Meryl Spencer - Academia.edu (original) (raw)

Papers by Meryl Spencer

Bulletin of the American Physical Society, Mar 9, 2018

arXiv (Cornell University), Sep 12, 2018

The alignment of cell-cell junctions and associated cortical actomyosin across multiple cells to ... more The alignment of cell-cell junctions and associated cortical actomyosin across multiple cells to form supracellular cables in an epithelium is an example of the long range tissue organization that drives morphogenesis. Here we demonstrate that the ability of tissues to assemble these parallel cables depends on the initial packing topology of the cells in the epithelium. Using a computational vertex model we develop two methods of measuring a disordered tissue's favorability to forming cables under an external stress. These measures quantify the deformation of cells and the distribution of tension in the tissue under stress. Using these measures we show that passive stress-induced cell flow reduces a tissues ability to form cables, whereas oriented divisions create a packing which can sustain multiple parallel cables. These measures are applied to a region of the the Drosophila demonstrating a shift to a more cable-friendly packing after a wave of oriented divisions in the region.

Physical review, Apr 25, 2016

In this paper we introduce a variant of the honeycomb lattice in which we create defects by rando... more In this paper we introduce a variant of the honeycomb lattice in which we create defects by randomly exchanging adjacent bonds, producing a random tiling with a distribution of polygon edges. We study the percolation properties on these lattices as a function of the number of exchanged bonds using a novel computational method. We find the site and bond percolation thresholds are consistent with other three-coordinated lattices with the same standard deviation in the degree distribution of the dual; here we can produce a continuum of lattices with a range of standard deviations in the distribution. These lattices should be useful for modeling other properties of random systems as well as percolation.

European Physical Journal E, 2017

In computer simulations of dry foams and of epithelial tissues, vertex models are often used to d... more In computer simulations of dry foams and of epithelial tissues, vertex models are often used to describe the shape and motion of individual cells. Although these models have been widely adopted, relatively little is known about their basic theoretical properties. For example, while fourfold vertices in real foams are always unstable, it remains unclear whether a simplified vertex model description has the same behavior. Here, we study vertex stability and the dynamics of T1 topological transitions in vertex models. We show that, when all edges have the same tension, stationary fourfold vertices in these models do indeed always break up. In contrast, when tensions are allowed to depend on edge orientation, fourfold vertices can become stable, as is observed in some biological systems. More generally, our formulation of vertex stability leads to an improved treatment of T1 transitions in simulations and paves the way for studies of more biologically realistic models that couple topological transitions to the dynamics of regulatory proteins.

2023 IEEE Aerospace Conference

Deep Blue (University of Michigan), 2018

This work would have not have been possible without the mentorship of my adviser David. Much of m... more This work would have not have been possible without the mentorship of my adviser David. Much of my thesis work relies on analysis of thousands of images taken by Jesus Lopez-Gay. I sustained a major spinal cord injury just as I started to write my thesis. I would not have been physically capable of finishing it, if not for the amazing medical care I received from my entire team at the neuro-ICU and 6A. I could not have afforded the care without medical benefits from my grad union GEO. Thank you from the bottom of my heart everyone who cooked me meals, cleaned my house, and gave me moral support throughout my long recovery. Special thanks to Patricia Klein for organizing my care, and my parents for their constant support. This work probably would have been possible without the support of my fellow graduate students, but it wouldn't have been nearly as fun. I'd like to thank my amazing first-year cohort especially, Paige, Rutu, Karishima, Chrisy and Kevin for working through Jackson with me, as well as Jessie, Joe, Glenn, Peter, Ansel, and Anthony for joining in second-year. John Ware has supported me from start to finish, from working through old qualifying exams through proofreading thesis chapters. My entire family has given me moral and finantial support throughout college and graduate school, even if they often didn't understand what I was doing. Thanks for sticking with me.

arXiv: Tissues and Organs, 2018

The alignment of cell-cell junctions and associated cortical actomyosin across multiple cells to ... more The alignment of cell-cell junctions and associated cortical actomyosin across multiple cells to form supracellular cables in an epithelium is an example of the long range tissue organization that drives morphogenesis. Here we demonstrate that the ability of tissues to assemble these parallel cables depends on the initial packing topology of the cells in the epithelium. Using a computational vertex model we develop two methods of measuring a disordered tissue's favorability to forming cables under an external stress. These measures quantify the deformation of cells and the distribution of tension in the tissue under stress. Using these measures we show that passive stress-induced cell flow reduces a tissue's ability to form cables, whereas oriented divisions create a packing which can sustain multiple parallel cables. These measures are applied to a region of the the Drosophila demonstrating a shift to a more cable-friendly packing after a wave of oriented divisions in the r...

Bulletin of the American Physical Society, 2018

Physical Review E, 2016

In this paper we introduce a variant of the honeycomb lattice in which we create defects by rando... more In this paper we introduce a variant of the honeycomb lattice in which we create defects by randomly exchanging adjacent bonds, producing a random tiling with a distribution of polygon edges. We study the percolation properties on these lattices as a function of the number of exchanged bonds using a novel computational method. We find the site and bond percolation thresholds are consistent with other three-coordinated lattices with the same standard deviation in the degree distribution of the dual; here we can produce a continuum of lattices with a range of standard deviations in the distribution. These lattices should be useful for modeling other properties of random systems as well as percolation.

The European Physical Journal E, 2017

In computer simulations of dry foams and of epithelial tissues, vertex models are often used to d... more In computer simulations of dry foams and of epithelial tissues, vertex models are often used to describe the shape and motion of individual cells. Although these models have been widely adopted, relatively little is known about their basic theoretical properties. For example, while fourfold vertices in real foams are always unstable, it remains unclear whether a simplified vertex model description has the same behavior. Here, we study vertex stability and the dynamics of T1 topological transitions in vertex models. We show that, when all edges have the same tension, stationary fourfold vertices in these models do indeed always break up. In contrast, when tensions are allowed to depend on edge orientation, fourfold vertices can become stable, as is observed in some biological systems. More generally, our formulation of vertex stability leads to an improved treatment of T1 transitions in simulations and paves the way for studies of more biologically realistic models that couple topological transitions to the dynamics of regulatory proteins.

Science, 2020

Biological systems tailor their properties and behavior to their size throughout development and ... more Biological systems tailor their properties and behavior to their size throughout development and in numerous aspects of physiology. However, such size scaling remains poorly understood as it applies to cell mechanics and mechanosensing. By examining how the Drosophila pupal dorsal thorax epithelium responds to morphogenetic forces, we found that the number of apical stress fibers (aSFs) anchored to adherens junctions scales with cell apical area to limit larger cell elongation under mechanical stress. aSFs cluster Hippo pathway components, thereby scaling Hippo signaling and proliferation with area. This scaling is promoted by tricellular junctions mediating an increase in aSF nucleation rate and lifetime in larger cells. Development, homeostasis, and repair entail epithelial cell size changes driven by mechanical forces; our work highlights how, in turn, mechanosensitivity scales with cell size.

Bulletin of the American Physical Society, Mar 9, 2018

arXiv (Cornell University), Sep 12, 2018

The alignment of cell-cell junctions and associated cortical actomyosin across multiple cells to ... more The alignment of cell-cell junctions and associated cortical actomyosin across multiple cells to form supracellular cables in an epithelium is an example of the long range tissue organization that drives morphogenesis. Here we demonstrate that the ability of tissues to assemble these parallel cables depends on the initial packing topology of the cells in the epithelium. Using a computational vertex model we develop two methods of measuring a disordered tissue's favorability to forming cables under an external stress. These measures quantify the deformation of cells and the distribution of tension in the tissue under stress. Using these measures we show that passive stress-induced cell flow reduces a tissues ability to form cables, whereas oriented divisions create a packing which can sustain multiple parallel cables. These measures are applied to a region of the the Drosophila demonstrating a shift to a more cable-friendly packing after a wave of oriented divisions in the region.

Physical review, Apr 25, 2016

In this paper we introduce a variant of the honeycomb lattice in which we create defects by rando... more In this paper we introduce a variant of the honeycomb lattice in which we create defects by randomly exchanging adjacent bonds, producing a random tiling with a distribution of polygon edges. We study the percolation properties on these lattices as a function of the number of exchanged bonds using a novel computational method. We find the site and bond percolation thresholds are consistent with other three-coordinated lattices with the same standard deviation in the degree distribution of the dual; here we can produce a continuum of lattices with a range of standard deviations in the distribution. These lattices should be useful for modeling other properties of random systems as well as percolation.

European Physical Journal E, 2017

In computer simulations of dry foams and of epithelial tissues, vertex models are often used to d... more In computer simulations of dry foams and of epithelial tissues, vertex models are often used to describe the shape and motion of individual cells. Although these models have been widely adopted, relatively little is known about their basic theoretical properties. For example, while fourfold vertices in real foams are always unstable, it remains unclear whether a simplified vertex model description has the same behavior. Here, we study vertex stability and the dynamics of T1 topological transitions in vertex models. We show that, when all edges have the same tension, stationary fourfold vertices in these models do indeed always break up. In contrast, when tensions are allowed to depend on edge orientation, fourfold vertices can become stable, as is observed in some biological systems. More generally, our formulation of vertex stability leads to an improved treatment of T1 transitions in simulations and paves the way for studies of more biologically realistic models that couple topological transitions to the dynamics of regulatory proteins.

2023 IEEE Aerospace Conference

Deep Blue (University of Michigan), 2018

This work would have not have been possible without the mentorship of my adviser David. Much of m... more This work would have not have been possible without the mentorship of my adviser David. Much of my thesis work relies on analysis of thousands of images taken by Jesus Lopez-Gay. I sustained a major spinal cord injury just as I started to write my thesis. I would not have been physically capable of finishing it, if not for the amazing medical care I received from my entire team at the neuro-ICU and 6A. I could not have afforded the care without medical benefits from my grad union GEO. Thank you from the bottom of my heart everyone who cooked me meals, cleaned my house, and gave me moral support throughout my long recovery. Special thanks to Patricia Klein for organizing my care, and my parents for their constant support. This work probably would have been possible without the support of my fellow graduate students, but it wouldn't have been nearly as fun. I'd like to thank my amazing first-year cohort especially, Paige, Rutu, Karishima, Chrisy and Kevin for working through Jackson with me, as well as Jessie, Joe, Glenn, Peter, Ansel, and Anthony for joining in second-year. John Ware has supported me from start to finish, from working through old qualifying exams through proofreading thesis chapters. My entire family has given me moral and finantial support throughout college and graduate school, even if they often didn't understand what I was doing. Thanks for sticking with me.

arXiv: Tissues and Organs, 2018

The alignment of cell-cell junctions and associated cortical actomyosin across multiple cells to ... more The alignment of cell-cell junctions and associated cortical actomyosin across multiple cells to form supracellular cables in an epithelium is an example of the long range tissue organization that drives morphogenesis. Here we demonstrate that the ability of tissues to assemble these parallel cables depends on the initial packing topology of the cells in the epithelium. Using a computational vertex model we develop two methods of measuring a disordered tissue's favorability to forming cables under an external stress. These measures quantify the deformation of cells and the distribution of tension in the tissue under stress. Using these measures we show that passive stress-induced cell flow reduces a tissue's ability to form cables, whereas oriented divisions create a packing which can sustain multiple parallel cables. These measures are applied to a region of the the Drosophila demonstrating a shift to a more cable-friendly packing after a wave of oriented divisions in the r...

Bulletin of the American Physical Society, 2018

Physical Review E, 2016

In this paper we introduce a variant of the honeycomb lattice in which we create defects by rando... more In this paper we introduce a variant of the honeycomb lattice in which we create defects by randomly exchanging adjacent bonds, producing a random tiling with a distribution of polygon edges. We study the percolation properties on these lattices as a function of the number of exchanged bonds using a novel computational method. We find the site and bond percolation thresholds are consistent with other three-coordinated lattices with the same standard deviation in the degree distribution of the dual; here we can produce a continuum of lattices with a range of standard deviations in the distribution. These lattices should be useful for modeling other properties of random systems as well as percolation.

The European Physical Journal E, 2017

In computer simulations of dry foams and of epithelial tissues, vertex models are often used to d... more In computer simulations of dry foams and of epithelial tissues, vertex models are often used to describe the shape and motion of individual cells. Although these models have been widely adopted, relatively little is known about their basic theoretical properties. For example, while fourfold vertices in real foams are always unstable, it remains unclear whether a simplified vertex model description has the same behavior. Here, we study vertex stability and the dynamics of T1 topological transitions in vertex models. We show that, when all edges have the same tension, stationary fourfold vertices in these models do indeed always break up. In contrast, when tensions are allowed to depend on edge orientation, fourfold vertices can become stable, as is observed in some biological systems. More generally, our formulation of vertex stability leads to an improved treatment of T1 transitions in simulations and paves the way for studies of more biologically realistic models that couple topological transitions to the dynamics of regulatory proteins.

Science, 2020

Biological systems tailor their properties and behavior to their size throughout development and ... more Biological systems tailor their properties and behavior to their size throughout development and in numerous aspects of physiology. However, such size scaling remains poorly understood as it applies to cell mechanics and mechanosensing. By examining how the Drosophila pupal dorsal thorax epithelium responds to morphogenetic forces, we found that the number of apical stress fibers (aSFs) anchored to adherens junctions scales with cell apical area to limit larger cell elongation under mechanical stress. aSFs cluster Hippo pathway components, thereby scaling Hippo signaling and proliferation with area. This scaling is promoted by tricellular junctions mediating an increase in aSF nucleation rate and lifetime in larger cells. Development, homeostasis, and repair entail epithelial cell size changes driven by mechanical forces; our work highlights how, in turn, mechanosensitivity scales with cell size.