Alterations in ZENK and glucagon RNA transcript expression during increased ocular growth in chickens

[摘要] Purpose: To examine in detail thetime-course of changes in Zif268, Egr-1, NGFI-A, and Krox-24 (ZENK)and pre-proglucagon (PPG) RNA transcript levels inthe chick retina during periods of increased ocular growth induced byform-deprivation and negative-lens wear. To further elucidate the roleof ZENK in the modulation of ocular growth, we investigated theeffect of intravitreal injections of the muscarinic antagonist atropineand the dopamine agonist2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene hydrobromide(ADTN), both of which block the development of experimental myopia, onthe expression of ZENK in eyes fitted with negative-lenses. Methods: Myopia was induced by fittingtranslucent diffusers or −10D polymethyl methacrylate (PMMA) lensesover one eye of the chicken. At times from 1 h to 10 days after fittingof the diffusers or negative lenses, retinal RNA transcript levels ofthe selected genes were determined by semi-quantitative real-timereverse transcriptase polymerase chain reaction (RT–PCR). For thepharmacology experiments, −10D lenses were fitted over the left eye ofchicks for a period of 1h. Intravitreal injections of atropine (10μl–25 mM), ADTN (10 μl–10 mM), or a vehicle solution were madeimmediately before fitting of the lenses. Results: ZENK RNA transcriptlevels were rapidly and persistently down-regulated following theattachment of the optical devices over the eye. With a delay relativeto ZENK, PPG transcript levels were alsodown-regulated. Induced changes in gene expression were similar forboth form-deprivation and negative-lens wear. When atropine or ADTNwere administered immediately before lens attachment, the rapiddown-regulation in ZENK RNA transcript levels normally seenfollowing 1 h of negative-lens wear was not seen, and ZENKtranscript levels rose above those values seen in control eyes.However, injection of atropine or ADTN into untreated eyes had noeffect on ZENK transcript levels. Conclusions: Both form-deprivation andnegative-lens wear modulated the retinal expression of ZENK andPPG RNA transcripts, with a similar time-course and strength ofresponse. The ability of the tested drugs to prevent thedown-regulation of ZENK in both lens-induced myopia (LIM) andform-deprivation myopia (FDM) suggests that atropine and ADTN actdirectly and rapidly on retinal circuits to enhance sensitivity earlyin the signaling process. These findings suggest that very similarmolecular pathways are involved in the changes in eye growth inresponse to form-deprivation and negative lenses at 1 h after thefitting of optical devices.Received: January 22, 2010Accepted: April 6,2010

[学科分类] 生物化学/生物物理