Physical, Molecular and Cellular Regulation of Sensory Organ Formation

New York University School Of Medicine, New York NY

Investigators

Abstract

ABSTRACT During nervous system development, tissues need to move and split to form neuronal cell clusters and layers. They use attractant gradients for guidance and cellular rearrangement for splitting. However, how attractant gradients are established and how tissues split in two is largely unclear. To address these questions, we use the posterior lateral line primordium migration in zebrafish as a model. The primordium is a group of about 140 cells that migrates along the body of the embryo and deposits 5–7 mechano-sensory organs called neuromasts from its back. It expresses the chemokine receptor Cxcr4 and follows a trail of the Cxcl12 chemokine. We have used this system to show that the primordium generates an Cxcl12 gradient across itself by sequestering Cxcl12 in its rear through the alternate Cxcl12 receptor Cxcr7, a chemokine scavenger receptor, and that the primordium couples actin flow to its substrate, the basement membrane, through integrins and exerts highest traction stresses (force per area) in its rear to push itself forward. In Aim 1, we will determine how the extracellular matrix and the migrating primordium together shape the distribution of Cxcl12a using an Cxcl12 signaling sensor and knock-in lines that we generated. In Aim 2, we will analyze the role of RhoA-mediated actomyosin contraction, cell-cell adhesion and cell- extracellular matrix adhesion in orchestrating the splitting off of neuromasts from the back of the primordium using cadherin-based tension sensors that we adopted to zebrafish and in vivo traction force microscopy that we recently developed. Our approach combines the optical accessibility of the zebrafish primordium with quantitative imaging, embryonic and genetic manipulations, and sensors for chemokine signaling, RhoA signaling, tension forces and traction stresses to provide a quantitative understanding of the physical, molecular and cellular mechanisms underlying tissue guidance and tissue splitting, two key aspects in assemblying the nervous system. We anticipate that our proposed studies will have two broad impacts on the field of nervous system development. First, they will provide a quantitative understanding of how attractant gradients are generated by migrating tissues. Second, they will unravel the mechanics of tissue splitting. These insights are key to understanding major biological and medical problems including defects in neuronal development and disease.