scholarly journals Identification of disease-relevant modulators of the SHH pathway in the developing brain

Development ◽  
2021 ◽  
Vol 148 (17) ◽  
Author(s):  
Nora Mecklenburg ◽  
Izabela Kowalczyk ◽  
Franziska Witte ◽  
Jessica Görne ◽  
Alena Laier ◽  
...  
Keyword(s):  
Primary Cilia ◽  
Modifier Genes ◽  
Microtubule Associated Proteins ◽  
Shh Pathway ◽  
Brain Malformations ◽  
Associated Proteins ◽  
Positive Regulators ◽  
Functional Analyses ◽  
The Brain ◽  
Variable Penetrance

ABSTRACT Pathogenic gene variants in humans that affect the sonic hedgehog (SHH) pathway lead to severe brain malformations with variable penetrance due to unknown modifier genes. To identify such modifiers, we established novel congenic mouse models. LRP2-deficient C57BL/6N mice suffer from heart outflow tract defects and holoprosencephaly caused by impaired SHH activity. These defects are fully rescued on a FVB/N background, indicating a strong influence of modifier genes. Applying comparative transcriptomics, we identified Pttg1 and Ulk4 as candidate modifiers upregulated in the rescue strain. Functional analyses showed that ULK4 and PTTG1, both microtubule-associated proteins, are positive regulators of SHH signaling, rendering the pathway more resilient to disturbances. In addition, we characterized ULK4 and PTTG1 as previously unidentified components of primary cilia in the neuroepithelium. The identification of genes that powerfully modulate the penetrance of genetic disturbances affecting the brain and heart is likely relevant to understanding the variability in human congenital disorders.

scholarly journals Identification of novel disease relevant genetic modifiers affecting the SHH pathway in the developing brain

2020 ◽  
Author(s):  
Nora Mecklenburg ◽  
Izabela Kowalczyk ◽  
Franziska Witte ◽  
Jessica Görne ◽  
Alena Laier ◽  
...  
Keyword(s):  
Primary Cilia ◽  
Genetic Modifiers ◽  
Microtubule Associated Proteins ◽  
Shh Pathway ◽  
Brain Malformations ◽  
Associated Proteins ◽  
Positive Regulators ◽  
Functional Analyses ◽  
The Brain ◽  
Variable Penetrance

SUMMARYPathogenic gene variants in humans affecting the sonic hedgehog (SHH) pathway lead to severe brain malformations with variable penetrance due to unknown genetic modifiers. To identify such modifiers, we established novel congenic mouse models. LRP2 deficient C57BL/6N mice suffer from heart outflow tract defects and holoprosencephaly caused by impaired SHH activity. These defects are fully rescued on FVB/N background indicating a strong influence of modifier genes. Applying comparative transcriptomics, we identified Pttg1 and Ulk4 as candidate modifiers upregulated in the rescue strain. Functional analyses showed that ULK4 and PTTG1, both microtubule-associated proteins, are new positive regulators of SHH signaling, rendering the pathway more resilient to disturbances. In addition, we characterized PTTG1 as a novel primary cilia component in the neuroepithelium. The identification of genes, that powerfully modulate the penetrance of genetic disturbances affecting the brain and heart, is likely relevant to understand variability in human congenital disorders.

Immunoreactive forms of erythrocyte spectrin and ankyrin in brain

1982 ◽  
Vol 299 (1095) ◽  
pp. 301-312 ◽  
Keyword(s):  
Molecular Mass ◽  
Erythrocyte Membranes ◽  
Microtubule Associated Proteins ◽  
Associated Proteins ◽  
Molecular Masses ◽  
Low Ionic Strength ◽  
Polypeptide Chains ◽  
The Brain ◽  
Total Membrane ◽  
Rotary Shadowing

Polypeptides immunologically related to erythrocyte spectrin and ankyrin have been detected in brain. The cross-reacting proteins include soluble as well as membrane-associated forms. A class of soluble cross-reacting polypeptides have been identified as high molecular mass microtubule-associated proteins (MAPS). MAP1, a group of polypeptides of molecular mass ca . 370 kDa contains a component that cross-reacts with anti-ankyrin IgG. MAP2, a polypeptide of molecular mass 300 kDa cross-reacts with anti-spectrin IgG, with the shared antigenic sites localized to the α chain of spectrin. The functional basis for structural homology between MAP1 and ankyrin may involve association with tubulin, since erythrocyte ankyrin binds to microtubules polymerized from pure brain tubulin. Spectrin did not associate with microtubules, but does have in common with MAP2 the ability to bind to actin (Brenner & Korn 1979; Sattilaro et al . 1981) and the shape of a flexible rod as visualized by rotary shadowing (Shotton et al . 1979; Voter & Erickson 1981). Immunoreactive forms of spectrin and ankyrin are also present in membrane fractions. A homologue of spectrin which constitutes 3% of the total membrane protein has been purified from low ionic strength extracts of membranes. This protein contains two non-identical polypeptide chains of molecular masses of 260 and 265 kDa, binds to F-actin, and displaces binding of erythrocyte spectrin to erythrocyte membranes. The brain protein pas been visualized by rotary shadowing as an extended rod-like molecule 195 nm in length. These studies indicate that the organization of proteins in the membrane-cytoskeleton complex of erythrocytes has direct relevance to other types of cells, and suggest the existence of families of proteins related to spectrin and ankyrin.

scholarly journals Exploring neurodegeneration at the atomic level

2018 ◽  
Vol 40 (5) ◽  
pp. 9-11
Author(s):  
Adam Tozer
Keyword(s):  
Amino Acids ◽  
Central Nervous System ◽  
Nervous System ◽  
Atomic Level ◽  
Tau Proteins ◽  
Microtubule Associated Proteins ◽  
Associated Proteins ◽  
The Central Nervous System ◽  
The Brain ◽  
Cell Maintenance

Tau proteins are microtubule-associated proteins essential for the correct functioning of neurons. This small family of proteins, 352–441 amino acids in length, are abundant in the brain and exist to stabilize microtubules in neurons and glia (non-neuronal cells of the central nervous system) to ensure correct trafficking of cellular cargo and cell maintenance.

scholarly journals LIS1 and DCX: Implications for Brain Development and Human Disease in Relation to Microtubules

Scientifica ◽  
2013 ◽  
Vol 2013 ◽  
pp. 1-17 ◽  
Author(s):  
Orly Reiner
Keyword(s):  
Brain Development ◽  
Neuronal Migration ◽  
Place Of Birth ◽  
Microtubule Associated Proteins ◽  
Final Destination ◽  
Brain Malformations ◽  
Wide Range ◽  
Associated Functions ◽  
Associated Proteins ◽  
Neuronal Polarization

Proper lamination of the cerebral cortex requires the orchestrated motility of neurons from their place of birth to their final destination. Improper neuronal migration may result in a wide range of diseases, including brain malformations, such as lissencephaly, mental retardation, schizophrenia, and autism. Ours and other studies have implicated that microtubules and microtubule-associated proteins play an important role in the regulation of neuronal polarization and neuronal migration. Here, we will review normal processes of brain development and neuronal migration, describe neuronal migration diseases, and will focus on the microtubule-associated functions of LIS1 and DCX, which participate in the regulation of neuronal migration and are involved in the human developmental brain disease, lissencephaly.

scholarly journals Map1b Is Required for Axon Guidance and Is Involved in the Development of the Central and Peripheral Nervous System

2000 ◽  
Vol 151 (6) ◽  
pp. 1169-1178 ◽  
Author(s):  
Arabella Meixner ◽  
Silke Haverkamp ◽  
Heinz Wässle ◽  
Susanne Führer ◽  
Johann Thalhammer ◽  
...  
Keyword(s):  
Nervous System ◽  
Nerve Conduction Velocity ◽  
Developmental Defect ◽  
Myelinated Fiber ◽  
Microtubule Associated Proteins ◽  
Associated Proteins ◽  
And Function ◽  
The Brain ◽  
Deficient Mice

Microtubule-associated proteins such as MAP1B have long been suspected to play an important role in neuronal differentiation, but proof has been lacking. Previous MAP1B gene targeting studies yielded contradictory and inconclusive results and did not reveal MAP1B function. In contrast to two earlier efforts, we now describe generation of a complete MAP1B null allele. Mice heterozygous for this MAP1B deletion were not affected. Homozygous mutants were viable but displayed a striking developmental defect in the brain, the selective absence of the corpus callosum, and the concomitant formation of myelinated fiber bundles consisting of misguided cortical axons. In addition, peripheral nerves of MAP1B-deficient mice had a reduced number of large myelinated axons. The myelin sheaths of the remaining axons were of reduced thickness, resulting in a decrease of nerve conduction velocity in the adult sciatic nerve. On the other hand, the anticipated involvement of MAP1B in retinal development and γ-aminobutyric acid C receptor clustering was not substantiated. Our results demonstrate an essential role of MAP1B in development and function of the nervous system and resolve a previous controversy over its importance.

scholarly journals Tau in Health and Neurodegenerative Diseases

2021 ◽  
Author(s):  
Dandan Chu ◽  
Fei Liu
Keyword(s):  
Neurodegenerative Diseases ◽  
Tau Protein ◽  
Dynamic Properties ◽  
Corticobasal Degeneration ◽  
Microtubule Associated Proteins ◽  
Associated Proteins ◽  
Argyrophilic Grain ◽  
The Brain ◽  
Filamentous Inclusions

Tau, one of the major microtubule-associated proteins, modulates the dynamic properties of microtubules in the mammalian nervous system. Tau is abundantly expressed in the brain, particularly in the hippocampus. Insoluble and filamentous inclusions of tau in neurons or glia are discovered in neurodegenerative diseases termed ‘tauopathies’, including Alzheimer’s disease (AD), argyrophilic grain disease (AGD), corticobasal degeneration (CBD), frontotemporal dementia (FTD), Pick’s disease (PiD) and progressive supranuclear palsy (PSP). Accumulation of intracellular neurofibrillary tangles (NFTs), which are composed of hyperphosphorylated tau, is directly correlated with the degree of Alzheimer\'s dementia. This chapter reviews the role of tau protein in physiological conditions and the pathological changes of tau related to neurodegenerative diseases. The applications of tau as a therapeutic target are also discussed.

Characterization of microtubules by dark-field STEM and replication

1991 ◽  
Vol 49 ◽  
pp. 152-153
Author(s):  
S.B. Andrews ◽  
R.D. Leapman ◽  
P.E. Gallant ◽  
T.S. Reese
Keyword(s):  
Protein Interactions ◽  
Low Dose ◽  
Unit Length ◽  
Dark Field ◽  
Carbon Films ◽  
Microtubule Associated Proteins ◽  
Molecular Weights ◽  
Freeze Dried ◽  
Protein Motors ◽  
Associated Proteins

As part of a study on protein interactions involved in microtubule (MT)-based transport, we used the VG HB501 field-emission STEM to obtain low-dose dark-field mass maps of isolated, taxol-stabilized MTs and correlated these micrographs with detailed stereo images from replicas of the same MTs. This approach promises to be useful for determining how protein motors interact with MTs. MTs prepared from bovine and squid brain tubulin were purified and free from microtubule-associated proteins (MAPs). These MTs (0.1-1 mg/ml tubulin) were adsorbed to 3-nm evaporated carbon films supported over Formvar nets on 600-m copper grids. Following adsorption, the grids were washed twice in buffer and then in either distilled water or in isotonic or hypotonic ammonium acetate, blotted, and plunge-frozen in ethane/propane cryogen (ca. -185 C). After cryotransfer into the STEM, specimens were freeze-dried and recooled to ca.-160 C for low-dose (<3000 e/nm2) dark-field mapping. The molecular weights per unit length of MT were determined relative to tobacco mosaic virus standards from elastic scattering intensities. Parallel grids were freeze-dried and rotary shadowed with Pt/C at 14°.

Filaments and membranes in the mitotic apparatus

1983 ◽  
Vol 41 ◽  
pp. 544-547
Author(s):  
Kent McDonald
Keyword(s):  
Intermediate Filaments ◽  
Mitotic Spindle ◽  
Mitotic Apparatus ◽  
Light Microscope Level ◽  
Microtubule Associated Proteins ◽  
Recent Developments ◽  
Associated Proteins ◽  
Force Generator ◽  
Spindle Function ◽  
Antibody Technology

At the light microscope level the recent developments and interest in antibody technology have permitted the localization of certain non-microtubule proteins within the mitotic spindle, e.g., calmodulin, actin, intermediate filaments, protein kinases and various microtubule associated proteins. Also, the use of fluorescent probes like chlorotetracycline suggest the presence of membranes in the spindle. Localization of non-microtubule structures in the spindle at the EM level has been less rewarding. Some mitosis researchers, e.g., Rarer, have maintained that actin is involved in mitosis movements though the bulk of evidence argues against this interpretation. Others suggest that a microtrabecular network such as found in chromatophore granule movement might be a possible force generator but there is little evidence for or against this view. At the level of regulation of spindle function, Harris and more recently Hepler have argued for the importance of studying spindle membranes. Hepler also believes that membranes might play a structural or mechanical role in moving chromosomes.

Analysis of the Mechanism of Microtubule Dynamic Instability Using a UV Microbeam to Sever Elongating Microtubules

1988 ◽  
Vol 46 ◽  
pp. 122-123
Author(s):  
R.A Walker ◽  
S. Inoue ◽  
E.D. Salmon
Keyword(s):  
Dynamic Instability ◽  
Microtubule Dynamic ◽  
Gtp Hydrolysis ◽  
Abrupt Transition ◽  
Microtubule Associated Proteins ◽  
Asymmetrical Structure ◽  
Associated Proteins

Microtubules polymerized in vitro from tubulin purified free of microtubule-associated proteins exhibit dynamic instability (1,2,3). Free microtubule ends exist in persistent phases of elongation or rapid shortening with infrequent, but, abrupt transitions between these phases. The abrupt transition from elongation to rapid shortening is termed catastrophe and the abrupt transition from rapid shortening to elongation is termed rescue. A microtubule is an asymmetrical structure. The plus end grows faster than the minus end. The frequency of catastrophe of the plus end is somewhat greater than the minus end, while the frequency of rescue of the plus end in much lower than for the minus end (4).The mechanism of catastrophe is controversial, but for both the plus and minus microtubule ends, catastrophe is thought to be dependent on GTP hydrolysis. Microtubule elongation occurs by the association of tubulin-GTP subunits to the growing end. Sometime after incorporation into an elongating microtubule end, the GTP is hydrolyzed to GDP, yielding a core of tubulin-GDP capped by tubulin-GTP (“GTP-cap”).

Molecular architecture and functions of the neuronal cytoskeleton

1990 ◽  
Vol 48 (3) ◽  
pp. 2-3
Author(s):  
Nobutaka Hirokawa
Keyword(s):  
Major Elements ◽  
Molecular Structures ◽  
Organelle Transport ◽  
Molecular Architecture ◽  
Neuronal Morphogenesis ◽  
Microtubule Associated Proteins ◽  
Associated Proteins ◽  
And Function ◽  
Small Clusters

In this symposium I will present our studies about the molecular architecture and function of the cytomatrix of the nerve cells. The nerve cell is a highly polarized cell composed of highly branched dendrites, cell body, and a single long axon along the direction of the impulse propagation. Each part of the neuron takes characteristic shapes for which the cytoskeleton provides the framework. The neuronal cytoskeletons play important roles on neuronal morphogenesis, organelle transport and the synaptic transmission. In the axon neurofilaments (NF) form dense arrays, while microtubules (MT) are arranged as small clusters among the NFs. On the other hand, MTs are distributed uniformly, whereas NFs tend to run solitarily or form small fascicles in the dendrites Quick freeze deep etch electron microscopy revealed various kinds of strands among MTs, NFs and membranous organelles (MO). These structures form major elements of the cytomatrix in the neuron. To investigate molecular nature and function of these filaments first we studied molecular structures of microtubule associated proteins (MAP1A, MAP1B, MAP2, MAP2C and tau), and microtubules reconstituted from MAPs and tubulin in vitro. These MAPs were all fibrous molecules with different length and formed arm like projections from the microtubule surface.

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