Mutations In PARK2 Gene Research Articles

Screening of mutations in PARK2 gene and Dopamine levels in Parkinson's disease (PD) patients in Coimbatore population, India

Background: Parkinson's disease (PD) is a neurodegenerative disorder accompanied by depletion of dopamine and loss of dopaminergic neurons (DA) in the brain that is believed to be responsible for the motor and non-motor symptoms of PD. Parkin belongs to the RBR family of E3 ubiquitin ligase, which is involved in varied cytosolic and mitochondrial functions. Parkin mutations lead to early synaptic damage and appear as a crucial gene having a vast functioning area in PD.

Exploring the Impact of PARK2 Mutations on the Total and Mitochondrial Proteome of Human Skin Fibroblasts.

Mutations in PARK2 gene are the most frequent cause of familial forms of Parkinson’s disease (PD). This gene encodes Parkin, an E3 ubiquitin ligase involved in several cellular mechanisms, including mitophagy. Parkin loss-of-function is responsible for the cellular accumulation of damaged mitochondria, which in turn determines an increment of reactive oxygen species (ROS) levels, lower ATP production, and apoptosis activation. Given the importance of mitochondrial dysfunction and mitophagy impairment in PD pathogenesis, the aim of the present study was to investigate both total and mitochondrial proteome alterations in human skin fibroblasts of PARK2-mutated patients. To this end, both total and mitochondria-enriched protein fractions from fibroblasts of five PARK2-mutated patients and five control subjects were analyzed by quantitative shotgun proteomics to identify proteins specifically altered by Parkin mutations (mass spectrometry proteomics data have been submitted to ProteomeXchange with the identifier PXD015880). Both the network-based and gene set enrichment analyses pointed out pathways in which Rab GTPase proteins are involved. To have a more comprehensive view of the mitochondrial alterations due to PARK2 mutations, we investigated the impact of Parkin loss on mitochondrial function and network morphology. We unveiled that the mitochondrial membrane potential was reduced in PARK2-mutated patients, without inducing PINK1 accumulation, even when triggered with the ionophore carbonyl cyanide m-chlorophenylhydrazone (CCCP). Lastly, the analysis of the mitochondrial network morphology did not reveal any significant alterations in PARK2-mutated patients compared to control subjects. Thus, our results suggested that the network morphology was not influenced by the mitochondrial depolarization and by the lack of Parkin, revealing a possible impairment of fission and, more in general, of mitochondrial dynamics. In conclusion, the present work highlighted new molecular factors and pathways altered by PARK2 mutations, which will unravel possible biochemical pathways altered in the sporadic form of PD.

Genetic study of a Parkinson's disease pedigree caused by compound heterozygous mutations in PARK2 gene

To explore the genetic basis for a Chinese pedigree where three siblings were affected with Parkinson's disease. Multiple ligation-dependent probe amplification (MLPA) and next-generation sequencing (NGS) were employed to detect the causative mutation. Sanger sequencing of cDNA was also used for verify the effect of mutation on the transcription of RNA. Heterozygous deletion of exon 3 of the PARK2 gene was detected by MLPA, while a heterozygous splice site variant c.619-3G>C was detected by NGS. Both mutations were shown to result in aberrant transcripts of the PARK2 gene (loss of exons 3 and 6, respectively) by Sanger sequencing of cDNA. Both mutations have co-segregated with the disease in the pedigree. Compound heterozygous mutations of the PARK2 gene probably underlie the disease in this pedigree. Identification of the splice site variant c.619-3G>C has expanded the mutation spectrum of the PARK2 gene.

The synaptic function of parkin.

Loss of function mutations in the gene PARK2, which encodes the protein parkin, cause autosomal recessive juvenile parkinsonism, a neurodegenerative disease characterized by degeneration of the dopaminergic neurons localized in the substantia nigra pars compacta. No therapy is effective in slowing disease progression mostly because the pathogenesis of the disease is yet to be understood. From accruing evidence suggesting that the protein parkin directly regulates synapses it can be hypothesized that PARK2 gene mutations lead to early synaptic damage that results in dopaminergic neuron loss over time. We review evidence that supports the role of parkin in modulating excitatory and dopaminergic synapse functions. We also discuss how these findings underpin the concept that autosomal recessive juvenile parkinsonism can be primarily a synaptopathy. Investigation into the molecular interactions between parkin and synaptic proteins may yield novel targets for pharmacologic interventions.

A comprehensive computational study on pathogenic mis-sense mutations spanning the RING2 and REP domains of Parkin protein

Various mutations in PARK2 gene, which encodes the protein parkin, are significantly associated with the onset of autosomal recessive juvenile Parkinson (ARJP) in neuronal cells. Parkin is a multi domain protein, the N-terminal part contains the Ubl and the C-terminal part consists of four zinc coordinating domains, viz., RING0, RING1, in between ring (IBR) and RING2. Disease mutations are spread over all the domains of Parkin, although mutations in some regions may affect the functionality of Parkin more adversely. The mutations in the RING2 domain are seen to abolish the neuroprotective E3 ligase activity of Parkin. In this current work, we carried out detailed in silico analysis to study the extent of pathogenicity of mutations spanning the Parkin RING2 domain and the adjoining REP region by SIFT, Mutation Accessor, PolyPhen2, SNPs and GO, GV/GD and I-mutant. To study the structural and functional implications of these mutations on RING2-REP domain of Parkin, we studied the solvent accessibility (SASA/RSA), hydrophobicity, intra-molecular hydrogen bonding profile and domain analysis by various computational tools. Finally, we analysed the interaction energy profiles of the mutants and compared them to the wild type protein using Discovery studio 2.5. By comparing the various analyses it could be safely concluded that except P437L and A379V mutations, all other mutations were potentially deleterious affecting various structural aspects of RING2 domain architecture. This study is based purely on computational approach which has the potential to identify disease mutations and the information could further be used in treatment of diseases and prognosis.

Proteomic Analysis of Parkin Isoforms Expression in Different Rat Brain Areas

PARK2 gene's mutations are related to the familial form of juvenile Parkinsonism, also known as the autosomic recessive juvenile Parkinsonism. This gene encodes for parkin, a 465-amino acid protein. To date, a large number of parkin isoforms, generated by an alternative splicing mechanism, have been described. Currently, Gene Bank lists 27 rat PARK2 transcripts, which matches to 20 exclusive parkin alternative splice variants. Despite the existence of these isoforms, most of the studies carried out so far, have been focused only on the originally cloned parkin. In this work we have analyzed the expression profile of parkin isoforms in some rat brain areas including prefrontal cortex, hippocampus, substantia nigra and cerebellum. To discriminate among these isoforms, we detected their localization through the use of two antibodies that are able to identify different domains of the parkin canonical sequence. Our analysis has revealed that at least fourteen parkin isoforms are expressed in rat brain with a various distribution in the regions analyzed. Our study might help to elucidate the pathophysiological role of these proteins in the central nervous system.

Neuropsychological assessment in patients with Parkinson's disease associated with PARK2 gene mutations: A case-control study

Neuropsychological assessment in patients with Parkinson's disease associated with PARK2 gene mutations: A case-control study

Phenotypical Differences in Neuronal Cultures Derived via Reprogramming the Fibroblasts from Patients Carrying Mutations in Parkinsonian Genes LRRK2 and PARK2.

Fibroblasts isolated from skin biopsy specimens from patients with genetic forms of Parkinson's disease, carriers of mutations in LRRK2 and PARK2 genes, and from a healthy volunteer were reprogrammed using lentiviral vectors into induced pluripotent stem cells (iPSC). iPSC were differentiated into neuron-like cells using a cocktail of differentiation factors (N2, B27, and Noggin). The iPSC lines derived from patients with different mutations and from a healthy volunteer cultured under the same conditions were characterized by different proportion of neuronal precursors and differentiated neurons. Control Po2 line contained 56% precursors, while B15 line with LRRK2 gene mutation (G2019S) contained 35% precursor cells. Similar regularities were characteristic of Tr5 culture carrying compound heterozygous mutations in PARK2 gene (del202-203AG and IVS1+1G/A) and containing 4% neuronal precursors. Further comparative studies of iPSC carrying various mutations and comparison with normal human cells will help to understand the molecular pathogenesis of some genetic variants of Parkinson's disease.

The KM-parkin-DB: A Sub-set MutationView Database Specialized for PARK2 (PARKIN) Variants.

We previously isolated PARKIN (PARK2) as a gene responsible for a unique sort of Parkinson disease, namely Autosomal Recessive Juvenile Parkinsonism (ARJP). In this study, we surveyed all the available literature describing PARK2 gene/Parkin protein mutations found in Parkinson disease patients. Only carefully evaluated data were deposited in the graphical database MutationView (http://mutview.dmb.med.keio.ac.jp) to construct KM-parkin-DB, an independent sub-set database. Forty-four articles were selected for data curation regarding clinical information such as ethnic origins, manifested symptoms, onset age, and hereditary patterns as well as mutation details including base changes and zygosity. A total of 366 cases were collected from 39 ethnic origins and 96 pathogenic mutations were found. PARK2 gene mutations were found also in some general Parkinson disease patients. The majority (63%) of mutations in PARK2 were restricted to two particular domains (UBL and RING1) of the Parkin protein. In these domains, two major mutations, a large deletion (DelEx3) and a point mutation (p.Arg275Trp), were located.

Autonomic involvement in Parkinsonian carriers of PARK2 gene mutations.

The objective of this study was to assess the presence of autonomic nervous system dysfunction in PARK2 mutation carriers. We performed a cross-sectional analysis of 8 PARK2 carriers (age: 60.1 ± 12.8 years) and 13 individuals with idiopathic PD (iPD) (age: 59.2 ± 8.9 years). Autonomic dysfunction was measured using the SCOPA-AUT questionnaire, non-invasive autonomic tests and responses of noradrenaline and vasopressin levels to postural changes. Myocardial sympathetic denervation was assessed with metaiodobenzylguanidine (MIBG) scintigraphy. This damage was further investigated in postmortem epicardial tissue of one PARK2 carrier and three control cases (two PD patients and one subject without PD). The prevalence of autonomic symptoms and orthostatic hypotension (OH) was lower in PARK2 mutation carriers than in iPD patients (SCOPA OUT: 3.4 ± 4.8 vs. 14.7 ± 7.2, p < 0.001; OH: present in three iPD patients but none of the PARK2 mutation carriers). Second, sympathetic myocardial denervation was less severe in PARK2 mutation carriers compared to controls, both in MIBG scintigraphy (late H/M uptake ratio: 1.52 ± 0.35 vs. 1.32 ± 0.25 p < 0.05) and in postmortem tissue study. Interestingly, axonal alpha-synuclein deposits were absent in epicardial tissue of the PARK2 mutation carrier while they were present in the two PD patients. Our study supports the view that autonomic nervous system dysfunction and myocardial sympathetic denervation are less pronounced in PARK2 mutation carriers than in individuals with iPD, suggesting that the involvement of small peripheral sympathetic nerve fibers is a minor pathological hallmark in PARK2 carriers.

PARK2 gene mutations in early onset Parkinson's disease patients of South India

With the etiology being unclear till date, a combination of age, genetic and environmental factors are known to play a significant role in the pathogenesis of Parkinson's disease. Mutations in PARK2 gene have been implicated to cause autosomal recessive early onset PD. We analyzed the 12 coding exons of PARK2 gene in 16 early onset PD patients of South Indian ethnicity. PARK2 mutations were present in 68% of the early onset cases. We report the presence of four PARK2 sequence variants c.1239G>C, c.171+25T>C, c.202A>G, c.601G>A, and a novel insertion mutation, c.798_799insA in the exon 7 of PARK2 gene. These results suggest that mutations in PARK2 gene may be a common cause of PD among South Indian early onset patients.

PARK2 variability in Polish Parkinson’s disease patients - interaction with mitochondrial haplogroups

Aims and objectivesA new pathomechanism of Parkinson’s disease (PD) involving regulation of mitochondrial functions was recently proposed. Parkin complexed with mitochondrial transcription factor A (TFAM) binds mtDNA and promotes mitochondrial biogenesis, which is abolished by PARK2 gene mutations. We have previously shown that mitochondrial haplogroups/clusters and TFAM common variation influenced PD risk. We investigate the role of PARK2 polymorphisms on PD risk and their interactions with mitochondrial haplogroups/clusters as well as with TFAM variability. Methods104 early-onset PD patients (EOPD, age at onset ≤50 years) were screened for PARK2 coding sequence changes including gene dosage alterations. Three selected PARK2 polymorphisms (S167N, V380L, D394N) were genotyped in 326 PD patients and 315 controls using TaqMan allelic discrimination assay. ResultsPARK2 screen revealed two heterozygous changes in two EOPD patients: exon 2 deletion and one novel synonymous variation (c.999C > A, P333P).In association study no differences in genotype/allele frequencies of S167N, V380L, D394N were found between analyzed groups. Stratification by mitochondrial clusters revealed higher frequency of V380L G/G genotype and allele G in PD patients, within HV cluster (p = 0.040; p = 0.022, respectively). Moreover, interaction between genotypes G/G V380L of PARK2 and G/G rs2306604 of TFAM, within HV cluster was significant (OR 2.05; CI 1.04–4.04; p = 0.038). ConclusionsOur results indicate that co-occurrence of G/G V380L PARK2 and G/G rs2306604 TFAM on the prooxidative HV cluster background can contribute to PD risk. We confirm low PARK2 mutation frequency in Polish EOPD patients.

Analysis of PARK2 gene exon rearrangements in Russian patients with sporadic Parkinson's disease

Deletions and duplications of single exons or exon groups account for a large proportion of the PARK2 gene mutations described in juvenile autosomal recessive Parkinson's disease (PD). We analyzed rearrangements in exons 1 to 12 of the PARK2 gene in Russian sporadic patients with early-onset PD (EOPD) and late-onset PD (LOPD). The frequency of EOPD and LOPD patients carrying these mutations was 12.4% and 3.8%, respectively. The most frequent rearrangements were detected in exons 3 and 4. The odds ratio for EOPD in individuals carrying PARK2 exon deletions and duplications was 13.95 (95% confidence interval [CI], 1.846-105.46; P = .0022). In addition, we found a correlation between exon rearrangements in PARK2 and the age at onset of PD, presence of dystonia, and symmetrical course of the disease. Exon rearrangements in the PARK2 gene play a significant role in the pathogenesis of sporadic PD in Russian patients.

Low frequency of the PARK2 gene mutations in Polish patients with the early-onset form of Parkinson disease

Objective Mutations in the PARK2 ( Parkin) gene result in an early-onset autosomal recessive form of Parkinson Disease (EO-PD). Although the frequency of the PARK2 mutations in EO-PD patients according to several studies is high and has been reported in up to 50% in familial and 19% in sporadic cases, these data remain controversial. Methods We performed PARK2 gene analysis for a group of 79 Polish EO-PD patients with onset of disease below the age of 40. All exons were directly sequenced and the exons' copy number variations were analyzed. Results Mutations in PARK2 gene were found in 3 patients (3.8%), in two sporadic cases in both alleles (2.5%) and in a familial case in only one allele (1.3%). We identified point mutations as well as exon rearrangements (duplication, deletion). Conclusions The frequency of the PARK2 mutations our Polish group with EO-PD seems to be lower than in other previously described groups.

Evidence for the presence of full-length PARK2 m RNA and Parkin protein in human blood

Research on Parkinson's disease fails to pinpoint a single gene or a gene product as the causative factor. However, the early onset form of the disease may be caused by mutations in PARK2 gene. Some studies related to the biochemistry or other aspects of the PARK2 gene or its product mostly used cDNA generated from substantia nigra of the mid-brain. This is essentially because the presence of the 1.4 kb full-length PARK2 cDNA in human leukocytes is, so far, not demonstrated although some splice variants and short RT-PCR products were reported. In this study, we synthesized a 1.4 kb full-length PARK2 cDNA from human leukocytes, cloned and expressed it both in Escherichia coli and in HeLa cells. The presence of Parkin protein was also demonstrated in human serum using Western blotting and MALDI-TOF analysis. The results of this study showed a simple way for routine amplification of PARK2 cDNA from human blood and may become a useful diagnostic tool in the future.

Molecular findings in familial Parkinson disease in Spain.

Several genetic errors in alpha-synuclein (Park1) and ubiquitin carboxyl-terminal-hydrolase L1(Park5) genes cause autosomal dominant familial Parkinson disease. Mutations in the parkin gene (Park2) are the major cause of autosomal recessive Parkinson disease. To analyze the clinical and molecular data of 19 Spanish kindreds (13 with recessive, 4 with dominant, and 2 with uncertain inheritance) who have familial Parkinson disease. We searched for the previously described mutations in Park1 and Park5 genes and for new or described mutations in Park2. We used single-strand conformation polymorphism, direct sequencing, and restriction digestion of polymerase chain reaction (PCR)-amplified genomic DNA for this study. None of these families have either Park1 or Park5 mutations. We found 5 different mutations in Park2 gene in 5 of the families with recessive inheritance. To our knowledge, 2 of these mutations, V56E and C212Y, have not been previously reported. The other mutations found (deletion of exons 3 and 5 and 225delA) have been described in other ethnic groups. Heterozygous carriers of a single Park2 mutation either were asymptomatic or developed clinical symptoms in late adulthood or after brief exposure to haloperidol therapy. Mutations in Park2 gene account for 38% of the families with recessive parkinsonism in Spain. We found 2 cases of simple heterozygous Park2 mutation carriers that developed clinical symptoms, either in late adulthood or after brief exposure to parkinsonizing agents. Thus, hereditary Parkinson disease has more variable clinical phenotype and molecular defects than previously thought since heterozygous mutations could be a risk factor for parkinsonism.