The chemokine networks in sponges: potential roles in morphogenesis, immunity and stem cell formation.
Porifera (sponges) are now well accepted as the phylum which branched off first from the common ancestor of all metazoans, the Urmetazoa. The transition to the Metazoa became possible because during this phase, cell-cell as well as cell-matrix adhesion molecules evolved which allowed the formation of a colonial stage of animals. The next prerequisite for the evolution to the Urmetazoa was the establishment of an effective immune system which, flanked by apoptosis, allowed the formation of a first level of individuation. In sponges (with the model Suberites domuncula and Geodia cydonium), the main mediators of the immune responses are the chemokines. Since sponges lack a vascular system and consequently blood cells (in the narrow sense), we have used the term chemokines (in a broad sense) to highlight that the complex network of intercellular mediators initiates besides differentiation processes also cell movement. In the present review, the cDNAs encoding the following chemokines were described and the roles of their deduced proteins during self-self and nonself recognition outlined: the allograft inflammatory factor, the glutathione peroxidase, the endothelial-monocyte-activating polypeptide, the pre-B-cell colony-enhancing factor and the myotrophin as well as an enzyme, the (2-5)A synthetase, which is involved in cytokine response in vertebrates. A further step required to reach the evolutionary step of the integrated stage of the Urmetazoa was the acquisition of a stem cell system. In this review, first markers for stem cells (mesenchymal stem cell-like protein) as well as for chemokines involved in the maintenance of stem cells (noggin and glia maturation factor) are described at the molecular level, and a first functional analysis is approached. Taken together, it is outlined that the chemokine network was essential for the establishment of metazoans, which evolved approximately 600 to 800 million years ago.
Institut für Physiologische Chemie, Abteilung Angewandte Molekularbiologie, Universität, Duesbergweg 6, 55099 Mainz, Germany.
W E G
WE
Müller
M
M
Wiens
I M
IM
Müller
H C
HC
Schröder
D015088:2',5'-Oligoadenylate Synthetase / Q000235:genetics / Q000502:physiology; D000595:Amino Acid Sequence; D000818:Animals; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000502:physiology; D018925:Chemokines / Q000235:genetics / Q000502:physiology*; D016207:Cytokines / Q000235:genetics / Q000502:physiology; D005979:Glutathione Peroxidase / Q000235:genetics / Q000502:physiology; D008954:Models, Biological; D008969:Molecular Sequence Data; D010802:Phylogeny; D011161:Porifera / Q000166:cytology / Q000235:genetics / Q000254:growth & development* / Q000276:immunology*; D017386:Sequence Homology, Amino Acid; D013234:Stem Cells / Q000166:cytology / Q000276:immunology; D014181:Transplantation Immunology
D002135:Calcium-Binding Proteins; D018925:Chemokines; D016207:Cytokines; D005979:Glutathione Peroxidase; D015088:2',5'-Oligoadenylate Synthetase