A unique talin homologue with a villin headpiece-like domain is required for multicellular morphogenesis in Dictyostelium

Molecules involved in the interaction between the extracellular matrix, cel l membrane and cytoskeleton are of central importance in morphogenesis, Tal in is a large cytoskeletal protein with a modular structure consisting of a n amino-terminal membrane-interacting domain, with sequence similarities to members of the band 4.1 family, and a carboxy-terminal region containing F -actin-binding and vinculin-binding domains [1,2]. It also interacts with t he cytoplasmic tail of beta integrins which. on the external face of the me mbrane, bind to extracellular matrix proteins [3], The possible roles of ta lin in multicellular morphogenesis in development remain largely unexplored , In Dictyostelium, a eukaryotic microorganism capable of multicellular mor phogenesis, a talin homologue (TALA) has previously been identified and sho wn to play an important role in cell-to-substrate adhesion and maintenance of normal elastic properties of the cell [4-6]. Here, we describe a second talin homologue (TALB) that is required for multicellular morphogenesis in the development of Dictyostelium, Unlike any other talin characterised to d ate, it contains an additional carboxy-terminal domain homologous to the vi llin headpiece.