Mortalin mutations are not a frequent cause of early-onset Parkinson disease.

Dysfunctional mitochondria and the mitochondrial chaperone mortalin (HSPA9, GRP75) have been implicated in the pathogenesis of Parkinson disease (PD). We screened 139 early-onset PD (EOPD) patients for mutations in mortalin revealing one missense change (p.L358P) that was absent in 279 control individuals. We also found one additional missense variant among the controls (p.T333K). Although both missense changes were predicted to be disease causing, we detected no differences in subcellular localization, mitochondrial morphology, or respiratory function between wild-type and mutant mortalin. These findings suggest that variants in mortalin (1) are not a major cause of EOPD; (2) occur in patients and controls; and (3) do not lead to functional impairment of mitochondria

ATP13A2 variants in early-onset Parkinson's disease patients and controls

Four genes responsible for recessively inherited forms of Parkinson's disease (PD) have been identified, including the recently discovered ATP13A2 (PARK9) gene. Our objective was to investigate the role of this gene in a large cohort of PD patients and controls. We extensively screened all 29 exons of the ATP13A2 coding region in 112 patients with early-onset PD (EOPD; <40 years) of mostly European ethnic origin and of 55 controls. We identified four carriers (3.6%) of novel single heterozygous ATP13A2 missense changes that were absent in controls. Interestingly, the carrier of one of these variants also harbored two mutations in the Parkin gene. None of the carriers had atypical features previously described in patients with two mutated ATP13A2 alleles (Kufor-Rakeb syndrome). Our data suggest that two mutated ATP13A2 alleles are not a common cause of PD. Although heterozygous variants are present in a considerable number of patients, they are - based on this relatively small sample

Analysis of blood-based gene expression in idiopathic Parkinson disease

International audienceObjective: To examine whether gene expression analysis of a large-scale Parkinson disease (PD) patient cohort produces a robust blood-based PD gene signature compared to previous studies that have used relatively small cohorts (≤220 samples).Methods: Whole-blood gene expression profiles were collected from a total of 523 individuals. After preprocessing, the data contained 486 gene profiles (n = 205 PD, n = 233 controls, n = 48 other neurodegenerative diseases) that were partitioned into training, validation, and independent test cohorts to identify and validate a gene signature. Batch-effect reduction and cross-validation were performed to ensure signature reliability. Finally, functional and pathway enrichment analyses were applied to the signature to identify PD-associated gene networks.Results: A gene signature of 100 probes that mapped to 87 genes, corresponding to 64 upregulated and 23 downregulated genes differentiating between patients with idiopathic PD and controls, was identified with the training cohort and successfully replicated in both an independent validation cohort (area under the curve [AUC] = 0.79, p = 7.13E-6) and a subsequent independent test cohort (AUC = 0.74, p = 4.2E-4). Network analysis of the signature revealed gene enrichment in pathways, including metabolism, oxidation, and ubiquitination/proteasomal activity, and misregulation of mitochondria-localized genes, including downregulation of COX4I1, ATP5A1, and VDAC3.Conclusions: We present a large-scale study of PD gene expression profiling. This work identifies a reliable blood-based PD signature and highlights the importance of large-scale patient cohorts in developing potential PD biomarkers