Meeting Abstract
Bone morphogenic proteins (BMPs) are a family of signaling molecules that specify cell fate in a concentration-dependent manner. BMPs and their antagonists function in dorsal-ventral (D-V) axis specification and neural fate specification in vertebrates and Drosophila. In hemichordates application of exogenous BMPs during development dorsalizes the animals, but does not repress neural fate specification, suggesting that BMP signaling may have played an ancestral role in D-V axis specification. There is little data on D-V axis and neural fate specification from spiralians (one of two major protostome clades). However, in the spiralian annelid Helobdella, short-range BMP5-8 and the antagonist Gremlin pattern the D-V axis in the prospective segmented ectoderm. BMPs also pattern the D-V axis in the annelid Platynereis dumerilii but do not appear to repress central nervous system development. The annelid Capitella teleta has a clear D-V axis, with an anterior brain and a ventral nerve cord. Brain development begins during gastrulation with the ingression of single cells from localized areas of anterior ectoderm. Ventral nerve cord development is less well characterized, but begins shortly after gastrulation. We assessed the role of BMPs at early cleavage stages and during gastrulation in C. teleta. After applying exogenous recombinant BMP4 protein at multiple time windows, we did not see clear evidence of abnormal D-V patterning. However, recombinant BMP4 clearly affected neural development, including formation of the brain and eyes. These findings contrast what has been observed in other spiralians, and raise questions about the ancestral function of BMP signaling.
