Reprogramming progeny cells of embryonic RPE to produce photoreceptors: development of advanced photoreceptor traits under the induction of neuroD.
OBJECTIVE
In examining the prospect of producing functional photoreceptors by reprogramming the differentiation of RPE progeny cells, this study was conducted to investigate whether reprogrammed cells can develop highly specialized ultrastructural and physiological traits that characterize retinal photoreceptors.


METHODS
Cultured chick RPE cells were reprogrammed to differentiate along the photoreceptor pathway by ectopic expression of neuroD. Cellular ultrastructure was examined with electron microscopy. Cellular physiology was studied by monitoring cellular free calcium (Ca(2+)) levels in dark-adapted cells in response to light and in light-bleached cells in response to 9-cis-retinal.


RESULTS
Reprogrammed cells were found to localize red opsin protein appropriately to the apex. These cells developed inner segments rich in mitochondria, and while in culture, some formed rudimentary outer segments, analogous to those of developing photoreceptors in the retina. In response to light, reprogrammed cells reduced their Ca(2+) levels, as observed with developing retinal photoreceptors in culture. Further, on exposure to 9-cis-retinal, the light-bleached, reprogrammed cells increased their Ca(2+) levels, reminiscent of visual cycle recovery.


CONCLUSIONS
These results indicate the potential of reprogrammed cells to develop advanced ultrastructural and physiological traits of photoreceptors and point to reprogramming progeny cells of embryonic RPE as a possible alternative in producing developing photoreceptors.
Liang
Lina
L
Department of Ophthalmology, University of Alabama at Birmingham, Birmingham, Alabama.
Yan
Run-Tao
RT
Li
Xiumei
X
Chimento
Melissa
M
Wang
Shu-Zhen
SZ
D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000096:biosynthesis* / Q000235:genetics; D002118:Calcium / Q000502:physiology; D018929:Cell Culture Techniques; D002454:Cell Differentiation; D002478:Cells, Cultured; D002645:Chickens; D003624:Darkness; D004224:Diterpenes; D005260:Female; D017403:In Situ Hybridization; D008027:Light; D009419:Nerve Tissue Proteins / Q000096:biosynthesis* / Q000235:genetics; D010786:Photoreceptor Cells / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D010857:Pigment Epithelium of Eye / Q000166:cytology / Q000502:physiology*; D012172:Retinaldehyde / Q000494:pharmacology
D051792:Basic Helix-Loop-Helix Proteins; D002118:Calcium; D004224:Diterpenes; D009419:Nerve Tissue Proteins; D012172:Retinaldehyde; C093564:Neurogenic differentiation factor 1; C031390:9-cis-retinal