1. Avaliar a associação do sub-haplótipo H1c com os índices neuropatológicos e cognição. Dados disponíveis:
- H1c está associado ao acúmulo de emaranhados neurofibrilares - H1c está associado a maior declínio cognitivo
2. Investigar a associação dos haplótipos e subhaplótipos com a doença de Parkinson. 3. Ampliar as análises eQTL(expression quantitative trait loci):
- Planejamos avaliar a interação do lócus MAPT com outros genes como APOE, SNCA e LRRK2 (trans-eQTL) e sua influência nas características motoras e cognitivas
4. Examinar a influências do splicing alternativo MAPT e índices neurpatológicos. Dados disponíveis:
- Menor nível da isoforma 202 (1N/4R) está associada a menor acúmulo de emaranhados neurofibrilares
- Maior nível de expressão da isoforma 002 (0N/4R) está associado ao maior acúmulo de emaranhados neurofibrilares.
4. Investigar o papel da epigenética no parkinsonismo em idosos e DP: - Metilação de DNA.
CONCLUSÕES
1. Parkinsonismo e, principalmente, bradicinesia em indivíduos idosos estavam associados ao haplótipo MAPT H2 do gene MAPT.
2. O haplótipo H2 estava fortemente associado a menor expressão de RNA total do gene MAPT.
3. Apesar do parkinsonismo global e seus quatro components não estarem associados com a expressão total MAPT, maiores escores de bradicinesia mostraram-se
associados a menor expressão da isoforma 1N/4R.
4. O haplótipo MAPT H2 também estava associado a menor expressão de 1N/4R, única isoforma associada ao parkinsonismo em idosos.
5. Quando adicionados ao mesmo modelo, a isoforma 1N/4R reduz o efeito do haplótipo H2 na bradicinesia em 16%, demonstrando que seu efeito é independente. 6. Observamos ainda que a idade estava independentemente associada a maiores escores de parkinsonismo e menor nível de expressão total MAPT.
7. Baseado em nossos resultados, sugerimos os seguintes mecanismos que podem contribuir para o surgimento de parkinsonismo, e principalmente bradicinesia, em idosos:
a) Splicing alternativo via menor expressão da isoforma 1N/4R. Desequilíbrio na expressão de isoformas tau-3R e 4R.
b) Presença do haplótipo H2 via menor expressão total de RNA do gene MAPT: disfunção metabólica neuronal e interação com agregados proteicos e DCV.
c) Avançar da idade via menor expressão total de RNA do gene MAPT: disfunção metabólica neuronal e interação com agregados proteicos e DCV.
d) Presença de H2 via mecanismos epigenéticos: metilação, acetilação de histonas, micro RNA.
SUMMARY
In prior work we have shown that the Parkinson’s Disease (PD) susceptibility locus
MAPT is associated with mild parkinsonian signs in older adults without a clinical
diagnosis of PD, but the biology underlying this association is unknown. Several studies have demonstrated that MAPT major haplotype H1 and subhaplotype H1c are associated with neurodegenerative diseases like Parkinson’s Disease, Alzheimer’s Disease, Progessive Supranuclear Palsy and Cortico-Basal Degeneration. Here, we refine our analysis of this important locus and assess the effect of MAPT haplotypes on alternative splicing and expression levels of MAPT to investigate the relation of transcriptomic effects to parkinsonism in older adults. We used ante-mortem and post-mortem data from participants in two clinicopathologic studies of aging, the Religious Order Study and the Memory and Aging Project. A measure of global parkinsonism and certain of its component measures such as bradykinesia, rigidity, tremor, and gait impairment were collected prospectively on an annual basis. In separate regression analyses The MAPT H2 haplotype was associated with lower total
MAPT expression (p=1.2x10-14) and global parkinsonism at both study entry
(p=0.0013) and proximate to death (p = 0.050). Specifically, haplotype H2 is primarily associated with bradykinesia in both assessments (p=0.00034 and p=0.0086). These associations remained following exclusion of subjects with PD diagnosis. Subhaplotype H1c is not associated with these traits. Moreover, we found that MAPT total expression is associated with age and decreases linearly with advancing age (p=0.00006). When we analysed MAPT alternative splicing, the expression of one isoform was inversely associated with global parkinsonism (p=0.0080) and bradykinesia (p=0.0089). Diminished 1N/4R isoform expression is also associated with H2 (p=0.0014), but their effects on bradykinesia are independent
(p_1N4R = 0.017, p_H2 = 0.12). Overall, these findings suggest that both, lower expression of MAPT haplotype H2 compared with H1 and MAPT alternative splicing and age, may partially account for the association of MAPT and parkinsonism in older adults and in some extent to age-related neurodegenerative diseases.
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The role of MAPT haplotype H2 and isoform 1N/4R in Parkinsonism of older adults
Guilherme T. Valenca, MD1,2,3,5, Gyan P. Srivastava, PhD3,5, Jamary Oliveira-Filho MD, MS, PhD2, Charles C. White, PhD3,4,5, Lei Yu, PhD6, Julie A. Schneider, MD6, Aron S. Buchman, MD6, Joshua M. Shulman MD, PhD 7,8, David A. Bennett, MD6, Philip L. De Jager, MD, PhD3,4,5
1. Movement Disorders Clinic, Roberto Santos General Hospital – Secretary of Health of State of Bahia, Brazil
2. Post-Graduate Program in Health Sciences, Federal University of Bahia, Salvador, BA, Brazil
3. Program in Translational Neuropsychiatric Genomics, Departments of Neurology & Psychiatry, Brigham and Women’s Hospital
4. Harvard Medical School
5. Program in Medical and Population Genetics, Broad Institute 6. Rush Alzheimer’s Disease Center, Rush University Medical Center
7. Departments of Neurology, Molecular and Human Genetics, and Neuroscience, and Program in Developmental Biology, Baylor College of Medicine, Houston, TX
8. Jan and Dan Duncan Neurological Research Institute, Texas Children’s Hospital, Houston, TX
Word count: 2,713 (Not including abstract, acknowledgement or references). Authors’ Contribution: all authors have participated actively in this project, and all
have seen and approved the final version of the paper.
Conflict of Interest: none of the authors has any direct or indirect conflicts of
interest, financial or otherwise, relating to the subject of our report.
Corresponding Author:
Philip L. De Jager, MD, PhD
Department of Neurology, Brigham and Women’s Hospital 77 Avenue Louis Pasteur, NRB 168C
Boston, MA 02115 Phone: 617 525-4529 Fax: 617 525-5333
ABSTRACT
Importance: In prior work we have shown that the Parkinson’s disease susceptibility
locus MAPT is associated with mild parkinsonian signs in older adults without a clinical diagnosis of PD. However, the molecular mechanism underlying this association is unknown.
Objective: We investigate the relationship between parkinsonism and MAPT
transcripts in older adults by assessing the effect of MAPT haplotypes on alternative splicing and expression levels of the most common isoforms.
Design: MAPT haplotypes, H1 and H2, subhaplotype H1c and RNA isoforms were examined in two cohorts of older individuals.
Setting: Two prospective clinicopathologic studies of aging, the Religious Order Study (ROS) and the Rush Memory and Aging Project (MAP).
Participants: For haplotype analysis, we evaluated 976 subjects with clinical,
genotyping and brain pathology data. For transcript analysis, we obtained MAPT gene and isoform-level expression from the dorsolateral prefrontal cortex for 505 of these subjects.
Main outcome measures: Using regression analysis, controlling for age, sex, study and neuropathology, we investigated the association of MAPT haplotypes and expression levels with global parkinsonism and specific parkinsonian signs.
Results: The MAPT H2 haplotype was associated with lower total MAPT expression (p=1.2x10-14) and global parkinsonism at both study entry (p=0.0013) and proximate to death (p = 0.050). Specifically, haplotype H2 is primarily associated with
bradykinesia in both assessments (p=0.00034 and p=0.0086). These associations remained following exclusion of subjects with PD diagnosis. Subhaplotype H1c is not associated with these traits. Moreover, we found that MAPT total expression is
associated with age and decreases linearly with advancing age (p=0.00006). When we analysed MAPT alternative splicing, the expression of one isoform was inversely associated with global parkinsonism (p=0.0080) and bradykinesia (p=0.0089). Diminished 1N/4R isoform expression is also associated with H2 (p=0.0014), but their effects on bradykinesia are independent (p_1N4R = 0.017, p_H2 = 0.12).
Conclusions and Relevance: Overall, our results suggest that age and H2 are
associated with higher parkinsonism score and decreased total MAPT RNA expression. Additionally, we found that H2 is associated with altered expression levels of specific isoforms. These findings may contribute to the understanding of the association between MAPT locus and parkinsonism in elderly subjects.
INTRODUCTION
Parkinsonian signs, characterized by bradykinesia, rigidity, tremor and gait disturbance, are common in older individuals1 and are associated with functional impairment, higher risk of cognitive decline, dementia and mortality2. Recently, several reports demonstrated an association between pathology in brainstem nuclei and cerebrovascular lesions with mild parkinsonism3,4. In previous work, we have shown that the Parkinson’s disease (PD) susceptibility locus MAPT is associated with mild parkinsonism in older adults without a clinical diagnosis of PD, but the
biological mechanism underlying this association is unknown5. The MAPT gene lies on chromosome 17q21, and its encoded protein Tau is involved in microtubule stability and interaction with the cytoskeleton6. Six isoforms of this protein, resulting from alternative splicing of exons 2, 3 and 10, are expressed in the adult human brain7. In the region containing MAPT, a single nucleotide polymorphism (SNP) tags
the two major haplotype clades, termed H1 and H2, which are defined by a large inversion containing MAPT as well as several other genes. Many studies in the past decade have shown that this locus affects disease risk: H1 and its sub haplotype H1c are reported to be associated with increased risk for certain age-related
neurodegenerative diseases, including PSP8,9,10,11, CBD10,11, Multiple System Atrophy
(MSA)12 and PD13,14. These nosological entities also share a clinical spectrum ranging from parkinsonism to dementia. Moreover, MAPT alternative splicing and expression have been shown to be important in neuropathological processes6,15. Our study refines the role of this locus in age-related parkinsonism and examines the hypothesis that the role of the MAPT haplotypes in age-related parkinsonism in older adults from the Religious Orders Study16 and Rush Memory Aging Project (MAP)17 may be mediated, in part, by alternative splicing. Exploring the pathophysiology of
mild parkinsonism in older individuals can lead us to a better understanding of motor phenotypes in age-related neurodegenerative diseases.
METHODS
Subjects selection from Cohort
All of the samples used in this project are from autopsied brains obtained from participants in two longitudinal studies of aging, the Religious Orders Study (ROS)16, started in 1994, and Rush Memory and Aging Project (MAP)17, started in 1997. Both studies were approved by the Institutional Review Board of Rush University Medical Center. All subjects were older and free of known dementia at the time of enrollment and were followed annually with detailed clinical evaluations with a signed informed consent and an Anatomical Gift Act for brain donation. In total, over 3,000
participants have enrolled and 1,200 autopsied to date. Of these, 976 brains were available for the present study.
Genotyping
DNA was extracted from whole blood, lymphocytes, or frozen postmortem brain tissue. Genotyping was done in three subsets. Genotyping of the first two sets of samples were generated using Affymetrix GeneChip 6.0 platform in 2009 at the Broad Institute’s Center for Genotyping, and the third set of samples were genotyped