Bidirectional neuronal migration coordinates retinal morphogenesis by preventing spatial competition

AbstractWhile the design of industrial products is often optimized for the sequential assembly of single components, organismal development is hallmarked by the concomitant occurrence of tissue growth and organization. Often this means that proliferating and differentiating cells occur at the same time in a shared tissue environment that continuously changes. How cells adapt to architectural changes in order to prevent spatial interference remains unclear. To understand how cell movements important for growth and organization are orchestrated, we here study the emergence of photoreceptor neurons that occur during the peak of retinal growth using zebrafish, human tissue and human organoids. Quantitative imaging reveals that successful retinal morphogenesis depends on active bidirectional photoreceptor translocation. This leads to a transient transfer of the entire cell population away from the apical proliferative zone. This migration pattern is driven by distinct cytoskeletal machineries, depending on direction: microtubules are required for basal translocation, while actomyosin drives apical movement. Blocking photoreceptor translocation leads to apical overcrowding that hampers progenitor movements. Thus, photoreceptor migration is crucial to prevent competition for space and thereby allows concurrent tissue growth and lamination. This shows that neuronal migration, in addition to its canonical role in cell positioning, is involved in coordinating morphogenesis.

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Scaling of cytoskeletal organization with cell size in Drosophila

Molecular Biology of the Cell ◽

10.1091/mbc.e16-10-0691 ◽

2017 ◽

Vol 28 (11) ◽

pp. 1519-1529 ◽

Cited By ~ 11

Author(s):

Alison K. Spencer ◽

Andrew J. Schaumberg ◽

Jennifer A. Zallen

Keyword(s):

Cell Size ◽

Quantitative Imaging ◽

Larval Growth ◽

Fold Increase ◽

Ventral Surface ◽

Tissue Growth ◽

Cell Length ◽

Drosophila Embryo ◽

Microtubule Network ◽

Wide Range

Spatially organized macromolecular complexes are essential for cell and tissue function, but the mechanisms that organize micron-scale structures within cells are not well understood. Microtubule-based structures such as mitotic spindles scale with cell size, but less is known about the scaling of actin structures within cells. Actin-rich denticle precursors cover the ventral surface of the Drosophila embryo and larva and provide templates for cuticular structures involved in larval locomotion. Using quantitative imaging and statistical modeling, we demonstrate that denticle number and spacing scale with cell length over a wide range of cell sizes in embryos and larvae. Denticle number and spacing are reduced under space-limited conditions, and both features robustly scale over a 10-fold increase in cell length during larval growth. We show that the relationship between cell length and denticle spacing can be recapitulated by specific mathematical equations in embryos and larvae and that accurate denticle spacing requires an intact microtubule network and the microtubule minus end–binding protein, Patronin. These results identify a novel mechanism of microtubule-dependent actin scaling that maintains precise patterns of actin organization during tissue growth.

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In utero Exposure to Anesthetics Alters Neuronal Migration Pattern in Developing Cerebral Cortex and Causes Postnatal Behavioral Deficits in Rats

Cerebral Cortex ◽

10.1093/cercor/bhz065 ◽

2019 ◽

Vol 29 (12) ◽

pp. 5285-5301 ◽

Cited By ~ 3

Author(s):

V Gluncic ◽

M Moric ◽

Y Chu ◽

V Hanko ◽

J Li ◽

...

Keyword(s):

Neuronal Migration ◽

Cortical Neurons ◽

In Utero ◽

Acid Decarboxylase ◽

In Utero Exposure ◽

Oxygen Control ◽

Pregnant Rats ◽

Behavioral Deficits ◽

Proliferative Zone ◽

The Impact

Abstract During fetal development, cerebral cortical neurons are generated in the proliferative zone along the ventricles and then migrate to their final positions. To examine the impact of in utero exposure to anesthetics on neuronal migration, we injected pregnant rats with bromodeoxyuridine to label fetal neurons generated at embryonic Day (E) 17 and then randomized these rats to 9 different groups receiving 3 different means of anesthesia (oxygen/control, propofol, isoflurane) for 3 exposure durations (20, 50, 120 min). Histological analysis of brains from 54 pups revealed that significant number of neurons in anesthetized animals failed to acquire their correct cortical position and remained dispersed within inappropriate cortical layers and/or adjacent white matter. Behavioral testing of 86 littermates pointed to abnormalities that correspond to the aberrations in the brain areas that are specifically developing during the E17. In the second set of experiments, fetal brains exposed to isoflurane at E16 had diminished expression of the reelin and glutamic acid decarboxylase 67, proteins critical for neuronal migration. Together, these results call for cautious use of anesthetics during the neuronal migration period in pregnancy and more comprehensive investigation of neurodevelopmental consequences for the fetus and possible consequences later in life.

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Comment: Capacity limits are caused by a finite resource, not spatial competition

10.31234/osf.io/2tg4n ◽

2019 ◽

Author(s):

Alex O. Holcombe

Keyword(s):

Object Tracking ◽

Spatial Competition ◽

Multiple Object Tracking ◽

Resource Theory ◽

Future Research ◽

Visual Object ◽

Object Representations ◽

Capacity Limits ◽

Finite Resource ◽

Spatial Interference

To explain capacity limits on cognition, Franconeri et al. [1] highlight spatial interference and competition among visual object representations in the limited space of cortical maps. Franconeri et al. describe this idea as a “concrete suggestion to guide future research” (p. 6), but in fact it has already been tested in three recent papers on multiple object tracking. The findings in each indicate that spatial interference does not explain the observed capacity limits and that traditional resource theory provides a better account.

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Replication of early and recent Zika virus isolates throughout mouse brain development

10.1101/177816 ◽

2017 ◽

Author(s):

Amy B Rosenfeld ◽

David J Doobin ◽

Audrey L Warren ◽

Vincent R Racaniello ◽

Richard B Vallee

Keyword(s):

Virus Infection ◽

Brain Development ◽

Zika Virus ◽

Neuronal Migration ◽

Brain Slice ◽

Late Gestation ◽

Grey Matter Volume ◽

Proliferative Zone ◽

Organotypic Brain Slice ◽

Brain Slice Cultures

AbstractFetal infection with Zika virus (ZIKV) can lead to congenital Zika virus syndrome (cZVS), which includes cortical malformations and microcephaly. The aspects of cortical development that are affected during virus infection are unknown. Using organotypic brain slice cultures generated from embryonic mice of various ages, sites of ZIKV replication including the neocortical proliferative zone and radial columns, as well as the developing midbrain, were identified. The infected radial units are surrounded by uninfected cells undergoing apoptosis, suggesting that programmed cell death may limit viral dissemination in the brain and may constrain virus associated injury. Therefore, a critical aspect of ZIKV induced neuropathology may be defined by death of uninfected cells. All ZIKV isolates assayed replicated efficiently in early and mid-gestation cultures, and two isolates examined replicated in late-gestation tissue. Alteration of neocortical cytoarchitecture, such as disruption of the highly-elongated basal processes of the radial glial progenitor cells, and impairment of postmitotic neuronal migration were also observed. These data suggest that all lineages of ZIKV tested are neurotropic, and that ZIKV infection interferes with multiple aspects of neurodevelopment that contribute to the complexity of cZVS.SignificanceZika virus infection has been associated with multiple pathologies of the central nervous system (CNS) including microcephaly, Guillain-Barré syndrome, lissencephaly, the loss of white and grey matter volume and acute myelitis. Using organotypic brain slice cultures, we determined that ZIKV replicates across different embryonic developmental stages, and viral infection can disrupt proper brain development leading to congenital CNS complications. These data illustrate that all lineages of ZIKV tested are neurotropic, and that infection may disrupt neuronal migration during brain development. The results expand our understanding of neuropathologies associated with congenital Zika virus syndrome.

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Infants’ cortex undergoes microstructural growth coupled with myelination during development

Communications Biology ◽

10.1038/s42003-021-02706-w ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Vaidehi S. Natu ◽

Mona Rosenke ◽

Hua Wu ◽

Francesca R. Querdasi ◽

Holly Kular ◽

...

Keyword(s):

Ex Vivo ◽

Human Life ◽

Quantitative Imaging ◽

Tissue Growth ◽

Early Infancy ◽

Brain Functions ◽

Quantitative Measurements ◽

Visual Areas ◽

Key Factor

AbstractDevelopment of cortical tissue during infancy is critical for the emergence of typical brain functions in cortex. However, how cortical microstructure develops during infancy remains unknown. We measured the longitudinal development of cortex from birth to six months of age using multimodal quantitative imaging of cortical microstructure. Here we show that infants’ cortex undergoes profound microstructural tissue growth during the first six months of human life. Comparison of postnatal to prenatal transcriptomic gene expression data demonstrates that myelination and synaptic processes are dominant contributors to this postnatal microstructural tissue growth. Using visual cortex as a model system, we find hierarchical microstructural growth: higher-level visual areas have less mature tissue at birth than earlier visual areas but grow at faster rates. This overturns the prominent view that visual areas that are most mature at birth develop fastest. Together, in vivo, longitudinal, and quantitative measurements, which we validated with ex vivo transcriptomic data, shed light on the rate, sequence, and biological mechanisms of developing cortical systems during early infancy. Importantly, our findings propose a hypothesis that cortical myelination is a key factor in cortical development during early infancy, which has important implications for diagnosis of neurodevelopmental disorders and delays in infants.

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Terminal neuron localization to the upper cortical plate is controlled by the transcription factor NEUROD2

10.1101/651273 ◽

2019 ◽

Author(s):

Gizem Guzelsoy ◽

Cansu Akkaya ◽

Dila Atak ◽

Cory D. Dunn ◽

Alkan Kabakcioglu ◽

...

Keyword(s):

Transcription Factor ◽

Neuronal Migration ◽

Cortical Neurons ◽

Cellular Localization ◽

Morphological Properties ◽

Cortical Plate ◽

Strong Increase ◽

Migration Process ◽

Proliferative Zone ◽

New Genes

AbstractExcitatory neurons of the mammalian cerebral cortex are organized into six functional layers characterized by unique patterns of connectivity, as well as distinctive physiological and morphological properties. Cortical layers appear after a highly regulated migration process in which cells move from the deeper, proliferative zone toward the superficial layers. Importantly, defects in this radial migration process have been implicated in neurodevelopmental and psychiatric diseases. Here we report that during the final stages of migration, transcription factor Neurogenic Differentiation 2 (Neurod2) contributes to terminal cellular localization within the cortical plate. In mice, in utero knockdown of Neurod2 results in reduced numbers of neurons localized to the uppermost region of the developing cortex, also termed the primitive cortical zone. Our ChIP-Seq and RNA-Seq analyses of genes regulated by NEUROD2 in the developing cortex identify a number of key target genes with known roles in Reelin signaling, a critical regulator of neuronal migration. Our focused analysis of regulation of the Reln gene, encoding the extracellular ligand REELIN, uncovers NEUROD2 binding to conserved E-box elements in multiple introns. Furthermore, we demonstrate that knockdown of NEUROD2 in primary cortical neurons results in a strong increase in Reln gene expression at the mRNA level, as well as a slight upregulation at the protein level. These data reveal a new role for NEUROD2 during the late stages of neuronal migration, and our analysis of its genomic targets offer new genes with potential roles in cortical lamination.

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Terminal neuron localization to the upper cortical plate is controlled by the transcription factor NEUROD2

Scientific Reports ◽

10.1038/s41598-019-56171-x ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 2

Author(s):

Gizem Guzelsoy ◽

Cansu Akkaya ◽

Dila Atak ◽

Cory D. Dunn ◽

Alkan Kabakcioglu ◽

...

Keyword(s):

Transcription Factor ◽

Neuronal Migration ◽

Cortical Neurons ◽

Cellular Localization ◽

Morphological Properties ◽

Cortical Plate ◽

Strong Increase ◽

Migration Process ◽

Proliferative Zone ◽

New Genes

AbstractExcitatory neurons of the mammalian cerebral cortex are organized into six functional layers characterized by unique patterns of connectivity, as well as distinctive physiological and morphological properties. Cortical layers appear after a highly regulated migration process in which cells move from the deeper, proliferative zone toward the superficial layers. Importantly, defects in this radial migration process have been implicated in neurodevelopmental and psychiatric diseases. Here we report that during the final stages of migration, transcription factor Neurogenic Differentiation 2 (Neurod2) contributes to terminal cellular localization within the cortical plate. In mice, in utero knockdown of Neurod2 resulted in reduced numbers of neurons localized to the uppermost region of the developing cortex, also termed the primitive cortical zone. Our ChIP-Seq and RNA-Seq analyses of genes regulated by NEUROD2 in the developing cortex identified a number of key target genes with known roles in Reelin signaling, a critical regulator of neuronal migration. Our focused analysis of regulation of the Reln gene, encoding the extracellular ligand REELIN, uncovered NEUROD2 binding to conserved E-box elements in multiple introns. Furthermore, we demonstrate that knockdown of NEUROD2 in primary cortical neurons resulted in a strong increase in Reln gene expression at the mRNA level, as well as a slight upregulation at the protein level. These data reveal a new role for NEUROD2 during the late stages of neuronal migration, and our analysis of its genomic targets offers new genes with potential roles in cortical lamination.

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3-D examination of the cytoskeletal sheets of mammalian eggs

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100124975 ◽

1992 ◽

Vol 50 (1) ◽

pp. 914-915

Author(s):

Carolyn A. Larabell ◽

David G. Capco ◽

G. Ian Gallicano ◽

Robert W. McGaughey ◽

Karsten Dierksen ◽

...

Keyword(s):

Actin Filaments ◽

Somatic Cells ◽

Freeze Fracture ◽

Blastocyst Stage ◽

Cell Cytoplasm ◽

Planar Structures ◽

Cytoskeletal Network ◽

Entire Cell ◽

Cytoskeletal Networks ◽

Mammalian Eggs

Mammalian eggs and embryos contain an elaborate cytoskeletal network of “sheets” which are distributed throughout the entire cell cytoplasm. Cytoskeletal sheets are long, planar structures unlike the cytoskeletal networks typical of somatic cells (actin filaments, microtubules, and intermediate filaments), which are filamentous. These sheets are not found in mammalian somatic cells nor are they found in nonmammalian eggs or embryos. Evidence that they are, indeed, cytoskeletal in nature is derived from studies demonstrating that 1) the sheets are retained in the detergent-resistant cytoskeleton fraction; 2) there are no associated membranes (determined by freeze-fracture); and 3) the sheets dissociate into filaments at the blastocyst stage of embryogenesis. Embedment-free sections of hamster eggs viewed at 60 kV show sheets running across the egg cytoplasm (Fig. 1). Although this approach provides excellent global views of the sheets and their reorganization during development, the mechanism of image formation for embedment-free sections does not permit evaluation of the sheets at high resolution.

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Fluorescent potentiometric dyes for membrane-potential imaging

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100168566 ◽

1994 ◽

Vol 52 ◽

pp. 166-167

Author(s):

Leslie M. Loew

Keyword(s):

Membrane Potential ◽

Single Cells ◽

Quantitative Imaging ◽

Optical Recording ◽

Biological Processes ◽

Major Focus ◽

The Past ◽

Excitable Systems ◽

Major Application ◽

The Impact

A major application of potentiometric dyes has been the multisite optical recording of electrical activity in excitable systems. After being championed by L.B. Cohen and his colleagues for the past 20 years, the impact of this technology is rapidly being felt and is spreading to an increasing number of neuroscience laboratories. A second class of experiments involves using dyes to image membrane potential distributions in single cells by digital imaging microscopy - a major focus of this lab. These studies usually do not require the temporal resolution of multisite optical recording, being primarily focussed on slow cell biological processes, and therefore can achieve much higher spatial resolution. We have developed 2 methods for quantitative imaging of membrane potential. One method uses dual wavelength imaging of membrane-staining dyes and the other uses quantitative 3D imaging of a fluorescent lipophilic cation; the dyes used in each case were synthesized for this purpose in this laboratory.

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Quantification of cell-surface expressed antigenic sites with 5-nm gold markers: Getting close to biologically relevant data

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100157231 ◽

1989 ◽

Vol 47 ◽

pp. 1050-1051

Author(s):

Etienne de Harven ◽

Hilary Christensen ◽

Richard Leung ◽

Cameron Ackerley

Keyword(s):

Cell Surface ◽

Human Peripheral Blood ◽

Contour Length ◽

Thin Sections ◽

Gold Particles ◽

Biologically Relevant ◽

Transmission Electron ◽

Entire Cell ◽

Electron Imaging ◽

Cell Contour

The T-derived subset of human peripheral blood normal lymphocytes has been selected as a model system to study the usefulness of 5 nm gold markers for quantification of single epitopes expressed on cell surfaces. The chosen epitopes are parts of the CD3 and CD5 molecules and can be specifically identified by hybridoma produced monoclonal antibodies (MoAbs; LEU-4 and LEU-1; Becton-Dick- inson, Mountain view, CA) . An indirect immunolabeling procedure, with goat anti-murine IgG adsorbed on the surface of 5 nm colloidal gold particles (GAM-G5, Janssen Pharmaceutica, Beerse, Belgium) has been used. Backscattered Electron Imaging (BEI) in a field emission scanning electronmicroscope (SEM) and transmission electron microscopy of thin sections of lymphocytes labeled before plastic embedding, were both used to identify and quantitate gold labeled cell surface sites, Estimating that the thickness of “silver” sections is approximately 60 nm and counting the number of gold particles on the entire cell perimeter, we calculated that, for LEU-4, the number of markers per um2 of cell surface is in the 140-160 range (Fig.l). Cell contour length measurements indicated that the surface of one lymphocyte is approximately 130-160 um2 that of a smooth sphere of identical diameter, reflecting the role of microvilli in expanding the surface area. The total number of gold labeled sites on the surface of one lymphocyte averages, therefore between 20,000 and 24,000 per cell.

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