Research

Our team’s research focuses on the systems biology and biomechanics of the development of the spinal column. We are interested in how cell signaling pathways are integrated to regulate the segmentation of the trunk during embryonic development and how cell migration, extracellular matrix (ECM) dynamics and biomechanics contribute to body elongation. We employ a variety of genetic, molecular, computational and imaging techniques in our research.                                                                                                                                            

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We study early vertebral column development in zebrafish.  Zebrafish embryos are transparent (Figure 1A) and thus particularly well suited for live imaging and embryological experiments (Figure 1B-C”).

 

Somites ultimately give rise to the vertebral column and ribs, skeletal muscle, and dermis (Figure 2A-C). In our studies we found that zebrafish Notch pathway mutants are defective in somite formation. These mutant zebrafish have an abnormal vertebral column and disorganized ribs (Figure 2D-F). Mutations in the human orthologues of these genes result in vertebral defects such as scoliosis. Furthermore, mutation of these genes in adults lead to cancer as the genes regulate cell behavior in both the developing embryo and the adult.

Our research has been noted by the Yale Daily News! - http://yaledailynews.com/blog/2016/02/16/protein-found-crucial-in-verteb….

The paraxial mesoderm of zebrafish embryos is covered by a dense network of fibers composed of the extracellular matrix protein Fibronectin (Figure 3A). In mutants lacking the primary receptors for Fibronectin, this dense matrix is significantly reduced and ECM fiber morphology is abnormal (Figure 3B).

We found that loss of cell-extracellular matrix adhesion leads to a trunk elongation defect without substantive alteration of cell migration. A systems-level analysis of cell motion in the extending trunk in the presence and absence of cell-extracellular matrix interactions points to a role of the extracellular matrix in defining tissue mechanics and inter-tissue adhesion necessary for elongation of the spinal column.

Cell migration, cell differentiation and tissue patterning become intertwined as the zebrafish embryo grows at its posterior end. To decipher how the flow of migrating cells within the trunk contribute to axis elongation, we combine live imaging, cell tracking (Figure 4) and metrics from fluid mechanics and soft matter physics. We developed a computational model of cell migration during body elongation based upon our quantitative in vivo data (Figure 5). This inter-disciplinary approach led us to identify changes in tissue fluidity revealed by reductions in the coherence of cell motion without alteration of cell velocity.

 

We are using quantitative imaging, including FCS, FCCS, FRET/FLIM and lightsheet imaging along with new fluorescent transgenes to study the defects in new mutants generated using CRISPR/cas9.

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