Meeting Abstract

S9.7  Wednesday, Jan. 6  The development of the mesentoblast in the gastropod Crepidula fornicata MARTINDALE, Mark Q.*; LEE, Patricia; HENRY, Jonathan Q.; Kewalo Marine Lab, Univ. Hawaii mqmartin@hawaii.edu

One of the hallmarks of the spiralian cleavage program is the ability to identify and compare the development of homologous cells in embryos from disparate taxonomic groups. One cell of particular importance in all spiralian embryos is the mesentoblast, termed 4d. This cell is said to be the sole progenitor of endomesoderm and this cell and or its precursor, the 3D macromere has “organizing” activity patterning the dorso-ventral axis. We have used microinjection and laser ablation to study in detail the early cleavage program and endodermal and mesodermal fates of 4d sublineages in the gastropod, Crepidula fornicata. These results can be compared to those in other spiralian taxa. Furthermore, we have carried out a molecular analysis of mesendoderm formation in Crepidula. Injections of synthetic mRNA encoding GFP-tagged beta-catenin into fertilized eggs reveal that this protein is selectively stabilized in the 4d mesentoblast lineage, consistent with a role in the development of endomesoderm. Experiments using truncated messages, reveal that the C-terminal end, which includes some of the armadillo repeats is necessary for the subsequent degradation of this protein within that lineage.