Cnox-2 is a HOM/HOX homeobox gene that we have identified in the simple metazoan Hydra vulgaris (Cnidaria: Hydrozoa). Cnox-2 is most closely related to anterior members of the Antennapedia gene complex from Drosophila, with the greatest similarity to Deformed. The Cnox-2 protein is expressed in the epithelial cells of adult hydra polyps in a region-specific pattern along the body axis, at a low...

A subrecursive rewriting framework for the classical Kirby and Paris hydra battle is introduced. The termination of a natural rewrite system RH for the Hydra battle is shown by using ordinals and additionally by proving an upper bound on the derivation lengths in terms of a fast growing function of ordinal index ε0. It is shown that the RH -derivation lengths cannot be bounded by a fast growing...

Numerous developmental control genes have been isolated in a variety of organisms by either homology cloning or system-specific strategies. Functional genetic tests, however, are available for only a few model organisms and particularly are missing in a number of animals that occupy key positions for understanding the evolution of development and gene function. Double-stranded RNA-mediated inte...

Signalling through fibroblast growth factors (FGFR) is essential for proper morphogenesis in higher evolved triploblastic organisms. By screening for genes induced during morphogenesis in the diploblastic Hydra, we identified a receptor tyrosine kinase (kringelchen) with high similarity to FGFR tyrosine kinases. The gene is dynamically upregulated during budding, the asexual propagation of Hydr...

A gene encoding a novel type of receptor protein-tyrosine kinase was identified in Hydra vulgaris. The extracellular portion of this receptor (which we have named Sweet Tooth) contains four C-type lectin-like domains (CTLDs). Comparison of the sequences of these domains with the sequences of the carbohydrate recognition domains of various vertebrate C-type lectins shows that Sweet Tooth CTLD1 a...

Growth and morphogenesis during embryonic development, asexual reproduction and regeneration require extensive remodeling of the extracellular matrix (ECM). We used the simple metazoan Hydra to examine the fate of ECM during tissue morphogenesis and asexual budding. In growing Hydra, epithelial cells constantly move towards the extremities of the animal and into outgrowing buds. It is not known...

In hydra, the endodermal epithelial cells carry out the digestive function together with the gland cells that produce zymogens and express the evolutionarily conserved gene Kazal1. To assess the hydra Kazal1 function, we silenced gene expression through double-stranded RNA feeding. A progressive Kazal1 silencing affected homeostatic conditions as evidenced by the low budding rate and the induce...

Hydra provides an interesting developmental model system where pattern formation processes are easily accessible to experimentation during regeneration. Previous studies have shown that the neuropeptide head activator affects cellular growth and head-specific cellular differentiation during head regeneration and budding. In order to investigate the signal transduction pathway and the regulatory...

Cell-cell interaction and cell rearrangement were examined in the process of epithelial sheet formation during regeneration from hydra cell aggregates. The ectodermal and endodermal epithelial cell layers of Hydra magnipapillata were separated by procaine treatment. Each of the separated layers was then dissociated into single cells and reaggregated to produce ectodermal or endodermal cell aggr...

Hydra provides a convenient system for the study of the regulation of a linear pattern of organization. Almost any region is capable of being reconstituted into the whole organism and regulation is always polarized, i.e. distal structures (hypostome and tentacles) are formed from distal ends and proximal structures (peduncle and basal disk) from proximal ends. Two models have recently been prop...