Ordered progression of nematogenesis from stem cells through differentiation stages in the tentacle bulb of Clytia hemisphaerica (Hydrozoa, Cnidaria).

摘要: Nematogenesis, the production of stinging cells (nematocytes) in Cnidaria, can be considered as a model neurogenic process. Most molecular data concern freshwater polyp Hydra, which nematocyte is scattered throughout body column ectoderm, mature then migrating to tentacles. We have characterized tentacular nematogenesis Clytia hemisphaerica hydromedusa and found it confined ectoderm tentacle bulb, specialized swelling at base. Analysis by variety light electron microscope techniques revealed that while cellular aspects are similar spatio-temporal characteristics markedly more ordered. The bulb nematogenic (TBE) was polarized, with clear progression successive nematoblast stages from proximal zone (comprising majority undifferentiated cells) distal end where starts. Pulse-chase labelling experiments demonstrated continuous displacement differentiating nematoblasts towards tip, proceeds rapidly than Hydra. Compact expression domains orthologues known nematogenesis-associated genes (Piwi, dickkopf-3, minicollagens NOWA) were correspondingly staggered along TBE. These distinct make TBE promising experimental system for understanding mechanisms regulating nematogenesis.