To get an insight into signaling cascades controlling developmental processes in Cnidarians we hunt for and make the use of so called early or immediate response genes. 

Early Response Genes

Serum Response Factor (SRF )

We have isolated the homologues of SRF from Hydra vulgaris (HvSRF) and Hydractinia echinata.
(HechSRF). Analysis of the local expression pattern of HvSRF and HechSRF by in situ hybridization reveals, that the message of this gene is predominantly expressed in the interstital cell lineage (I-cells) of Hydra and of Hydractinia. The I-cells are one of the totipotent (multipotent) stem cell pools of the animals giving rise to nerve cells, nematocytes, gland cells and germ cells. All cells of the lineage express SRF until they show a morphological visible kind of differentiation. 
The temporal expression pattern of HvSRF follows a daily rhythm possibly triggered by feeding. Shortly after feeding the message decreases and increases again later. Prolonged starvation of the animals causes an increase of the message

Northern analysis of HechSRF reveals, that the message is unchanged during embryogenesis and larval development and increases shortly after induction of metamorphosis. In situ hybridization indicates that labeled cells becomes distinguishable during larval development. They give rise to the I-cell lineage in the endoderm of the larva. During metamorphosis the labeled cells move from the endoderm into the ectoderm like the I-cells do. 

HvSRF and HechSRF are the first known genes in Cnidarians, which message is expressed predominantly in all members of the I-cell lineage, which have not yet visibly started to differentiate. We expect to get a better understanding of I-cell specific signaling cascades during developmental processes in Cnidarians. 
Work is in progress to find upstream or downstream members of the signaling cascade involving SRF. 

TIS11 (Tristetraproline family)

We have isolated fragments containing the conserved region of the homologues of TIS11 from Hydra vulgaris (HvTIS11) and Hydractinia echinata (HechTIS11).

work is in progress
 

Publications:

U. Hoffmann, M Kroiher (2001) A poosible role for the cnidarian homologue of serum response factor in decision making by undifferentiatied cells. Development 236, 304-315