However, developing an AAV mediated gene therapy for CRB-associated retinopathies is more challenging due to the large size of CRB1 and CRB2 cDNA (4.4 kb and 3.9 kb, respectively) which approach the AAV packaging limit (~ 5.0 kb, including inverted terminal repeats), a disorder affecting three different cell types (cones, rods, and MCs), and the complex functions of CRB as structural and signaling transmembrane proteins [101–103]. The gene discussed is CRB1; the disease is retinal disorder.