Prenylation of rab6a as a potency assay for choroideremia gene therapy

Choroideremia (CHM) is a rare, X-linked recessive retinal dystrophy caused by mutations in the CHM gene. This gene encodes for Rab escort protein 1 (REP1), which is ubiquitously expressed in human cells and plays a key role in intracellular trafficking through the prenylation of RabGTPases. Deficiency of REP1 prevents Rab proteins of being prenylated and delivered to the target membrane, causing cellular dysfunction and ultimately cell death. As the use of adeno-associated viral (AAV) vectors for choroideremia gene therapy becomes a clinical reality, there is a need for reliable and sensitive assays to determine the activity of exogenously delivered CHM. In vitro prenylation using a biotinylated lipid donor and a Rab protein as a substrate has been proven to assess REP1 function. 142 Molecular Therapy Vol. 25 No 5S1 May 2017 Pharmacology, Toxicology and Assay Development Molecular Therapy Here we describe an in vitro potency assay using Rab6a to test AAV vectors for choroideremia gene therap