A micromere induction signal is activated by β-catenin and acts through Notch to initiate specification of secondary mesenchyme cells in the sea urchin embryo

• DOI: 10.1242/dev.127.23.5113
• Publication Date: 2021-04-26T04:25:25Z
• Authors: David R. McClay; Robert E. Peterson; Ryan C. Range; Anne M. Winter-Vann; Michael J. Ferkowicz
• Keywords: Mesenchyme; Cleavage (geology); Polarity in embryogenesis; Embryonic Induction

At fourth cleavage of sea urchin embryos four micromeres at the vegetal pole separate from macromeres just above them in an unequal cleavage. The have capacity to induce a second axis if transplanted animal and absence results failure macromere progeny specify secondary mesenchyme cells (SMCs). This suggests that SMCs. We demonstrate require nuclear beta-catenin exhibit SMC induction activity. Transplantation studies show much hemisphere is competent receive signal. SMCs, most likely through direct contact with progeny, or cell diameter away. quantitative more SMCs are induced by than one. Temporal signal passed between eighth tenth If removed hosts cleavage, rescued they later After addition induction-competent micromereless fails For be micromere signal, must enter nuclei. Notch receptor. Signaling-competent fail express dominant-negative Notch. Expression activated construct rescues specification micromeres. These data consistent model whereby enters nuclei and, as consequence, produce inductive ligand. Between In order receptive first transport their nuclei, one consequence pathway becomes transduce As maternally expressed macromeres, additional components downstream for these