Abstract Background Across the Metazoa, similar genetic programs are found in the development of analogous, independently evolved, morphological features.The functional significance of this reuse and the underlying mechanisms of co-option remain unclear.Cephalopods have evolved a highly acute visual system with a cup-shaped retina and a novel Bowling Balls refractive lens in the anterior, important for a number of sophisticated behaviors including predation, mating, and camouflage.
Almost nothing is known about the molecular-genetics of lens development in the cephalopod.Results Here we identify the co-option of the canonical bilaterian limb patterning program during cephalopod lens development, a functionally unrelated structure.We show radial expression of transcription factors SP6-9/sp1, Dlx/dll, Pbx/exd, Meis/hth, and a Prdl homolog in the squid Doryteuthis pealeii, similar to expression required in Drosophila limb development.
We assess the role of ORG VIRGIN SHEA BUTTER Wnt signaling in the cephalopod lens, a positive regulator in the developing Drosophila limb, and find the regulatory relationship reversed, with ectopic Wnt signaling leading to lens loss.Conclusion This regulatory divergence suggests that duplication of SP6-9 in cephalopods may mediate the co-option of the limb patterning program.Thus, our study suggests that this program could perform a more universal developmental function in radial patterning and highlights how canonical genetic programs are repurposed in novel structures.