Genotype-phenotype correlations between GBA mutations and Parkinson disease risk and onset.

BACKGROUND: Mutations in GBA and LRRK2 genes have been implicated in Parkinson disease (PD), particularly in Ashkenazi Jews. METHODS: An Israeli Ashkenazi cohort of 420 patients with PD, 333 elderly controls, and 3,805 young controls was screened for eight GBA mutations, which are associated with mild (N370S, R496H) and severe (84GG, IVS2 + 1, V394L, D409H, L444P, RecTL) Gaucher disease. Patients with PD and elderly controls were also genotyped for LRRK2 G2019S. RESULTS: GBA carrier frequency was 17.9% in patients with PD compared to 4.2% in elderly and 6.35% in young controls. The proportion of severe mutation carriers among PD patient GBA carriers was 29% compared to 7% among young controls. Severe and mild GBA mutations increased the risk of developing PD by 13.6- and 2.2-fold, and affected the average age at PD onset (AAO), 55.7 and 57.9 years, compared to 60.7 years in patients without known GBA or LRRK2 mutations. CONCLUSIONS: These data demonstrate genotype-phenotype correlations between different GBA mutations and Parkinson disease (PD) risk and AAO in Ashkenazi Jews. Additionally, an earlier AAO was observed in LRRK2 G2019S carrier PD patients. Finally, these data demonstrate that a surprisingly high frequency, more than one third of our patient population, carried a mutation in GBA or LRRK2.

The LRRK2 G2019S mutation in Ashkenazi Jews with Parkinson disease: is there a gender effect?

BACKGROUND: Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are the most common genetic determinant of Parkinson disease (PD) identified to date, and have been implicated in both familial and sporadic forms of the disease. The G2019S change in LRRK2 exon 41 has been associated with disease at varying frequencies in Asian, European, North American, and North African populations, and is particularly prevalent among Ashkenazi Jews. METHODS: We assessed the occurrence of the LRRK2 G2019S, I2012T, I2020T, and R1441G/C/H mutations in our cohort of Jewish Israeli patients with PD, and determined the LRRK2 haplotypes in 76 G2019S-carriers detected and in 50 noncarrier Ashkenazi patients, using six microsatellite markers that span the entire gene. RESULTS: Only the G2019S mutation was identified among our patients with PD, 14.8% in the Ashkenazi and 2.7% in the non-Ashkenazi patients, and in 26% and 10.6% of the Ashkenazi familial and apparently sporadic cases. The carrier frequencies in the Ashkenazi and non-Ashkenazi control samples were 2.4% and 0.4%. A common shared haplotype was detected in all non-Ashkenazi and half-Ashkenazi carriers and in all full-Ashkenazi carriers tested, except two. Women and patients with a positive family history of PD were significantly over-represented among the G2019S mutation carriers. Age at disease onset was similar in carriers and noncarriers. CONCLUSIONS: Our data suggest that the LRRK2 G2019S mutation plays an important role in the causality of familial and sporadic Parkinson disease (PD) in Israel and that gender affects its frequency among patients. Although testing symptomatic patients may help establish the diagnosis of PD, the value of screening asymptomatic individuals remains questionable until the penetrance and age-dependent risk of this mutation are more accurately assessed, and specific disease prevention or modifying interventions become available.