RNA interference for apoptosis signal-regulating kinase-1 (ASK-1) rescues photoreceptor death in the rd1 mouse.
OBJECTIVE
To evaluate whether RNA interference against apoptosis signal-regulating kinase-1 (ASK-1), a gene involved in stress-induced apoptosis, inhibits photoreceptor death in retinal degeneration 1 (rd1) mice.


METHODS
Retinal explants from rd1 mice were subjected to organ cultures on postnatal day 9 (P9). Short interfering RNA (siRNA) for ASK-1 was transfected into cultured retinas at the onset of experiments. Real-time PCR was performed to evaluate the natural expression of ASK-1 mRNA and its inhibition with siRNA. Retinal explants were fixed at P13 and P16, and consecutive cryosections were prepared. Histological and immunohistochemical examinations including TUNEL assays were performed.


RESULTS
In preliminary experiments, the incorporation of fluorescent siRNA was found in cells in the outer nuclear and inner nuclear layers on the day following transfection. The expression of ASK-1 mRNA increased with time, which was suppressed more than 70% by siRNA. ASK-1 immunopositive cells were found mostly in the outer nuclear layers, and the number of immunopositive cells was remarkably reduced in retinas treated with siRNA for ASK-1 compared to untreated controls. The thickness of outer nuclear layers of control retinas decreased with time, while the thickness of siRNA transfected retinas was significantly preserved compared to control at P16 (p=0.0021). In TUNEL assays, siRNA for ASK-1 significantly decreased TUNEL-positive cells (49% and 42% of controls at P13 and 16, p=0.039 and 0.0028, respectively).


CONCLUSIONS
RNA interference against ASK-1 may provide a benefit by inhibiting photoreceptor apoptosis in rd1 mice.
Sekimukai
Daisuke
D
Department of Surgery, Division of Ophthalmology, Kobe University Graduate School of Medicine, Kobe, Japan.
Honda
Shigeru
S
Negi
Akira
A
D000818:Animals; D017209:Apoptosis; D015971:Gene Expression Regulation, Enzymologic; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D048848:MAP Kinase Kinase Kinase 5 / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D020419:Photoreceptor Cells, Vertebrate / Q000201:enzymology* / Q000473:pathology*; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D012162:Retinal Degeneration / Q000201:enzymology* / Q000473:pathology*
D012333:RNA, Messenger; D034741:RNA, Small Interfering; D048848:MAP Kinase Kinase Kinase 5; C482859:Map3k5 protein, mouse