Biomarker discovery for juvenile neuronal ceroid lipofuscinosis

? DESCRIPTION (provided by applicant): Juvenile neuronal ceroid lipofuscinosis (JNCL) is one of the most frequently encountered of the NCLs, a group of clinically-related but genetically-distinct monogenic lysosomal storage diseases that primarily affect children and young adults. JNCL is caused by mutations in the gene CLN3 and is characterized by progressive neurodegeneration that is manifested by increasingly severe seizures, loss of vision, mental deterioration and premature death. There is no cure for JNCL. CLN3 is a lysosomal transmembrane protein, limiting opportunities for replacement therapies but there are additional reasons why progress towards treatment for JNCL lags behind other forms of NCL. First, an unclear understanding of the cellular function of the CLN3 protein means that rational therapeutic strategies are not currently feasible. Second, there are no readily measurable endpoints for correction of CLN3 defects in cultured cells, thus drug screening in vitro is difficut or impossible. Third, while other NCL mouse models recapitulate their respective diseases to a high degree, Cln3 mutant mice have a highly attenuated phenotype relative to JNCL, with evidence for subtle behavioral deficits, CNS pathology and retinal degeneration but no overt phenotype. As a result, drug screening or validation in vivo is a major challenge. Fourth, in current and future clinical trials for JNCL, long-term disease progression will be evaluated using clinical rating scales but there are no short-term measures to optimize treatment regimens. The goal of this study is to address these areas by identifying protein changes that predict and shed light on CLN3 function. We will identify and validate biomarkers that reflect disease at the cellular level with the rationale that these will provide the most immediate and responsive measures of correction of the fundamental defect. First, we will use proteomic methods to identify proteins with specifically altered expression in multiple human JNCL samples to maximize the chances of identifying potentially useful candidates. We will analyze postmortem JNCL brain and CSF samples as well as cultured cells from JNCL patients. These will include fibroblasts and lymphoblasts as well induced pluripotent stem cell-derived neurons. The use of cell-lines broadens the scope of our discovery efforts and is free of the multiple complexities associated with physiological samples, allowing us to clearly define responses to the primary defect at the cellular level. In addition, using cultured cells, the specificity of response of selct candidates can be determined by introducing normal copies of the CLN3 protein. Second, we will validate select candidates in vivo using the Cln3 knockout mouse model of JNCL. The proposed study builds upon our extensive experience with the NCLs and our expertise in cutting-edge proteomics. Results may provide clinically-useful biomarkers for JNCL as well as responsive protein surrogates that allow for the development of novel cell-based drug screens. In addition, this study may provide valuable insights into the function of CLN3 and the pathophysiology of JNCL.