title: Developing rods transplanted into the degenerating retina of Crx-knockout mice exhibit neural activity similar to native photoreceptors.
abstract: Replacement of dysfunctional or dying photoreceptors offers a promising approach for retinal neurodegenerative diseases, including age-related macular degeneration and retinitis pigmentosa. Several studies have demonstrated the integration and differentiation of developing rod photoreceptors when transplanted in wild-type or degenerating retina; however, the physiology and function of the donor cells are not adequately defined. Here, we describe the physiological properties of developing rod photoreceptors that are tagged with green fluorescent protein (GFP) driven by the promoter of rod differentiation factor, Nrl. GFP-tagged developing rods show Ca(2 +) responses and rectifier outward currents that are smaller than those observed in fully developed photoreceptors, suggesting their immature developmental state. These immature rods also exhibit hyperpolarization-activated current (Ih ) induced by the activation of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels. When transplanted into the subretinal space of wild-type or retinal degeneration mice, GFP-tagged developing rods can integrate into the photoreceptor outer nuclear layer in wild-type mouse retina and exhibit Ca(2 +) responses and membrane current comparable to native rod photoreceptors. A proportion of grafted rods develop rhodopsin-positive outer segment-like structures within 2 weeks after transplantation into the retina of Crx-knockout mice and produce rectifier outward current and Ih upon membrane depolarization and hyperpolarization. GFP-positive rods derived from induced pluripotent stem (iPS) cells also display similar membrane current Ih as native developing rod photoreceptors, express rod-specific phototransduction genes, and HCN-1 channels. We conclude that Nrl-promoter-driven GFP-tagged donor photoreceptors exhibit physiological characteristics of rods and that iPS cell-derived rods in vitro may provide a renewable source for cell-replacement therapy.
authors.affiliation: Laboratory for Retinal Regeneration, Center for Developmental Biology, RIKEN, Kobe, Japan. kohei.homma@nih.gov
authors.forename: Kohei
authors.initials: K
authors.lastname: Homma
authors.forename: Satoshi
authors.initials: S
authors.lastname: Okamoto
authors.forename: Michiko
authors.initials: M
authors.lastname: Mandai
authors.forename: Norimoto
authors.initials: N
authors.lastname: Gotoh
authors.forename: Harsha K
authors.initials: HK
authors.lastname: Rajasimha
authors.forename: Yi-Sheng
authors.initials: YS
authors.lastname: Chang
authors.forename: Shan
authors.initials: S
authors.lastname: Chen
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.forename: Tiziana
authors.initials: T
authors.lastname: Cogliati
authors.forename: Anand
authors.initials: A
authors.lastname: Swaroop
authors.forename: Masayo
authors.initials: M
authors.lastname: Takahashi
mesh_terms: D000818:Animals; D050976:Basic-Leucine Zipper Transcription Factors / Q000235:genetics / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002454:Cell Differentiation / Q000235:genetics; D002478:Cells, Cultured; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels / Q000235:genetics / Q000378:metabolism; D057026:Induced Pluripotent Stem Cells / Q000378:metabolism / Q000502:physiology; D008564:Membrane Potentials / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D020419:Photoreceptor Cells, Vertebrate / Q000378:metabolism / Q000502:physiology*; D011401:Promoter Regions, Genetic; D012160:Retina / Q000378:metabolism / Q000502:physiology*; D012162:Retinal Degeneration / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology / Q000628:therapy*; D017948:Retinal Rod Photoreceptor Cells / Q000378:metabolism / Q000502:physiology* / Q000637:transplantation*; D033581:Stem Cell Transplantation; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism
chemical_list: D050976:Basic-Leucine Zipper Transcription Factors; D005136:Eye Proteins; D018398:Homeodomain Proteins; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; C084884:Nrl protein, mouse; D015534:Trans-Activators; C109288:cone rod homeobox protein; D049452:Green Fluorescent Proteins; D002118:Calcium