Abstract
Background. HTRA2 has already been nominated as PARK13 which may cause Parkinson's disease, though there are still discrepancies among these results. Recently, Gulsuner et al.'s study found that HTRA2 p.G399S is responsible for hereditary essential tremor and homozygotes of this allele develop Parkinson's disease by examining a six-generation family segregating essential tremor and essential tremor coexisting with Parkinson's disease. We performed this study to validate the condition of HTRA2 gene in Chinese familial essential tremor and familial Parkinson's disease patients, especially essential tremor. Methods. We directly sequenced all eight exons, exon-intron boundaries, and part of the introns in 101 familial essential tremor patients, 105 familial Parkinson's disease patients, and 100 healthy controls. Results. No exonic variant was identified, while one exon-intron boundary variant (rs2241028) and one intron variant (rs2241027) were detected, both with no clinical significance and uncertain function. There was no difference in allele, genotype, and haplotype between groups. Conclusions. HTRA2 exonic variant might be rare among Chinese Parkinson's disease and essential tremor patients with family history, and HTRA2 may not be the cause of familial Parkinson's disease and essential tremor in China.
Highlights
As two of the most prevalent tremor disorders, essential tremor (ET) and Parkinson’s disease (PD), which are estimated to constitute 0.9% and 0.3% of worldwide population, respectively, are considered as distinctively different entities formerly [1, 2]
The patients and controls in the study are well matched for mean age (p = 0.12 for familial essential tremor (FET) and p = 0.86 for familial Parkinson’s disease (FPD)) and sex distribution (p = 0.52 for FET and p = 0.52 for FPD) (Table 1)
Another study revealed that high temperature requirement A2 (HTRA2) was regulated by PINK1, which might contribute to early-onset PD, in the proteolytic activity [22]
Summary
As two of the most prevalent tremor disorders, essential tremor (ET) and Parkinson’s disease (PD), which are estimated to constitute 0.9% and 0.3% of worldwide population, respectively, are considered as distinctively different entities formerly [1, 2]. A research by Gulsuner and colleagues examining a six-generation family segregating ET and ET coexisting with PD revealed that HTRA2 p.G399S is responsible for hereditary essential tremor and homozygotes for this allele develop Parkinson’s disease [13]. To validate the condition in Chinese familial essential tremor (FET) and familial Parkinson’s disease (FPD) patients, we performed a Sanger sequencing of eight exons and exon-intron boundaries of HTRA2 instead of just one variant (p.G399S). Gulsuner et al.’s study found that HTRA2 p.G399S is responsible for hereditary essential tremor and homozygotes of this allele develop Parkinson’s disease by examining a six-generation family segregating essential tremor and essential tremor coexisting with Parkinson’s disease. We performed this study to validate the condition of HTRA2 gene in Chinese familial essential tremor and familial Parkinson’s disease patients, especially essential tremor. HTRA2 exonic variant might be rare among Chinese Parkinson’s disease and essential tremor patients with family history, and HTRA2 may not be the cause of familial Parkinson’s disease and essential tremor in China
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