Genome Wide Association Studies (GWAS) en Enfermedad de Parkinson

Asociaciones validadas entre variantes genéticas y riesgo de EP

Recién vuelvo del Congreso de la MDS en Buenos Aires.

Algunas notas en relación a variantes actualmente validadas en genes asociadas al riesgo de desarrollar EP "esporádico" o "multifactorial".

Gene: GBA
Variante: mutaciones loss of function en heterocigosis
Nota: más frecuente en judíos azhkenazi
Ref.: N Eng J Med 2009;361:1651-1661

Gene: SNCA
Variante: Rep 1 (promotor)
Nota: alteraciones de la expresión génica de alfa sinucleína
Ref.: JAMA 2006;296:661-670

Gene: MAPT
Variante: H1/H2 (inversión de región que incluye al gene completo)
Nota: mutaciones en este gene causantes de demencia FT con parkinsonismo-17
Ref.: Ann Neurol. 2007 Aug;62(2):137-44

Gene: LRRK2
Variantes: R1628P y G2385R
Nota: asociación solamente demostrada en asiáticos
Ref.: Neuroreport 2007;18:273-275

Uno de los fundadores de Google y la investigación en Genética de la Enfermedad de Parkinson

Artículo en Revista Wired.

MDS en Buenos Aires 2010

Ya está disponible el programa científico del 14th International Congress of Parkinson´s Disease and Movement Disorders.
Allí estaremos.

Google, 23andme y financiación para investigación en genética de la Enfermedad de Parkinson

Sergey Brin, co-fundador de la empresa Google, donará millones de dólares para financiar investigaciones sobre los factores genéticos y ambientales que provocan la Enfermedad de Parkinson (EP).

Los estudios genómicos se llevarán a cabo en la empresa 23andMe, un emprendimiento comercial co-fundado por su esposa Anna Wojcicki.

De la información liberada se desprende que planean reclutar on-line a un amplio grupo de pacientes para formar una cohorte bien caracterizada a nivel clínico y de factores ambientales que pudieran promover el desarrollo de EP (también mediante formularios online). De la misma manera generarán un grupo de controles sanos (usuarios del servicio de 23andme que den su consentimiento).

Con las posibilidades de genotipeado de esta empresa, o mediante convenios con centros de investigación genómica, se pueden desarrollar diversos métodos de búsqueda de genes involucrados en al EP. Varios de los cuales ya se han utilizado y han dado buenos resultados hasta el momento. Es de imaginar que con grandes números de pacientes, con una buena base de datos aportados por los voluntarios y la potencia de las nuevas tecnologías de análisis genómico, esta cohorte puede ser una herramienta poderosa en la investigación de las causas de la EP.

Estaremos atentos a ver qué ocurre.

Algunos links adicionales sobre el tema:

The Times 12/3/2009 'Google founder Sergey Brin pays for Parkinson's gene trial'
The Times 12/3/2009 'Google's Sergey Brin and Larry Page harness data to fight disease'
The New York Times 12/3/2009 'Google co-founder backs vast Parkinson's study'

Avances en patogenia de la EP

Recientemente fue publicado el comentario:

Rejko Krüger, LRRK2 in Parkinson's disease – drawing the curtain of penetrance: a commentary, BMC Medicine 2008, 6:33.

Sobre el trabajo:

Latourelle JC, Sun M, Lew MF, Suchowersky O, Klein C, Golbe LI, Mark MH, Growdon JH, Wooten F, et al.: The G2019S mutation in LRRK2 is not fully penetrant: The GenePD study. BMC Medicine 2008; 6:32.

Se trata de una excelente y breve revisión de la genética de la EP en general y de la asociada a la mutación G2019S del gene LRRK2. El autor comenta el trabajo mencionado, que muestra una penetrancia incompleta de esta mutación y un efecto de genes modificadores del efecto de la misma. Muestra como la complejidad etiológica y de los mecanismos que llevan a la EP se va desentrañando a partir de los estudios de genética molecular.

Otro excelente trabajo que colabora en este sentido es:

Aaron D Gitler, Alessandra Chesi, Melissa L Geddie, Katherine E Strathearn, Shusei Hamamichi, Kathryn J Hill et al, a-Synuclein is part of a diverse and highly conserved interaction network that includes PARK9 and manganese toxicity, Nature Genetics 2008; doi:10.1038/ng.300.

En el mismo, los autores analizan las interacciones proteicas de la alfa sinucleína con otra de las proteínas involucradas en la EP: ATP13A2 (PARK9). Además muestran el efecto de la alfa sinucleína como protectora sobre la exposición al manganeso (reportado como un factor ambiental que favorece la aparicion de EP).

Personal Genome Project en Wired Magazine

Un interesante articulo sobre un interesante proyecto para la Medicina Genomica.

Mutaciones y EP en Uruguay primeros datos

Recientemente se han publicado los primeros estudios moleculares en pacientes uruguayos con EP. Los primeros resultados muestran que casi un 5% de los pacientes urguayos de EP tienen una de las dos mutaciones frecuentes en el gene LRRK2 (PARK8).


Parkinsonism Relat Disord. 2008 Nov 1.

LRRK2 mutations in patients with Parkinson's disease from Peru and Uruguay.

Mata IF, Cosentino C, Marca V, Torres L, Mazzetti P, Ortega O, Raggio V, Aljanati R, Buzó R, Yearout D, Dieguez E, Zabetian CP.

Geriatric Research Education and Clinical Center, VA Puget Sound Health Care System, Seattle, WA, USA; Department of Neurology, University of Washington, Seattle, WA, USA.

Variation in the leucine-rich repeat kinase 2 (LRRK2) gene represents the most common genetic determinant of Parkinson's disease (PD) identified to date. While the frequency and distribution of LRRK2 mutations have been well-studied in Europe and North America, few data are available from South America. To address this gap in knowledge, we screened two cohorts of patients with PD from Peru (n=240) and Uruguay (n=125) for the three most common LRRK2 mutations (R1441C, R1441G, G2019S). We identified at total of seven patients with mutations, one with R1441G, and six with G2019S. The carrier frequency was significantly greater in the Uruguayan cohort (4.8%) than in the Peruvian cohort (0.4%; p=0.007). This likely resulted from a greater admixture proportion in the Peruvian sample. Haplotype analyses suggested that G2019S was probably brought to Peru and Uruguay by European settlers. In contrast, the origin of R1441G in our cohort was not clear, as the patient with this mutation had a background haplotype that was clearly distinct from that reported in carriers from Europe and North America. Our data add to a growing body of evidence indicating that LRRK2 mutations are widely distributed across South America but might differ by region in prevalence.

Nuevos factores de riesgo genéticos para la enfermedad de Parkinson

A larga lista de variantes genéticas que reportábamos días atrás, y la aun mas larga lista en exploración, debemos agregar la confirmación de estas dos variantes que actúan como significativos factores de riesgo de EP multifactorial, es decir, aquellas formas que, en general, aparecen esporádicamente y con un inicio tardío (que constituyen la mayoría de los casos de EP).

Así como en los últimos anos se han delineado bien las formas de EP causadas por genes de efecto mayor (monogénicas o cuasi-monogénicas) parece irse conformando un “perfil genómico de riesgo” de EP, de forma similar a como se ha ido conformando para otras afecciones (fundamentalmente la enfermedad cardiovascular arteriosclerótica).


J Neural Transm. 2008 Aug;115(8):1141-8. Epub 2008 Apr 30.
A comprehensive genetic study of the proteasomal subunit S6 ATPase in German Parkinson's disease patients.
Wahl C, Kautzmann S, Krebiehl G, Strauss K, Woitalla D, Müller T, Bauer P, Riess O, Krüger R.
Laboratory of Functional Neurogenomics, Center of Neurology and Hertie-Institute for Clinical Brain Research, University of Tübingen, Hoppe-Seyler-Str. 3, 72076, Tubingen, Germany.
Dysfunction of proteasomal protein degradation is involved in neurodegeneration in Parkinson's disease (PD). Recently we identified the regulatory proteasomal subunit S6 ATPase as a novel interactor of synphilin-1, which is a substrate of the ubiquitin-ligase Parkin (PARK2) and an interacting protein of alpha-synuclein (PARK1). To further investigate a potential role in the pathogenesis of PD, we performed a detailed mutation analysis of the S6 ATPase gene in a large sample of 486 German sporadic and familial PD patients. Direct sequencing revealed two novel intronic variants. An insertion/deletion variant in intron 5 of the S6 ATPase gene was more frequent in patients compared to controls. Moreover, this variant was significantly more frequent in early-onset compared to late-onset PD patients. The identification of a genetic link between a regulatory proteasomal subunit and PD further underscores the relevance of disturbed protein degradation in PD.


Hum Genet. 2008 Oct;124(3):287-8. Epub 2008 Sep 10.
LRRK2 R1628P increases risk of Parkinson's disease: replication evidence.
Tan EK, Tan LC, Lim HQ, Li R, Tang M, Yih Y, Pavanni R, Prakash KM, Fook-Chong S, Zhao Y.
Department of Neurology, Singapore General Hospital, National Neuroscience Institute, Outram Road, Singapore, 169608, Singapore. gnrtek@sgh.com.sg
We showed that the frequency of a LRRK2 variant (c.4883G > C, R1628P) was higher in Parkinson's disease (PD) compared to controls (8.4 vs. 3.4%, P = 0.046, OR 2.5, 95% CI 1.1-5.6). In the multivariate logistic regression (with adjustments made for the effect of age, age of onset, and gender), the heterozygous R1628P genotype was associated with an increased risk of PD compared to controls (OR 3.3, 95% CI 1.4- 7.9, P = 0.007). We provided an independent confirmation that the R1628P variant increases the risk of PD among Chinese.

Ensayos de Terapia Génica en Enfermedad de Parkinson

Estos son los ensayos publicados recientemente sobre Terapia Génica en EP.
Han sido realizados en modelos animales, células en cultivo y en seres humanos (Fase I).


Neurology. 2008 May 20;70(21):1980-3. Epub 2008 Apr 9.
Results from a phase I safety trial of hAADC gene therapy for Parkinson disease.
Eberling JL, Jagust WJ, Christine CW, Starr P, Larson P, Bankiewicz KS, Aminoff MJ.
Department of Molecular Imaging and Neuroscience, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. jleberling@lbl.gov
BACKGROUND: In a primate model of Parkinson disease (PD), intrastriatal infusion of an adeno-associated viral (AAV) vector containing the human aromatic l-amino acid decarboxylase (hAADC) gene results in robust gene expression. After gene transfer, low doses of systemically administered l-dopa are converted to dopamine in the transduced striatal neurons, resulting in behavioral improvement without the side effects typically associated with higher doses of l-dopa. These studies led to the initiation of a phase I safety trial. Here we report the findings for the first cohort of five patients. METHODS: Patients with moderate to advanced PD received bilateral infusion of a low dose of the AAV-hAADC vector into the putamen. PET scans using the AADC tracer, 6-[18F]fluoro-l-m-tyrosine (FMT), were performed at baseline and at 1 and 6 months after infusion as an in vivo measure of gene expression. RESULTS: PET results showed an average 30% increase in FMT uptake (K(i)(c)) in the putamen after gene transfer. Preliminary analysis of clinical data indicates a modest improvement, but absence of a control and the nonblinded analyses make interpretation difficult. CONCLUSIONS: Thus far, this gene therapy approach has been well tolerated and shows PET evidence of sustained gene expression. These initial findings demonstrate the safety of the therapy; higher doses of adeno-associated viral vector containing the human aromatic l-amino acid decarboxylase gene in the next cohort of patients may further increase dopamine production in the putamen and provide more profound clinical benefit.

Lancet. 2007 Jun 23;369(9579):2097-105.
Safety and tolerability of gene therapy with an adeno-associated virus (AAV) borne GAD gene for Parkinson's disease: an open label, phase I trial.
Kaplitt MG, Feigin A, Tang C, Fitzsimons HL, Mattis P, Lawlor PA, Bland RJ, Young D, Strybing K, Eidelberg D, During MJ.
Department of Neurological Surgery, Weill Medical College of Cornell University, New York, NY, USA.
BACKGROUND: Dopaminergic neuronal loss in Parkinson's disease leads to changes in the circuitry of the basal ganglia, such as decreased inhibitory GABAergic input to the subthalamic nucleus. We aimed to measure the safety, tolerability, and potential efficacy of transfer of glutamic acid decarboxylase (GAD) gene with adeno-associated virus (AAV) into the subthalamic nucleus of patients with Parkinson's disease. METHODS: We did an open label, safety and tolerability trial of unilateral subthalamic viral vector (AAV-GAD) injection in 11 men and 1 woman with Parkinson's disease (mean age 58.2, SD=5.7 years). Four patients received low-dose, four medium-dose, and four high-dose AAV-GAD at New York Presbyterian Hospital. Inclusion criteria consisted of Hoehn and Yahr stage 3 or greater, motor fluctuations with substantial off time, and age 70 years or less. Patients were assessed clinically both off and on medication at baseline and after 1, 3, 6, and 12 months at North Shore Hospital. Efficacy measures included the Unified Parkinson's Disease Rating Scale (UPDRS), scales of activities of daily living (ADL), neuropsychological testing, and PET imaging with 18F-fluorodeoxyglucose. The trial is registered with the ClinicalTrials.gov registry, number NCT00195143. FINDINGS: All patients who enrolled had surgery, and there were no dropouts or patients lost to follow-up. There were no adverse events related to gene therapy. Significant improvements in motor UPDRS scores (p=0.0015), predominantly on the side of the body that was contralateral to surgery, were seen 3 months after gene therapy and persisted up to 12 months. PET scans revealed a substantial reduction in thalamic metabolism that was restricted to the treated hemisphere, and a correlation between clinical motor scores and brain metabolism in the supplementary motor area. INTERPRETATION: AAV-GAD gene therapy of the subthalamic nucleus is safe and well tolerated by patients with advanced Parkinson's disease, suggesting that in-vivo gene therapy in the adult brain might be safe for various neurodegenerative diseases.

J Gene Med. 2007 Jul;9(7):605-12.
Comparison of cDNA and genomic forms of tyrosine hydroxylase gene therapy of the brain with Trojan horse liposomes.
Xia CF, Chu C, Li J, Wang Y, Zhang Y, Boado RJ, Pardridge WM.
Department of Medicine, UCLA, Los Angeles, CA 90024, USA.
BACKGROUND: The present study examines whether chromosomal derived forms of therapeutic genes can be delivered to brain following intravenous administration. The brain expression of a rat tyrosine hydroxylase (TH) cDNA is compared to the brain expression of a plasmid DNA encoding the 18 kb rat TH gene. METHODS: TH gene expression is measured in cell culture and in vivo in brain in experimental Parkinson's disease (PD). A total of four eukaryotic expression plasmids encoding rat TH were engineered wherein the size of the TH expression cassette ranged from 1.5 kb, in the case of the cDNA form of the gene, to 17.5 kb, in the case of the largest size genomic construct. The TH expression plasmids were delivered to either cultured cells or to rat brain in vivo with Trojan horse liposomes (THLs), which target the non-viral plasmid DNA to cells via cell membrane receptors. RESULTS: The pattern of TH gene expression in cell culture and in vivo was similar: the cDNA form of the TH gene was fast-acting with short duration of action, and the genomic form of the TH gene was slow-acting with longer duration of action. The most sustained replacement of striatal TH enzyme activity in experimental PD was produced by combination gene therapy where both the cDNA and the genomic forms of the TH gene were administered simultaneously. CONCLUSIONS: Eukaryotic expression plasmids encoding genomic forms of therapeutic genes, as large as 18 kb, can be successfully incorporated in THLs and delivered to brain following intravenous administration.

Gene Ther. 2006 Dec;13(23):1639-44.
Koike H, Ishida A, Shimamura M, Mizuno S, Nakamura T, Ogihara T et al, Prevention of onset of Parkinson's disease by in vivo gene transfer of human hepatocyte growth factor in rodent model: a model of gene therapy for Parkinson's disease.
Division of Clinical Gene Therapy, Graduate School of Medicine, Osaka University, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan.
Parkinson's disease (PD) is a neurodegenerative disorder characterized by the loss of dopaminergic neurons in the substantia nigra (SNi). As neurotrophic factors support the survival and enhance the function of dopaminergic neurons, gene therapy using neurotrophic factors has become the center of interest. Thus, we focused on hepatocyte growth factor (HGF) as a neurotrophic and angiogenic growth factor. At 7 days before injection of 6-hydroxydopamine into the SNi, stereotaxic transfection of human HGF or lacZ plasmid was performed into the unilateral striatum of rats. Expression of human HGF in the injected sites could be detected in rats transfected with HGF plasmid DNA, using immunohistochemical staining. Consistently, human immunoreactive HGF protein could be detected at least up to 12 days after transfection. Interestingly, PD rats transfected with lacZ demonstrated amphetamine-induced rotational asymmetry. However, transfection of HGF plasmid DNA resulted in significant inhibition of abnormal rotation up to 24 weeks in a dose-dependent manner. Over 90% of dopaminergic neurons were lost in PD rats transfected with lacZ, whereas over 70% survived in rats transfected with HGF, as assessed by immunohistochemical staining. Overall, the present study demonstrated that overexpression of HGF prevented neuronal death in a PD rat model, providing a potential novel therapy for PD.