ISL1 and retinal degeneration: To investigate the contribution of residual host HCs and graft-derived HCs to host-graft synapses, RO sheets lacking RBCs by deletion of Islet1 gene (gROs, Figure S3) were transplanted into rd1/L7-GFP/Cx57-tdTomato mice with well-advanced retinal degeneration (Table S2).