Abrogation Of Phenotype By Small Molecule Read-Through Compounds In A Human Model Of Ataxia Telangiectasia

OBJECTIVE: To develop a human in vitro model of Ataxia Telangiectais (A-T) for efficient screening of novel therapeutic compounds. BACKGROUND: Ataxia Telangiectasia (A-T) is an early onset progressive neurodegenerative disease caused by loss of function mutations in ATM. ATM protein is a kinase that plays a crucial role in cellular response to double stranded-DNA break. Thus far, animal models of A-T have failed to show many aspects of the disease, including progressive cerebellar ataxia, the most debilitating symptom in A-T patients. DESIGN/METHODS: Using lenti-virus that harbors reprogramming Yamanaka factors, we reprogrammed A-T patient9s fibroblasts into induced pluripotent stem cells (iPSC). These iPSCs were characterized for their pluripotency by immunostaining and teratoma assay. These iPSCs were then differentiated into neural lineages, including neuroprogenitor and neurons. These neural derivatives were subjected to gamma irradiation to induce double-stranded DNA break. ATM activity was measured by the degree of ATM phosphorylation using immunofluoresence. Response to DNA damage was monitored by the presence of gamma-H2AX, a histone variant involved in DNA repair. The neural derivatives were treated with small molecule read through (SMRT) compounds that induce misread mRNA around termination codons. The effect of SMRT compounds on ATM activity by ATM phosphorylation and double stranded DNA repair measured by gamma-H2AX were evaluated. RESULTS: This model resembles several key aspects of the disease in neural progenitor cells and neurons. Furthermore, we show that small molecule read through (SMRT) compounds that induce misread mRNA around termination codons, restore ATM activity and improved response to DNA damage. CONCLUSIONS: This in vitro model, therefore, allows for efficient screening of novel compounds, identify target effects, and preclinical testing on relevant cell types for the study and treatment of A-T. Supported by: CIRM grant #RT2-01920. Disclosure: Dr. Lee has nothing to disclose. Dr. Martin has nothing to disclose. Dr. Nakamura has nothing to disclose. Dr. Azghadi has nothing to disclose. Dr. Amiri has nothing to disclose. Dr. Perlman has received research support from Santhera Pharmaceuticals. Dr. Gatti has nothing to disclose. Dr. Hu has nothing to disclose. Dr. Lowry has nothing to disclose.