Browsing by Author "Guerreiro, RJ"
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- Analysis of Parkinson disease patients from Portugal for mutations in SNCA, PRKN, PINK1 and LRRK2.Publication . Brás, JM; Guerreiro, RJ; Morgadinho, A; Januário, C; Dias, M; Calado, A; Semedo, C; Oliveira, CR; Hardy, J; Singleton, ABACKGROUND: Mutations in the genes PRKN and LRRK2 are the most frequent known genetic lesions among Parkinson's disease patients. We have previously reported that in the Portuguese population the LRRK2 c.6055G > A; p.G2019S mutation has one of the highest frequencies in Europe. METHODS: Here, we follow up on those results, screening not only LRRK2, but also PRKN, SNCA and PINK1 in a cohort of early-onset and late-onset familial Portuguese Parkinson disease patients. This series comprises 66 patients selected from a consecutive series of 132 patients. This selection was made in order to include only early onset patients (age at onset below 50 years) or late-onset patients with a positive family history (at least one affected relative). All genes were sequenced bi-directionally, and, additionally, SNCA, PRKN and PINK1 were subjected to gene dosage analysis. RESULTS: We found mutations both in LRRK2 and PRKN, while the remaining genes yielded no mutations. Seven of the studied patients showed pathogenic mutations, in homozygosity or compound heterozygosity for PRKN, and heterozygosity for LRRK2. CONCLUSION: Mutations are common in Portuguese patients with Parkinson's disease, and these results clearly have implications not only for the genetic diagnosis, but also for the genetic counseling of these patients.
- Association of HFE common mutations with Parkinson's disease, Alzheimer's disease and mild cognitive impairment in a Portuguese cohort.Publication . Guerreiro, RJ; Brás, JM; Santana, I; Januário, C; Morgadinho, A; Ribeiro, MH; Hardy, J; Singleton, A; Oliveira, CRBACKGROUND: Pathological brain iron deposition has been implicated as a source of neurotoxic reactive oxygen species in Alzheimer (AD) and Parkinson diseases (PD). Iron metabolism is associated with the gene hemochromatosis (HFE Human genome nomenclature committee ID:4886), and mutations in HFE are a cause of the iron mismetabolism disease, hemochromatosis. Several reports have tested the association of HFE variants with neurodegenerative diseases, such as AD and PD with conflicting results. METHODS: Genotypes were analysed for the two most common variants of HFE in a series of 130 AD, 55 Mild Cognitive Impairment (MCI) and 132 PD patients. Additionally, a series of 115 healthy age-matched controls was also screened. RESULTS: A statistically significant association was found in the PD group when compared to controls, showing that the presence of the C282Y variant allele may confer higher risk for developing the disease. CONCLUSION: Taken together these results suggest that the common variants in HFE may be a risk factor for PD, but not for AD in the Portuguese population.
- G2019S dardarin substitution is a common cause of Parkinson's disease in a Portuguese cohort.Publication . Brás, JM; Guerreiro, RJ; Ribeiro, MH; Januário, C; Morgadinho, A; Oliveira, CR; Hardy, J; Singleton, ALRRK2 mutations have recently been described in families with Parkinson's disease. Here we show that one of them (G2019S) is present in 6% (7 of 124) unrelated cases of disease in a clinic-based sample series from central Portugal, but not present in 126 controls from the same population. Thus, LRRK2 mutations appear to be a common cause of typical Parkinson's disease and as such will alter clinical practice.
- Genetic screening of Alzheimer's disease genes in Iberian and African samples yields novel mutations in presenilins and APPPublication . Guerreiro, RJ; Baquero, M; Blesa, R; Boada, M; Bras, JM; Bullido, MJ; Calado, A; Crook, R; Ferreira, C; Frank, A; Machado, A; Oliveira, CR; Santana, IMutations in three genes (PSEN1, PSEN2, and APP) have been identified in patients with early-onset (<65 years) Alzheimer's disease (AD). We performed a screening for mutations in the coding regions of presenilins, as well as exons 16 and 17 of the APP gene in a total of 231 patients from the Iberian peninsular with a clinical diagnosis of early-onset AD (mean age at onset of 52.9 years; range 31-64). We found three novel mutations in PSEN1, one novel mutation in PSEN2, and a novel mutation in the APP gene. Four previously described mutations in PSEN1 were also found. The same analysis was carried in 121 elderly healthy controls from the Iberian peninsular, and a set of 130 individuals from seven African populations belonging to the Centre d'Etude du Polymorphisme Humain-Human Genome Diversity Panel (CEPH-HGDP), in order to determine the extent of normal variability in these genes. Interestingly, in the latter series, we found five new non-synonymous changes in all three genes and a presenilin 2 variant (R62H) that has been previously related to AD. In some of these mutations, the pathologic consequence is uncertain and needs further investigation. To address this question we propose and use a systematic algorithm to classify the putative pathology of AD mutations.