The patterning of tissues by morphogens is a fundamental aspect of multicellular development, and morphogen misregulation has been implicated in developmental disorders and cancer. Recent work suggests that morphogenetic patterning is more complex than originally envisioned, with multiple spatiotemporal feedbacks and extracellular morphogen modulators impacting the formation and interpretation of morphogen gradients. Understanding morphogen patterning circuits thus will require levels of genetic control and quantitative analysis difficult to achieve in embryos. Here, we propose a complementary, synthetic approach to this problem in which we will reconstitute morphogen gradient formation from the bottom up, piece by piece. Specifically, we will reconstitute gradient formation in spatially extended monolayer cell cultures using cells engineered to secrete and respond to the morphogen bone morphogenetic protein (BMP), which is critical in embryonic patterning and has been implicated in many disorders (especially those of the musculoskeletal system). Using quantitative time-lapse microscopy, we will monitor the spatiotemporal dynamics of gradient formation at the level of individual cells. This system will provide a platform for systematically measuring the effects of factors that modulate BMP gradients, including glypicans, secreted inhibitors, and receptors. Finally, we will reconstruct a shuttling circuit proposed to underlie key functional capabilities such as gradient sharpening and gene dosage robustness. Through these reconstructions we will be able to determine the sufficiency of this circuit and understand the design principles that enable basic features of developmental patterning. We expect that this bottom-up, synthetic approach will be broadly useful in understanding the foundations of pattern formation by other morphogens and the misregulation of morphogen systems in disease states. This approach also will be useful in the design of regenerative medicine therapies. Career development activities will complement this research program in enabling the applicant to become an independent investigator.

Public Health Relevance

Molecules called morphogens pattern tissues in developing mammalian embryos, and misregulation of morphogens causes or contributes to developmental disorders and cancer. Morphogen control systems are quite elaborate, and understanding them in living organisms is challenging. The proposed research will develop and apply an engineering-like, reconstruction-based approach to understanding the control mechanisms for a particular class of morphogen;this will contribute to the understanding of disorders linked to thi morphogen class and to the design of regenerative medicine therapies.

National Institute of Health (NIH)
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Postdoctoral Individual National Research Service Award (F32)
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Special Emphasis Panel (ZRG1)
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Tyree, Bernadette
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California Institute of Technology
Schools of Arts and Sciences
United States
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Li, Pulin; Markson, Joseph S; Wang, Sheng et al. (2018) Morphogen gradient reconstitution reveals Hedgehog pathway design principles. Science 360:543-548
Markson, Joseph S; Elowitz, Michael B (2014) Synthetic biology of multicellular systems: new platforms and applications for animal cells and organisms. ACS Synth Biol 3:875-6