Principles of pattern formation in animal developmentd

5 June 2009

Sean Megason
Department of Systems Biology
Harvard Medical School


Most of what we know about "systems level principles" comes from the study of bacteria and cultured cells. These experimental systems are advantageous for study from a systems level perspective because spatial dimensions can often be ignored, steady-state can be assumed, and optimality can be invoked as a guiding principle. But what about embryonic development of animals? Are the circuits that propel development forward fundamentally different from those that control environmental sensing in bacteria and homeostasis in cultured cells? Animal development is messy--it occurs in a complex 3-dimensional multicellular space, arguably never operates at steady state, and one look at the known wiring diagrams for development would make the most steadfast advocate of Intelligent Design question the intelligence of the designer. What is the meaning of "principles" in such a nihilistic world? Do real principles of development even exist or just evolutionarily constrained homologies? And if principles do exist, how can we hope to learn them? I will discuss these questions in the context of my lab's search for both the principles and the "actuals" of how fish are created.

current theory lunch schedule