Heterozygous mutations in genes causing parkinsonism: monogenic disorders go complex

Università degli Studi di Messina, Messina, Sicily, Italy
The Lancet Neurology (Impact Factor: 21.9). 08/2007; 6(7):576-8. DOI: 10.1016/S1474-4422(07)70158-8
Source: PubMed
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    ABSTRACT: Mutations in the PINK1 gene, encoding a mitochondrial protein kinase, represent the second cause of autosomal recessive parkinsonism (ARP) after Parkin. While homozygous or compound heterozygous mutations in these genes are unequivocally causative of ARP, the role of single heterozygous mutations is still largely debated. An intriguing hypothesis suggests that these mutations could represent a risk factor to develop parkinsonism, by contributing to nigral cell degeneration. Since the substantia nigra plays an important role in temporal processing of sensory stimuli, as revealed from studies in idiopathic PD, we sought to investigate whether any subclinical sensory abnormalities could be detected in patients with PINK1- related parkinsonism and in unaffected PINK1 heterozygous carriers. We adopted a psychophysical method, the temporal discrimination paradigm, to assess PINK1 homozygous patients, unaffected relatives who were heterozygous carriers of the same mutations and healthy control subjects. Temporal discrimination threshold (TDT) and temporal order judgement (TOJ) for pairs of tactile, visual or visuo-tactile stimuli were measured according to a standardized protocol. Higher mean tactile and visuo-tactile TDTs and TOJs were detected in PINK1 mutation carriers, including not only homozygous patients but also healthy heterozygotes, compared to control subjects (for all comparisons, p < 0.001). In clinically unaffected subjects, the mere presence of a heterozygous PINK1 mutation is sufficient to determine sensory alterations which can be disclosed by a psychophysical task. Deficits in temporal processing might be considered as subclinical signs of alteration at least in PINK1-related parkinsonism.
    Full-text · Article · Jul 2008 · Journal of Neurology
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    ABSTRACT: Genetic forms of parkinsonism are interesting for two particular reasons. First, finding a gene identifies a cause for a disease that would otherwise be unexplained. Second, finding several genes for the same disorder allows us to reconstruct molecular pathways that, in the example of Parkinson's disease, are be associated with the survival of dopamine neurons in the substantia nigra. Two rare causes of parkinsonism, DJ-1 and PINK1, are associated with mitochondria. This organelle has long been linked with Parkinson's disease, and recent results are starting to show how mutations impact mitochondrial function. In this short review, I will discuss how we can use some of this information to understand why it is that neurons become dysfunctional in PD.
    Preview · Article · Jan 2010 · Movement Disorders
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    ABSTRACT: The prevalence of depression in Parkinson's disease (PD) varies greatly. In this study, we investigated major depressive disorder (MDD) and depressive symptoms without MDD in patients with PD. The psychopathological characteristics of depressive symptoms were assessed by a psychiatric interview. A total of 105 Japanese patients with PD without dementia were included. The Japanese version of the Beck Depression Inventory-II (BDI-II) with a cutoff score of 13/14 was used to screen for depression. Using a structured interview, a comprehensive psychiatric evaluation of patients with BDI-II scores >13 (high BDI patients) was completed using the criteria of the Diagnostic and Statistical Manual of Mental Disorders (DSM)-IV-TR. Forty patients (38%) had a BDI-II >13, but 29 did not show any depressed mood. Five cases met the criteria for MDD (three current, two past) and one patient was diagnosed with minor depressive disorder. A slight depressed mood that was associated with worrying about PD was seen in 6 of 34 patients without any depressive disorder and fluctuated with aggravation of PD symptoms in two of these patients. For the diagnosis of MDD, the number of positive items from the DSM-IV-TR definition of MDD is most important and useful for differentiating MDD and non-MDD. The low-prevalence rate of MDD in our patient population suggests that PD may be a psychological stressor for MDD, but does not necessarily induce MDD.
    Preview · Article · Jan 2010 · Movement Disorders
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