant difference between groups for allele frequency distributions of the (TA)n polymorphism even after separation of the migraine-affected individuals into subgroups of MA and MO affected patients. This is in contradiction to Mochi et al. who found a positive association of this variant with MO. Our study discusses possible differences between the two studies and extends this research by investigating circulating cholesterol levels in a migraine-affected population.

Association analysis of somatostatin receptor (SSTR1 and SSTR2) polymorphisms in breast cancer and solar keratosis

The presence of somatostatin receptors (SSTR1-5) in tumour cells indicates a potential for somatostatin to bind and suppress growth, as well as allowing for therapeutic treatment with somatostatin analogues. The genes for SSTR1 and SSTR2 have been shown to contain dinucleotide repeat polymorphisms. We have performed association studies on breast cancer and solar keratosis populations to determine whether these genes play a role in the development of these conditions. Results showed that there was no significant difference between SSTR1 and SSTR2 polymorphism frequencies in the tested breast cancer population (P = 0.59 and P = 0.54, respectively) nor the solar keratosis population (P = 0.10 and P = 0.883, respectively) as compared to unaffected populations. Hence, these studies do not support a role for these receptor genes in either breast cancer or solar keratosis lesions.

Association of estrogen receptor and glucocorticoid receptor gene polymorphisms with sporadic breast cancer

We have utilized a cross-sectional association approach to investigate sporadic breast cancer. Polymorphisms in 2 candidate genes, ESRalpha and GRL, were examined in an unrelated breast cancer-affected and age-matched control population. Several polymorphic regions within the ESRalpha gene have been identified, and some alleles of these polymorphisms have been found to occur at increased levels in breast-cancer patients. Additionally, variations in GRL have the potential to disrupt cell transcription and may be associated with cancer formation. We analyzed 3 polymorphisms, from codons 10 (TCT to TCC), 325 (CCC to CCG) and 594 (ACA to ACG) of ESRalpha, and a highly polymorphic dinucleotide repeat, D5S207, located within 200 kb of the GRL. When allelic frequencies of the codon 594 (exon 8) ESR polymorphism were compared between affected and unaffected populations, a significant difference was observed (p = 0.005). Results from the D5S207 dinucleotide repeat located near GRL also indicated a significant difference between the tested case and control populations (p = 0.001). Allelic frequencies of the codon 10 and codon 325 ESR polymorphisms were not significantly different between populations (p = 0.152 and 0.181, respectively). Our results indicate that specific alleles of the ESR gene (alpha subtype) and a marker for the GRL gene locus are associated with sporadic breast-cancer development in the tested Caucasian population and justify further investigation of the role of these and other nuclear steroid receptors in the etiology of breast cancer.

Migraine association and linkage analyses of the human 5-hydroxytryptamine (5HT2A) receptor gene

5-Hydroxytryptamine (5HT), commonly known as serotonin, which predominantly serves as an inhibitory neurotransmitter in the brain, has long been implicated in migraine pathophysiology. This study tested an Mspl polymorphism in the human 5HT2A receptor gene (HTR2A) and a closely linked microsatellite marker (D13S126), for linkage and association with common migraine. In the association analyses, no significant differences were found between the migraine and control populations for both the Mspl polymorphism and the D13S126 microsatellite marker. The linkage studies involving three families comprising 36 affected members were analysed using both parametric (FASTLINK) and non-parametric (MFLINK and APM) techniques. Significant close linkage was indicated between the Mspl polymorphism and the D13S126 microsatellite marker at a recombination fraction (θ) of zero (lod score=7.15). Linkage results for the Mspl polymorphism were not very informative in the three families, producing maximum and minimum lod scores of only 0.35 and 0.39 at recombination fractions (θ) of 0.2 and 0.00, respectively. However, linkage analysis between the D13S126 marker and migraine indicated significant non-linkage (lod2) up to a recombination fraction (θ) of 0.028. Results from this study exclude the HTR2A gene, which has been localized to chromosome 13q14-q21, for involvement with common migraine.

Cross-sectional study of a microsatellite marker in the low densitity lipoprotein receptor gene in obese normotensives

1. The low density lipoprotein receptor is an important regulator of serum cholesterol which may have implications for the development of both hypertension and obesity. In this study, genotypes for a low density lipoprotein receptor gene (LDLR) dinucleotide polymorphism were determined in both lean and obese normotensive populations. 2. In previous cross-sectional association studies an ApaLI and a HincII polymorphism for LDLR were shown to be associated with obesity in essential hypertensives. However, these polymorphisms did not show an association with obesity in normotensives. 3. In contrast, this study reports that preliminary results for an LDLR microsatellite marker, located more towards the 3' end of the gene, show a significant association with obesity in the normotensive population studied. These results indicate that LDLR could play an important role in the development of obesity, which might be independent of hypertension.

An investigation of the 5-HT2C receptor gene as a migraine candidate gene

Migraine is a common complex disorder, currently classified into two main subtypes, migraine with aura (MA) and migraine without aura (MO). The strong preponderance of females to males suggests an X-linked genetic component. Recent studies have identified an X chromosomal susceptibility region (Xq24-q28) in two typical migraine pedigrees. This region harbours a potential candidate gene for the disorder, the serotonin receptor 2C (5-HT2C) gene. This study involved a linkage and association approach to investigate two single nucleotide variants in the 5-HT2C gene. In addition, exonic coding regions of the 5-HT2C gene were also sequenced for mutations in X-linked migraine pedigrees. Results of this study did not detect any linkage or association, and no disease causing mutations were identified. Hence, results for this study do not support a significant role of the 5-HT 2C gene in migraine predisposition. © 2003 Wiley-Liss, Inc.

Independent, marked associations of alleles of the insulin receptor and dipeptidyl carboxypeptidase-I genes with essential hypertension

1. There is evidence to suggest that essential hypertension is a polygenic disorder and that it arises from yet-to-be-identified predisposing variants of certain genes that influence blood pressure. The cloning of various hormone, enzyme, adrenoceptor and hormone receptor genes whose products are involved in blood pressure control and the identification of polymorphisms of these has permitted us to test their genetic association with hypertension. 2. Cross-sectional analyses of a number of candidate gene markers were performed in hypertensive and normotensive subjects who were selected on the basis of both parents being either hypertensive or normotensive, respectively, and the difference in total alleles on all chromosomes for each polymorphism between the hypertensive and normotensive groups was test by χ analysis with one degree of freedom. 3. A marked association was observed between hypertension and insertion alleles of polymorphisms of the insulin receptor gene (INSR) (P<0.0040) and the dipeptidyl carboxypeptidase-1 (angiotensin I-converting enzyme; kininase II) gene (DCP1) (P<0.0018). No association with hypertension was evident, however, for polymorphisms of the growth hormone, low-density lipoprotein receptor, renal kallikrein, α2- and β1-adrenoreceptor, atrial natriuretic factor and insulin genes. 4. All but one of the hypertensive subjects had at least one of the hypertension-associated alleles, and although subjects homozygous for both were three times more frequent in the hypertensive group, examination of the nine possible genotypes suggested that the INSR and DCP1 alleles are independent markers for hypertension. 5. The present results suggest that genetic variant(s) in close linkage disequilibrium with polymorphisms at INSR and DCP1 may be involved in part in the aetiology of essential hypertension.

Association of a low density lipoprotein receptor microsatellite variant with obesity

OBJECTIVE To determine whether a microsatellite polymorphism located towards the 3' end of the low density lipoprotein receptor gene (LDLR) is associated with obesity. DESIGN A cross-sectional case-control study. SUBJECTS One hundred and seven obese individuals, defined as a body mass index (BMI) ≤ 26 kg/m2, and 163 lean individuals, defined as a BMI < 26 kg/m2. MEASUREMENTS BMI, blood pressure, serum lipids, alleles of LDLR microsatellite (106 bp, 108 bp and 112 bp). RESULTS There was a significant association between variants of the LDLR microsatellite and obesity, in the overall tested population, due to a contributing effect in females (χ2 = 12.3, P = 0.002), but not in males (χ2 = 0.3, P = 0.87). In females, individuals with the 106 bp allele were more likely to be lean, while individuals with the 112 bp and/or 108 bp alleles tended to be obese. CONCLUSIONS These results suggest that in females, LDLR may play a role in the development of obesity.

Association of a RFLP for the insulin receptor gene, but not insulin, with essential hypertension

Insulin has cardiovascular actions and patients with essential hypertension display insulin resistance. A cross-sectional study of the R1 RFLP of the insulin receptor gene (INSR) was carried out in 67 hypertensive (HT) and 75 normotensive (NT) subjects whose parents had a similar blood pressure status at age ≥50. The frequency of the minor (+) allele was 0.31 in HTs and 0.44 in NTs, and the difference between observed alleles in all subjects in each group was significant (χ2 = 4.8, P<0.05). Allele frequencies of a BglI RFLP of the insulin gene, however, did not differ between the HT and NT groups. The data thus provide evidence in favour of an association of HT with a polymorphism at the INSR locus (19p 13.3-13.2), so implicating this locus, and possibly a genetic variant of the insulin receptor itself, in HT.

Non-linkage of insulin receptor locus with essential hypertension in an affected pedigree

A recent cross-sectional study has demonstrated a significant association of the R1 RsaI restriction fragment length polymorphism of the insulin receptor gene (INSR) with human essential hypertension. In the present study, an alternative approach, involving linkage analysis, was carried out using 8 hypertensive families with 5 or more affected members. Five of the families were found to be informative and in one of these pedigrees a conclusion of non-linkage of INSR and hypertension could be made on the basis of an obligate recombinant in one generation which yielded a Lod score of - ∞ at a recombination fraction (θ) of zero. In another family, the largest studied, a positive Lod score was obtained at θ = 0, but this was below the level required for a conclusion of linkage. Lod score at θ = 0 for a marker at the insulin locus in this family was negative. The present study has thus demonstrated one pedigree in which hypertension is not linked to the insulin receptor locus.

Association of HincII RFLP of low density lipoprotein receptor gene with obesity in essential hypertensives

Obese (BMI ≥ 26 kg/m 2; n = 51) and lean (BMI <26 kg/m 2; n = 61) Caucasian patients with severe, familial essential hypertension, were compared with respect to genotype and allele frequencies of a HincII RFLP of the low density lipoprotein receptor gene (LDLR). A similar analysis was performed in obese (n = 28) and lean (n = 68) normotensives. A significant association of the C allele of the T→C variant responsible for this RFLP was seen with obesity (χ 2 = 4.6, P = 0.029) in the hypertensive, but not in the normotensive, group (odds ratio = 3.0 for the CC genotype and 2.7 for CT). Furthermore, BMI tracked with genotypes of this allele in the hypertensives (P = 0.046). No significant genotypic relationship was apparent for plasma lipids. Significant linkage disequilibrium was, moreover, noted between the HincII RFLP and an ApaLI RFLP (χ 2 = 33, P<0.0005) that has previously shown even stronger association with obesity (odds ratio 19.6 for cases homozygous for the susceptibility allele and 15.2 for het-erozygotes). The present study therefore adds to our previous evidence implicating LDLR as a locus for obesity in patients with essential hypertension.