RAB39B gene mutations are not linked to familial Parkinson's disease in China.

Recently, RAB39B mutations were reported to be a causative factor in patients with Parkinson's disease (PD). To validate the role of RAB39B in familial PD, a total of 195 subjects consisting of 108 PD families with autosomal-dominant (AD) inheritance and 87 PD families with autosomal-recessive (AR) inheritance in the Chinese Han population from mainland China were included in this study. We did not identify any variants in the coding region or the exon-intron boundaries of the gene by Sanger sequencing method in the DNA samples of 180 patients (100 with AD and 80 with AR). Furthermore, we did not find any variants in the RAB39B gene when Whole-exome sequencing (WES) was applied to DNA samples from 15 patients (8 with AD and 7 with AR) for further genetic analysis. Additionally, when quantitative real-time PCR was used to exclude large rearrangement variants in these patients, we found no dosage mutations in RAB39B gene. Our results suggest that RAB39B mutation is very rare in familial PD and may not be a major cause of familial PD in the Chinese Han Population.

The GBA, DYRK1A and MS4A6A polymorphisms influence the age at onset of Chinese Parkinson patients.

Parkinson's disease (PD) is known as the most common neurodegenerative disease after Alzheimer's disease (AD). The precise pathogenic mechanism of PD remains unclear, but genetic and environmental factors are widely recognized to be associated with it. Although many associated genes have been discovered, they account for only a few PD patients. Recently, there are growing evidences indicating that patients with PD and AD share similarities in clinical features, pathology and genetic risks. However, no study has been conducted on the relations between AD associated genes and age at onset (AAO) of PD. In this study, we have detected 14 single nucleotide polymorphisms (SNPs) in 9 AD genome wide association studies top hit genes and 4 SNPs in 4 PD-cognitive impairment related genes among 297 Chinese PD patients. Through the linear regression analysis, we identified the significant associations of the GBA L444P mutation and DYRK1A rs8126696 T allele with the earlier AAO in PD patients, and the A allele at MS4A6A rs610932 with the delayed AAO of PD. This is the first report of significant associations of DYRK1A and MS4A6A SNPs and the AAO of PD. On account of their effects both in AD and PD, it is indicated that AD and PD possibly share some common pathways.

The Progress of Induced Pluripotent Stem Cells as Models of Parkinson's Disease.

In recent years, induced pluripotent stem cells (iPSCs) were widely used for investigating the mechanisms of Parkinson's disease (PD). Somatic cells from patients with SNCA (α-synuclein), LRRK2 (leucine-rich repeat kinase 2), PINK1 (PTEN induced putative kinase 1), Parkin mutations, and at-risk individuals carrying GBA (ß-glucocerebrosidase) mutations have been successfully induced to iPSCs and subsequently differentiated into dopaminergic (DA) neurons. Importantly, some PD-related cell phenotypes, including α-synuclein aggregation, mitophagy, damaged mitochondrial DNA, and mitochondrial dysfunction, have been described in these iPSCs models, which further investigated the pathogenesis of PD. In 2007, Takahashi et al. and Vodyanik et al. generated iPSCs from human somatic cells for the first time. Since then, patients derived iPSCs were applied for disease modeling, drug discovery and screening, autologous cell replacement therapy, and other biological applications. iPSC research has now become a hot topic in a wide range of fields. This review summarizes the recent progress of PD patients derived iPSC models in pathogenic mechanism investigation and potential clinical applications, especially their promising strategy in pharmacological study and DA neurons transplantation therapy. However, the challenges of iPSC transplantation still exist, and it has a long way to go before it can be used in clinical application.

Relationship between Alzheimer's disease GWAS-linked top hits and risk of Parkinson's disease with or without cognitive decline: a Chinese population-based study.

Alzheimer's disease (AD), Parkinson's disease (PD), and cognitive impairment in PD have overlapping clinical and pathological features. To examine whether there is a genetic link for these diseases, we performed a case-control study in Chinese population to evaluate the association of AD genome-wide association studies top hits with both PD and cognitive function in PD, investigating 13 single-nucleotide polymorphisms in 9 genes (BIN1, CLU, ABCA7, CR1, PICALM, MS4A6A, CD33, MS4A4E, and CD2AP). A total of 454 controls and 442 PD patients were genotyped, including 75 mild cognitive impairment and 99 dementia. As a result, no significant association of the AD-susceptibility loci was identified in PD cases, PD-dementia, or PD-mild cognitive impairment. Our findings imply that the 13 single-nucleotide polymorphisms from AD genome-wide association studies may not play major role in the genetic predisposition with PD and cognitive function in PD in a Chinese population.

Association study between SMPD1 p.L302P and sporadic Parkinson's disease in ethnic Chinese population.

PURPOSE: The protein encoded by sphingomyelin phosphodiesterase 1, acid lysosomal (SMPD1) is a lysosomal acid sphingomyelinase. While there are increasing evidences to suggest that lysosomal enzyme defects and Parkinson's disease (PD) have strong associations, and recently, SMPD1 p.L302P (c.T911C, NM_000543) was found to be a risk factor for PD in Ashkenazi Jewish ancestry population, we try to investigate the possible association between SMPD1 p.L302P and sporadic PD in ethnic Chinese population. METHODS: 455 sporadic PD and 476 health controls were included in our study. SMPD1 p.L302P (c.T911C) was genotyped by matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS) and the results were confirmed by Sanger sequencing. RESULTS: Our results showed that none of 455 sporadic PD and 476 health controls carried p.L302P. All of the 931 subjects' genotypes were wild type TT. Our data indicated that in an ethnic Chinese population, p.L302P did not appear to be enriched in sporadic PD, and p.L302P may not be a risk factor for Chinese sporadic PD. And combine our data with the results from previous studies, we found that all of the 2,268 participants of Chinese population carrying no p.L302P. CONCLUSIONS: We could make a conclusion that p.L302P may not be common events for Chinese population. Sequencing of SMPD1 gene to find additional novel rare variants in the SMPD1 gene in diverse populations is needed.

LRRK2 A419V variant is a risk factor for Parkinson's disease in Asian population.

Recently, LRRK2 A419V (rs34594498) was reported associating with Parkinson's disease (PD) in Asian population; yet the conclusion is still unobvious. We conducted a case-control study to determine the potential associations between A419V and PD in Chinese population. Five hundred PD patients and 574 health controls were genotyped. Our results showed, A419V has a significantly higher frequency among PD patients than the controls (p = 0.025, odds ratio [OR] = 2.57, 95% confidence interval [CI] [1.13-5.86]), especially in early-onset PD (p = 0.027, OR = 10.40, 95% CI [1.31-82.89]). And PD patients who carried A419V have a lower Minimum-Mental State Examination scores than PD patients who did not (p = 0.04). We also conducted a meta-analysis on A419V. In Asian population, A419V was detected at a significantly higher frequency among PD patients in contrast to controls: Z = 2.47, p = 0.01, OR = 2.11, 95% CI [1.17-3.82]. When only considering the Chinese population, the difference was more obvious with Z = 3.41, p = 0.0007, OR = 2.07, 95% CI [1.36-3.14]. The results suggest LRRK2 A419V appears to be a risk factor for PD in Asian, especially in early-onset patients. Finally, larger sample with centering on young or cognitive impairment PD patients in Asian would be preferable for further confirmation.

Involvement of Bcl-2-associated athanogene (BAG)-family proteins in the neuroprotection by rasagiline.

Rasagiline, a novel monoamine oxidase (MAO)-B inhibitor, has a mild to moderate effect in relieving Parkinson's disease (PD) symptoms as well as unique neuroprotective effects. Previous studies demonstrated rasagiline protect neurons by regulating Bcl-2 family proteins. Our study aimed to study whether Bcl-2-associated athanogene (BAG)-family proteins, which were reported closely associated with neurodegenerative disease, were involved in the neuroprotective effect of rasagiline. We found that after the administration of 1-methy1-4-phenvl-1,2,3,6-tetrahvdropvridine (MPTP), BAG2 and BAG5 proteins were up-regulated in the substantia nigra dopaminergic neurons of PD mouse model. A further increase of BAG2 and BAG5 was detected after intragastric administration of rasagiline to post-MPTP lesioned mice. Thus, the current study proved the association of BAG family proteins with PD, and suggested the involvement and a positive role of BAG2, BAG5 in the neuroprotection of rasagiline. These preliminary results implicate a novel pathway for further study on neuroprotection of rasagiline.

Analysis of several loci from genome-wide association studies in Parkinson's disease in mainland China.

Large-scale meta-analyses of genome-wide association studies in Parkinson's disease (PD) have identified a number of susceptibility loci in sporadic PD. Since the characteristics of those loci in a Han Chinese population from mainland China were unknown, we performed a case-control replication study in this population and evaluated several single nucleotide polymorphisms (SNPs) identified in a recent GWAS-meta-analysis. In total, 933 subjects comprised of 460 PD patients and 473 controls were genotyped. We found strong evidence of an association for rs708723 in RAB7L1 in the total sample (genotype p=0.01, allele p=0.01, OR=0.78, 95% CI=0.65-0.94). With rs156429 in GPNMB, there was a significant difference in genotype and allele distribution between male PD patients and the control subgroup (genotype p=0.01, allele p=0.01, OR=0.67, 95% CI=0.49-0.92). However, we did not observe any significant difference in genotype or allele distribution between PD and control for rs34016896 in NMD3 and rs6812193 in STBD1.