Regionally distinct GFAP promoter expression plays a role in off-target neuron expression following AAV5 transduction.

Astrocyte to neuron reprogramming has been performed using viral delivery of neurogenic transcription factors in GFAP expressing cells. Recent reports of off-target expression in cortical neurons following adeno-associated virus (AAV) transduction to deliver the neurogenic factors have confounded our understanding of the efficacy of direct cellular reprogramming. To shed light on potential mechanisms that may underlie the neuronal off-target expression of GFAP promoter driven expression of neurogenic factors in neurons, two regionally distinct cortices were compared-the motor cortex (MC) and medial prefrontal cortex (mPFC)-and investigated: (1) the regional tropism and astrocyte transduction with an AAV5-GFAP vector, (2) the expression of Gfap in MC and mPFC neurons; and (3) material transfer between astrocytes and neurons.