RNA Aptamer Selection Against Alpha-Synuclein As a Diagnostic Tool For Parkinson’s Disease

Full Proposal

Final Manuscript

Alpha-synuclein (asynuc) is the primary component of Lewy bodies, which are known to be associated with Parkinson’s disease and other Lewy Body Diseases (Yokota et al. 2010). Aggregation and improper folding of asynuc can lead to the formation of Lewy bodies. This can cause damage to neurons and lead to cell death, which disrupts dopamine pathways in the brain.

Figure 1.) Lewy Body presentation in a human SN neuron. The Lewy Body is the blurry purple circle in the center of the photo. (from http://neuropathology.neoucom.edu/chapter9/images9/9-lb2.jpg)

Currently, the diagnosis of PD is based on the patient’s medical history and a neurological examination for deficient motor function. However, the accuracy of diagnosis is between 75 and 90% because many cases have uncommon presentations, especially in the early stages of the disease. The most accurate diagnosis of PD comes from finding Lewy bodies in the brain during autopsy.

Asynuc has been shown to accumulate in the cerebrospinal fluid and blood plasma of patients with PD (Tinsley et al.2010). An RNA aptamer with a high specificity and binding affinity for asynuc could be used to test the level of asynuc in a patient’s blood plasma. The aptamer would have a reporter sequence attached, which would indicate when the aptamer was bound to its target. An elevated level of asynuc would signify the presence of PD and could be a very useful diagnostic and research tool for the disease.

An antibody and DNA aptamer for asynuc have already been discovered. An RNA aptamer will expand PD research opportunities and might be more effective in reporting elevated levels of asynuc. RNA aptamers for asynuc will be selected for using the SELEX method. The specific aims of this project are to find an aptamer with high affinity and specificity for asynuc and to attach a reporter sequence that will indicate when asynuc is attached to the aptamer.

Figure 2. ) An RNA aptamer with a reporter sequence can be selected for that signifies the presence of its target, asynuc, when bound. This can be used to find elevated levels of asynuc in blood plasma.

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References:

Scott, DA et al. (2010) "A pathologic cascade leading to synaptic dysfunction in alpha-synuclein-induced neurodegeneration." J Neurosci. 30(24):8083-95.

Tinsley,RB et al. (2010) "Sensitive and specific detection of alpha-synuclein in human plasma." J Neurosci. 88(12):2693-700.

Yokota, O et al. (2010) "Effect of topographical distribution of alpha-synuclein pathology on TDP-43 accumulation in Lewy body disease." Acta Neuropathol. [Epub ahead of print]

Tsukakoshi, K et al. (2010) "Screening of DNA aptamer which binds to alpha-synuclein." Biotechnol Lett. 32(5):643-8