Homozygous and heterozygous PINK1 mutations: Considerations for diagnosis and care of Parkinson's disease patients
ABSTRACT The first mutations described in PINK1 were homozygous. More recently, heterozygous mutations have been reported but the role of heterozygosity in disease pathogenesis is still debated. We describe two unrelated cases with PINK1 mutations (homozygous nonsense and heterozygous missense) that highlight issues regarding the role of heterozygous mutations and the utility of genetic screening in patient care.
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ABSTRACT: Background Mutations in the PINK1 gene are the second most frequent cause of autosomal recessive early-onset parkinsonism.Methods We evaluated five affected PINK1 homozygous and 14 heterozygous mutation carriers from two large Italian families over a 12-year follow-up period. Motor, nonmotor, cognitive, psychiatric, and behavioral profiles were systematically assessed. Four homozygotes and eight heterozygotes underwent magnetic resonance imaging.ResultsAll homozygotes showed a mild progression of motor signs and a persistent excellent response to levodopa. All but one patient complained of nonmotor symptoms and sleep impairment. Three presented impulse control disorders and two anxiety and apathy. All obtained abnormal scores at Montreal Cognitive Assessment (MoCA) and in tests sensitive to frontal functions; one presented a global cognitive impairment.Three heterozygotes showed motor signs and were diagnosed as possibly affected. They had nonmotor symptoms and cognitive impairment, and two of them showed mild bilateral temporal atrophy. Five unaffected heterozygotes reported abnormal scores at MoCA and low performances at tests sensitive to frontal functions.Conclusion We expanded the phenotypic profile of PINK1-related parkinsonism, including psychiatric and cognitive features as part of clinical presentation. © 2014 International Parkinson and Movement Disorder SocietyMovement Disorders 10/2014; 29(12). DOI:10.1002/mds.25994 · 5.63 Impact Factor
05/2012, Degree: PhD
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ABSTRACT: Background Recessive mutations in the PTEN-induced putative kinase 1 (PINK1) gene cause early-onset Parkinson's disease (EOPD). The clinical phenotype of families that have this PINK1-associated disease may present with different symptoms, including typical PD. The loss of the PINK1 protein may lead to mitochondrial dysfunction, which causes dopaminergic neuron death. Methods The clinical phenotypes of a large Polish family with EOPD and an identified PINK1 homozygous nonsense mutation were assessed. Ubiquitination and degradation of mitochondrial parkin substrates as well as mitochondrial bioenergetics were investigated as direct functional readouts for PINK1's kinase activity in biopsied dermal fibroblasts. Results A four-generation family was genealogically evaluated. Genetic screening identified two affected subjects who were both homozygous carriers of the pathogenic PINK1 p.Q456X substitution. Both patients presented with dystonia and gait disorders at symptom onset. Seven heterozygous mutation carriers remained unaffected. Functional studies revealed that the PINK1 p.Q456X protein is non-functional in activating the downstream ubiquitin ligase parkin and priming the ubiquitination of its substrates, and that the RNA levels of PINK1 were significantly reduced. Conclusions The PINK1 p.Q456X mutation leads to a decrease in mRNA and a loss of protein function. The foot dystonia and gait disorders seen at disease onset in affected members of our family, which were accompanied by parkinsonism had a similar clinical presentation to what has been described in previous reports of PINK1 mutation carriers.Parkinsonism & Related Disorders 09/2014; DOI:10.1016/j.parkreldis.2014.08.019 · 4.13 Impact Factor