Molecular specification of cell lines in the embryo of Platynereis (Annelida).

In this study we describe the site and moment of histospecific differentiation in developmental stages of the annelid Platynereis dumerilii by use of biochemical markers. The monoclonal antibody (mab) OI7 and uncloned hybridoma supernatants (pAb's) OI8, OI10, OI46 and OI69 recognize neural antigens that appear asynchronously during development. By an enzymatic test, acetylcholinesterase (AChE) was found specific for nervous tissue as well. The patterns of neural structures labelled by antibodies differ, however, from those revealed by AChE staining. Experimental inhibition of transcription (with actinomycin D) and of translation (using puromycin) demonstrate that the expression of histospecific neural markers depends on both zygotic transcription and subsequent translation. The mAb OI64 labels epidermal (and neural) gland cells. The antibody 4D9, raised against the engrailed protein of Drosophila, labels single rows of ciliated cells at the posterior border of segments.