Development, Vol 125, Issue 20 4033-4044, Copyright © 1998 by Company of Biologists

JOURNAL ARTICLES

Specification of first quartet micromeres in Ilyanassa involves inherited factors and position with respect to the inducing D macromere

HC Sweet
Zoology Department, Center for Developmental Biology, The University of Texas at Austin, Austin, TX 78712, USA. hsweet+@andrew.cmu.edu

In the embryos of the gastropod Ilyanassa obsoleta, the development of several ectodermal structures requires an inductive interaction between the micromeres and the D macromere. The first quartet micromeres (1a, 1b, 1c and 1d) contribute to the head of the larva and descendants of 1a and 1c normally develop the eyes. The eyes do not develop if 1a and 1c are removed at the eight-cell stage. However, regulative eye development may occur if the precursors of 1a and 1c are removed at the two- or four-cell stage. One purpose of this study was to demonstrate which cells of the cleavage-stage embryo have the potential to develop an eye. The results of blastomere deletion experiments suggest that only the first quartet micromeres have this ability. In addition, the 1b micromere was found to be equivalent to 1a and 1c, but 1d was found to have a poorer eye-forming ability. A second purpose of this study was to examine how eye development is normally restricted to the 1a and 1c micromeres. Cell transplantation experiments demonstrate that the proximity of a first quartet micromere relative to the inducing D macromere is important for determining whether or not it will go on to develop an eye. The 1b micromere may not develop an eye during normal development because it is too far from the D macromere. However, the eye-forming ability of the 1d micromere is not influenced by its close position to the D macromere, but is restricted by its polar lobe lineage.

This article has been cited by other articles:

				M. Goulding Cell contact-dependent positioning of the D cleavage plane restricts eye development in the Ilyanassa embryo Development, March 15, 2003; 130(6): 1181 - 1191. [Abstract] [Full Text] [PDF]

				J. Lambert and L. Nagy MAPK signaling by the D quadrant embryonic organizer of the mollusc Ilyanassa obsoleta Development, January 1, 2001; 128(1): 45 - 56. [Abstract] [PDF]