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James D. Lauderdale, Ashley Margret Rasys, Shana HW Pau, Katie Irwin, Sherry Luo, Douglas B Menke; Eye Development in the Brown Anole Lizard Anolis sagrei. Invest. Ophthalmol. Vis. Sci. 2018;59(9):593.
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© ARVO (1962-2015); The Authors (2016-present)
Detailed analyses of eye development have only been performed in a handful of vertebrate model systems—including zebrafish, frog, chicken, and mouse. In an effort to elucidate conserved developmental mechanisms responsible for formation of the vertebrate eye, we are working to establish the Anolis sagrei, a bifoveated lizard, as a new model organism for the study of reptilian eye development. In this study, we present a comprehensive histological analysis of retina, lens, cornea, iris/ciliary body, and conus papillaris development in the brown anole lizard.
Eggs from our breeding lizard colony were collected and incubated at 27.8°C and 70% humidity to capture stages throughout embryonic development. Upon removal from its shell, lizard embryos were staged following criteria laid out by Sanger et al., 2008; embryos younger than those described by the Sanger staging series were designated with the prefix “PL” for pre-laying. After euthanasia, eyes were dissected, placed in Bouin’s fixative, processed for paraffin sectioning, and labeled with Hematoxylin and Eosin stains.
During early eye development—optic cup, lens pit, and vesicle formation transpire between stages PL 1-5. In mid development, lens growth rapidly occurs (St 5-13) and cornea layers—epithelial, stroma, and endothelial have become noticeable (St 6-9). By stage 10, iris and ciliary body are morphologically distinct. Organization of the retina layers begins at the center retina region (St 6), sweeps towards the temporal area (St 7-8) before progressing to the nasal region (St 9). The conus papillaris which develops from the choroidal epithelium after choroid fissure closure extends from the optic stock to the ventral region of the iris and continues to lengthen and thicken as the eye grows (St 3-19). By late development, the center and temporal foveae develop. Prior to this event, the eye undergoes a period of an asymmetrical growth resulting in ocular elongation followed by retraction localized to the presumptive foveae areas.
This study represents a thorough characterization of eye formation in the Anolis lizard. Data generated here will enable future work exploring the role of conserved and diverged regulatory mechanisms that govern vertebrate eye development in squamates.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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