Expression and assembly properties of the recently identified “thread” keratins TKα
and TKγ in the zebrafish Danio rerio
Sebastian Neumann, Michael Schaffeld
Institut für Zoologie, Johannes Gutenberg-Universität Mainz
Keratins form the two most complex groups of intermediate filament (IF) proteins, assembling into filaments of type I/type II heterodimers. The thread keratins α and γ were first discovered in the hagfish slime, but since then have been considered a highly specialized group of IF-proteins, possibly only present in this ancient vertebrate group. Recently we discovered that both thread keratins are also present in other vertebrates, including teleosts and amphibians and that TKα is indeed best characterized as a type II keratin, whereas TKγ represents a rather ancient type I keratin. However, to-date little is known about thread keratin properties, expression and function in these animals. We therefore produced the respective recombinant proteins from zebrafish, (a) to investigate their assembly properties, (b) to establish an overlay assay enabling us to identify the thread keratins in cytoskeletal preparations and (c) to raise antibodies specific for both thread keratins in zebrafish to trace their expression patterns. Here we present our first results, which already indicate that TKα and TKγ do not show the typical behaviour known for other keratins, in that at least TKα is capable of forming homopolymeric, filamentous structures. Moreover, for the first time we have been able to identify TKα at the protein level, indicating that it is present in different larval stages as well as in adult zebrafish. [We thank Prof. Jürgen Markl for his interest and support].