The hypothetical ancestral animal the Urmetazoa: Telomerase activity in sponges [Porifera]

Sponges (Porifera) represent the lowest metazoan phylum, characterized by a pronounced plasticity in the determination of cell lineages, and they are the closest related taxon to the hypothetical ancestral animal, the Urmetazoa, from which the metazoan lineages diverged. In a first approach to elucidate the molecular mechanisms controlling the switch from the cell lineage with a putative indefinite growth capacity to senescent, somatic cells, the activity of the telomerase as an indicator for immortality has been determined. The studies were performed with the marine demosponges Suberites domuncula and Geodia cydonium, in vivo with tissue but also in vitro using the primmorph system. Primmorphs are formed from dissociated cells which have retained their proliferation potency. It was found that the activity of telomerase in tissue of both sponges is high. Based on this and additional findings it is assumed that the separation of the senescent sponge cell lineage from the immortal germ-/somatic cell lineage is triggered by the loss of contact to cell adhesion factors. First evidence is included which suggests that the final progress of the senescent telomerase- negative cells to cell death is caused by apoptosis. Sundjeri (Porifera) predstavljaju najnize kolo metazoa, koje karakterise izrazita plasticnost u odredjivanju evolutivnih linija, i najblizi su takson hipoteticnoj prvobitnoj zivotinji, nazvanoj prametazoa, od koje su divergirale evolutivne linije metazoa. U prvom pristupu razjasnjavanju molekulskih mehanizama koji kontrolisu prelaz od celijske linije sa pretpostavljenom neogranicenom sposobnoscu rastenja ka somatskim celijama koje stare, odredjena je aktivnost telomeraze, kao indikatora besmrtnosti. Proucavanja su radjena na morskim demospongijama Suberites domuncula i Geodia cydonium, sa tkivom in vivo, ali i in vitro, koriscenjem primorfnog sistema. Primorfi se grade od disosovanih celija koje su zadrzale sposobnost proliferacije. Nadjeno je da je aktivnost telomeraze u tkivu oba sundjera visoka. Na osnovu ovog i dodatnih nalaza, moze se pretpostaviti da je odvajanje evolutivne linije celija sundjera, koje stare, od linije besmrtnih reproduktivnih/somatskih celija prouzrokovano gubitkom kontakta sa celijskim adhezionim faktorima. Ukljucen je prvi dokaz koji sugerise da je konacni prelaz od telomerazno-negativnih celija koje stare, ka celijskoj smrti prouzrokovan apoptozom. .