Neuroscience 2005 Abstract
| Presentation Number: | 360.4 |
|---|---|
| Abstract Title: | Haplotype-specific gene expression at the human <i>tau</i> locus. |
| Authors: |
Caffrey, T.*1
; Paracchini, S.1
; Wade-Martins, R.1
1Univ. of Oxford, Oxford, United Kingdom |
| Primary Theme and Topics |
Disorders of the Nervous System - Neurodegenerative and Movement Disorders -- Dementia: Tau |
| Session: |
360. Tau and Tau Kinases III Slide |
| Presentation Time: | Monday, November 14, 2005 8:45 AM-9:00 AM |
| Location: | Washington Convention Center - Room 152A |
| Keywords: | MAPT, GENE EXPRESSION, NEURODEGENERATION, GENETICS |
The human MAPT, or tau, locus is divided into two haplotypes, H1 and H2, with H1 being associated with the sporadic neurodegenerative dementias, Progressive Supranuclear Palsy (PSP) and Corticobasal Degeneration (CBD). In PSP and CBD it has been shown there is an increase in expression of transcript and protein incorporating exon 10, encoding an extra microtubule binding repeat, in brain regions affected by neurodegeneration.
We therefore propose that polymorphisms within the MAPT H1 haplotype sequence are responsible for subtle, higher levels of exon 10+, or 4R, tau transcript expression from H1 chromosomes, leading, over time, to a greater susceptibility to neurodegenerative disease. To investigate this hypothesis, we examined allele-specific expression in heterozygous cell lines and post-mortem brain tissues. The expression assays use haplotype-defining SNPs to perform allele-specific primer extensions, followed by quantitation of the extension products on the Sequenom MALDI-TOF platform.
We first identified two heterozygous H1/H2 neuroblastoma cell lines from a panel of 14 which we then differentiated using retinoic acid and brain-derived neurotrophic factor to express neuronal markers. MAPT expression analysis in differentiated cells showed greater H1 expression compared to H2 in both total tau, and exon 10+, transcripts. We then genotyped 20 pathology-free and 5 PSP post-mortem brain tissue samples from the Oxford Project to Investigate Memory and Ageing and identified six H1/H2 heterozygotes, including one PSP case. Tau mRNA expression was examined in the globus pallidus and the frontal cortex, areas affected in PSP and CBD, respectively. Using two coding SNPs in exon 9 to specifically tag transcripts from each haplotype we have found a significant overrepresentation of the H1 transcript in total cellular exon 10+ MAPT mRNA, a result consistent with our original hypothesis. To investigate these results in greater detail, we have developed an allele specific RT-PCR assay which will determine the relative ratio of 3R:4R tau expression from each chromosome in our H1/H2 samples.
We therefore propose that polymorphisms within the MAPT H1 haplotype sequence are responsible for subtle, higher levels of exon 10+, or 4R, tau transcript expression from H1 chromosomes, leading, over time, to a greater susceptibility to neurodegenerative disease. To investigate this hypothesis, we examined allele-specific expression in heterozygous cell lines and post-mortem brain tissues. The expression assays use haplotype-defining SNPs to perform allele-specific primer extensions, followed by quantitation of the extension products on the Sequenom MALDI-TOF platform.
We first identified two heterozygous H1/H2 neuroblastoma cell lines from a panel of 14 which we then differentiated using retinoic acid and brain-derived neurotrophic factor to express neuronal markers. MAPT expression analysis in differentiated cells showed greater H1 expression compared to H2 in both total tau, and exon 10+, transcripts. We then genotyped 20 pathology-free and 5 PSP post-mortem brain tissue samples from the Oxford Project to Investigate Memory and Ageing and identified six H1/H2 heterozygotes, including one PSP case. Tau mRNA expression was examined in the globus pallidus and the frontal cortex, areas affected in PSP and CBD, respectively. Using two coding SNPs in exon 9 to specifically tag transcripts from each haplotype we have found a significant overrepresentation of the H1 transcript in total cellular exon 10+ MAPT mRNA, a result consistent with our original hypothesis. To investigate these results in greater detail, we have developed an allele specific RT-PCR assay which will determine the relative ratio of 3R:4R tau expression from each chromosome in our H1/H2 samples.
Supported by Wellcome Trust
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2005 Neuroscience Meeting Planner. Washington, DC: Society for Neuroscience, 2005. Online.
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