PLA2G6 gene mutation in autosomal recessive early-onset parkinsonism in a Chinese cohort

PARK14 PLA2G6 mutants are defective in preventing rotenone-induced mitochondrial dysfunction, ROS generation and activation of mitochondrial apoptotic pathway

Mutations in the gene encoding Ca²⁺-independent phospholipase A₂ group 6 (PLA2G6) cause the recessive familial type 14 of Parkinson’s disease (PARK14). Mitochondrial dysfunction is involved in the pathogenesis of Parkinson’s disease (PD). PLA2G6 is believed to be required for maintaining mitochondrial function. In the present study, rotenone-induced cellular model of PD was used to investigate possible molecular pathogenic mechanism of PARK14 mutant PLA2G6-induced PD. Overexpression of wild-type (WT) PLA2G6 ameliorated rotenone-induced apoptotic death of SH-SY5Y dopaminergic cells. PARK14 mutant (D331Y), (G517C), (T572I), (R632W), (N659S) or (R741Q) PLA2G6 failed to prevent rotenone-induced activation of mitochondrial apoptotic pathway and exert a neuroprotective effect. WT PLA2G6, but not PARK14 mutant PLA2G6, prevented rotenone-induced mitophagy impairment. In contrast to WT PLA2G6, PARK14 mutant PLA2G6 was ineffective in attenuating rotenone-induced decrease in mitochondrial membrane potential and increase in the level of mitochondrial superoxide. WT PLA2G6, but not PARK14 PLA2G6 mutants, restored enzyme activity of mitochondrial complex I and cellular ATP content in rotenone-treated SH-SY5Y dopaminergic cells. In contrast to WT PLA2G6, PARK14 mutant PLA2G6 failed to prevent rotenone-induced mitochondrial lipid peroxidation and cytochrome c release. These results suggest that PARK14 PLA2G6 mutants lose their ability to maintain mitochondrial function and are defective inpreventing mitochondrial dysfunction, ROS production and activation of mitochondrial apoptotic pathway in rotenone-induced cellular model of PD.

Genetics of Parkinson's Disease: Genotype-Phenotype Correlations

Since the first discovery of a specific genetic defect in the SNCA gene, encoding for α-synuclein, as a causative factor for Parkinson's disease 20 years ago, a multitude of other genes have been linked to this disease in rare cases with Mendelian inheritance. Furthermore, the genetic contribution to the much more common sporadic disease has been demonstrated through case control association studies and, more recently, genome-wide association studies. Interestingly, some of the genes with Mendelian inheritance, such as SNCA, are also relevant to the sporadic disease, suggesting common pathogenetic mechanisms. In this review, we place an emphasis on Mendelian forms, and in particular genetic defects which present predominantly with Parkinsonism. We provide details into the particular phenotypes associated with each genetic defect, with a particular emphasis on nonmotor symptoms. For genetic defects for whom a sufficient number of patients has been assessed, there are evident genotype-phenotype correlations. However, it should be noted that patients with the same causative mutation may present with distinctly divergent phenotypes. This phenotypic variability may be due to genetic, epigenetic or environmental factors. From a clinical and genetic point of view, it will be especially interesting in the future to identify genetic factors that modify disease penetrance, the age of onset or other specific phenotypic features.

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.

DNAJC6 mutations are not common causes of early onset Parkinson's disease in Chinese Han population

DNAJC6 has been reported as a causative gene for early onset Parkinson's disease (EOPD) in some populations, and different mutations have been reported to be associated with EOPD. However, Until now, there is limited information about DNAJC6 gene test in sporadic EOPD patients in Chinese population. Herein, we performed comprehensive DNAJC6 mutation screenings in 117 EOPD patients from Chinese population. None of the reported disease-causing mutations were found. However, we identified a novel non-synonymous heterozygous variant c.2798T>C (p.Val933Ala). Bioinformatics analysis demonstrate that the c.2798T>C variant exhibits highly conserved residues across species. Our data suggests that DNAJC6 mutations are not common causes of EOPD in Chinese population.

Identification of Novel Compound Mutations in PLA2G6-Associated Neurodegeneration Patient with Characteristic MRI Imaging

Neurodegeneration with brain iron accumulation comprises a heterogeneous group of disorders characterized clinically by progressive motor dysfunction. Accurate identification of de novo and rare inherited mutations is important for determining causative genes of undiagnosed neurological diseases. In the present study, we report a unique case with cerebellar ataxia symptoms and social communication difficulties in an intermarriage family. MRI showed a marked cerebellar atrophy and the "eye-of-the-tiger"-like sign in the medial globus pallidus. Potential genetic defects were screened by whole-exome sequencing (WES) for the patient and four additional family members. A previously undescribed de novo missense mutation (c.1634A>G, p.K545R) in the exon 12 of the PLA2G6 gene was identified. A second rare variant c.1077G>A at the end of exon 7 was also identified, which was inherited from the mother, and resulted in a frame-shift mutation (c.1074_1077del.GTCG) due to an alternative splicing. In conclusion, the identification of the "eye-of-the-tiger"-like sign in the globus pallidus of the patient expands the phenotypic spectrum of PLA2G6-associated disorders and reveals its value in differential diagnosis of PLA2G6-associated disorders.

Clinical heterogeneity of PLA2G6-related Parkinsonism: analysis of two Saudi families

Background

Recessive mutations in PLA2G6 have been associated with different neurodegenerative disorders, including infantile neuroaxonal dystrophy, neurodegeneration with brain iron accumulation and more recently, early-onset dystonia parkinsonism.

Method

Targeted-next generation sequencing using a custom Neurology panel, containing 758 OMIM-listed genes implicated in neurological disorders, was carried out in two index cases from two different Saudi families displaying early-onset levodopa-responsive Parkinsonism with pyramidal signs and additional clinical features. The detected mutations were verified in the index cases and available family members by direct sequencing.

Results and conclusion

We identified a previously described PLA2G6 homozygous p.R741Q mutation in three affected and two asymptomatic individuals from two Saudi families. Our finding reinforces the notion of the broadness of the clinical spectrum of PLA2G6-related neurodegeneration.

Electronic supplementary material

The online version of this article (doi:10.1186/s13104-016-2102-7) contains supplementary material, which is available to authorized users.

Genetic Analysis of PLA2G6 in 22 Indian Families with Infantile Neuroaxonal Dystrophy, Atypical Late-Onset Neuroaxonal Dystrophy and Dystonia Parkinsonism Complex

Mutations in PLA2G6 were identified in patients with a spectrum of neurodegenerative conditions, such as infantile neuroaxonal dystrophy (INAD), atypical late-onset neuroaxonal dystrophy (ANAD) and dystonia parkinsonism complex (DPC). However, there is no report on the genetic analysis of families with members affected with INAD, ANAD and DPC from India. Therefore, the main aim of this study was to perform genetic analysis of 22 Indian families with INAD, ANAD and DPC. DNA sequence analysis of the entire coding region of PLA2G6 identified 13 different mutations, including five novel ones (p.Leu224Pro, p.Asp283Asn, p.Arg329Cys, p.Leu491Phe, and p.Arg649His), in 12/22 (54.55%) families with INAD and ANAD. Interestingly, one patient with INAD was homozygous for two different mutations, p.Leu491Phe and p.Ala516Val, and thus harboured four mutant alleles. With these mutations, the total number of mutations in this gene reaches 129. The absence of mutations in 10/22 (45.45%) families suggests that the mutations could be in deep intronic or promoter regions of this gene or these families could have mutations in a yet to be identified gene. The present study increases the mutation landscape of PLA2G6. The present finding will be useful for genetic diagnosis, carrier detection and genetic counselling to families included in this study and other families with similar disease condition.

Progressive Axonal Degeneration of Nigrostriatal Dopaminergic Neurons in Calcium-Independent Phospholipase A2β Knockout Mice

Calcium-independent phospholipase A₂β (iPLA₂β, PLA2G6) is essential for the remodeling of membrane glycerophospholipids. Mutations in this gene are responsible for autosomal recessive, young onset, L-dopa-responsive parkinsonism (PARK14), suggesting a neurodegenerative condition in the nigrostriatal dopaminergic system in patients with PLA2G6 mutations. We previously observed slowly progressive motor deficits in iPLA₂β-knockout (KO) mice. To clarify whether a deficiency of iPLA₂β leads to the degeneration of nigrostriatal dopaminergic neurons, we analyzed the striatum of iPLA₂β-KO mice. At all clinical stages, nerve terminals in the striatum were immunopositive for tyrosine hydroxylase (TH) and dopamine transporter (DAT) in wild-type (WT) control mice. In iPLA₂β-KO mice, focal loss of nerve terminals positive for TH and DAT was found from 56 weeks (early clinical stage), although iPLA₂β-KO mice at 56 weeks showed no significant decrease in the number of dopaminergic neurons in the substantia nigra compared with age-matched WT mice, as reported previously. At 100 weeks (late clinical stage), greater decreases in DAT immunoreactivity were observed in the striatum of iPLA₂β-KO mice. Moreover, strongly TH-positive structures, presumed to be deformed axons, were observed in the neuropils of the striatum of iPLA₂β-KO mice starting at 15 weeks (preclinical stage) and increased with age. These results suggest that the degeneration of dopaminergic neurons occurs mainly in the distal region of axons in iPLA₂β-KO mice.

PLA2G6 Mutations Related to Distinct Phenotypes: A New Case with Early-onset Parkinsonism

Background

PLA2G6-associated neurodegeneration (PLAN) is a recessive neurodegenerative disorder characterized by three distinct phenotypes: infantile neuroaxonal dystrophy (INAD), atypical neuroaxonal dystrophy (atypical NAD), and PLA2G6-related dystonia–parkinsonism.

Methods

A consanguineous index case from Turkey was diagnosed with early-onset Parkinsonism at the Istanbul Faculty of Medicine. She and her unaffected brother were subjected to whole-genome sequencing.

Results

In this report, we describe a 33-year-old index case with parental consanguinity and early-onset Parkinsonism. Whole-genome sequencing of this individual revealed that a homozygous p.R747W mutation in PLA2G6 segregates with the disease in this family

Discussion

This result supports the importance of prioritizing this gene in mutational analysis of autosomal recessive Parkinsonism, and confirms the clinical heterogeneity of PLAN.

Mitochondrial dysfunction and defects in lipid homeostasis as therapeutic targets in neurodegeneration with brain iron accumulation

The PLA2G6 gene encodes a group VIA calcium independent phospholipase A2 (iPLA2β), which hydrolyses glycerophospholipids to release fatty acids and lysophospholipids. Mutations in PLA2G6 are associated with a number of neurodegenerative disorders including neurodegeneration with brain iron accumulation (NBIA), infantile neuroaxonal dystrophy (INAD), and dystonia parkinsonism, collectively known as PLA2G6-associated neurodegeneration (PLAN). Recently Kinghorn et al. demonstrated in Drosophila and PLA2G6 mutant fibroblasts that loss of normal PLA2G6 activity is associated with mitochondrial dysfunction and mitochondrial lipid peroxidation. Furthermore, they were able to show the beneficial effects of deuterated polyunsaturated fatty acids (D-PUFAs), which reduce lipid peroxidation. D-PUFAs were able to rescue the locomotor deficits of flies lacking the fly ortholog of PLA2G6 (iPLA2-VIA), as well as the mitochondrial abnormalities in PLA2G6 mutant fibroblasts. This work demonstrated that the iPLA2-VIA knockout fly is a useful organism to dissect the mechanisms of pathogenesis of PLAN, and that further investigation is required to determine the therapeutic potential of D-PUFAs in patients with PLA2G6 mutations. The fruit fly has also been used to study some of the other genetic causes of NBIA, and here we also describe what is known about the mechanisms of pathogenesis of these NBIA variants. Mitochondrial dysfunction, defects in lipid metabolism, as well as defective Coenzyme A (CoA) biosynthesis, have all been implicated in some genetic forms of NBIA, including PANK2, CoASY, C12orf19 and FA2H.

Novel PLA2G6 mutations associated with an exonic deletion due to non-allelic homologous recombination in a patient with infantile neuroaxonal dystrophy

Novel PLA2G6 mutations associated with p.Asp283Asn and a unique intragenic deletion of exons 4 and 5 due to non-allelic homologous recombination were identified in a Japanese female patient with typical infantile neuroaxonal dystrophy. The patient showed progressive tetraplegia beginning at 9 months. An electroencephalogram showed a diffuse increase in fast waves, and brain magnetic resonance imaging showed progressive brain atrophy and T2 hypointensity in the globus pallidus.

F-box protein 7 mutations promote protein aggregation in mitochondria and inhibit mitophagy

The mutations of F-box protein 7 (FBXO7) gene (T22M, R378G and R498X) are associated with a severe form of autosomal recessive juvenile-onset Parkinson's disease (PD) (PARK 15). Here we demonstrated that wild-type (WT) FBXO7 is a stress response protein and it can play both cytoprotective and neurotoxic roles. The WT FBXO7 protein is vital to cell mitophagy and can facilitate mitophagy to protect cells, whereas mutant FBXO7 inhibits mitophagy. Upon stress, the endogenous WT FBXO7 gets up-regulated, concentrates into mitochondria and forms FBXO7 aggregates in mitochondria. However, FBXO7 mutations aggravate deleterious FBXO7 aggregation in mitochondria. The FBXO7 aggregation and toxicity can be alleviated by Proline, glutathione (GSH) and coenzyme Q10, whereas deleterious FBXO7 aggregation in mitochondria can be aggravated by prohibitin 1 (PHB1), a mitochondrial protease inhibitor. The overexpression of WT FBXO7 could lead to FBXO7 protein aggregation and dopamine neuron degeneration in transgenic Drosophila heads. The elevated FBXO7 expression and aggregation were identified in human fibroblast cells from PD patients. FBXO7 can also form aggregates in brains of PD and Alzheimer's disease. Our study provides novel pathophysiologic insights and suggests that FBXO7 may be a potential therapeutic target in FBXO7-linked neuron degeneration in PD.

PLA2G6-associated Dystonia-Parkinsonism: Case Report and Literature Review

Background

Phospholipase-associated neurodegeneration (PLAN) caused by PLA2G6 mutations is a recessively inherited disorder with three known phenotypes: the typical infantile onset neuroaxonal dystrophy (INAD); an atypical later onset form (atypical NAD); and the more recently recognized young-onset dystonia–parkinsonism (PLAN-DP).

Case Report

We report the clinical, radiological, and genetic findings of a young Pakistani male with PLAN-DP. We review 11 previously published case reports cited in PubMed, and summarize the demographic, clinical, genetic, and radiological data of the 23 patients described in those articles.

Discussion

PLAN-DP presents with diverse motor, autonomic, and neuropsychiatric features and should be considered in the differential diagnosis of patients with young-onset neurodegenerative disorders.

Calcium-independent phospholipases A2 and their roles in biological processes and diseases

Among the family of phospholipases A2 (PLA2s) are the Ca(2+)-independent PLA2s (iPLA2s) and they are designated group VI iPLA2s. In relation to secretory and cytosolic PLA2s, the iPLA2s are more recently described and details of their expression and roles in biological functions are rapidly emerging. The iPLA2s or patatin-like phospholipases (PNPLAs) are intracellular enzymes that do not require Ca(2+) for activity, and contain lipase (GXSXG) and nucleotide-binding (GXGXXG) consensus sequences. Though nine PNPLAs have been recognized, PNPLA8 (membrane-associated iPLA2γ) and PNPLA9 (cytosol-associated iPLA2β) are the most widely studied and understood. The iPLA2s manifest a variety of activities in addition to phospholipase, are ubiquitously expressed, and participate in a multitude of biological processes, including fat catabolism, cell differentiation, maintenance of mitochondrial integrity, phospholipid remodeling, cell proliferation, signal transduction, and cell death. As might be expected, increased or decreased expression of iPLA2s can have profound effects on the metabolic state, CNS function, cardiovascular performance, and cell survival; therefore, dysregulation of iPLA2s can be a critical factor in the development of many diseases. This review is aimed at providing a general framework of the current understanding of the iPLA2s and discussion of the potential mechanisms of action of the iPLA2s and related involved lipid mediators.

Recessive truncating NALCN mutation in infantile neuroaxonal dystrophy with facial dysmorphism

BACKGROUND

Infantile neuroaxonal dystrophy (INAD) is a recessive disease that results in total neurological degeneration and death in childhood. PLA2G6 mutation is the underlying genetic defect, but rare genetic heterogeneity has been demonstrated. One of the five families we studied did not link to PLA2G6 locus, and in the family one of the two affected siblings additionally had atypical features including facial dysmorphism, pectus carinatum, scoliosis, pes varus, zygodactyly and bilateral cryptorchidism as well as cerebellar atrophy, as previously reported.

METHODS

Sural biopsy was investigated by electron microscopy. PLA2G6 was screened for mutations by Sanger sequencing. In the mutation-free family, candidate disease loci were found via linkage analysis using data from single nucleotide polymorphism genome scans. Exome sequencing was applied to find the variants at the loci.

RESULTS

PLA2G6 mutations were identified in four families including the one with an unusually severe phenotype that led to death within the first 2 years of life. In the remaining family, seven candidate loci totalling 15.2 Mb were found and a homozygous truncating mutation p.Q642X was identified in NALCN at 13q32.3. The patients are around 20-years-old.

CONCLUSIONS

NALCN is the gene responsible for INAD with facial dysmorphism. The patients have lived to adulthood despite severe growth and neuromotor retardation. NALCN forms a voltage-independent ion channel with a role in the regulation of neuronal excitability. Our findings broaden the spectrum of genes associated with neuroaxonal dystrophy. Testing infants with idiopathic severe growth retardation and neurodegeneration for NALCN mutations could benefit families.

Neurodegeneration with brain iron accumulation

PURPOSE OF REVIEW

Recent years have witnessed the discoveries of several genes causing neurodegeneration with brain iron accumulation (NBIA) and subsequently their novel classification scheme was suggested. The first results of treatments with modern chelating drugs are also being published.

RECENT FINDINGS

Most recently, mutations in the c19orf12 gene encoding a mitochondrial protein of unknown function were identified in patients suffering from hitherto unknown NBIA presenting with a clinical phenotype similar to pantothenate kinase-associated neurodegeneration (PKAN) but with a slightly later onset. A case study has shown that mutations in the fatty-acid 2-hydroxylase gene may lead to various phenotypes combining the features of leukodystrophy and NBIA, supporting that abnormal metabolism of myelin and iron accumulation may have a common cause. A phase-II pilot study did not find any clinical improvement after chelating treatment in a group of PKAN patients. However, benefits of chelating treatment have been observed in individual patients with PKAN and idiopathic NBIA in another study.

SUMMARY

This review gives an outline of the clinical presentations of recently discovered NBIA syndromes and summarizes the clues to their differential diagnosis. While chelating treatment still remains experimental, advances have been made regarding the indications of deep brain stimulation in symptomatic treatment of NBIAs manifesting with generalized dystonia.

Follow-up study of 25 Chinese children with PLA2G6-associated neurodegeneration

BACKGROUND

To perform a follow-up of 25 Chinese children with gene-confirmed PLA2G6-associated neurodegeneration (PLAN).

METHODS

We recruited patients with infantile neuroaxonal dystrophy (INAD) according to the criteria proposed by Nardocci et al. Follow-up was conducted from 7 months to 8 years after the first visit. The PLA2G6 gene was sequenced, and copy number variation (CNV) was detected in patients with only one mutant allele and in mutation-negative patients. Patients with late-onset PLAN until 2012 were reviewed.

RESULTS

All patients with INAD exhibited rapid decline in motor and mental function, consistent with previous reports from other populations. Epileptic seizures occurred in 16.7%. One teenager with late-onset PLAN was diagnosed and followed up. The age of disease onset in published late-onset PLAN ranged between 18 months and 37 years. Initial presentations included gait instability (79.0%), mood/behavior changes (10.5%), dysarthria (5.26%) and cognitive deterioration (5.3%). Compared with INAD, cerebellar atrophy (42.1%) was less frequent in the late-onset cases, with cerebral atrophy more common (71.4%). Brain iron accumulation was seen in 52.6%. PLA2G6 mutations were identified by DNA sequencing in 92.3% of clinically diagnosed INAD cases and in the late-onset case. Twenty-seven different mutations were found, of which 13 were novel. No CNVs were detected. Maternal uniparental disomy was confirmed in one INAD case.

CONCLUSIONS

This is the largest report on PLAN in the Chinese population. We suggest that PLA2G6 should be screened in any patient exhibiting progressive gait disturbance, bradykinesia, dysarthria, tremors, mood/behavior changes or cognitive decline, especially when associated with cerebellar atrophy and/or iron accumulation and/or cerebral atrophy.

Glucocerebrosidase involvement in Parkinson disease and other synucleinopathies

Mutations in both copies (homozygous or compound heterozygous) of the gene encoding the lysosomal enzyme glucocerebrosidase, which cleaves the glycolipid glucocerebroside into glucose and ceramide cause Gaucher disease. However, multiple independent studies have also reported an association between GBA mutations and Parkinsonism with an increased frequency of heterozygous GBA mutations in various cohorts of patients with parkinsonism and other Lewy body disorders. Furthermore, GBA mutation carriers exhibit diverse parkinsonian phenotypes and present a diffuse pattern of Lewy body distribution in the cerebral cortex. This review provides an overview of the genetic basis for this association in various diseases with dysfunction of the central nervous system in which affected individuals developed Parkinsonian symptoms. The emerging clinical, pathological, and genetic studies in neuronal synucleinopathies suggest a common underlying mechanism in the etiology of these neurodegenerative disorders.

Association between PLA2G6 gene polymorphisms and Parkinson's disease in the Chinese Han population

The PLA2G6 gene encodes a group VIA calcium-independent phospholipase A(2), and has been suggested as the causative gene for autosomal recessive dystonia-parkinsonism. We conducted a case-control study using 531 mainland Chinese Parkinson's disease (PD) patients and 561 healthy controls, and genotyped 4 tag single nucleotide polymorphisms (SNPs) of the PLA2G6 gene: rs4375, rs2267369, rs132985, and rs2284063. Logistic regression analysis revealed no difference in genotype or allele frequencies for any of the SNPs between the sporadic PD group and control group. Similarly, comparison of SNPs in patients with either early-onset (EOPD, ≤ 50 years) or late-onset (>50 years) PD revealed no statistical differences from controls. We detected no significant association of the 4 SNPs with PD at the genotypic level, after adjustment for age. The rs132985 genotype frequency showed a difference in male patients but not in female patients, but the P value did not survive Bonferroni correction (Pcorr = 0.068). We found that the rs132985 A-rs2284063 C haplotype is marginally associated with increased risk of developing PD (P = 0.048) after 10,000 permutations. These findings suggest that PLA2G6 is not a susceptibility gene for PD in our population. However, a broader examination and a replication of this study in other populations are needed.

PLA2G6 mutations in PARK14-linked young-onset parkinsonism and sporadic Parkinson's disease

Mutations of PLA2G6 gene have been lately proposed to be the causative gene for PARK14 in patients with autosomal recessive young-onset parkinsonism (YOPD). The role of PLA2G6 mutations as a risk factor for Parkinson's disease is not clear. To study the PLA2G6 mutations in PARK14-linked patients and its association with the onset of sporadic Parkinson's disease (sPD), sequencing and gene dosage analyses were carried out in 25 patients (onset age ≦30 years) then the identified variants were assessed in 956 sporadic PD (sPD) patients and 802 age-matched healthy controls. Four genetic variants were identified; one patient had homozygous c.991G > T (p.Asp331Tyr) mutation, two had compound heterozygous c.991G > T/c.1077G > A (p.Met358IlefsX) mutation, one had single c.1976A > G (p.Asn659Ser) mutation, and one patient had an exon 1 hetero-deletion. The c.1077G > A mutation resulted in a 4-bp deletion in leukocyte mRNA by activating a cryptic splice site in exon 7. Only p.Asp331Tyr was identified in four sPD patients and four controls. The onset age for PLA2G6 mutation carriers was younger than that for sPD (29.86 ± 8.59 vs. 56.84 ± 11.33 years, P = 0.0002). The analysis of previously reported PARK14 patients revealed that those who carried a truncated mutation tended to have a complicated phenotype and atrophies of cortex and cerebellum. In conclusion, PLA2G6 mutation was the second common genetic cause after PRKN mutation in our YOPD patients and might be a risk factor for early-onset PD in Han Chinese. Additionally, mutation data should be interpreted carefully because even a synonymous mutation could cause abnormal mRNA splicing.