The Novel Role of Cilia in Astrocyte Sevelopment

PROJECT SUMMARY Astrocytes are the most abundant glial cell in the brain and are essential for neural circuit formation and neuron function. Astrocytes have an indispensable role in the developing brain, yet our fundamental understanding of how astrocytes develop trails our knowledge of neuron development. To develop, astrocytes must proliferate at the proper time, genetically differentiate, and morphologically mature. Astrocyte dysfunction contributes to the pathology of several neurodevelopmental disorders, yet these mechanisms are poorly understood. Both neurons and astrocytes possess a primary cilium, a slender microtubule projection, that serves as a specialized signaling center for the cell. Cilia are critical regulators of neuron development. However, despite astrocytes having a primary cilium, the function of astrocyte cilia remains unknown. Disruptions to cilia result in a class of disorders termed ciliopathies that often result in a spectrum of neurological abnormalities. We must establish a fundamental understanding of astrocyte cilia because it is likely that they contribute to such neurodevelopmental diseases. The goal of my research is to create foundational knowledge of the roles that cilia play in astrocyte development. My preliminary data indicate that astrocyte cilia are necessary for several stages of astrocyte development. Loss of astrocyte cilia results in altered proliferation, abnormal cellular morphology, and disrupted expression of developmental astrocyte genes. Therefore, I hypothesize that astrocyte cilia are critical to regulate astrocyte proliferation and differentiation. This project aims to 1) determine how cilia regulate astrocyte proliferation and 2) define the role of cilia in astrocyte differentiation. I will use mouse models to genetically ablate cilia at distinct timepoints, specifically in astrocytes, to investigate the requirements of cilia at different stages of astrocyte development. I will determine whether cilia regulate the timing and rate of astrocyte proliferation. Then, to further define how cilia regulate proliferation, I will monitor cell cycle progression. Next, I will define whether cilia are required for astrocyte differentiation by conducting a morphological analysis of astrocyte size, spacing, and branching features. Finally, I will conduct a transcriptomics analysis to determine whether cilia regulate the genetic program of developing astrocytes. I will also examine astrocyte transcriptional expression at the cellular level to define whether cilia impact differentiation in specific populations of cortical astrocytes. The proposed experiments will reveal novel functions of astrocyte cilia and establish a foundation for the roles of ciliary signaling in astrocyte development. This work will increase fundamental knowledge about astrocyte cilia and how astrocytes develop to improve our understanding of astrocyte contribution to neurodevelopmental diseases.