Anoles (and Alligators) Give a New View on the Evolution of Vertebrate Eevelopment

One of the key features of vertebrates is the backbone, which is formed in development by a clock-like segmentation process called somitogenesis. Most of what we know about the genes that control somitogenesis comes from studies of just 4 vertebrate species–the mouse, the chicken, the African clawed frog (Xenopus laevis), and the zebrafish. Until now, we haven’t had a good window into the evolution of somitogenesis from the perspective of a non-avian reptile. The green anole (Anolis carolinensis) is now providing this perspective as a 5^th model system for molecular developmental studies.

In a recently published paper (Eckalbar et al., Developmental Biology, 2012), we have shown that green anole embryos share molecular features of somitogenesis with the mouse and the chicken, which are also amniotes. Surprisingly, the green anole also retains expression patterns that match those of the non-amniote species, Xenopus and zebrafish, and that have been lost in the mouse and chick. The American alligator (Alligator mississippiensis), which together with birds are classified in a group called the Archosauria, are intermediate in somitogenesis features between anoles and chicken. These findings reshape our view of what was happening in the backbone development of the amniote ancestor, the first vertebrate whose eggs were fully adapted for life on land.

For those in the anole research community, RNA-Seq transcriptome data sets (Illumina HiSeq2000; 28 and 38 somite-pair stages) have been released together with this paper. Transcriptome data links can be found at the AnolisGenome portal and also directly from the NIH Gene Expression Omnibus. We aim to get more transcriptome sequence to the Anolis research community in 2012.