title: Perspective: Identification of genetic variants associated with dopaminergic compensatory mechanisms in early Parkinson's disease.
abstract: Parkinson's disease (PD) is slowly progressive, and heterogeneity of its severity among individuals may be due to endogenous mechanisms that counterbalance the striatal dopamine loss. In this perspective paper, we introduce a neuroimaging-genetic approach to identify genetic variants, which may contribute to this compensation. First, we briefly review current known potential compensatory mechanisms for premotor and early disease PD, located in the striatum and other brain regions. Then, we claim that a mismatch between mild symptomatic disease, manifested by low motor score on the Unified PD Rating Scale (UPDRS), and extensive Nigro-Striatal (NS) degeneration, manifested by reduced uptake of [(123)I]FP-CIT, is indicative of compensatory processes. If genetic variants are associated with the severity of motor symptoms, while the level of striatal terminals degeneration measured by ligand uptake is taken into account and controlled in the analysis, then these variants may be involved in functional compensatory mechanisms for striatal dopamine deficit. To demonstrate feasibility of this approach, we performed a small "proof of concept" study (candidate gene design) in a sample of 28 Jewish PD patients, and preliminary results are presented.
authors.affiliation: Biological Psychiatry Laboratory, Department of Psychiatry, Hadassah - Hebrew University Medical Center Jerusalem, Israel.
authors.forename: Lior
authors.initials: L
authors.lastname: Greenbaum
authors.forename: Mordechai
authors.initials: M
authors.lastname: Lorberboym
authors.forename: Eldad
authors.initials: E
authors.lastname: Melamed
authors.forename: Amihai
authors.initials: A
authors.lastname: Rigbi
authors.forename: Yael
authors.initials: Y
authors.lastname: Barhum
authors.forename: Yoav
authors.initials: Y
authors.lastname: Kohn
authors.forename: Alexander
authors.initials: A
authors.lastname: Khlebtovsky
authors.forename: Bernard
authors.initials: B
authors.lastname: Lerer
authors.forename: Ruth
authors.initials: R
authors.lastname: Djaldetti
keywords: FP-CIT SPECT; Parkinson's disease; compensatory mechanisms; neuroimaging genetics; tyrosine hydroxylase