Centriole assembly and function for centrosome and cilia biology

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PROJECT SUMMARY/ABSTRACT Overview. Centrioles, and the centrosomes they scaffold, organize the cell, and provide the foundation for development and tissue homeostasis. To do this, centrioles exert control over the cell's microtubule (MT) network, providing a micron-scale framework for intracellular trafficking, intracellular and extracellular signaling, genome segregation, cell morphology, and cell mobility. To perform these roles, centrioles change through the cell cycle via the processes of new centriole assembly and modulations to scaffolding functions. During a normal cell cycle, centrioles nucleate the sensory and signaling compartment of cilia in G0/G1, duplicate coincident with the genome during S-phase, and organize the mitotic spindle during mitosis. In cancer and Trisomy 21 (the cause of Down syndrome), these mechanisms are disrupted. In specialized multiciliated cell types, centrioles nucleate motile cilia which generate fluid flows necessary for reproduction, development, and respiratory airway function. How centrioles are controlled, function and resist mechanical forces remain poorly understood. Goals for five years. We aim to dissect poorly understood mechanisms in how centrioles duplicate, how MT- based intracellular trafficking and cilia are controlled by centrosome protein dosage, and how centrioles provide the foundation for mechanical forces from motile cilia. We will investigate novel controls of centriole duplication either through spatial distributions of regulatory factors or through mRNA metabolism that generates functionally different proteins from the same gene. We will determine how imbalances in centriole number and centriole protein dosage, as observed in cancer and Trisomy 21, impact cytoplasmic MTs and intracellular trafficking for primary cilia formation and signaling. Finally, we will illuminate how centrioles act as force capacitors for motile cilia through connections to neighboring centrioles and the cell cortex and ask if they transmit forces back to cilia. These projects will establish the fundamental mechanics of centrioles as they assemble primary cilia for signaling and motile cilia for hydrodynamic flow. Vision for program. Discoveries in the fundamentals of centriole and centrosome biology, focusing on MT- dependent trafficking and mechanical force resistance, will have broad implications for understanding aspects of development, mechanobiology, and disease. Changes in RNA metabolism have a critical role in development, and by establishing mRNA processing events that affect centrioles and the MT network we anticipate identifying targets important for specialized cell types that utilize their MT networks in very different ways. Furthermore, our current studies in Trisomy 21 are pointing toward exciting future directions for understanding the cellular basis of cardiac, immune, and secretory cell systems directly impacted in Down syndrome.