In many studied animal species, including mammals, the future oocyte develops within a cluster of cells that exchange molecules and organelles through a network of cytoplasmic bridges, which are formed by stabilized and reinforced cytokinetic furrows. While the formation and structure of this interesting class of multicellular systems has been extensively studied, their dynamics is poorly understood, leaving many critical questions about oocyte determination and development unanswered. I will investigate two of these questions in Drosophila, an experimental model that continues to provide valuable insights into general mechanisms of animal oogenesis. Using experimental, modeling, and computational approaches, I will investigate how one cell within the germline cell cluster is chosen to be the future oocyte and how the germline cell cluster comprising the oocyte and supporting nurse cells grows during development. Specifically, Aim 1 is designed to evaluate the differential contributions of the prepatterning and self-organizing mechanisms of oocyte determination. Focusing on the fusome, a membranous structure that is essential for intercellular communication in early oogenesis, and on a recently discovered positive feedback loop involving mRNA localization and translation, I will establish data- driven mathematical models for oocyte selection. In parallel, Aim 2 will investigate growth of the oocyte and supporting cells, using the germline cluster as a tractable system for exploring how the scaling laws established by studies of single cell growth are altered when cells grow together. In particular, I will focus on size regulation of nuclei and nucleoli, aiming to understand how their sizes adjust to rapidly increasing cell volumes within the germline cell cluster. The completion of these proposed studies, which are supported by strong preliminary results, including a machine learning approach for 3D image reconstructions and morphometric analysis, should provide new insights into some of the first steps of animal oogenesis.
The proposed work will establish new quantitative approaches for studies of oocyte specification and collective cell size regulation during Drosophila oogenesis, an experimental system that continues to reveal highly conserved mechanisms of female germline development and provides unique opportunities for the integration of genetic, imaging, and computational techniques.
