Engineering enhancers in adeno-associated viral vectors to target specific expression in motor neurons

Abstract

Developing adeno-associated virus (AAV) vectors that specifically express transgenes in motor neurons can circumvent toxicities associated with off-target expression, such as dorsal root ganglion (DRG) degeneration and peripheral neuropathy observed in several gene therapy programs in spinal muscular atrophy and amyotrophic lateral sclerosis. Our strategy is to identify enhancer elements that drive specific expression of the transgene in motor neurons. By profiling differentially open chromatin regions in motor neurons, we selected and tested four candidate enhancer sequences. One of our candidates, Enh98, exhibited highly specific expression in the spinal cord motor neurons. We found that the core region and key transcription factor binding sites of Enh98 are necessary for the specific expression pattern. We have made major advancements towards developing motor neuron-specific AAV vectors that would enable safer and more effective gene therapies for patients with motor neuron disorders.