Meeting Abstract

36-1   10:00 - 10:15  Asymmetrically expressed factors contribute to early embryo regulation in acoel Hofstenia miamia Rock, AQ*; Srivastava , M; Harvard University, Organismic and Evolutionary Biology arock@g.harvard.edu

Embryogenesis is a process universal to all animals; however only some animals can remake all cell types through whole-body regeneration. Little is known about the relation between regeneration and development, so we sought to find frameworks for comparing the two processes. The three-banded panther worm, Hofstenia miamia, is an emerging model organism that allows us to study both whole-body regeneration and development mechanistically. We first determined the “regenerative” potential of the embryo. Hofstenia embryos undergo a highly stereotyped cleavage program, duet cleavage; after the first symmetric division, the cells undergo a series of asymmetrical cleavages, where the smaller micromeres cleave from the larger macromeres. We have found that, when isolated from the embryo, 4-cell macromeres, not micromeres, have the potential to continue developing into adult worms and that Hofstenia embryos display regulative development. The 4-cell macromere can create cell types that have already been fated to the 4-cell micromere. By using lineage tracing, we have determined the origin of these cell types, which are unique when compared to the canonical embryonic origin. Additionally, using single-cell RNA sequencing, we have identified factors that are innately differentially expressed between the regulative and non-regulative blastomeres and may be contributing to the cell’s plasticity. This work establishes a mechanism for comparing the recovery of missing cell types in the developing embryo and a regenerating adult.