Changes in the expression of Pax6 RNA transcripts in the retina during periods of altered ocular growth in chickens

Genome-wide mapping studies have suggested a possible role for Pax6 in the development of myopia. We therefore investigated the expression of Pax6 RNA transcripts in the chicken retina during periods of increased ocular growth, induced by form-deprivation and negative lens-wear, and during periods of decreased ocular growth, induced by diffuser removal from previously form-deprived eyes, and plus lens-wear. Levels of Pax6 RNA transcripts in the chicken retina were measured using semi-quantitative real-time RT-PCR, at times between 1 h and 10 days after the fitting of diffusers or negative lenses, and at times between 1h and 3 days following the removal of diffusers from previously form-deprived eyes, or the addition of plus lenses. Pax6 expression was unaffected during the initial 3 days of the response to form-deprivation or negative lens-wear, when rapid rates of growth are well-established. Alterations in the expression of Pax6 RNA transcripts were only observed after 7-10 days of form-deprivation (7 days, -15.7 ± 5.3%; 10 days, -32.0 ± 10.3%), with a similar response not seen during negative lens-wear, when eye growth also increases, suggesting that these alterations are specific to form-deprivation, rather to changes in the rate of eye growth. The late changes in Pax6 expression observed during form-deprivation were rapidly reversed after diffuser removal, with the levels of Pax6 RNA transcripts returning to those seen in control birds by 3 days (1 h, -27.8 ± 4.7%; 1 day, -16.9 ± 4.8%; 3 days + 1.0 ± 8.6%). Analogous changes were not seen in response to positive lenses in which eye growth is also slowed. Overall, the findings of this study do not support a role for Pax6 in the modulation of ocular growth during visual manipulation.