Abstract

Eukaryotic cells contain a variety of complex morphologies that can substantially alter the transport, distribution, and encounter kinetics of particles. In this talk, we will focus on transport within tubular network structures, employing mathematical results and simulations, together with quantitative analysis of imaging data, to explore the impact of network morphology on transport. We will begin by considering diffusive particle movement through looped organelle networks formed by the endoplasmic reticulum (ER) and mitochondria. We show that global search times on such networks can be approximated based on total network edge length and loop number, and that the heterogeneity of network structures can result in reaction hot-spots. A potential role of ER network architecture in modulating local calcium release kinetics will be discussed. We then turn to consider the distribution of punctate organelles in the branched tree networks found in dendritic projections of neuronal cells. Specifically, mitochondrial distributions in Drosophila sensory dendrites are found to exhibit two robust features: a distal enhancement of mitochondrial density, and an equitable distribution of mitochondria between asymmetric sister subtrees. Simple scaling laws for dendritic branch width and mitochondrial transport are shown to account for both of these features. Overall, physical modeling of disparate cellular systems highlights the importance of intracellular network morphology in determining particle distribution within the cell.