α-syn and SNP rs356219 as a potential biomarker in blood for Parkinson's disease in Mexican Mestizos.

Clinical criteria diagnose Parkinson's disease (PD), therefore, it is crucial to find biological elements that could support diagnosis or even act as prognostic tools of PD. The SNCA gene codifies a protein called α - synuclein; several studies associate genetic and biochemical factors of SNCA with PD, including transcript and plasmatic protein levels, however, contradictory evidence indicates inconclusive results. We aim to compare SNCA mRNA expression, plasmatic α-syn protein and rs356219 SNP between PD cases and a control group, and to identify a potential biomarker in Mexican mestizos', focusing on these three components determined in blood. We included 88 PD patients and 88 age-matched controls. We observed higher α-syn protein and decreased SNCA mRNA levels in PD subjects, compared to control group (p = 0.044 and p < 0.001, respectively). A statistically significant difference was found in allelic and genotypic frequencies of SNP rs356219 between PD patients and normal subjects (p = 0.006 and p = 0.023, respectively). Logistic regression analysis determined as optimal predictors of PD the GG genotype of SNP rs356219 (OR 2.49; p = 0.006) in a recessive model and α-syn protein (OR 1.057; p = 0.033). Furthermore, the G allele of SNP rs356219 was associated with higher plasmatic α-syn and mRNA levels in PD subjects. The receiver operating curves (ROC) distinguished PD from healthy controls with good sensitivity and specificity considering the plasmatic α-syn protein (AUC = 0.693, Sensitivity = 66.7 %, Specificity = 63.9 %) or a predictive probability of plasmatic α-syn protein and SNP rs356219 in a single model (AUC = 0.692, Sensitivity = 62.3 %, Specificity = 62.5 %). The performance of this classifier model in PD at early stage (n = 31) increase the discriminant power in both, plasmatic α-syn protein (AUC = 0.779, Sensitivity = 72.7 %, Specificity = 73.9 %) and predictive probability (AUC = 0.707, Sensitivity = 63.6 %, Specificity = 62.5 %). We propose that α-syn protein and SNP rs356219 together may work as a good signature of PD, and they can be suggested as a non-invasive biomarker of PD risk.

Differences in MTHFR and LRRK2 variant's association with sporadic Parkinson's disease in Mexican Mestizos correlated to Native American ancestry.

Parkinson's disease (PD), a common neurodegenerative disorder, has a complex etiology where environmental and genetic factors intervene. While a number of genes and variants have been identified in recent decades as causative or protective agents of this condition, a limited number of studies have been conducted in mixed populations, such as Mexican Mestizos. The historical convergence of two founding groups and three ethnicities, and the increasing north-to-south gradient of Native American ancestry in Mexico resulted in a subpopulation structure with considerable genetic diversity. In this work, we investigate the influence of 21 known susceptibility variants for PD. Our case-control study, with a cohort of 311 Mexican Mestizo subjects, found a significant risk association for the variant rs1491942 in LRRK2. However, when stratification by ancestry was performed, a risk effect for MTHFR rs1801133 was observed only in the group with the highest percentage of European ancestry, and the PD risk effect for LRRK2 rs1491942 was significant in subjects with a higher ratio of Native American ancestry. Meta-analyses of these SNP revealed the effect of LRRK2 rs1491942 to be even more significant than previously described in populations of European descent. Although corroboration is necessary, our findings suggest that polymorphism rs1491942 may be useful as a risk marker of PD in Mexican Mestizos with greater Native American ancestry. The absence of associations with the remaining known risk factors is, in itself, a relevant finding and invites further research into the shared risk factors' role in the pathophysiological mechanisms of this neurodegenerative disorder.

rs3764435 Associated With Parkinson's Disease in Mexican Mestizos: Case-Control Study Reveals Protective Effects Against Disease Development and Cognitive Impairment.

Parkinson's disease (PD) is the second most common movement disorder. Genetic risk factors provide information about the pathophysiology of PD that could potentially be used as biomarkers. The ALDH1A1 gene encodes for the aldehyde dehydrogenase enzyme, which is involved in the disposal of toxic metabolites of dopamine. Due to the cytotoxic nature of aldehydes, their detoxification is essential for cellular homeostasis. It has been reported that ALDH1A1 expression levels and activity are decreased in PD patients. A deficit in ALDH1A1 activity in the substantia nigra, may lead to the accumulation of neurotoxic aldehydes and eventually the cell death seen in PD. One of the single nucleotide polymorphisms (SNP) that may modulate ALDH1A1 activity levels is rs3764435 (A/C). To investigate whether a statistical association exists between PD and the SNP rs3764435, we carried out a population-based Case-Control association study (120 PD patients and 178 non-PD subjects) in Mexican mestizos. DNA was extracted from blood samples and genotyped for rs3764435 using real-time PCR. A significant difference was found between PD cases and controls in both allelic and genotypic frequencies. The calculated OR showed that the C/C genotype is a protective factor under the codominant and recessive models of inheritance. However, after stratifying by sex, the protective role of this genotype is conserved only in men. Also, under the codominant and dominant models, rs3764435 appears to exert a protective effect against cognitive impairment in PD patients. Here for the first time, we show an association between PD and rs3764435 in a Mexican mestizo population, suggesting it confers neuroprotection for dementia in PD and is neuroprotective against developing PD in the males of this population. While analysis of the SNP looks favorable, replication of our study in cell lines or rs3764435 KO mice is required to validate these results.