Emergence of a Hexagonal Lattice of Differentiated Cells by Tissue-Scale Mechanics

Pattern formation of biological structures involves the arrangement of different types of cells in an ordered spatial configuration.

In this Presidential Lecture, Richard Carthew will describe his team’s work investigating the mechanism of patterning the Drosophila (fruit fly) compound eye into a precise hexagonal lattice of photoreceptor clusters called ommatidia. Previous studies led to a long-standing biochemical model whereby a reaction-diffusion process is templated by recently formed ommatidia to propagate a molecular prepattern across the eye tissue. Instead, we find that the templating mechanism is mechano-chemical; newly born columns of ommatidia serve as a template to spatially pattern cell flows that move the cells in the tissue into position to form each new column of ommatidia. Thus, the self-organization of a regular pattern of cell fates in an epithelium is mechanically driven.

Carthew is the Owen L. Coon Professor of Molecular Biosciences at Northwestern University. Born and raised in Toronto, Canada, he received a Ph.D. in biology from MIT. After a postdoctoral stint at the University of California, Berkeley, he held a faculty position at the University of Pittsburgh before joining the faculty at Northwestern University in 2001. He is the inaugural director of the NSF-Simons National Institute for Theory and Mathematics in Biology, established in 2023 in Chicago. His primary research focuses on the patterns of shape and form in complex animals. He was also a pioneer in elucidating the mechanisms whereby small RNA molecules can regulate gene expression across the eukaryota (nucleus-bearing cellular life). Carthew is a Helen Hay Whitney Fellow and a Pew Biomedical Scholar.