CAREER: Mechanistic studies of cilium proteins in cell signaling

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).

Most cells in our body have a primary cilium (a single hair-like projection on their cell surface) that allows them to interact with each other via chemical signals. This ancient and mysterious organelle acts like a radio antenna, allowing cells to receive different information, depending on which kinds of receptors their antenna contains. Gene mutations affecting ciliary signaling have been implicated in a host of diseases that result in the malformation and dysfunction of multiple organs.

This project focuses on primary cilia in the developing brain. During brain formation, the progenitor cells that give rise to nerve cells (neurons) coordinate with each other to make sure that specific type of neurons are produced in the correct location at the right time. Surprisingly little is known about which receptors in their primary cilia allow effective communication.

This project will document the full catalog of receptors situated in the primary cilia of neural progenitor cells using novel techniques that selectively label cilium proteins with a special tag named biotin, and then identify these marked proteins using mass spectrometry. It will also decipher the mechanisms by which some of these proteins influence developmental decisions.

Pilot studies have already identified proteins previously shown to control brain development that are unexpectedly operating in the cilium. Overall, the results of this project will provide novel insights into how neural cell progenitors coordinate to build the brain. They advance our understanding of how brain development works and will also help us to better understand brain developmental disorders.

In addition, this project will engage local K-12 students and high school teachers in laboratory research, aiming to inspire a sustained interest in the biological sciences among local youth, as well as implementing an integrated educational program to promote participation and retention of students from underrepresented minorities in biological research. These activities will substantially improve education in life science in the socioeconomically disadvantaged California Central Valley.

Neural progenitors in the developing brain (also known as Radial Glia, RG) produce all of the brain’s neurons in a time- and space-specific manner. Different neuronal types are generated at distinct developmental stages and in discrete brain regions. This process is highly coordinated via cell signaling sensed by the RG primary cilia.

Defects in cilium function lead to ciliopathies, a wide-ranging spectrum of disorders that usually involve brain structural defects. Yet a systematic understanding of RG cilium signaling pathways is lacking. This project will identify new signaling proteins in RG cilia by leveraging a new proximity labeling tool (TurboID) and a novel transgenic mouse model in which TurboID is selectively expressed in the cilium of RG cells.

Quantitative proteomic studies with rigorous controls will reveal bona fide cilium proteins operating in discrete brain regions and across different developmental stages. Pilot studies with cilium-targeted TurboID have surprisingly revealed cilium localization of a protein previously reported to regulate neurogenesis through undetermined mechanisms.

Preliminary data show that this protein operates in the cilium to regulate Hedgehog signaling, the best-described pathway in the cilium. Investigating the interaction between this new cilium protein and Hedgehog signaling will reveal new regulatory mechanisms in embryonic neurogenesis, and demonstrate how cilium proteomics can help solve standing long-questions in brain development.

By systemically unveiling the signaling pathways used by RG cilia with spatiotemporal resolution, this project will also chart new directions for future neurodevelopmental studies.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.