Juliano CE, Voronina E, Stack C, Aldrich M, Cameron AR (2006) Germ line determinants are not localized early in sea urchin development, but do accumulate in the small micromere
Spatial aspects of cell interactions involved in the determination of dorsoventral polarity in equally cleaving gastropods and regulative abilities of their embryos, as studied by micromere
deletions in Lymnaea and Patella.
A regulatory gene network that directs micromere
specification in the sea urchin embryo.
A Ral/MEK/ERK signaling pathway is required for development of the sea urchin embryo micromere
lineage through phosphorylation of the transcription factor Ets.
For instance, addition of a single micromere
to isolated rings of animal or vegetal cells resulted in a ciliated blob, whereas the addition of four micromeres
resulted in a normal pluteus.
The fourth cleavage appeared asynchronous: the macromeres divided first to produce a transient 12-cell stage, followed by a 13-cell stage as one first-quartet micromere
consistently divided before the other three (Fig.
The 4d micromere
plays a significant role, giving rise to the paired mesentoblast cells MEL and MER.
obsoleta Hb-like proteins are expressed in every micromere
and macromere nucleus from one cell to at least the sixth cleavage division.
Molluscs, like most other lophotrochozoans, exhibit a highly conserved pattern of spiral cleavage that generates four macromeres surmounted by four tiers of micromere
Pmarl drives specification of skeletogenic cells-- the micromere
descendants (Oliveri et al.
It remained attached to the vegetal pole of the embryo as a spherical packet of red-colored cytoplasm ("red body") at least through the period when micromere
quartets were generated (Fig.
differentiation in the sea urchin embryo: expression of primary mesenchyme cell specific antigen during development.