224. Induced Pluripotent Stem Cells as a Model To Test Gene Augmentation Therapy for Choroideremia

Abstract

Choroideremia (CHM) is an X-linked, blinding, inherited retinal degeneration that is symptomatic in childhood and leads to total blindness in midlife. The disease is characterized by the degeneration of photoreceptors, retinal pigment epithelium (RPE) and choriocapillaris. The causative factor for CHM was identifi ed as a defect in the Rab Escort Protein 1 (REP1) which is involved in prenylation of Rab proteins. The nature and onset of the disease and the size of the gene makes CHM an excellent target for recombinant adeno-associated virus (rAAV) mediated gene therapy. However, the animal model of this disease is not an exact replica of the condition and is not readily available. Therefore, we generated and evaluated induced pluripotent stems cells (iPSCs) from CHM subjects as in vitro models to explore the potential of gene augmentation therapy. A recombinant adeno-associated virus (AAV2) was generated that delivers the wild-type human CHM cDNA driven by a constitutive promoter. Infection of iPSCs with AAV2-CHM resulted in the expression of the CHM protein and rescue of enzymatic function in the defective cells. The gene transfer is effi cient and appears to be safe in the short-term, as shown by studies in affected cells and in normalsighted animal models. These studies not only aid in deciphering the pathogenetic mechanisms of the disease, but also pave the way for a human gene therapy clinical trial for CHM.