Evaluation of the MTHFR A1298C variant in leukoaraiosis

Integrated analysis of microRNA and mRNA expression profiling identifies BAIAP3 as a novel target of dysregulated hsa-miR-1972 in age-related white matter lesions

White matter lesions known as leukoaraiosis (LA) are cerebral white matter hyperintensities observed in elderly individuals. Currently, no reliable molecular biomarkers are available for monitoring their progression over time. To identify biomarkers for the onset and progression of LA, we analyzed whole blood-based, microRNA expression profiles of leukoaraiosis, validated those exhibiting significant microRNA changes in clinical subjects by means of quantitative real-time polymerase chain reactions and determined the function of miRNA in cell lines by means of microRNA mimic transfection assays. A total of seven microRNAs were found to be significantly down-regulated in leukoaraiosis. Among the microRNAs, hsa-miR-1972 was downregulated during the early onset phase of leukoaraiosis, as confirmed in independent patients, and it was found to target leukoaraiosis-dependent BAIAP3, decreasing its expression in 293T cell lines. Functional enrichment analysis revealed that significantly dysregulated miRNAs-mRNAs changes associated with the onset of leukoaraiosis were involved in neurogenesis, neuronal development, and differentiation. Taken together, the study identified a set of candidate microRNA biomarkers that may usefully monitor the onset and progression of leukoaraiosis. Given the enrichment of leukoaraiosis-associated microRNAs and mRNAs in neuron part and membrane system, BAIAP3 could potentially represent a novel target of hsa-miR-1972 in leukoaraiosis through which microRNAs are involved in the pathogenesis of white matter lesions.

WITHDRAWN: Whole genome sequencing identifies novel NOTCH3 mutations for leukoaraiosis

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Analysis of genetic polymorphisms associated with leukoaraiosis in the southern Chinese population: A case-control study

Leukoaraiosis (LA) is a frequent neuroimaging finding commonly observed on brain MRIs of elderly people with prevalence ranging from 50% to 100%. Multiple susceptibility genes or genetic risk factors for LA have been identified in subjects of European descent. Here, we report the first replication study on several common and novel genetic variations in the Chinese population. In this study, a total of 244 subjects (201 LA patients and 43 controls) were enrolled according to our new and strict definition for LA. Subsequently, 6 genetic variants at 5 genes, rs3744028 in TRIM65, rs1055129 in TRIM47, rs1135889 in FBF1, rs1052053 in PMF1, and rs1801133 (C677T) and rs1801131(A1298C) in MTHFR, were selected for genotyping using polymerase chain reaction (PCR)-based pyrosequencing and restriction fragment length polymorphism (RFLP) together with capillary electrophoresis (CE) and agarose gel electrophoresis. Finally, Pearson's χ and multivariate logistic regression tests were used to examine the associations between the genotypes and LA. Among these candidate polymorphisms, except for rs1052053 and rs1801131, rs1135889 (P = 0.012) showed significant associations with LA in the dominant model, and the other 3 SNPs, rs3744028 (P = 0.043), rs1055129 (P = 0.038), and rs1801133 (P = 0.027), showed significant associations with LA in the recessive model. However, these differences no longer remained significant after adjusting for age, gender, hypertension, and diabetes mellitus and applying Bonferroni correction or Sidak correction for multiple testing. These results suggest that the above-mentioned genetic variants are not associated with LA risk. In summary, the study did not replicate the susceptibility of rs3744028, rs1055129, and rs1135889 at the Chr17q25 locus for LA nor did it find any other significant results for rs1052053, rs1801133, and rs1801131 in the Chinese population. It strongly indicated the ethnic differences in the genetics of LA. However, the associations of rs3744028 (TRIM65), rs1055129 (TRIM47), rs1135889 (FBF1), and rs1801133 (MTHFR) with LA before Bonferroni correction and Sidak correction for multiple testing are worth highlighting. Thus, we believe that a genome-wide association study and candidate gene association studies are needed to reassess the previous findings and screen novel risk genes for LA in China.

Candidate-gene analysis of white matter hyperintensities on neuroimaging

BACKGROUND

White matter hyperintensities (WMH) are a common radiographic finding and may be a useful endophenotype for small vessel diseases. Given high heritability of WMH, we hypothesised that certain genotypes may predispose individuals to these lesions and consequently, to an increased risk of stroke, dementia and death. We performed a meta-analysis of studies investigating candidate genes and WMH to elucidate the genetic susceptibility to WMH and tested associated variants in a new independent WMH cohort. We assessed a causal relationship of WMH to methylene tetrahydrofolate reductase (MTHFR).

METHODS

Database searches through March 2014 were undertaken and studies investigating candidate genes in WMH were assessed. Associated variants were tested in a new independent ischaemic cohort of 1202 WMH patients. Mendelian randomization was undertaken to assess a causal relationship between WMH and MTHFR.

RESULTS

We identified 43 case-control studies interrogating eight polymorphisms in seven genes covering 6,314 WMH cases and 15,461 controls. Fixed-effects meta-analysis found that the C-allele containing genotypes of the aldosterone synthase CYP11B2 T(-344)C gene polymorphism were associated with a decreased risk of WMH (OR=0.61; 95% CI, 0.44 to 0.84; p=0.003). Using mendelian randomisation the association among MTHFR C677T, homocysteine levels and WMH, approached, but did not reach, significance (expected OR=1.75; 95% CI, 0.90-3.41; observed OR=1.68; 95% CI, 0.97-2.94). Neither CYP11B2 T(-344)C nor MTHFR C677T were significantly associated when tested in a new independent cohort of 1202 patients with WMH.

CONCLUSIONS

There is a genetic basis to WMH but anonymous genome wide and exome studies are more likely to provide novel loci of interest.

Decreased Number of Mitochondria in Leukoaraiosis

BACKGROUND AND AIMS

Leukoaraiosis (LA), one of the most frequent causes of an age-associated cognitive decline, can be associated with a poor quality of life, leading overall to far-reaching public health problems. Chronic hypoxia of the white matter of the brain may be a factor triggering this entity. LA may develop as a consequence of chronically insufficient cellular energy production and the accumulation of free radicals.

METHODS

In this context, after hypothesizing that the number of healthy mitochondria can be crucial in this complex process, a case-control LA study was carried out in which we analyzed the numbers of deleted and non-deleted mitochondria (the common D-loop deletion) per white blood cell. A total of 234 patients with LA and 123 MRI alteration-free subjects served as a control group.

RESULTS

Interestingly, it emerged that the ratio of deleted relative to non-deleted mitochondria is strongly associated with the risk of LA. The calculated K ratio in the LA group was significantly lower than the K ratio in the controls (LA: K 0.37 95% CI 0.05; controls: K 0.48, 95% CI 0.076, p < 0.001).

CONCLUSIONS

Our study suggests that the ratio of the dmDNA and mDNA can be of great importance in the pathogenesis of LA.

Genetic associations of leukoaraiosis indicate pathophysiological mechanisms in white matter lesions etiology

Leukoaraiosis (LA), also called white matter lesions (WMLs) and white matter hyperintensities (WMHs), is a frequent neuroimaging finding commonly seen on magnetic resonance imaging brain scans of elderly people with prevalence ranging from 50% to 100%. Although it remains asymptomatic, LA is not considered to be benign, and it is showed to be related to a host of poor clinical outcomes and increases the risk of disability, dementia, depression, stroke, and the overall morbidity and mortality. Pathologically, LA is characterized by loss of myelin and axons, patchy demyelination, and denudation of ependyma in regions of WMH. Age and hypertension are the most importantly established risk factors for LA. However, the precise pathogenic mechanisms remain unclear. Together with the previous findings, our recent genetic results strongly supported that LA is associated with immune response and neuroinflammation. Therefore, we confidently hypothesized that LA was not only a common neuroimaging phenomenon in the elderly but also an emerging neuroinflammatory disorder in the central nervous system. This article focusing on neuroimaging classification, genetics basis, and putative molecular mechanism introduced the basic knowledge and current status of LA and put forward some of our research ideas and results from our molecular genetics research, which may pave the way for deciphering the putative pathogenic mechanism, risk factor, epigenetic index, and its application in diagnostic agents or drug target for prevention and treatment. Thus, it could provide clinicians and researchers with a specific and modern overview of LA to enable the understanding of recent progress and future directions in this illness.

Small vessel disease and memory loss: what the clinician needs to know to preserve patients' brain health

Small vessel disease (SVD) in the brain manifests in the periventricular and deep white matter and radiographically is described as "leukoaraiosis". It is increasingly recognized as a cause of morbidity from middle age onward and this clinical relevance has paralleled advances in the field of neuroradiology. Overall, SVD is a heterogenous group of vascular disorders that may be asymptomatic, or a harbinger of many conditions that jeopardize brain health. Management and prevention focuses on blood pressure control, lifestyle modification, and symptomatic treatment.