Life Sciences Commons^™

How To Build A Cortex: Coordinated Assembly Of Cortical Septins And Actomyosin In The Leader Bleb, Asia Marie Paguntalan

Master's Theses

In confined spaces, migrating cells can undergo mesenchymal-to-amoeboid transitions by altering their cortical dynamics and adhesion with the environment. Septins frequently associate with cortical actin and non-muscle myosin (NMII), but the functional nature of these interactions remains unclear. Upon non-adhesive confinement and NMII enrichment, fibroblasts can switch to a fast, leader bleb-based mode of motility, characterized by the absence of adhesions and stress fibers and formation of a single, elongated leader bleb. During this transition, cortical actin remodeling and polarized NMII contractility drive leader bleb stabilization by generating long-range cortical flows, in coordination with changes in septin localization and assembly …

Adherens Junctions And The Actomyosin Network Regulate Organ Growth By Modulating Hippo Pathway Activity In Drosophila, Chih-Chao Yang

Dissertations & Theses (Open Access)

Adherens junctions (AJs) and basolateral modules are important for the establishment and maintenance of apico-basal polarity. Loss of AJs and basolateral module members lead to tumor formation, as well as poor prognosis for metastasis. Recently, in mammalian studies it has been shown that loss of either AJ or basolateral module members deregulate Yorkie activity, the downstream transcriptional effector of the Hippo pathway. Importantly, it is unclear if AJ and basolateral components act through the same or parallel mechanisms to regulate Yorkie activity.

Here, we dissect how loss of AJ and basolateral components affects Hippo signaling in Drosophila. Surprisingly, while …

Rho Kinase Regulates Basement Membrane Dynamics To Coordinate Salivary Gland Branching Morphogenesis And Tissue Organization, William Patrick Daley

Legacy Theses & Dissertations (2009 - 2024)

Branching morphogenesis is a developmental mechanism utilized by many organs, including the salivary gland, lung, kidney, and mammary gland, to increase the epithelial surface area for secretion or absorption. The embryonic submandibular salivary gland (SMG) is a classic model for studying tissue morphogenesis in three dimensions ex vivo. Salivary gland development requires distinct but overlapping processes: morphogenesis, the actual physical rearrangement of cells into complex three dimensional structures, and cytodifferentiation, the process by which these cells begin to take on their own specialized function. Polarization, or the organization of cells into a cohesive tissue structure, also occurs concurrently during organ …

The Tem1 Small Gtpase Controls Actomyosin And Septin Dynamics During Cytokinesis, John Lippincott, Katie Shannon, Wenying Shou, Raymond J. Deshaies, Rong Li

Biological Sciences Faculty Research & Creative Works

Cytokinesis in budding yeast involves an actomyosin-based ring which assembles in a multistepped fashion during the cell cycle and constricts during cytokinesis. In this report, we have investigated the structural and regulatory events that occur at the onset of cytokinesis. The septins, which form an hour-glass like structure during early stages of the cell cycle, undergo dynamic rearrangements prior to cell division: the hourglass structure splits into two separate rings. The contractile ring, localized between the septin double rings, immediately undergoes contraction. Septin ring splitting is independent of actomyosin ring contraction as it still occurs in mutants where contraction fails. …

The Multiple Roles Of Cyk1p In The Assembly And Function Of The Actomyosin Ring In Budding Yeast, Katie Shannon, Rong Li

Biological Sciences Faculty Research & Creative Works

The budding yeast IQGAP-like protein Cyk1p/Iqg1p localizes to the mother-bud junction during anaphase and has been shown to be required for the completion of cytokinesis. In this study, video microscopy analysis of cells expressing green fluorescent protein-tagged Cyk1p/Iqg1p demonstrates that Cyk1p/Iqg1p is a dynamic component of the contractile ring during cytokinesis. Furthermore, in the absence of Cyk1p/Iqg1p, myosin II fails to undergo the contraction-like size change at the end of mitosis. To understand the mechanistic role of Cyk1p/Iqg1p in actomyosin ring assembly and dynamics, we have investigated the role of the structural domains that Cyk1p/Iqg1p shares with IQGAPs. An amino …

A Kinetic Investigation Of The Mechanism Of Muscle Contraction With A Series Of Nucleotides, Wei Jiang

Theses and Dissertations in Biomedical Sciences

Muscle contraction is thought to be accomplished by sliding of myosin filaments along actin filaments. Although actomyosin naturally uses ATP as an energy source, it can also use other nucleoside triphosphates (NTP) as substrates. In this work, the dependence of rate and equilibrium constants of the various steps in the muscle contraction mechanism upon nucleotide structure was investigated to unravel the dependence of the mechanical properties of the muscle upon changes in different biochemical steps of the mechanism.

The experiments measuring the dissociation of actomyosin by NTP (or mant-NTP) shows that both the rate constant of actomyosin-S1 dissociation and second …