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.

Genetic analysis of TREM2 variants in Chinese Han patients with sporadic Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder after Alzheimer's disease and is characterized by the degeneration of dopaminergic neurons in substantia nigra. Recently, rs75932628 (p.R47H) of the triggering receptor expressed on myeloid cells 2 gene (TREM2) was identified to be associated with PD in American, Spanish, Irish, and Polish population. To explore whether TREM2 variants are related to susceptibility of sporadic PD in Chinese Han population, we designed a case-control comparison study and studied two variants rs75932628 (p.R47H) and rs2234253 (p.T96K) of the TREM2 gene in 512 Chinese Han patients with sporadic PD and 512 age, gender and ethnicity matched normal controls from Mainland China. No variant for either rs75932628 or rs2234253 was found in both PD and control cohorts. Our data suggest that neither variant rs75932628 nor rs2234253 be a major susceptibility factor of sporadic PD in Chinese Han population from Mainland China.

Association of the mt-ND2 5178A/C polymorphism with Parkinson's disease

Mitochondria play an important role in the etiology of Parkinson's disease (PD). While mutations in the mitochondrial DNA (mtDNA) have been shown to accumulate in PD, no specific mtDNA polymorphisms have been associated with susceptibility or resistance to PD. A cytosine to adenine transversion at base pair 5178 in the mtDNA has been associated with increased longevity and resistance against a number of age related disorders and has been shown to decrease mitochondrial reactive oxygen species (ROS) production. We sought to determine whether 5178A is associated with resistance against PD in a Han Chinese population. To assess its association with PD, we genotyped 484 idiopathic PD patients and 710 control individuals for 5178C/A. Genotyping was performed using restriction fragment length polymorphism (RFLP) analysis. There was no significant association between 5178A and PD (P=0.308) when analyzing the entire population. However, sub-group analysis revealed that in males the frequency of 5178A was significantly lower in PD patients (27.7% in controls vs 20.0% in PD patients, P=0.027). Stratification of the population by age showed that this trend held across age groups but only reached statistical significance in males aged 60-70 (29.1% in controls vs 14.05 in PD patients, P=0.011). In conclusion, we demonstrated that the frequency of 5178A was significantly decreased in male PD patients in a Han Chinese population. This polymorphism may be associated with resistance against the development of PD when in combination with loci on the Y chromosome.

The experience of Parkinson's disease: a systematic review and meta-ethnography

There has been little attempt to summarise and synthesise qualitative studies concerning the experience and perception of living with Parkinson's disease. Bringing this information together would provide a background to understand the importance of an individual's social identity on their well-being and hope. Three primary aims were identified (a) understanding the importance of social identity and meaningful activities on individuals' well-being, (b) identifying factors and strategies that influence well-being and hope, and (c) establishing a model that relates to an individual's hope and well-being. Three stages were undertaken including a traditional electronic search, a critical appraisal of articles, and a synthesis of studies. Qualitative articles were included that considered the experience of living with Parkinson's disease. Thirty seven articles were located and included in the review. Five themes were identified and the themes were used to inform development of a new model of hope enablement. The current review furthered understanding of how physical symptoms and the experience of Parkinson's disease affect the individual's well-being and hope. Social identity was established as a key factor that influenced an individual's well-being. Being able to maintain, retain, or develop social identities was essential for the well-being and hope of individuals with Parkinson's disease. Understanding the factors which prevent or can facilitate this is essential.

α-Synuclein rs356219 polymorphisms in patients with Gaucher disease and Parkinson disease

Mutations in β-glucocerebrosidase, the genetic defect in Gaucher disease (GD), are an important susceptibility factor for Parkinson disease (PD). A PD effector is α-synuclein (SNCA) hypothesized to selectively interact with β-glucocerebrosidase under lysosomal conditions. SNCA polymorphism rs356219 may be associated with early-age-onset PD, common among patients with GD+PD. The objective of this study was to ascertain rs356219 genotypes of GD+PD patients. All GD+PD patients at our Gaucher referral clinic were asked to participate. A GD-only sex-, age-, GD genotype-, and enzyme therapy (ERT)-matched control was found for each GD+PD participant. Student's t-test was used (p-value <0.05 as significant). There were 14 GD+PD patients: all Ashkenazi Jewish; 11 males (78.6%); mean (range) age diagnosed GD 34.2 (5-62) years; 50% N370S homozygous; mild to moderate GD; 3 asplenic and only these have osteonecrosis; 5 received ERT; mean age (range) diagnosed PD was 57.8 (43-70) years; first PD sign was tremor in 9 (64.3%); cognitive dysfunction in all. In GD+PD, frequency for AG+GG (9) was greater than AA (5); in GD only, there was equality (7). Odds Ratio risk for PD increases with number minor alleles: but not significantly greater among GD+PD than GD only; in aggregate, there was no difference between cohorts for frequency of minor alleles. The limitation of this study is few GD+PD, albeit virtually all the GD+PD cohort >500 adult GD patients in our clinic. Nonetheless, as a foray into potential genetic GD susceptibility for a synucleinopathy, this study suggests the need for collaboration to achieve larger sample size.

Polarization of the effects of autoimmune and neurodegenerative risk alleles in leukocytes

To extend our understanding of the genetic basis of human immune function and dysfunction, we performed an expression quantitative trait locus (eQTL) study of purified CD4(+) T cells and monocytes, representing adaptive and innate immunity, in a multi-ethnic cohort of 461 healthy individuals. Context-specific cis- and trans-eQTLs were identified, and cross-population mapping allowed, in some cases, putative functional assignment of candidate causal regulatory variants for disease-associated loci. We note an over-representation of T cell-specific eQTLs among susceptibility alleles for autoimmune diseases and of monocyte-specific eQTLs among Alzheimer's and Parkinson's disease variants. This polarization implicates specific immune cell types in these diseases and points to the need to identify the cell-autonomous effects of disease susceptibility variants.

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 between polymorphism of dopamine β-hydroxylase gene and Parkinson's disease in Uygurs and Hans of Xinjiang]

OBJECTIVE

To explore the relationship between dopamine β-hydroxylase gene polymorphisms and Parkinson's disease (PD) in Uygurs and Hans populations of Xinjiang.

METHODS

The polymorphisms of DBH gene were determined by polymerase chain-reaction restriction fragment length polymorphism (PCR-RFLP) in 239 PD patients (including 100 Uygurs and 141 Hans) and 232 health controls (including 103 Uygurs and 129 Hans).

RESULTS

The genotypic or allelic distribution of DBH gene had significant differences between PD and control groups in both Uygur and Han populations (P < 0.05). The genotypic or allelic frequencies were significantly different between Han PD and control groups (P < 0.05). The genotypic or allelic frequencies in those aged 65 years or above were significantly different from that in others (P < 0.05). There was a significant increase of PD in A2 allele carriers (OR = 1.965, P < 0.05). And the frequencies of A2 allele in female PD patients were higher than those in female controls (P < 0.05) and A2 allele carriers had a significant increase of PD (OR = 1.696, P < 0.05).

CONCLUSION

Different between Uygurs and Hans of Xinjiang, DBH5 TaqI polymorphisms may be associated with PD in Hans. A2 allele carriers are often found in females and those aged 65 years or above.

[Comparison of clinical symptoms for Uygur and Han Parkinson's disease patients]

OBJECTIVE

To explore the characteristics of clinical symptoms in Uygur and Han patients with Parkinson's disease (PD).

METHODS

The unified Parkinson's disease rating scale (UPDRS), Hoehn-Yahr, mini-mental state examination (MMSE) scale, Alzheimer disease cooperative study-activities of daily living (ADCS-ADL) and neuropsychiatric inventory (NPI) were administered to 91 Uygur and 173 Han PD patients from Xinjiang Urumqi and surrounding region from June 2008 to September 2011 to compare the characteristics of clinical symptoms between Uygur and Han patients.

RESULTS

The subjects of drug treatment in Han [108 (62.34%)] were more than in Uygur [36 (39.56%), (P < 0.05)]. However there were no significant differences in the subjects of effective treatment between two groups (P > 0.05). No significant inter-group differences existed in the scores of Hoehn-Yahr (P > 0.05). Compare with moderate and severe group in Hoehn-Yahr, there were no significant differences in the scores of ADL, UPDRS II and UPDRS III between two groups (P > 0.05). The subjects of resting tremor, increased muscle tone and bradykinesia as the presenting symptoms in Uygur [8 (19.05%)] were more than in Han [7 (7.07%), (P < 0.05)]. And the subjects of N-type progressive in Uygur [36 (85.71%)] were more than in Han [48 (48.48%), (P < 0.05)]. There were no significant differences in other presenting symptoms, initial site, on-off phenomenon and dyskinesia between two groups (P > 0.05). No significant differences existed in the scores of MMSE and NPI between two groups (P > 0.05).

CONCLUSION

No significant differences exist in typical motor symptoms, severity of disease, activities of daily living, cognitive dysfunction and psychiatric symptoms between Uygur and Han. But N-type progressive is more common in Uygur. And the presenting symptoms of resting tremor, increased muscle tone and bradykinesia are also higher in Uygur.

Prevalence of nocturia in Parkinson's disease patients from various ethnicities

OBJECTIVES

One of the most common non-motor symptoms in Parkinson's disease (PD) is nocturia. This paper seeks to address the prevalence of nocturia in PD and correlate it to various factors such as gender, Hoehn and Yahr (H&Y) stage, age, and ethnicities.

METHODS

In particular, 332 PD patients were seen in a community movement disorders clinic and their charts were analyzed from 2005 to 2010. Within this population, more than one-third (34.9%) patients were diagnosed with nocturia.

RESULTS

Age, gender, and PD stage were significant predictors of nocturia in PD. With every one-year increase in age, the odds of developing nocturia in PD increases by 3.1% while an increase in H&Y stage increases the odds of nocturia in PD by 1.645 times. Also, males had greater odds of experiencing nocturia in PD. Ethnicities alone were of no significant importance. However, after performing interaction analyses, Asian and Indian males, especially, were at significantly greater risk than other ethnicities.

DISCUSSION

Future research is indeed required to understand why certain ethnicities are especially at risk. Clinicians must also be aware of the epidemiology of nocturia in PD to prevent and treat this debilitating symptom.

Genetic analysis of the S100B gene in Chinese patients with Parkinson disease

There is growing evidence that genetic abnormalities play an important role in the pathogenesis of Parkinson disease (PD). At least 18 genetic loci and 13 disease-related genes for parkinsonism have been identified. The S100 calcium-binding beta (S100B), which is expressed and secreted by astrocytes, has been found to be associated with PD. To evaluate whether the S100B variants are related to PD in Chinese Han population, we conducted genetic examination of the S100B gene in 502 PD patients from Mainland China. We did identify two known variants c.279+4T>C (rs187503470) and c.99C>G (p.Leu33Leu, rs1051169) in our patients. Neither of these two variants is predicted to change amino acid or splice site, indicating that they are not pathogenic mutations. Our results suggest that mutations in the coding region or intron/exon boundaries of the S100B gene play little or no role in the development of PD in Chinese population.

Association studies of MMP-9 in Parkinson's disease and amyotrophic lateral sclerosis

Parkinson’s disease (PD) and amyotrophic lateral sclerosis (ALS) share several clinical and neuropathologic features, and studies suggest that several gene mutations and polymorphisms are involved in both conditions. Matrix metalloproteinase-9 (MMP-9) is implicated in the pathogenesis of PD and ALS, and the C(−1562)T polymorphism in the MMP-9 gene leads to higher promoter activity. We therefore investigated whether this polymorphism predisposes to both PD and sporadic ALS (sALS). Samples from 351 subjects with PD and 351 healthy controls from two major cities in China were compared, while samples from 226 subjects with sALS were compared to the same number of controls from three centers in China. A possible association between the C(−1562)T polymorphism in the MMP-9 gene and PD or sALS was assessed by restriction fragment length polymorphism (RFLP) analysis. Our results show a significant association between the C(−1562)T polymorphism in the MMP-9 gene and risk of PD (odds ratio = 2.268, 95% CI 1.506–3.416, p<0.001) as well as risk of sALS (odds ratio = 2.163, 95% CI 1.233–3.796, p = 0.006), supporting a role for MMP-9 polymorphism in the risk for PD and sALS.

Patterns of linkage disequilibrium of LRRK2 across different races: implications for genetic association studies

Genome Wide Association Studies (GWASs) have identified trait-associated polymorphisms via a hypothesis-free approach. However, it is challenging when attempting to reproduce GWAS findings in different populations as it fundamentally relies on the similar patterns of linkage disequilibrium (LD) between the unknown causal variants and the genotyped single nucleotide polymorphisms (SNPs). To address this potential limitation, we examined the regional LD pattern of leucine-rich repeat kinase 2 (LRRK2) gene, which is responsible for both autosomal dominant and sporadic Parkinson’s disease (PD), in Caucasians (CEU), Japanese (JPT) and Chinese (CHB) from HapMap and Chinese (CHS), Malays (MAS) and Indians (INS) from the Singapore Genome Variation Project (SGVP) utilizing the traditional heatmaps and targeted analysis of LRRK2 gene via Monte Carlo simulation through varLD scores of these ethnic groups. Both heatmaps and targeted analysis showed that LD pattern of JPT was different from that of INS (P=0.0001); while LD pattern of CEU was different from that in Asian except for INS (all P=0.0001). Our study suggests that there is a higher chance to detect associations between PD and those trait-associated SNPs of LRRK2 gene found in Caucasian studies in INS, while those found in Japanese studies are likely to be better replicated among CHB.

MCCC1/LAMP3 reduces risk of sporadic Parkinson's disease in Han Chinese

BACKGROUND

A recent large-scale replication and heterogeneity study reported the new described GWAS locus (MCCC1/LAMP3 rs11711441) was associated with a reduced risk of Parkinson disease (PD) in Asian and Caucasian populations. Its role is still unknown in a Han Chinese population from mainland China. We genotyped the rs11711441 variant to investigate the association with risk of PD.

METHODS

Using a case-control methodology, a total of 1428 Han Chinese study subjects were genotyped. We also conducted further stratified analysis according to age at onset and compared the clinical characteristics of GA + AA subjects with GG subjects.

RESULTS

In this study, we confirmed that the A allele of MCCC1/LAMP3 (rs11711441) polymorphism reduces the risk to develop sporadic PD (P = 0.043). Additionally, subjects with GA + AA genotypes have a reduced risk compared to those with GG genotype (P = 0.022). The association was seen among the older age group (P = 0.014), but was not significant among the younger age group (P = 0.641). No significant differences were observed in gender, age at onset, and onset symptoms between GA + AA subjects and GG subjects.

CONCLUSION

Our study, the first from Mainland China demonstrates that MCCC1/LAMP3 (rs11711441) is associated with a lower risk of PD. Further studies in additional Chinese populations and other cohorts will be useful.

Lack of association between BST1 polymorphisms and sporadic Parkinson's disease in a Japanese population

Several genome-wide association studies and case-control studies have investigated the relationships between single nucleotide polymorphisms (SNPs) in the BST1 gene and Parkinson's disease (PD), but the results have been inconsistent. We examined the relationships between SNPs rs11931532, rs12645693, and rs11724635 and the risk of sporadic PD in Japan. Included were 229 cases within 6years of onset of PD as defined according to the UK PD Society Brain Bank clinical diagnostic criteria. Controls were 357 inpatients and outpatients without neurodegenerative disease. SNPs rs11931532 and rs12645693 were not significantly related to sporadic PD. Compared with a reference group of subjects with the CC genotype of SNP rs11724635, those with the AA genotype had a marginally significantly increased risk of sporadic PD: the adjusted OR was 1.57 (95% CI: 0.95-2.61, P=0.08). No significant interactions were found between BST1 SNP rs11724635 and smoking or caffeine intake with respect to sporadic PD. The current study failed to detect significant relationships between BST1 SNPs rs11931532, rs12645693, and rs11724635 and sporadic PD; however, the relationship between SNP rs11724635 and sporadic PD was of borderline significance. We do not find evidence for interactions between smoking or caffeine intake and SNP rs11724635 affecting sporadic PD.

LRRK2 A419V is not associated with Parkinson's disease in different Chinese populations

It has been suggested that a common LRRK2 polymorphic variant (A419V (rs34594498 C >T)) may be a risk factor among Asians (especially in Taiwan). In this study, we examined this variant in a larger and independent Taiwan cohort. We found the frequency of the variant (A419V) to be very rare in our Taiwan PD and controls (?0.6%). Further studies were conducted in two other Chinese populations (Singapore and China), comprising of a total of 3004 subjects including 1517 PD patients and 1487 control subjects. However, our multi-center Chinese study revealed that the frequency of the variant was rare (?0.4%) and was not associated with risk of PD, suggesting that the variant is not a major risk factor for PD among Chinese, at least in our study population.

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.

Penetrance of LRRK2 G2385R and R1628P is modified by common PD-associated genetic variants

Variants in the LRRK2 gene are well-characterized genetic predisposing factors for PD worldwide, and LRRK2-associated PD is often indistinguishable from idiopathic PD (IPD). However, considerable heterogeneity of LRRK2-PD suggests the existence of additional genetic and/or environmental modifiers for LRRK2 carriers, which have yet to be confirmed by large-scale human studies. In a Chinese cohort consisting of 2013 sporadic PD patients and 1971 controls, we investigated the modification of the two Asian-specific LRRK2 variants, G2385R and R1628P, by variants of five other PD-associated genes/loci (SNCA, MAPT, GBA, BST1, PARK16). Of all the PD patients, 13.1% carried LRRK2 G2385R and/or R1628P variant. Among these carriers, a total of 15 different polygenic genotypes were detected representing different combination patterns between LRRK2 variants and those of the other genes/loci, which, alone or in combination, significantly modified the LRRK2-related risk for PD and the patients' ages at onset (AAOs). These results not only represent the largest replication data affirming the association between PD and all the six genes/loci in Chinese, but for the first time suggest that multiple PD-associated genetic factors modify both the penetrance and AAO of LRRK2 parkinsonism. This finding may have important implications for elucidating pathophysiologic mechanisms relevant to both LRRK2-associated and idiopathic PD. However, testing interactions among multiple genes by genetic association studies is still challenging. Future studies with much larger sample sizes are needed to confirm our findings.

Association study of SCARB2 rs6812193 polymorphism with Parkinson's disease in Han Chinese

Recently, a nucleotide polymorphism rs6812193 near SCARB2 was found to be significantly associated with Parkinson's disease (PD) in populations of European ancestry. Herein, we conducted a case-control study with attempt to further evaluate the association between SNP rs6812193 and PD in a Chinese population from mainland China. rs6812193 was genotyped by PCR-RFLP technique in 449 PD patients and 452 controls in a Chinese population. In our study, we did not detect statistically significant differences between cases and controls in terms of both allele and genotype distribution of the rs6812193 polymorphism (P=0.97 and P=0.77, respectively), even after stratification by age at onset. Our data do not support the association of SNP rs6812193 with PD in Han Chinese of mainland China.

Assessment of substantia nigra echogenicity in German and Filipino populations using a portable ultrasound system

OBJECTIVES

Transcranial sonography of the substantia nigra for diagnosing premotor stages of Parkinson disease has been attracting increasing interest. Standard reference values defining an abnormal increased echogenic size (hyperechogenicity) of the substantia nigra have been established in several populations using high-end stationary ultrasound systems. It is unknown whether a portable ultrasound system can be appropriately used and how the Filipino population would compare with the well-studied white population.

METHODS

We prospectively studied substantia nigra echogenic sizes and third ventricle widths in 71 healthy adult German participants and 30 age- and sex-matched Filipino participants using both a well-established stationary ultrasound system (in the German cohort) and a recently distributed portable ultrasound system (in both ethnic cohorts).

RESULTS

Mean substantia nigra echogenic sizes, cutoff values defining abnormal hyperechogenicity, and intra-rater reliability were similar with both systems and in both ethnic cohorts studied. The Filipino and German participants did not differ with respect to the frequency of insufficient insonation conditions (each 3%) and substantia nigra hyperechogenicity (10% versus 9%; P = .80). However, third ventricle widths were smaller in the Filipino than the German participants (mean ± SD, 1.6 ± 1.1 versus 2.4 ± 1.0 mm; P = .004).

CONCLUSIONS

The frequency of substantia nigra hyperechogenicity appears to be homogeneous in white and Asian populations. Screening for this feature may well be performed with a present-day portable ultrasound system.

Lrrk2 p.Q1111H substitution and Parkinson's disease in Latin America

Mutations in the LRRK2 gene are the most common genetic cause of Parkinson's disease, with frequencies displaying a high degree of population-specificity. Although more than 100 coding substitutions have been identified, only seven have been proven to be highly penetrant pathogenic mutations. Studies however are lacking in non-white populations. Recently, Lrrk2 p.Q1111H (rs78365431) was identified in two affected Hispanic brothers and absent in 386 non-Hispanic white healthy controls. We therefore screened this variant in 1460 individuals (1150 PD patients and 310 healthy controls) from 4 Latin American countries (Peru, Chile, Uruguay and Argentina). In our case-control series from Peru and Chile we observed an increased frequency of Lrrk2 p.Q1111H in patients (7.9%) compared to controls (5.4%) although the difference did not reach significance (OR 1.38; p = 0.10). In addition, the frequency of Lrrk2 p.Q1111H varied greatly between populations and further screening in a set of pure Amerindian and pure Spanish controls suggested that this variant likely originated in an Amerindian population. Further studies in other Latin American populations are warranted to assess its role as a risk factor for Parkinson's disease. Screening in Parkinson's disease patients from under-represented populations will increase our understanding of the role of LRRK2 variants in disease risk worldwide.

Low frequency of common LRRK2 mutations in Mexican patients with Parkinson's disease

Mutations in leucine-rich repeat kinase 2 gene (LRRK2) account for as much as 5-6% of familial Parkinson's disease (PD) and 1-2% of sporadic PD. These mutations represent the most frequent cause of autosomal dominant PD, particularly in certain ethnic groups. In this first report concerning LRRK2 mutations in Mexican-mestizos, we screened 319 consecutive PD patients (186 males; 133 females; mean age at onset: 52.4 years) for LRRK2 mutations in exons 31 and 41 and for the mutation in exon 35, which produces the Y1699C substitution. Three (0.94%) patients, two with sporadic PD and one with familial PD (disease mean age at onset, 53.3 years), were heterozygous for LRRK2 mutations. Of these three, two patients had one of two different mutations in exon 31 (R1441G and R1441H, respectively); the other patient carried the G2019S mutation in exon 41. The Y1699C mutation was absent from this PD sample. Four additional subjects, unaffected relatives of one PD patient with a mutation in LRRK2, were subsequently genetically tested. None of the three LRRK2 mutations identified was present in 200 neurologically healthy Mexican control individuals. These findings have important implications for molecular testing of LRRK2 mutations in Mexican PD patients.