Our data suggest that a genetic approach could be useful in providing molecular support to the hypothesis that hypersensitivity of the dopaminergic system may represent the pathophysiologic basis of migraine, at least in a subgroup of patients.

To assess the possibility of an association between TNF gene polymorphisms and migraine without aura, a case-control study was performed in a Sardinian sample. Migraine without aura is a complex genetic disease in which susceptibility and environmental factors contribute towards its development. Several studies suggest that tumour necrosis factors (TNF) (TNF-alpha and lymphotoxin-alpha or TNF-ss) may be involved in the pathophysiology of migraine. The TNF-alpha and TNF-ss genes are located on chromosome 6p21.3 in the human leukocyte antigene (HLA) class III region. We evaluated 299 patients affected by migraine without aura (I.H.S. criteria 2004) and 278 migraine-free controls. The polymorphisms G308A of the TNF- alpha gene, and G252A of TNF-beta gene were determined by NcoI restriction fragment length polymorphism analysis. We found a statistically significant difference in allele (p = 0.018; OR = 1.46 95 % CI: 1.066 to 2.023) and genotype (trend chi2 = 5.46, df = 1, p = 0.019) frequencies of TNF-beta gene, between cases and controls. Allele and genotype frequencies of TNF-alpha polymorphism did not differ significantly between the two groups. These data suggest that subjects with the TNFB2 allele have a low risk of developing migraine without aura and/or that the polymorphism of the TNF-beta gene is in linkage disequilibrium with other migraine responsible genes in the HLA region.

1 In the present study we provide evidence for a saturable, Mg2+/ATP-and temperature-dependent, tetrabenazine-, dopamine-, and amphetamine-sensitive uptake of l-methyl-4-phenylpyridinium ion (MPP+) in synaptic vesicles from mouse striatum. 2 Similarity in the properties of the vesicular uptake suggests that in the striatum dopamine and MPP+ share the vesicular carrier. 3 The presence of MPP+ vesicular uptake in dopamine-rich regions such as striatum, olfactory, tubercles and hypothalamus, as well as its absence in cerebellum, cortex and pons-medulla, suggest that monoamine vesicular carriers differ between highly and poorly dopamine-innervated regions. 4 The restriction of active MPP+ uptake to the dopaminergic regions, which reflects the previously shown distribution of [3H]-MPP+ binding sites in mouse brain membranes, indicates MPP+ as a marker of the vesicular carrier for dopamine in dopaminergic neurones. 5 A role in MPP+ neurotoxicity is suggested for this region-specific, vesicular storage of the toxin.

Several lines of evidence point to a role for dopamine in mood disorders and, in particular, in bipolar disorders. In line with a considerable amount of evidence, the dopamine D1 receptor gene (DRD1) is considered to be a good candidate gene for bipolar disorders. Several studies did not find any association between bipolar 1 patients and DRD1. In this study, we investigate a possible association between BP disorder and -48A/G polymorphism of the DRD1. We genotyped 107 bipolar 1 patients and 129 healthy control subjects of exclusively Sardinian descent. A statistically significant difference in genotype (chi2 = 6.29, df = 2, P = 0.042) and allele (chi2 = 5.46, df=1, P = 0.019; OR = 1.53, 95% CI = 1.08-2.16) frequencies was found, suggesting an association between the DRD1 gene and bipolar I disorder (BP I) in the Sardinian population.

No abstract

Association analysis of candidate genes may represent a strategy for clarifying the genetic components involved in bipolar disorder. Polymorphism at dopamine receptor genes DRD2, DRD4, and dopamine and serotonin transporter genes (DAT, SERT) has been used in previous association studies. Some authors have reported positive association between certain alleles and bipolar disorder, using the case-control design. In this family-based association study of DRD2, DRD4, DAT, and SERT, the distribution of parental nontransmitted alleles was compared with that of alleles transmitted to 53 Sardinian probands suffering from bipolar disorder. The transmission disequilibrium test (TDT) was used to detect any disproportionate transmission of alleles by heterozygous parents to affected children. No differences were found between the allele distribution of polymorphisms at DRD2, DRD4, DAT, and SERT in probands and parental nontransmitted chromosomes. TDT did not reveal any difference between transmitted and nontransmitted alleles. Our results do not support the hypothesis of a role for DRD2, DRD4, DAT, or SERT in bipolar disorder. Previously reported positive associations between DRD2 or SERT and bipolar disorder were conceivably due to stratification dependent on the case-control design, even though our sample might have failed to detect small associations due to limited power.

No abstract

The discovery of the genetic factors implicated in the predisposition to complex diseases may greatly profit from genetic studies in isolated populations. In this perspective, we performed a genome-wide scan using 507 microsatellite markers, with an average interval size of 7.6 cM, on a sample of 88 nuclear families with at least two affected sibs with bipolar disorder recruited in the Sardinian population. An initial analysis yielded non-parametric linkage exceeding 3.4 with P-values <0.0003 at two adjacent markers, D1S206 and D1S435 in the 1p22-p21 chromosomal region. Moreover, positive linkage ranging between 2.0 and 3.0 was obtained for other loci in several cases in regions that have already been linked to predisposition to bipolar disorder, such as 5p15.33, 8q24.13, and 11q14.3. A subsequent analysis of the 1p22-p21 region using the same set of families and a dense panel of 20 new microsatellite markers, spaced at 1.2 cM on average, reinforced the finding of suggestive linkage for this region. Interestingly, NPL values above 2.1 and P-values <0.02 were obtained for a cluster of 10 markers comprising D1S435. Thus, this study suggests that the 1p22-p21 region may contain a new locus participating to the genetic susceptibility to bipolar disorder and reproduces positive linkage for several other loci already implicated in this pathology. Since the Sardinian population presents a peculiar genetic homogeneity, these results may pave the way to further studies for replication in this population contributing to the rapid discovery of the genetic factors predisposing to bipolar disorder.