Gene expression in Anolis sagrei suggests conservation of patterning mechanisms drives formation of two high acuity areas

As humans we enjoy high acuity color vision. A specialized area in our retinas, the fovea, endows us with this ability. Some vertebrates, such as the Anolis sagrei (brown anole), have two such areas. Whether different species use conserved developmental mechanism(s), and whether the same mechanism is used in one organism to pattern both foveae, are herein addressed in the brown anole. We observed that the expression of canonical axis patterning genes is conserved in the anole retina. Retinoic acid and Fgf signaling pathways were found to define two discrete domains corresponding to emerging foveae. Comparative spatial analyses of early gene expression patterns among anole, chick, and human revealed conserved patterns in the anlage of the high acuity areas of each species. Variation in foveal number could arise through spatial redeployment of conserved patterning programs.