title: The use of induced pluripotent stem cells to reveal pathogenic gene mutations and explore treatments for retinitis pigmentosa.
abstract: BACKGROUND
  Retinitis pigmentosa (RP) is an inherited human retinal disorder that causes progressive photoreceptor cell loss, leading to severe vision impairment or blindness. However, no effective therapy has been established to date. Although genetic mutations have been identified, the available clinical data are not always sufficient to elucidate the roles of these mutations in disease pathogenesis, a situation that is partially due to differences in genetic backgrounds.
  
  
  RESULTS
  We generated induced pluripotent stem cells (iPSCs) from an RP patient carrying a rhodopsin mutation (E181K). Using helper-dependent adenoviral vector (HDAdV) gene transfer, the mutation was corrected in the patient's iPSCs and also introduced into control iPSCs. The cells were then subjected to retinal differentiation; the resulting rod photoreceptor cells were labeled with an Nrl promoter-driven enhanced green fluorescent protein (EGFP)-carrying adenovirus and purified using flow cytometry after 5 weeks of culture. Using this approach, we found a reduced survival rate in the photoreceptor cells with the E181K mutation, which was correlated with the increased expression of endoplasmic reticulum (ER) stress and apoptotic markers. The screening of therapeutic reagents showed that rapamycin, PP242, AICAR, NQDI-1, and salubrinal promoted the survival of the patient's iPSC-derived photoreceptor cells, with a concomitant reduction in markers of ER stress and apoptosis. Additionally, autophagy markers were found to be correlated with ER stress, suggesting that autophagy was reduced by suppressing ER stress-induced apoptotic changes.
  
  
  CONCLUSIONS
  The use of RP patient-derived iPSCs combined with genome editing provided a versatile cellular system with which to define the roles of genetic mutations in isogenic iPSCs with or without mutation and also provided a system that can be used to explore candidate therapeutic approaches.
authors.forename: Tetsu
authors.initials: T
authors.lastname: Yoshida
authors.affiliation: Laboratory of Retinal Cell Biology, Department of Ophthalmology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku 160-8582, Tokyo, Japan. ozawa@a5.keio.jp.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Ozawa
authors.forename: Keiichiro
authors.initials: K
authors.lastname: Suzuki
authors.forename: Kenya
authors.initials: K
authors.lastname: Yuki
authors.forename: Manabu
authors.initials: M
authors.lastname: Ohyama
authors.forename: Wado
authors.initials: W
authors.lastname: Akamatsu
authors.forename: Yumi
authors.initials: Y
authors.lastname: Matsuzaki
authors.forename: Shigeto
authors.initials: S
authors.lastname: Shimmura
authors.forename: Kohnosuke
authors.initials: K
authors.lastname: Mitani
authors.forename: Kazuo
authors.initials: K
authors.lastname: Tsubota
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Okano
mesh_terms: D017209:Apoptosis; D001343:Autophagy; D001483:Base Sequence; D015415:Biomarkers / Q000378:metabolism; D002454:Cell Differentiation; D002460:Cell Line; D004353:Drug Evaluation, Preclinical; D059865:Endoplasmic Reticulum Stress; D005260:Female; D018390:Gene Targeting; D006801:Humans; D057026:Induced Pluripotent Stem Cells / Q000166:cytology*; D008875:Middle Aged; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics*; D017948:Retinal Rod Photoreceptor Cells / Q000378:metabolism / Q000473:pathology; D012174:Retinitis Pigmentosa / Q000235:genetics* / Q000628:therapy*; D012243:Rhodopsin / Q000235:genetics*
chemical_list: D015415:Biomarkers; D050505:Mutant Proteins; D012243:Rhodopsin