Influence of heterozygosity for parkin mutation on onset age in familial Parkinson disease: the GenePD study.
ABSTRACT The PARK2 gene at 6q26 encodes parkin, whose inactivation is implicated in an early-onset autosomal recessive form of Parkinson disease (PD).
To evaluate the influence of heterozygosity for parkin mutation on onset age in a sample of families with at least 2 PD-affected members.
Clinical and genetic study.
Twenty collaborative clinical sites.
Patients with familial PD collected in the GenePD study. Studied families were selected for (1) affected sibling pairs sharing 2 alleles identical by state at PARK2 (D6S305) or (2) 1 or more family members with onset age younger than 54 years, regardless of D6S305 status. At least 1 member from each of 183 families underwent comprehensive screening for deletion/insertion variants and point mutations in PARK2.
Mutations in the parkin gene were screened by means of single-stranded conformation polymorphism and sequencing in all 12 coding exons and flanking intronic sequences for point mutations and duplex quantitative polymerase chain reaction in all exons for rearrangement, duplication, and deletion.
Mutations were found in 23 families (12.6% of those screened). Among the mutation-positive families, 10 (43%) contained compound heterozygotes; 3 (13%), homozygotes; and 10 (43%), heterozygotes. The onset age in patients with parkin gene mutations ranged from 20 to 76 years. Patients with 1 parkin mutation had an 11.7-year age at onset than did patients with none (P = .04), and patients with 2 or more parkin mutations had a 13.2-year decrease in age at onset compared with patients with 1 mutation (P = .04).
These data indicate that parkin mutations are not rare in multiply affected sibships, and that heterozygous mutation carrier status in PARK2 significantly influences age at onset of PD.
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ABSTRACT: 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 1.4kb 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 1.4kb 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.Neuroscience Letters 07/2009; 460(3):196-200. · 2.11 Impact Factor