Spinocerebellar ataxia type 10 (SCA10), an autosomal dominant cerebellar ataxia, is caused by a large expansion mutation of intronic ATTCT pentanucleotide repeat in the ATXN10 gene. Our studies have suggested that toxic RNA rather than altered function of the protein product of ATXN10 is the likely cause of SCA10. We showed that the untranslated RNA transcript of the expanded repeat is accumulated in intracellular foci and interacts with heterogeneous nuclear ribonucleoprotein K (hnRNP K). Preliminary data from cell culture and transgenic mouse models suggested that expression of (AUUCU) 500 repeats causes deleterious downstream events similar to those seen in cells and a brain of SCA10 patient. Knockdown of hnRNP K recapitulates some of these events in cell culture. The goal of this application is to demonstrate that the sequestration of hnRNP K plays a key role in SCA10 pathogenesis and to determine the relative contribution of this mechanism to the entire pathogenicity in SCA10. Our central hypothesis is that the major pathogenic mechanism of SCA10 is an RNA gain-of-function that causes functional loss of hnRNP K. To examine this hypothesis we propose: ? Aim 1: Demonstrate binding of the expanded AUUCU repeat RNA to hnRNP K. We will perform unbiased searches of interacting proteins by pull-down/mass spectroscopy studies and in-silico bioinformatics, followed by co-immunoprecipitation, electromobility shift assay and high-throughput crosslinking studies. ? Aim 2: Obtain evidence that hnRNP K sequestration causes neuronal dysfunction and cell death. We will recapitulate downstream changes found in the SCA10 brain and SCA10 models, such as activation of apoptotic pathways and abnormal alternative splicing of a variety of transcripts, by knockdown of hnRNP K in wild-type mice and cell cultures including neural cells derived from induced pluripotent stem (iPS) cells. ? Aim 3: Determine the relative contribution of hnRNP K to the SCA10 pathogenicity by examining the degree of rescue achieved by over-expression of hnRNP K in cell culture and transgenic mouse models. These studies will firmly establish the pathogenic role of hnRNP K and provide a therapeutic target.

Public Health Relevance

SCA10 is a rare but one of the prototypes of disorders caused by toxic RNA. Toxic RNA is an emerging theme in a variety of disorders. This study will focus on hnRNP K, a protein with multiple essential functions for viability of cells and an interest to a wie variety of biomedical researchers. Our data on functional deficiency of hnRNP K will be important for understanding the mechanism of SCA10 and other disorders.

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
Research Project (R01)
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Cell Death in Neurodegeneration Study Section (CDIN)
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Gwinn, Katrina
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University of Florida
Schools of Medicine
United States
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McFarland, Karen N; Liu, Jilin; Landrian, Ivette et al. (2014) Repeat interruptions in spinocerebellar ataxia type 10 expansions are strongly associated with epileptic seizures. Neurogenetics 15:59-64
Matilla-Duenas, A; Ashizawa, T; Brice, A et al. (2014) Consensus paper: pathological mechanisms underlying neurodegeneration in spinocerebellar ataxias. Cerebellum 13:269-302
Xia, Guangbin; McFarland, Karen N; Wang, Kang et al. (2013) Purkinje cell loss is the major brain pathology of spinocerebellar ataxia type 10. J Neurol Neurosurg Psychiatry 84:1409-11
Bushara, Khalaf; Bower, Matthew; Liu, Jilin et al. (2013) Expansion of the Spinocerebellar ataxia type 10 (SCA10) repeat in a patient with Sioux Native American ancestry. PLoS One 8:e81342
Teive, Helio A G; Ashizawa, Tetsuo (2013) Spinocerebellar ataxia type 10: from Amerindians to Latin Americans. Curr Neurol Neurosci Rep 13:393