(5dz) Engineering Analysis of Developing Organs: Experiments and Theory

In developing new strategies for building tissues and treating degenerative tissue diseases, there is a great need to study developmental biology from an engineering perspective. Using genetics, imaging, and computational analysis, my graduate work has focused on: 1. assigning the functions of regulatory subcircuits (network motifs) that control the patterning of epithelial tissues, and 2. deciphering the spatial “code” of morphogenesis. We use Drosophila oogenesis as an accessible and established model system for studying the formation of 3D tubes, called dorsal appendages (DAs), from a 2D field of epithelial cells.

Quantitative analysis of pattern formation and regulatory sub-circuits. First, I have characterized the function of multiple negative feedback loops, which provide spatial control over the specification of cells that will later form the DAs. This work provides the first quantitative analysis of multiple EGFR inhibitors during Drosophila oogenesis. In the future, I plan on extending techniques of multiple simultaneous genetic perturbations and computational model analysis to assign patterning functions to subcomponents of regulatory circuits.

Parsing the grammar of epithelial morphogenesis. Second, I have investigated the regulation and function of potential effectors of morphogenesis, which translate the patterning of cellular properties (mechanics and motility) of a 2D epithelial sheet into a final 3D organ. Toward this end, I performed a screen for the expression patterns of cadherins, which are Ca+-dependent cell adhesion molecules. We found that 9/17 of Drosophila cadherins were differentially expressed during oogenesis. The diversity of patterns suggests that a “combinatorial code” of cadherin expression may play a role in segregating several cell sub-populations. Further, I studied the function and regulation of one of the patterned cadherins, Cad74A. I found that Cad74A is repressed by a Zn-finger transcription factor, Broad, a potential master regulator of DA morphogenesis. Ectopic expression of Cad74A in two groups of cells normally lacking Cad74A severely disrupts the formation of the dorsal appendages, showing that the differential expression of Cad74A plays a role in the formation of the tubular eggshell structures. In the future, I propose manipulating the spatial expression profiles of multiple adhesion genes, monitoring cell morphology and developing biomechanical models to decode the spatial “grammar” of morphogenesis.