Functional role of non-genetic variability

Throughout biology isogenic cell populations exhibit phenotypic diversity and collective behavior. These properties complicate the treatment of diseases and our mechanistic understanding of biology because they give rise to emergent behaviors that are not directly predicted from the structures and functions of proteins.

One of our major goals is to understand how phenotypic heterogeneity in isogenic populations affects complex functions such as chemical sensing, adaptation, motility; and how the balance between phenotypic heterogeneity and collective behavior shapes population performance. How do we quantify individual cell performance and trace it back to molecules? What is the origin of cell-to-cell differences in performances? To what extend such variability is under selection? How does the shape of such  distribution affects population success?

Computational principles of bacterial navigation

During navigation towards a signal source, directional changes by the organism result in changes in the signal it is likely to experience next. Thus, behavior feeds back onto the signal and the statistics of signal and behavior are intrinsically related. Using bacterial chemotaxis in E. coli as a model system we are trying to understand how such feedback shapes the statistics of behavior, signal, and performance during navigation of chemical gradients. Cells travel also in groups by communicating between themselves. We are examining how diversity modulate group migration.

Deciphering the neural computation underlying olfactory navigation

Insects transmit diseases and destroy crops. The sense of smell is key for insects to find food and mate. Understanding how insect navigate odor plumes is therefore critical in the fight against pest and vector borne diseases. A major difficulty in understanding the sense of smell is to simultaneously characterize the signal (odor concentration in space and time) and the walking or flying behavior of the insect. We recently developed a novel assay to do so and are using it to decipher the neural computation underlying olfactory navigation.

The role of time in odor coding

We want to understand how identity and intensity of odor signals are represented in the brain. We use Drosophila as a model system to investigate the role of the temporal activation of the olfactory sensory neurons (ORNs) in odor coding. How do different receptors filter odor stimuli? Is there a logic in the diversity of response dynamics observed for different odors? How do dynamics at the sensory input affect odor information processing and behavior? We combine in vivo electrophysiological recordings from the sensory neurons, with measurements of odor signals and genetic manipulations. In recent years we have examined the dynamical properties of ORNs and discovered key adaptation modalities to the mean and variance of the signal.

How to grow a straight spine?

This is a theory project in collaboration with Scott Holley’s lab where all the experiments are done. Elongation of the vertebrate body axis is driven by collective cell migration and cell proliferation at the posteriorly advancing embryonic tailbud. Within the Zebrafish tailbud an ordered stream of cells symmetrically bifurcates to form the left and right halves of the presomitic mesoderm. Maintaining bilateral symmetry during this process is critical to avoid catastrophic spine deformation. Using direct comparison between experimental data and a simple biophysical model of cell migration we are examining how the migratory behavior of individual cells affects tissue properties over long distances.