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The freshwater polyp Hydra vulgaris is ideal for the investigation of developmental processes, because of its simple body, divided in head, gastric region and foot. Its ability to regenerate missing body parts makes this animal immortal. Hydra is able to reproduce sexually or asexually by budding. Through treatment with lithium chloride it is possible to interfere with this highly regulated pattern formation: In polyps treated with 1 mM LiCl budding is inhibited and ectopic feet form along the body axis.
To identify genes involved in signalling pathways during foot formation a LiCl induced cDNA library was scanned. Three transcripts (K10-7, MK55 and MK97) with a possible function in the foot region could be isolated.
The cDNA K10-7 is expressed in the foot region. The deduced, small protein has similarity with the EGF-like domain of tenascin and teneurin proteins. Members of these protein families play morphoregulatory roles during development and rearrangement of tissue. Through adhesive and anti-adhesive effects, mainly involving migrating cells, these proteins are involved in boundary formation between developing tissues. It’s possible that K10-7 acts in a similar way to transdifferentiate ectodermal cells into foot specific glad cells. Due to expression studies with double-labeling in situ hybridization K10-7 may also interact with Kringelchen, a FGF-receptor, and be involved in boundary formation during budding.
The foot specific cDNAs MK55 and MK97 are members of a huge protein family in Hydra showing sequence similarity to Rhamnose-binding proteins and. These proteins may be released from glad cells into the mucus of the foot. MK55 and MK97 may protect the basal end of the Hydra through agglutination of Bacteria.
Beside these foot specific cDNAs also the transkript MK38 was characterized. MK38 is expressed ubiquitous in the endoderm with exception of the hypostom. Due to sequence similarity to the microtubule binding protein family MAP215/Dis1 its proposed that MK38 is involved in cell division as well.
In a second project the RNA interference method (RNAi) which has been successfully established in H. magnipapillata should also used in H. vulgaris to characterise the function of the former described genes. Four different electroporation units which all induce different electric plusses were used to find gently conditions for the electroporation. All conditions tested in this study couldn’t induce RNAi effects in H. vulgaris.