Impaired iPLA2ß activity affects iron uptake and storage without iron accumulation: An in vitro study excluding decreased iPLA2ß activity as the cause of iron deposition in PLAN.

PLA2G6-associated neurodegeneration (PLAN, NBIA2) is the second most common type of neurodegeneration with brain iron accumulation (NBIA), caused by recessive mutations of PLA2G6 gene, which encodes Ca2+-independent phospholipase A2ß (iPLA2ß). In most PLAN cases, decreased iPLA2ß activity and iron deposition was observed meanwhile, and researchers also identified a PLA2G6 mutation family without iron deposition shown by MRI images. This brought us the question of whether decreased iPLA2ß activity was the cause of iron deposition in PLAN. In this study, we used S-BEL as the antagonist of iPLA2ß to block its activity and used SH-SY5Y cells as the expression system. We incubated SH-SY5Y cells with different concentrations of S-BEL. The results showed that decreased iPLA2ß activity led no obvious iron accumulation, while changes of cells state and activation of apoptosis were observed. To further investigate the cause of unchanged iron level, we examined the cellular iron regulatory proteins involved in iron uptake, storage and export. The results were as follows: TfR1 (iron uptake protein) expression was decreased, the expression of ferritin heavy chain and light chain (iron storage protein) was increased. There was no alteration of the expression of DMT1 (iron uptake protein) and FPN1 (iron export protein). Under the condition of decreased iPLA2ß activity, there was no obvious iron accumulation but iron uptake activity decreased and iron storage activity increased. Therefore, we speculate that the decreased iPLA2ß activity may not be the main reason for iron deposition in PLAN.

Polygenic determinants of Parkinson's disease in a Chinese population.

It has been reported that some single-nucleotide polymorphisms (SNPs) are associated with the risk of Parkinson's disease (PD), but whether a combination of these SNPs would have a stronger association with PD than any individual SNP is unknown. Sixteen SNPs located in the 8 genes and/or loci (SNCA, LRRK2, MAPT, GBA, HLA-DR, BST1, PARK16, and PARK17) were analyzed in a Chinese cohort consisting of 1061 well-characterized PD patients and 1066 control subjects from Central South of Mainland China. We found that Rep1, rs356165, and rs11931074 in SNCA gene; G2385R in LRRK2 gene; rs4698412 in BST1 gene; rs1564282 in PARK17; and L444P in GBA gene were associated with PD with adjustment of sex and age (p < 0.05) in the analysis of 16 variants. PD risk increased when Rep1 and rs11931074, G2385R, rs1564282, rs4698412; rs11931074 and G2385R, rs1564282, rs4698412; G2385R and rs1564282, rs4698412; and rs1564282 and rs4698412 were combined for the association analysis. In addition, PD risk increased cumulatively with the increasing number of variants (odds ratio for carrying 3 variants, 3.494). In summary, we confirmed that Rep1, rs356165, and rs11931074 in SNCA gene, G2385R in LRRK2 gene, rs4698412 in BST1 gene, rs1564282 in PARK17, and L444P in GBA gene have an independent and combined significant association with PD. SNPs in these 4 genes have a cumulative effect with PD.

The BAG2 and BAG5 proteins inhibit the ubiquitination of pathogenic ataxin3-80Q.

The expansion of a polyglutamine domain in the protein ataxin3 causes spinocerebellar ataxia type-3 (SCA3). However, there is little information to date about the upstream proteins in the ubiquitin-proteasome system of pathogenic ataxin3-80Q. Here, we report that BAG2 (Bcl-2 associated athanogene family protein 2) and BAG5 (Bcl-2-associated athanogene family protein 5) stabilise pathogenic ataxin3-80Q by inhibiting its ubiquitination as determined based on western blotting and co-immunofluorescence experiments. The association of the BAG2 and BAG5 proteins with pathogenic ataxin3-80Q strengthens the important roles of the BAG family in neurodegenerative diseases.

Association analysis of STK39, MCCC1/LAMP3 and sporadic PD in the Chinese Han population.

With the completion of the Human Genome Project, GWAS have been widely used in exploring the genetic studies of complex diseases. A meta-analysis of datasets from five Parkinson's disease GWAS from the USA and Europe found 11 loci that surpassed the threshold for genome-wide significance (p<5×10(-8)), and five were newly identified loci (ACMSD, STK39, MCCC1/LAMP3, SYT11 and CCDC62/HIP1R). Another GWAS of the Ashkenazi Jewish population also identified loci in STK39 and LAMP3. Because the association between the STK39 and MCCC1/LAMP3 genes and PD was confirmed in different populations, we conducted a case-control cohort to clarify the association between the four single nucleotide polymorphism (SNP) loci (rs2102808 and rs3754775 in the STK39; rs11711441 and rs12493050 in the MCCC1/LAMP3) and PD in the Chinese Han population. Polymerase chain reaction and direct DNA sequencing analyses were used to detect the four variations in a case-control cohort comprised of 993 ethnic Chinese subjects. We found that in the detection of the rs11711441, there was a significant difference between ungrouped populations, early-onset PD, late-onset PD, male PD, female PD and the corresponding control group in allele and genotype frequency (p<0.001, OR<1). In the detection of the rs2102808, rs3754775 and rs12493050, ungrouped populations, early-onset PD, late-onset PD, male PD or female PD with the corresponding control group showed no significant difference in allele and genotype frequency (p>0.0125). Our findings suggested that the allele G of rs11711441 of the MCCC1/LAMP3 gene can decrease the risk of PD in Chinese population. No statistically significant difference in genotype frequency between cases and controls was observed for the other three SNPs.

Association study between SNP rs150689919 in the DNA demethylation gene, TET1, and Parkinson's disease in Chinese Han population.

BACKGROUND: Recent studies suggest that epigenetic factors may play an important role in the pathogenesis of Parkinson's disease (PD). In our previous work, we sequenced the exomes of sixteen patients from eight Chinese PD families using whole exome sequencing technology, consequently three patients from different pedigrees were found sharing the variant c.1460C > T (rs150689919) in the coding region of the Tet methyl cytosine dioxygenase 1 (TET1) gene. METHODS: In order to evaluate the possible association between sporadic PD and the single nucleotide polymorphism (SNP) rs150689919 in TET1, a case-control cohort study was conducted in 514 sporadic PD patients and 529 normal controls. Genotyping was determined by PCR and direct sequencing. Statistical significance was analyzed by the Chi-squared test. RESULTS: There was no statistical significance in TET1 rs150689919 genotype or allele frequencies between the PD cases and healthy controls, even after being stratified by gender and age at onset. CONCLUSIONS: Our findings suggest that rs150689919 in TET1 may not be associated with PD in Chinese population. However, due to the limited data in this study, replication studies in larger sample and other populations are required.

Clinical features and [11C]-CFT PET analysis of PARK2, PARK6, PARK7-linked autosomal recessive early onset Parkinsonism.

Mutations in the Parkin, PINK1, and DJ-1 genes can cause autosomal recessive early onset Parkinsonism. We studied three families with the mutations of the Parkin, PINK1 and DJ-1 genes, respectively, with a dopamine transporter ligand [(11)C]-CFT positron emission tomography. A marked bilaterally and dissymmetrically decrement of [(11)C]-CFT uptake was found in all these patients, and putamen as well as caudate nucleus was affected. We also found asymptomatic Parkin and PINK1 heterozygotes showed a mild but significant decrement in [(11)C]-CFT uptake, but this phenomenon was not found in the DJ-1-heterozygotes. Our results suggested the three autosomal recessive forms of early onset are similar to each other on pathophysiological grounds, a sub-clinical disease process in Parkin and PINK1-heterozygotes, but not in DJ-1-heterozygotes.

R492X mutation in PTEN-induced putative kinase 1 induced cellular mitochondrial dysfunction and oxidative stress.

The identification of rare monogenic forms of Parkinson's disease (PD) has provided tremendous insights into the molecular pathogenesis of the disorder. Mitochondrial dysfunction and oxidative stress are thought to play a prominent role in the pathogenesis of PD, but how the monogenic mutation gene causes the disease onset or progression is largely unknown. In this study we investigated the effects of wild-type and R492X mutation in the PTEN-induced putative kinase 1 (PINK1). Cell cultures show that R492X PINK1 mutation induces the generation of cellular reactive oxidative species (ROS), degrades cell membrane potential, causes cytochrome C (Cyt.C) release from mitochondrial to cytoplasm, attenuates mitochondrial complex I activity, and lastly, causes changes in mitochondrial numbers and morphology; especially when cells are treated with 1-Methyl-4-phenylpyridinium ion (MPP(+)). Our results suggest that the R492X mutation can cause mitochondrial dysfunction and oxidative stress and can associate with MPP(+) to induce mitochondrial dysfunction and oxidative stress.

Mutation analysis of Parkin, PINK1 and DJ-1 genes in Chinese patients with sporadic early onset parkinsonism.

Early onset parkinsonism (EOP) has been associated with mutations in the Parkin, PINK1, and DJ-1 genes. We studied the prevalence of mutations in all three genes in 127 unrelated Chinese patients with apparently sporadic EOP using direct sequencing analysis and real-time quantitative PCR analysis assay. There are 16 patients (12.6%) with mutations of Parkin gene, four patients (3.1%) with mutations of PINK1 gene, and three patients (2.4%) with mutation of DJ-1 gene. In conclusion, Parkin gene mutation is the most common pathogenic factor in Chinese patients with sporadic EOP. Mutations of DJ-1 and PINK1 gene are also found in Chinese patients with sporadic EOP.

Mutation analysis of Parkin, PINK1, DJ-1 and ATP13A2 genes in Chinese patients with autosomal recessive early-onset Parkinsonism.

Autosomal recessive early-onset Parkinsonism (AREP) has been associated with mutations in the Parkin, PINK1, DJ-1, and ATP13A2 genes. We studied the prevalence of mutations in all four genes in 29 Chinese unrelated families with AREP using direct sequencing analysis and real-time quantitative PCR analysis assay. There are 14 families (48.3%) with mutations of Parkin gene, 2 families (6.9%) with mutations of PINK1 gene, and 1 family (3.4%) with mutation of DJ-1 gene. No pathogenic mutations in ATP13A2 gene were found in these families. Three Parkin gene mutations (c.G859T, c.1069-1074delGTGTCC, and c.T1422C) and one DJ-1 gene mutation (c.T29C) have not been reported previously. In conclusion, Parkin gene mutation is the most common pathogenic factor in Chinese patients with AREP. Mutations of DJ-1 and PINK1 gene are also found in Chinese families with AREP. Mutations in ATP13A2 gene may be rare in Chinese families with AREP.

[Mutation analysis of DJ1 gene in patients with autosomal recessive early-onset Parkinsonism].

OBJECTIVE: To investigate the mutation characteristics of DJ1 gene in Chinese patients with autosomal recessive early-onset Parkinsonism (AR-EP). METHODS: Mutations of DJ1 gene were screened by polymerase chain reaction combined with DNA direct sequencing in index patients with AR-EP from 11 unrelated families. RESULTS: No pathogenetic mutations in the DJ1 gene were detected in this group. Six intronic DJ1 polymorphisms (IVS1-15T-->C, IVS4+30T-->G, IVS4+45G-->A, IVS4+46G-->A, IVS5+31G-->A, g.168-185del) were found. Three of them (IVS1-15T-->C, IVS4+45G-->A, IVS4+46G-->A) were not reported previously. CONCLUSION: DJ1 mutations were rare in Chinese patients with autosomal recessive early-onset Parkinsonism.

[Spastin gene mutation in Chinese patients with hereditary spastic paraplegia].

OBJECTIVE: To investigate the mutation characteristics of spastin gene in Chinese patients with hereditary spastic paraplegia (HSP) and thus provide a basis for the gene diagnosis of HSP. METHODS: Mutation of spastin gene was screened by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) combined with DNA direct sequencing in 31 unrelated affected HSP individuals in China, of whom 22 were from autosomal dominant families and 9 were sporadic HSP patients. Co-segregation analysis was carried out after the finding of abnormal SSCP bands. RESULTS: Six cases were found to have abnormal SCP bands, and among them, two missense mutations (T1258A, A1293G in exon 8) and one deletion mutation (1667delACT or 1668delCTA or 1669delTAC in exon 14) were found and all of them were not reported previously. They were all co-segregated with the disease and were localized within the functional domain of spastin gene. Besides, T1258A was seen in two unrelated families. CONCLUSION: The mutation rate (18.2%) in autosomal dominant HSP in Chinese patients is comparatively low. Point mutation is the major mutation type and exon 8 may be the mutation hot spot.