Zebrafish vimentin: molecular characterization, assembly properties and developmental expression

To provide a basis for the investigation of the intermediate filament (IF) protein vimentin in one of the most promising experimental vertebrate syste ms, the zebrafish (Danio rerio), we have isolated a cDNA clone of high sequ ence identity to and with the characteristic features of human vimentin. Us ing this clone we produced recombinant zebrafish vimentin and studied its a ssembly behaviour. Unlike other vimentins, zebrafish vimentin formed unusua lly thick filaments when assembled at temperatures below 21 degrees C. At 3 7 degrees C few filaments were observed, which often also terminated in agg regated masses, indicating that its assembly was severely disturbed at this temperature. Between 21 and 34 degrees C apparently normal Ifs were genera ted. By viscometry, the temperature optimum of assembly was determined to b e around 28 degrees C. At this temperature, zebrafish vimentin partially re scued, in mixing experiments, the temperature-dependent assembly defect of trout vimentin. Therefore it is apparently able to "instruct'' the misorgan ized trout vimentin such that it can enter normal Ifs. This feature, that a ssembly is best at the normal body temperature of various species, puts mor e weight on the assumption that vimentin is vital for some aspects of gener ating functional adult tissues. Remarkably, like in most other vertebrates, zebrafish vimentin appears to be an abundant factor in the lens and the re tina as well as transiently, during development, in various parts of the ce ntral and peripheral nervous system. Therefore, promising cell biological i nvestigations may now be performed with cells involved in the generation of the vertebrate eye and brain, and, in particular, the retina. Moreover, th e power of genetics of the zebrafish system may be employed to investigate functional properties of vimentin in vivo.