Abstract
Abstract: :
Purpose: Emmetropisation is a vision-dependent process which requires retinal signals to regulate scleral growth. In preliminary studies using differential gene display in our laboratory, it was shown that alpha-B-crystallin expression was up-regulated in the retinas of chickens after one day of form-deprivation. Ishibashi et al. (1) have shown that other members of the crystallin family are also up-regulated after longer periods of form-deprivation. In this study, we have investigated whether alpha-B-crystallin is differentially expressed in the retinas of chickens recovering from form-deprivation myopia after removal of the diffuser. Methods: Chickens were kept in 12:12 light/dark cycle. Twenty chickens were form-deprived, to induce myopia, by fitting a translucent diffuser over one eye on day 4 (G [goggled]). Ten chickens were left as normal controls (N). On day 14, goggles were removed from half the chickens in group G, to produce the de-goggled (D) group, in which the rate of eye growth is reduced. Chickens were then killed either 6 or 12h later. Messenger RNA was extracted from the retinas pooled in each group. Gene expression was studied by northern blot hybridisation using a 217bp alpha-B-crystallin probe corresponding to the cDNA fragment isolated in our initial differential gene display experiments. Results: Alpha-B-crystallin transcript (∼650 bp) was up-regulated in retinas in form-deprived eyes on day 14, after 10 days of form-deprivation (∼125% of expression in normal eye). The transcript was down-regulated in the de-goggled condition relative to the level in the retinas from form-deprived eyes 6 and 12h after removal of the diffusers, and to below the levels in retinas from control eyes after 12h. Conclusion: The level of alpha-B-crystallin expression in the retina is increased under conditions where growth rates of the sclera are high, and decreased where the rate of scleral growth is suppressed. Alpha-B-crystallin may therefore play a role as part of the signalling pathway within the retina that generates a growth control signal that is ultimately transmitted to the sclera. 1. Ishabashi et al., Experimental Eye Research 70 (2000)153-158
Keywords: 481 myopia • 554 retina • 417 gene/expression