Caroline McKeown - Academia.edu (original) (raw)

Papers by Caroline McKeown

Cultured chicken embryonic cardiomyocyte fixed and stained for alpha-actinin using a monoclonal a... more Cultured chicken embryonic cardiomyocyte fixed and stained for alpha-actinin using a monoclonal antibody and Alexa-546 as a secondary fluorescent antibody. Imaged by widefield epifluorescence on a Zeiss Axioplan microscope with a 63x objective. Image taken with a Hamamatsu Orca-ER CCD camera. Scale bar is 6um.

Cultured chicken embryonic cardiomyocyte transfected with GFP control vector in the nucleus, stai... more Cultured chicken embryonic cardiomyocyte transfected with GFP control vector in the nucleus, stained with alpha-actinin at the Z-lines in red and Tropomodulin1 (at the pointed ends of the actin filaments) in blue. Epifluorescence imaged on a Zeiss Axioplan microscope.

Page 1. GENETIC ANALYSIS OF THE ALP/ENIGMA FAMILY OF CYTOSKELETAL PDZ-LIM PROTEINS IN CAENORHABDI... more Page 1. GENETIC ANALYSIS OF THE ALP/ENIGMA FAMILY OF CYTOSKELETAL PDZ-LIM PROTEINS IN CAENORHABDITIS ELEGANS by Caroline Rose McKeown A dissertation submitted to the faculty of The University of ...

Tropomodulin isoforms regulate thin filament pointed-end capping and skeletal muscle physiology

G3 Genes|Genomes|Genetics, 2021

Amphibian metamorphosis is a transitional period that involves significant changes in the cell-ty... more Amphibian metamorphosis is a transitional period that involves significant changes in the cell-type populations and biological processes occurring in the brain. Analysis of gene expression dynamics during this process may provide insight into the molecular events underlying these changes. We conducted differential gene expression analyses of the developing Xenopus laevis tadpole brain during this period in two ways: first, over stages of the development in the midbrain and, second, across regions of the brain at a single developmental stage. We found that genes pertaining to positive regulation of neural progenitor cell proliferation as well as known progenitor cell markers were upregulated in the midbrain prior to metamorphic climax; concurrently, expression of cell cycle timing regulators decreased across this period, supporting the notion that cell cycle lengthening contributes to a decrease in proliferation by the end of metamorphosis. We also found that at the start of metamorp...

In developing Xenopus tadpoles, the optic tectum begins to receive patterned visual input while v... more In developing Xenopus tadpoles, the optic tectum begins to receive patterned visual input while visuomotor circuits are still undergoing neurogenesis and circuit assembly. This visual input regulates neural progenitor cell fate decisions such that maintaining tadpoles in the dark increases proliferation, expanding the progenitor pool, while visual stimulation promotes neuronal differentiation. To identify regulators of activity-dependent neural progenitor cell fate, we used RNA-Seq to profile the transcriptomes of proliferating neural progenitor cells and newly-differentiated immature neurons. Out of 1,130 differentially expressed (DE) transcripts, we identified six DE transcription factors which are predicted to regulate the majority of the other DE transcripts. Here we focused on Breast cancer 1 (BRCA1) and the ETS-family transcription factor, ELK-1. BRCA1 is known for its role in cancers, but relatively little is known about its potential role in regulating neural progenitor cell...

Development, 1998

Morphogenesis transforms the C. elegans embryo from a ball of cells into a vermiform larva. Durin... more Morphogenesis transforms the C. elegans embryo from a ball of cells into a vermiform larva. During this transformation, the embryo increases fourfold in length; present data indicates this elongation results from contraction of the epidermal actin cytoskeleton. In sma-1 mutants, the extent of embryonic elongation is decreased and the resulting sma-1 larvae, although viable, are shorter than normal. We find that sma-1 mutants elongate for the same length of time as wild-type embryos, but at a decreased rate. The sma-1 mutants we have isolated vary in phenotypic severity, with the most severe alleles showing the greatest decrease in elongation rate. The sma-1 gene encodes a homolog of betaH-spectrin, a novel beta-spectrin isoform first identified in Drosophila. sma-1 RNA is expressed in epithelial tissues in the C. elegans embryo: in the embryonic epidermis at the start of morphogenesis and subsequently in the developing pharynx, intestine and excretory cell. In Drosophila, betaH-spec...

Development, 2020

In the Materials and Methods section, the concentration of rapamycin used was incorrect. Correcte... more In the Materials and Methods section, the concentration of rapamycin used was incorrect. Corrected: mTOR was blocked with a bath solution containing 10 µM rapamycin (Sigma-Aldrich) diluted in rearing media for up to 48 h. Original: mTOR was blocked with a bath solution containing 10 mM rapamycin (Sigma-Aldrich) diluted in rearing media for up to 48 h. Both the online full-text and PDF versions have been updated.

Journal of Neurophysiology, 2018

Traumatic brain injuries introduce functional and structural circuit deficits that must be repair... more Traumatic brain injuries introduce functional and structural circuit deficits that must be repaired for an organism to regain function. We developed an injury model in which Xenopus laevis tadpoles are given a penetrating stab wound that damages the optic tectal circuit and impairs visuomotor behavior. In tadpoles, as in other systems, injury induces neurogenesis. The newly generated neurons are thought to integrate into the existing circuit; however, whether they integrate via the same mechanisms that govern normal neuronal maturation during development is not understood. Development of the functional visuomotor circuit in Xenopus is driven by sensory activity. We hypothesized that enhanced visual experience would improve recovery from injury by facilitating integration of newly generated neurons into the tectal circuit. We labeled newly generated neurons in the injured tectum by green fluorescent protein expression and examined their circuit integration using electrophysiology and...

Development

Journal of Neurophysiology, 2011

The balance of inhibitory to excitatory (I/E) synaptic inputs is thought to control information p... more The balance of inhibitory to excitatory (I/E) synaptic inputs is thought to control information processing and behavioral output of the central nervous system. We sought to test the effects of the decreased or increased I/E ratio on visual circuit function and visually guided behavior in Xenopus tadpoles. We selectively decreased inhibitory synaptic transmission in optic tectal neurons by knocking down the γ2 subunit of the GABAAreceptors (GABAAR) using antisense morpholino oligonucleotides or by expressing a peptide corresponding to an intracellular loop of the γ2 subunit, called ICL, which interferes with anchoring GABAAR at synapses. Recordings of miniature inhibitory postsynaptic currents (mIPSCs) and miniature excitatory PSCs (mEPSCs) showed that these treatments decreased the frequency of mIPSCs compared with control tectal neurons without affecting mEPSC frequency, resulting in an ∼50% decrease in the ratio of I/E synaptic input. ICL expression and γ2-subunit knockdown also d...

The Journal of General Physiology, 2010

Journal of Comparative Neurology, 2013

Nonmammalian vertebrates have a remarkable capacity to regenerate brain tissue in response to cen... more Nonmammalian vertebrates have a remarkable capacity to regenerate brain tissue in response to central nervous system (CNS) injury. Nevertheless, it is not clear whether animals recover lost function after injury or whether injury-induced cell proliferation mediates recovery. We address these questions using the visual system and visually-guided behavior in Xenopus laevis tadpoles. We established a reproducible means to produce a unilateral focal injury to optic tectal neurons without damaging retinotectal axons. We then assayed a tectally-mediated visual avoidance behavior to evaluate behavioral impairment and recovery. Focal ablation of part of the optic tectum prevents the visual avoidance response to moving stimuli. Animals recover the behavior over the week following injury. Injury induces a burst of proliferation of tectal progenitor cells based on phospho-histone H3 immunolabeling and experiments showing that Musashiimmunoreactive tectal progenitors incorporate the thymi-dine analog chlorodeoxyuridine after injury. Pulse chase experiments indicate that the newly-generated cells differentiate into N-b-tubulin-immunoreactive neurons. Furthermore, in vivo time-lapse imaging shows that Sox2expressing neural progenitors divide in response to injury and generate neurons with elaborate dendritic arbors. These experiments indicate that new neurons are generated in response to injury. To test if neurogenesis is necessary for recovery from injury, we blocked cell proliferation in vivo and found that recovery of the visual avoidance behavior is inhibited by drugs that block cell proliferation. Moreover, behavioral recovery is facilitated by changes in visual experience that increase tectal progenitor cell proliferation. Our data indicate that neurogenesis in the optic tectum is critical for recovery of visuallyguided behavior after injury.

Developmental Dynamics, 2014

Background-We explored a function for tropomyosin (TM) in mammalian myofibril assembly and cardia... more Background-We explored a function for tropomyosin (TM) in mammalian myofibril assembly and cardiac development by analyzing a deletion in the mouse TPM1 gene targeting αTM1, the major striated muscle TM isoform. Results-Mice lacking αTM1 are embryonic lethal at E9.5 with enlarged, misshapen, and nonbeating hearts characterized by an abnormally thin myocardium and reduced trabeculae. αTM1deficient cardiomyocytes do not assemble striated myofibrils, instead displaying aberrant nonstriated F-actin fibrils with α-actinin puncta dispersed irregularly along their lengths. αTM1's binding partner, tropomodulin1 (Tmod1), is also disorganized, and both myomesin-containing thick filaments as well as titin Z1Z2 fail to assemble in a striated pattern. Adherens junctions are reduced in size in αTM1-deficient cardiomyocytes, α-actinin/F-actin adherens belts fail to assemble at apical cell-cell contacts, and cell contours are highly irregular, resulting in abnormal cell shapes and a highly folded cardiac surface. In addition, Tmod1-deficient cardiomyocytes exhibit failure of α-actinin/F-actin adherens belt assembly. Conclusions-Absence of αTM1 resulting in unstable F-actin may preclude sarcomere formation and/or lead to degeneration of partially assembled sarcomeres due to unregulated actomyosin interactions. Our data also identify a novel αTM1/Tmod1-based pathway stabilizing F-actin at cell-cell junctions, which may be required for maintenance of cell shapes during embryonic cardiac morphogenesis.

Current Biology, 2006

A recent study has shown that the giant protein nebulin maintains the lengths of actin filaments ... more A recent study has shown that the giant protein nebulin maintains the lengths of actin filaments in striated muscle cells. Although on the surface, nebulin looks like a molecular ruler, it may be playing a more complex role in regulating dynamics at the pointed end of actin filaments in striated muscle.

Circulation Research, 2008

Tropomodulin (Tmod)1 caps the pointed ends of actin filaments in sarcomeres of striated muscle my... more Tropomodulin (Tmod)1 caps the pointed ends of actin filaments in sarcomeres of striated muscle myofibrils and in the erythrocyte membrane skeleton. Targeted deletion of mouse Tmod1 leads to defects in cardiac development, fragility of primitive erythroid cells, and an absence of yolk sac vasculogenesis, followed by embryonic lethality at embryonic day 9.5. The Tmod1-null embryonic hearts do not undergo looping morphogenesis and the cardiomyocytes fail to assemble striated myofibrils with regulated F-actin lengths. To test whether embryonic lethality of Tmod1 nulls results from defects in cardiac myofibrillogenesis and development or from erythroid cell fragility and subsequent defects in yolk sac vasculogenesis, we expressed Tmod1 specifically in the myocardium of the Tmod1-null mice under the control of the α-myosin heavy chain promoter Tg(αMHC-Tmod1). In contrast to Tmod1-null embryos, which fail to undergo cardiac looping and have defective yolk sac vasculogenesis, both cardiac a...