Meeting Abstract

S9.2  Wednesday, Jan. 6  Cell and molecular mechanisms involved in the establishment of the D quadrant in the Gastropod, Crepidula fornicata HENRY, JJ*; PERRY, KJ; University of Illinois; University of Illinois j-henry4@illinois.edu

In spiralian embryos cells of the D quadrant play a key role in establishing the dorsoventral axis and in organizing subsequent development of other cell quadrants. Laser ablation experiments were undertaken to characterize the timing of cell interactions involved in the specification of the D quadrant and its subsequent organizer activity in the snail, Crepidula fornicata. As is the case in other equal-cleaving sprialians, the dorsal, D quadrant is specified by animal-vegetal inductive interactions early during development. Unlike the case in other spiralians, however, it is the fourth quartet micromere derived from the D quadrant, (i.e., the mesentoblast, 4d) that serves as the key organizer for subsequent development in this species. Functional molecular analyses suggest that specific elements of the TGF-beta super family are involved in the specification of the D quadrant in C. fornicata. Furthermore, 454 pyro-sequencing, PCR and RACE reactions were undertaken to recover clones encoding numerous BMP, TGF-beta, nodal, ALK receptor, Smad, and Smurf proteins, as well as other elements of various TGF-beta signaling pathways. In situ RNA hybridization reveals that many of these messages, as well as others, exhibit specific patterns of localization to particular embryonic cell lineages during early development, which also appear to be consistent with roles of these factors in establishing specific cell fates during development.