Green cone opsin and rhodopsin regulation by CNTF and staurosporine in cultured chick photoreceptors.
OBJECTIVE
To investigate the regulation of visual pigment expression in chick embryo photoreceptor cells by ciliary neurotrophic factor (CNTF), and by the protein kinase inhibitor staurosporine.


METHODS
Embryonic day (ED) 8 chick embryo retinal cells were dissociated and cultured at low densities for 3 days, either in control medium or in medium supplemented with CNTF or staurosporine. The cultures were analyzed by immunocytochemistry with the monoclonal antibody Rho4D2, which recognizes chicken rhodopsin and green cone pigment, and by reverse transcription-polymerase chain reaction (RT-PCR) and Northern blot analysis to investigate visual pigment expression at the mRNA level.


RESULTS
CNTF increased the number of Rho4D2-immunoreactive photoreceptors in retinal cell cultures, in agreement with previous reports. RT-PCR and Northern blot analysis, however, showed that rhodopsin mRNA was undetectable in both control and CNTF-treated cultures but that CNTF induced significant increases in mRNA levels for the green cone pigment. Staurosporine-treated cultures also had more Rho4D2-immunoreactive cells than control cultures, but this increase was accompanied by induction of rhodopsin expression, with concomitant decreases in levels of green cone pigment mRNA. No significant differences were found between CNTF- or staurosporine-treated cultures and the corresponding control cultures regarding the red cone pigment, which was expressed in all cases, and the blue and violet pigments, which were not detected in any of the samples.


CONCLUSIONS
The results suggest that multiple regulatory systems control visual pigment expression during differentiation of chick embryo photoreceptor cells. CNTF appears to stimulate specifically the differentiation of green cones, without the previously suggested effects on the differentiation of rod photoreceptors in ED 8 chick retinal cultures.
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Johns Hopkins University School of Medicine, The Wilmer Eye Institute, Baltimore, Maryland, USA.
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D000818:Animals; D015152:Blotting, Northern; D002478:Cells, Cultured; D002642:Chick Embryo; D020934:Ciliary Neurotrophic Factor / Q000494:pharmacology*; D017931:DNA Primers / Q000737:chemistry; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D007124:Immunoenzyme Techniques; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D012333:RNA, Messenger / Q000378:metabolism; D017949:Retinal Cone Photoreceptor Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D017948:Retinal Rod Photoreceptor Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012243:Rhodopsin / Q000235:genetics / Q000378:metabolism*; D017299:Rod Opsins / Q000235:genetics / Q000378:metabolism*; D019311:Staurosporine / Q000494:pharmacology*
D020934:Ciliary Neurotrophic Factor; D017931:DNA Primers; D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D017299:Rod Opsins; D012243:Rhodopsin; D011493:Protein Kinase C; D019311:Staurosporine