Mitochondrial haplogroups in Basque multiple sclerosis patients

Mitochondrial DNA haplogroup analysis in Saudi Arab patients with multiple sclerosis

Previous studies have suggested that mitochondrial DNA (mtDNA) variants are associated with multiple sclerosis (MS), a complex neurodegenerative immune-mediated disease of the central nervous system. Since mtDNA is maternally inherited without recombination, specific mtDNA variants defining genetic background are associated with the susceptibility to human diseases. To assess the contribution of mtDNA haplogroups to the predisposition of MS in an Arab population, we analysed sequencing data of mitochondrial genomes from 47 native Saudi Arab individuals including 23 patients with relapsing-remitting MS (RRMS) and 24 healthy controls. All patients and controls could be classified into ten haplogroups. The European-specific haplogroup U was more prevalent in patients than in the controls (26.1% vs. 4.2%), whereas haplogroup T was only present in patients and haplogroups HV and N were only found in controls. Haplogroup U was significantly association with increased risk of MS (odds ratio = 6.26, p<0.05), although the association did not maintain significance after adjustment for multiple comparisons. Haplotype U was more prevalent in patients with younger age of onset (p = 0.006), but there was no relationship between haplotype U and disease severity, disease duration or EDSS and age-matched carriers and non-carriers of haplogroup U (p>0.05). Definition site of haplogroup U include the variant m.12308A>G in MT-TL2 gene which was found to affect highly conserved position within the variable arm of tRNALeu(CUN) and thus may impact mitochondrial protein synthesis, and two other variants namely m.11467A>G in MT-ND4 gene and m.12372G>A in MT-ND5 gene which were previously linked with mitochondrial function. Despite the small number of subjects, which may limit the statistical power of the study, our results showed for the first time a possible contribution of haplogroup U to the predisposition to MS in an Arab population. These findings warrant further validation in a large cohort to distinguish a genuine effect specific to MS from a chance finding due to small sampling.

[The role of mitochondria in pathological mechanisms of innate immunity in multiple]

The review discusses the role of mitochondria in multiple sclerosis (MS). Previously, damage to the mitochondria was regarded as a manifestation of secondary damage to axons and neurons, i.e. as a marker of neurodenegation. Recently, the role of mitochondria in the early stages of MS development, when they could participate in the activation of innate immunity and trigger activation of autoimmune responses of acquired immunity, has been increasingly discussed. The role of polymorphism mitochondrial DNA changes in MS is discussed.

Mitochondrial genome and risk of multiple sclerosis

Mitochondrial DNA (mtDNA) polymorphism makes a certain contribution to the formation of a genetic risk of multiple sclerosis (MS).

Objective: to analyze the frequency of mtDNA variants in patients with MS and control individuals in the Russian population. A similar study was conducted for the first time.

Patients and methods. The polymorphism of mtDNA was studied in the Russian population: in 283 unrelated patients with relapsing-remitting MS and in 290 unrelated healthy controls matched for gender and age.

Results and discussion. The frequency of haplogroup J in the patients with MS was twice higher than that in the control group (p=0.0055) (odds ratio (OR) 2.00; 95% confidence interval (CI). 1.21–3.41). This association was mostly observed in women (p=0.0083) (OR 2.20; 95% CI, 1.19–4.03). There was also a significant association of the A allele of MT-ND5 (m. 13708G>A) with MS (p=0.03) (OR 1.89; 95% CI 1.11–3.32). Sex stratification showed that the association with MS was significant only in women (p=0.009; OR, 2.52; 95% CI, 1.29–5.14). Further investigations will aim to analyze mtDNA variability (at the level of individual polymorphisms, haplogroups, and whole genome) in patients with relapsing-remitting MS and in those with primary progressive MS versus healthy individuals and patients with relapsing-remitting MS according to disease severity.

Conclusion. The data obtained in the Russian population suggest that mtDNA variations are involved in MS risk, to a greater extent in women. 

Oldies but Goldies mtDNA Population Variants and Neurodegenerative Diseases

mtDNA is transmitted through the maternal line and its sequence variability, which is population specific, is assumed to be phenotypically neutral. However, several studies have shown associations between the variants defining some genetic backgrounds and the susceptibility to several pathogenic phenotypes, including neurodegenerative diseases. Many of these studies have found that some of these variants impact many of these phenotypes, including the ones defining the Caucasian haplogroups H, J, and Uk, while others, such as the ones defining the T haplogroup, have phenotype specific associations. In this review, we will focus on those that have shown a pleiotropic effect in population studies in neurological diseases. We will also explore their bioenergetic and genomic characteristics in order to provide an insight into the role of these variants in disease. Given the importance of mitochondrial population variants in neurodegenerative diseases a deeper analysis of their effects might unravel new mechanisms of disease and help design new strategies for successful treatments.

Involvement of Mitochondria in Neurodegeneration in Multiple Sclerosis

Functional disruption and neuronal loss followed by progressive dysfunction of the nervous system underlies the pathogenesis of numerous disorders defined as "neurodegenerative diseases". Multiple sclerosis, a chronic inflammatory demyelinating disease of the central nervous system resulting in serious neurological dysfunctions and disability, is one of the most common neurodegenerative diseases. Recent studies suggest that disturbances in mitochondrial functioning are key factors leading to neurodegeneration. In this review, we consider data on mitochondrial dysfunctions in multiple sclerosis, which were obtained both with patients and with animal models. The contemporary data indicate that the axonal degeneration in multiple sclerosis largely results from the activation of Ca2+-dependent proteases and from misbalance of ion homeostasis caused by energy deficiency. The genetic studies analyzing association of mitochondrial DNA polymorphic variants in multiple sclerosis suggest the participation of mitochondrial genome variability in the development of this disease, although questions of the involvement of individual genomic variants are far from being resolved.

MtDNA T4216C variation in multiple sclerosis: a systematic review and meta-analysis

MtDNA T4216C variation has frequently been investigated in Multiple Sclerosis (MS) patients; nonetheless, controversy has existed about the evidence of association of this variation with susceptibility to MS. The present systematic review and meta-analysis converge the results of the preceding publications, pertaining to association of mtDNA T4216C variation with susceptibility to MS, into a common conclusion. A computerized literature search in English was carried out to retrieve relevant publications from which required data were extracted. Using a fixed effect model, pooled odds ratio (OR), 95 % confidence interval (95 % CI), and P value were calculated for association of mtDNA T4216C variation with susceptibility to MS. The pooled results showed that there was a significant association between mtDNA T4216C variation and MS (OR = 1.38, 95 % CI = 1.13-1.67, P = 0.001). The present systematic review and meta-analysis suggest that mtDNA T4216C variation is a contributory factor in susceptibility to MS.

Stressed cybrids model demyelinated axons in multiple sclerosis

Multiple sclerosis is likely caused by a complex interaction of multiple genes and environmental factors. The contribution of mitochondrial DNA genetic backgrounds has been frequently reported. To evaluate the effect of mitochondrial DNA haplogroups in the same genetic and environmental circumstances, we have built human transmitochondrial cell lines and simulated the effect of axon demyelination, one of the hallmarks of multiple sclerosis pathology, by altering the ionic gradients through the plasmalemma and increasing ATP consumption. In this model, mitochondrial biogenesis is observed. This process is larger in Uk cybrids, which mirrors their lower oxidative phosphorylation capacity in basal conditions. This model replicates a process occurring in both patients suffering from multiple sclerosis and several animal models of axon demyelination. Therefore, it can be used to analyze the contribution of various mitochondrial DNA genotypes to multiple sclerosis. In this sense, a longer or stronger energy stress, such as that associated with demyelinated axons in multiple sclerosis, could make Uk individuals more susceptible to this pathology. Finally, pharmacologic compounds targeted to mitochondrial biogenesis could be a potential therapy for multiple sclerosis.

HLA-DRB1*15:01 and multiple sclerosis: a female association?

BACKGROUND

The association between multiple sclerosis (MS) and the HLA-DRB1*15:01 haplotype has been proven to be strong, but its molecular basis remains unclear. Vitamin D receptor (VDR) gene variants and sex have been proposed to modulate this association.

OBJECTIVES

1) Test the association of MS with *15:01 and VDR variants; 2) check whether VDR variants and/or sex modulate the risk conferred by *15:01; 3) study whether *15:01, VDR variants and/or sex affect HLA II gene expression.

METHODS

Peripheral blood from 364 MS patients and 513 healthy controls was obtained and DNA and total RNA were extracted from leukocytes. HLA-DRB1, DRB5 and DQA1 gene expression measurements and *15:01 genotyping were performed by qPCR. VDR variants were genotyped by PCR-RFLP.

RESULTS

Our data confirms that the *15:01 haplotype confers a higher risk of suffering from MS (OR = 1.364; 95% CI = 1.107-1.681). No association was found between VDR variants and MS, but they were shown to moderately modulate the risk conferred by *15:01. Sex confers a much stronger modulation and the *15:01-MS association seems to be female specific. A higher *15:01 frequency has been observed in Basques (45.1%). *15:01 positive samples showed a significant overexpression of DRB1 (p < 0.001), DRB5 (p < 0.001) and DQA1 (p = 0.004) in patients. DRB1 (p = 0.004) and DRB5 (p < 0.001) were also overexpressed in *15:01 controls.

CONCLUSIONS

We confirm the *15:01-MS association and support that it is female specific. The relevance of ethnic origin on association studies has also been highlighted. HLA-DRB1*15:01 seems to be a haplotype consistently linked to high HLA II gene expression.

May "mitochondrial eve" and mitochondrial haplogroups play a role in neurodegeneration and Alzheimer's disease?

Mitochondria, the powerhouse of the cell, play a critical role in several metabolic processes and apoptotic pathways. Multiple evidences suggest that mitochondria may be crucial in ageing-related neurodegenerative diseases. Moreover, mitochondrial haplogroups have been linked to multiple area of medicine, from normal ageing to diseases, including neurodegeneration. Polymorphisms within the mitochondrial genome might lead to impaired energy generation and to increased amount of reactive oxygen species, having either susceptibility or protective role in several diseases. Here, we highlight the role of the mitochondrial haplogroups in the pathogenetic cascade leading to diseases, with special attention to Alzheimer's disease.

Mitochondrial mutation in Iranian patients with multiple sclerosis, correlation between haplogroups H, A and clinical manifestations

As multiple sclerosis (MS) has long been known to be associated with Leber, hereditary optic neuropathy (LHON), a disease caused by mitochondrial (mtDNA) mutations, in this study we assessed possible involvement of mtDNA point mutation in MS patients. Fifty-two MS patients whose disease was confirmed with revised McDonald criteria and referred to Iranian Center of Neurological Research of Imam Khomeini hospital during 2006-2007 entered the study. Secondary mtDNA mutations, age, gender, clinical disability according to expanded disability status scale (EDSS), course of the disease, and presenting symptoms were the variables investigated in this study. DNA purification was performed by Diatom DNA Extraction Kit. Analysis of data was done by SPSS V11.5. The prevalent mutations with frequency of 19.2% were J, L, and T haplogroups. Haplotype A was more prevalent in patients with younger age of onset (P-value = 0.012) and high proportion of haplogroup H was associated with optic nerve involvement (P-value = 0.015). No motor symptoms were seen in haplogroup H patients. There is no significant relationship between duration of the disease and EDSS in different mutation of mtDNA.

The role of mitochondrial haplogroups in non-arteritic anterior ischemic optic neuropathy

AIMS

To investigate a possible association between mitochondrial haplogroups and non-arteritic anterior ischemic optic neuropathy (NAION).

METHODS

We compared the prevalence of various mitochondrial haplogroups in 24 NAION patients and 552 maternally unrelated ethnic controls. All patients and controls were Saudi Arabs.

RESULTS

NAION patients had substantially more potentially pathologic mtDNA nucleotide changes (10/24) than Controls (0/159) and a significantly elevated mean relative mtDNA content (2.62 +/- 1.21) than controls (1.33 +/- 0.34; p < or = 0.001). There was no statistically significant difference between patients and controls for any of the mitochondrial haplogroups tested.

CONCLUSIONS

Mitochondrial haplogroups do not appear to contribute to the pathogenesis of NAION in this cohort; however, mitochondrial abnormalities still seem likely to play a role.

Association between synapsin III gene promoter SNPs and multiple sclerosis in Basque patients

BACKGROUND

Synapsins are a family of neuron-specific phosphoproteins, one of whose subunits is encoded by the SYN3 gene. This gene is located close to one of the multiple sclerosis susceptibility regions (in 22q13.1). Two single-nucleotide polymorphisms (SNPs) (rs133945 and rs133946) in the promoter region of this gene have been proposed as factors protecting against MS. This relationship is not clear because another report failed to found such association.

OBJECTIVES

In an attempt to clarify this association, the frequency of these SNPs was analyzed in a population of 221 Spanish MS patients with a cluster of 72 Basque patients and in 373 controls with a cluster of 138 controls of a Basque origin.

METHODS

The SNis analysis was performed by 9 PCR.

RESULTS

According to our findings, these SNPs are differently distributed in the two populations. This significant bias should therefore be taken into account in association studies. Our data suggest that the C/C genotype in rs133946 and the G/G genotype in rs133945 could be protecting factors against MS in the Basque population.

Investigation of the role of mitochondrial DNA in multiple sclerosis susceptibility

Several lines of evidence suggest that mitochondrial genetic factors may influence susceptibility to multiple sclerosis. To explore this hypothesis further, we re-sequenced the mitochondrial genome (mtDNA) from 159 patients with multiple sclerosis and completed a haplogroup analysis including a further 835 patients and 1,506 controls. A trend towards over-representation of super-haplogroup U was the only evidence for association with mtDNA that we identified in these samples. In a parallel analysis of nuclear encoded mitochondrial genes, we also found a trend towards association with the complex I gene, NDUFS2. These results add to the evidence suggesting that variation in mtDNA and nuclear encoded mitochondrial genes may contribute to disease susceptibility in multiple sclerosis.

Influence of CCR5-Δ32 genotype in Spanish population with multiple sclerosis

A number of association studies have explored the relationship between the CCR5-Delta32 allele and the risk of developing multiple sclerosis (MS), with varying results. In light of the results of several studies that have analyzed the role of the allele in MS, it has been proposed that the allele is involved in the etiopathogeny of the disease. Our study revealed a statistically significant difference between the study group and the control group for the carriers of at least one deleted allele (P = 0.027). The allele was more frequent in the control group, which suggests a possible protective effect of this deletion against MS. When ethnic origin was taken into account in the same analysis, we saw that the bulk of the difference was attributable to the Basque group, although the trend was also visible in the control group. Consideration of ethnic origin is therefore essential for the analysis of our sample. CCR5-Delta32 allele distribution was higher in the Basque control population than in the Basque MS population, which suggests that it confers a protective effect against MS. Relevant values were a P value of 0.008 and an odds ratio of 0.168 (95% confidence interval, 0.038 to 0.737).

UCP2 and mitochondrial haplogroups as a multiple sclerosis risk factor

In the actual scenario of the search for further genetic susceptibility factors, a recent paper noted an SNP in the UCP2 gene as a multiple sclerosis (MS) risk factor. UCP2 is a member of the mitochondrial proton transport family, which uncouples proton entry in the mitochondrial matrix from ATP synthesis. mtDNA haplogroups are also associated with ATP production, and are linked with mitochondrial proton transport. In this work, we studied the UCP2 SNP and the mitochondrial haplogroups distribution in a Spanish MS population, with a population sub-group of Basque-origin patients. Our results confirm the link between UCP2 SNP and MS, and show a slight relation between this SNP and mitochondrial haplogroups.

CD24 V/V is an allele associated with the risk of developing multiple sclerosis in the Spanish population

The allele C in the CD24 gene has been related to multiple sclerosis (MS). In this work we check this single nucleotide polymorphism (SNP) in a population of 135 patients and 285 controls. Our results confirm the association between the V/V genotype at aa 57 of this gene and MS and highlight the importance of taking into account the origin of the subjects to avoid a population bias.