MOLECULAR EVIDENCE FOR THE PRESENCE OF A DEVELOPMENTAL GENE IN THE LOWEST ANIMALS - IDENTIFICATION OF A HOMEOBOX-LIKE GENE IN THE MARINE SPONGE GEODIA-CYDONIUM

During the development of higher animals, morphogenetic programs are s witched on which are frequently controlled by homeotic genes. Until no w these genes have not been identified in the lowest animals, the mari ne sponges. Since sponges show (i) an antero-posterior and/or dorso-ve ntral axis during embryogenesis and (ii) a complex differentiation pat tern during spicula formation, we hypothesized that in sponges homeoti c genes - if present - are also involved in the control of these proce sses. Therefore, we searched for homeobox or homeobox-like sequences i n the marine sponge Geodia cydonium, Here we describe a homeobox-like sequence from these animals; it was isolated from a cDNA library of an adult specimen, The deduced amino acid sequence of the complete homeo domain shares over 70% similarity with other homeodomain sequences, in cluding those from hydra, insects and vertebrates, These data indicate that the sponge homeodomain-like sequence is similar with respect to structure to those of other animals and may suggest that the sponge ho meodomain-like sequence(s) might function during developmental process es and/or during spiculogenesis in a similar manner to that known for higher animals.