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Pax-6 expression in posthatch chick retina during and recovery from form-deprivation myopia
Suraj P Bhat1, Sylvia A Rayner, Scott C Chau
1Jules Stein Eye Institute, University of California, Los Angeles, CA 90095, USA. bhat@jsei.ucla.edu
Insights
Form-deprivation myopia (FDM) in chick eyes disrupts normal Pax-6 expression patterns. Recovery from FDM does not fully restore Pax-6 levels, indicating impeded visual development.
Area of Science:
- Developmental biology
- Ophthalmology
- Molecular biology
Background:
- Pax-6 gene expression is crucial for retinal development and function.
- Pax-6 exhibits a biphasic expression pattern in posthatch chick retinas, correlating with eye growth.
- Form-deprivation myopia (FDM) is known to disrupt normal eye growth patterns.
Purpose of the Study:
- To investigate the effect of FDM and subsequent recovery on Pax-6 gene expression in posthatch chick eyes.
- To understand the molecular changes associated with FDM-induced visual development disruption.
- To evaluate the suitability of contralateral eyes as controls in FDM studies.
Main Methods:
- Quantitative RT-PCR was used to measure Pax-6 transcript levels.
- Chick eyes were subjected to 2 weeks of FDM, followed by 2 weeks of recovery.
- Expression levels were compared between occluded eyes, contralateral eyes, and normal control eyes.
Main Results:
- No drastic changes in Pax-6 transcripts were observed in occluded or contralateral eyes immediately after FDM compared to controls.
- Contralateral eyes showed similar, but not identical, molecular changes to occluded eyes, questioning their use as normal controls.
- After recovery, occluded eyes had significantly lower Pax-6 expression than normal control eyes.
Conclusions:
- FDM significantly impacts Pax-6 expression levels in developing chick retinas.
- The contralateral eye is not a reliable 'normal' control for FDM studies.
- FDM exposure appears to impede developmental progression towards emmetropia, as evidenced by persistent alterations in Pax-6 expression.
Abstract:
The expression of Pax-6 in fully-differentiated chick retina remains largely confined to the amacrine and ganglion cell layers. In the developing posthatch chick retina, Pax-6 expression shows a biphasic pattern; a decrease by posthatch day 17 followed by a steady increase in the adult eye. Interestingly, we find that this biphasic expression of Pax-6 is reflected in the biphasic growth pattern of the posthatch chick eye, which is disrupted by form-deprivation myopia (FDM). We have now examined the pattern of Pax-6 accumulation in 3-day-old chick eyes subjected to 2 weeks of FDM followed by 2 weeks of recovery from FDM. Quantitative RT-PCR (with a homologous internal control) revealed that after 2 weeks of occlusion the contralateral non occluded eyes, the occluded eyes and the normal nonexperimental chick eyes did not show any drastic changes in the number of Pax-6 transcripts. The data obtained suggests that the contralateral eye does not represent a 'normal' control eye; similar but nonidentical changes are seen, at the molecular level, in both the contralateral and the occluded eyes. Comparisons with the control nonexperimental animals, however, are meaningful. Even after 2 weeks of recovery under normal light conditions, the occluded eyes do not seem to reach the same level of Pax-6 expression (number of molecules per mg tissue) as seen in normal control eyes, suggesting that exposure of the posthatch chick eye to FDM impedes developmental progression that normally culminates in emmetropia.
