NR2E3, a photoreceptor-specific orphan nuclear receptor, is believed to play a pivotal role in the differentiation of photoreceptors. Mutations in NR2E3 result in syndromes characterized by excess blue cones and loss 
of rods: enhanced S-cone syndrome (ESCS). This lentivirus expresses human NR2E3 under the control of the Tet promoter.