Gene augmentation and read-through rescue channelopathy in an iPSC-RPE model of congenital blindness

Mutations in the KCNJ13 gene are known to cause Leber Congenital Amaurosis (LCA16), an inherited pediatric blindness. KCNJ13 gene encodes the Kir7.1 subunit protein which acts as a tetrameric inwardly rectifying potassium ion channel in the retinal pigment epithelium to maintain ionic homeostasis thereby allowing photoreceptors to encode visual information. We sought to determine if genetic approaches might be effective in treating blindness due to mutations in KCNJ13. We developed patient-derived hiPSC-RPE carrying an autosomal recessive nonsense mutation in the KCNJ13 gene (c.158G>A, p.Trp53X). We performed biochemical and electrophysiology assays of Kir7.1 function. Both small molecule read-through drug and gene-therapy approaches were tested using this disease-in-a-dish approach. We found that the LCA16 hiPSC-RPE had normal morphology but did not express a functional Kir7.1 channel and was unable to demonstrate normal physiology. Following read-through drug treatment, the LCA16 hiPSC cells were hyperpolarized by 30 mV and Kir7.1 current was restored. Similarly, loss-of-function of Kir7.1 channel was circumvented by lentiviral gene delivery to the hiPSC-RPE cells. In either approach, Kir7.1 protein was expressing normally with restoration of membrane potential and Kir7.1 current. Loss-of-function mutation in Kir7.1 is a cause of LCA. Using either read-through therapy or gene augmentation, we rescued Kir7.1 channel function in patient-derived iPSC-RPE cells via a precision medicine approach.