Meeting Abstract
Tektins are a family of microtubule stabilizing coiled-coil domain proteins. As many as five Tektins have been identified in vertebrates where they have been shown to play an important role in sperm flagellar function, while four Tektin homologs in sea urchin are involved in regulating propoer cilia and flagella length and motility. In addition, a single Tektin homolog in the unicellular algae C. reinhardtii has been implicated in axonemal defects, indicating an ancient conserved function. While Tektins have been studied extensively in sea urchin and mammals, very little work has been done on Tektin expression and function outside the deuterostomes or on the evolutionary relationships of Tektin proteins throughout the Metazoa. Here we present the first comprehensive phylogenetic analysis of Tektin proteins in the Metazoa as well as the first comprehensive study of Tektin expression in a non-deuterostome model: the polychaete Platynereis dumerilii. We find that the last common ancestor of the Metazoa had two Tektins, while the last common ancestor of the bilaterians had four. A duplication event early in the vertebrate lineage gave rise to extant Tektin-3 and Tektin-5, while an independent duplication event early in the spiralian lineage gave rise to Tektin-3/5A and Tektin-3/5B. We show that all five Tektins are likely involved in ciliary function in P. dumerilii, with four Tektins expressed in all ciliated cells, while the fifth Tektin, Tektin-3/5B, is expressed only in posterior ciliated cells. Furthermore, hyperciliated embryos treated with Azakenpaullone show expanded expression domains for all Tektins. Thus Tektin involvement in ciliary function is more widely conserved among the Metazoa than previously shown, and future studies in Tektins using spiralian, ecdysozoan and nonbilaterian models may help shed more light on the evolution of cilia in the Metazoa.
