Phylogenetic analysis of vertebrate and invertebrate Delta/Serrate/LAG-2 (DSL) proteins

Delta/Serrate/LAG-2 (DSL) proteins are putative transmembrane signaling mol ecules that regulate cell differentiation in metazoans. DSL proteins are ch aracterized by the presence of a motif unique to these proteins, the DSL mo tif, and a variable number of tandemly repeated copies of an epidermal grow th factor-like (EGF) motif. We have completed a phylogenetic analysis of 15 DSL proteins from eight species. Our findings reveal that at least one gen e duplication occurred prior to the divergence of the Drosophila melanogast er and vertebrate lineages, with subsequent duplications in vertebrates. Th e three known Caenorhabditis elegans proteins likely arose by two independe nt duplications in the nematode lineage. Analysis of EGF repeats suggests t hat EGF 2 has been conserved among DSL proteins in vertebrates and D. melan ogaster. The sequences of two EGF repeats have been perfectly conserved in vertebrate orthologs: EGF 2 in Delta and EGF 15 in Jagged/Serrate. Finally, the linear order of EGF repeats has been conserved in the vertebrate Jagge d/Serrate orthologs and vertebrate Delta orthologs, (C) 1999 Academic Press .