Cerebrospinal fluid biomarker discovery in PSP and related tauopathies
Lead researchers Dr Rohan de Silva (from November 2006) and Professor Gavin Giovannoni (until November 2006)
Co-researchers Dr Connie Luk, Dr Janice Holton, Dr David Williams, Dr Kevin Mills, Professor Tamas Revesz, and Professor Andrew Lees
Institution Institute of Neurology, University College London
Duration 4 years
Start August 2005 End July 2009
Grant £156,395
Aims of research
To:
• establish a CSF, serum and DNA library on patients with suspected PSP, related tauopathies and other neurodegenerative diseases
• obtain pathological confirmation of the diagnosis where possible
• apply discovery-based technologies (proteomics) to the samples in an attempt to discover novel diagnostic markers
• validate markers in collaborative studies involving larger cohorts of subjects
About the research
The initial aim of this work was to establish a cerebrospinal fluid (CSF), serum and DNA library of patients with PSP and related disorders presenting at the movement disorders clinics at Queen Square. Following this, the bulk of the work would involve proteomics analysis of CSF with a view to identifying protein markers for the differential diagnosis of various movement disorders. A protocol is now in place whereby CSF and blood are obtained from patients presenting in clinic. CSF is stored at -80°C and DNA is isolated from the blood for genetic analysis. Due to delays in the installation of essential equipment at the core proteomics unit, we initiated the development of an alternate method for the sensitive and specific analysis of abnormal tau protein in the CSF.
Findings
The primary feature in the PSP brain is the abnormal accumulation of clumps of tau protein (called neurofibrillary tangles) within the nerve cells. Tau protein can be divided into three- or four- microtubule-binding repeat domains (3R-tau and 4R-tau) and in the healthy brain there are about equal levels of both. In PSP, there is a large increase in 4R-tau. In the mélange of tens of thousands of different proteins and protein variants within the cell forming the building blocks and functional elements, it may seem an impossible task tracking individual proteins. Yet we can do this by using antibodies which specifically recognize single proteins. In our laboratory we have developed two antibodies that recognize 3-R and 4-R tau and have used them to successfully develop an ‘enzyme-linked immunosorbent assay' (ELISA) that allows us to detect and compare the levels of 3R-tau and 4R-tau in the brain. Unfortunately, we have not yet achieved sufficient sensitivity for CSF-tau, which typically has 1000-10000 times less tau than the brain. Work is ongoing and our next step is to further improve the sensitivity of this ELISA to enable CSF measurements.
What will the outcome of this research mean for people with PSP?
The ELISA method we have developed will be useful in the postmortem diagnosis of PSP and in further PSP research.
CSF circulates continuously in the space around the brain and spinal cord. If brain components, including proteins leak into the space due to infection, injury or neurodegeneration, these may circulate with the CSF down the spinal cord. CSF can be obtained from patients by a relatively safe, painless and non-invasive method and may therefore give us a good surrogate for measuring components in the brain without having to resort to brain biopsy. Development of a method to measure 3R-tau and 4R-tau in CSF could therefore provide us with a tool to diagnose PSP and to diagnose it at an early stage. To date, definitive diagnosis of PSP can only be made by postmortem examination of the brain. A means to achieve earlier and better diagnosis would be of huge benefit to patients and would enable any new treatments to be administered at the earliest opportunity.
Publications arising from the research
Luk, C.M., Giovannoni, G., Williams, D.R., Lees, A.J., de Silva, R. (2008) Development of a sensitive ELISA for quantification of three repeat and four repeat tau isoforms in tauopathies (in preparation)
National/international presentations given on this work
Cure PSP (Society for PSP) International Symposium, Washington DC, November 2005
Weblink Reta Lila Weston Institute of Neurological Studies