Alladi Ramakrishnan Hall

Regulated tissue fluidity steers zebrafish body elongation

Amitabha Nandi

Department of Molecular, Cellular and Developmental Biology, Yale University,

The tailbud is the posterior leading edge of the growing vertebrate embryo consisting of motile progenitors of the axial skeleton, musculature and spinal cord. We study the 3D cell flow field of the zebrafish tailbud and identify changes in tissue fluidity revealed by reductions in the net directed movement. Cells maintain a directed posterior flow wherein the polarization between individual cell motion is high, reflecting ordered collective migration. In the tailbud they make sharp bilateral turns facilitated by extensive cell mixing due to an increased directional variability of individual cell motions. Manipulation of Wnt or Fgf signaling affects the coherence of the flow but has different consequence for trunk and tail extension. Our study suggest that a balance between the polarization of the individual cells motion and the rate of cell flow determines whether body elongation is linear or congestion forms within the flow and the body axis becomes contorted.