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Axonal pathfind

Shen-Ju Chou, Shubha Tole
A hundred years after Lhx2 ortholog apterous was identified as a critical regulator of wing development in Drosophila, LIM-HD gene family members have proved to be versatile and powerful components of the molecular machinery that executes the blueprint of embryogenesis across vertebrate and invertebrate species. Here, we focus on the spatio-temporally varied functions of LIM-homeodomain transcription factor LHX2 in the developing mouse forebrain. Right from its earliest known role in telencephalic and eye field patterning, to the control of the neuron-glia cell fate switch, and the regulation of axon pathfinding and dendritic arborization in late embryonic stages, LHX2 has been identified as a fundamental, temporally dynamic, always necessary, and often sufficient factor in a range of critical developmental phenomena...
March 6, 2018: Brain Research
Nancy B Schwartz, Miriam S Domowicz
Proteoglycans are diverse, complex extracellular/cell surface macromolecules composed of a central core protein with covalently-linked glycosaminoglycan (GAG) chains; both of these components contribute to the growing list of important bio-active functions attributed to proteoglycans. Increasingly, attention has been paid to the roles of proteoglycans in nervous tissue development due to their highly regulated spatio/temporal expression patterns, whereby they promote/inhibit neurite outgrowth, participate in specification and maturation of various precursor cell types, and regulate cell behaviors like migration, axonal pathfinding, synaptogenesis, and plasticity...
March 7, 2018: FEBS Letters
Grace McMacken, Dan Cox, Andreas Roos, Juliane Müller, Roger Whittaker, Hanns Lochmüller
Inherited defects of the neuromuscular junction (NMJ) comprise an increasingly diverse range of disorders, termed congenital myasthenic syndromes (CMS). Therapies acting on the sympathetic nervous system, including the selective β2 adrenergic agonist salbutamol and the α and β adrenergic agonist ephedrine, have become standard treatment for several types of CMS. However, the mechanism of the therapeutic effect of sympathomimetics in these disorders is not understood. Here, we examined the effect of salbutamol on NMJ development using zebrafish with deficiency of the key postsynaptic proteins Dok-7 and MuSK...
February 16, 2018: Human Molecular Genetics
Huai Huang, Tao Yang, Qiangqiang Shao, Tanushree Majumder, Kristopher Mell, Guofa Liu
Heterozygous missense mutations in human TUBB3 gene result in a spectrum of brain malformations associated with defects in axon guidance, neuronal migration and differentiation. However, the molecular mechanisms underlying mutation-related axon guidance abnormalities are unclear. Recent studies have shown that netrin-1, a canonical guidance cue, induced the interaction of TUBB3 with the netrin receptor deleted in colorectal cancer (DCC). Furthermore, TUBB3 is required for netrin-1-induced axon outgrowth, branching and pathfinding...
January 27, 2018: Neuroscience
Kritika S Katiyar, Carla C Winter, Wisberty J Gordián-Vélez, John C O'Donnell, Yeri J Song, Nicole S Hernandez, Laura A Struzyna, D Kacy Cullen
Neurotrauma and neurodegenerative disease often result in lasting neurological deficits due to the limited capacity of the central nervous system (CNS) to replace lost neurons and regenerate axonal pathways. However, during nervous system development, neuronal migration and axonal extension often occur along pathways formed by other cells, referred to as "living scaffolds". Seeking to emulate these mechanisms and to design a strategy that circumvents the inhibitory environment of the CNS, this manuscript presents a protocol to fabricate tissue engineered astrocyte-based "living scaffolds"...
January 10, 2018: Journal of Visualized Experiments: JoVE
Reza Asadollahi, Justin E Strauss, Martin Zenker, Oliver Beuing, Simon Edvardson, Orly Elpeleg, Tim M Strom, Pascal Joset, Dunja Niedrist, Christine Otte, Beatrice Oneda, Paranchai Boonsawat, Silvia Azzarello-Burri, Deborah Bartholdi, Michael Papik, Markus Zweier, Cordula Haas, Arif B Ekici, Alessandra Baumer, Eugen Boltshauser, Katharina Steindl, Michael Nothnagel, Albert Schinzel, Esther T Stoeckli, Anita Rauch
Acrocallosal syndrome (ACLS) is an autosomal recessive neurodevelopmental disorder caused by KIF7 defects and belongs to the heterogeneous group of ciliopathies related to Joubert syndrome (JBTS). While ACLS is characterized by macrocephaly, prominent forehead, depressed nasal bridge, and hypertelorism, facial dysmorphism has not been emphasized in JBTS cohorts with molecular diagnosis. To evaluate the specificity and etiology of ACLS craniofacial features, we performed whole exome or targeted Sanger sequencing in patients with the aforementioned overlapping craniofacial appearance but variable additional ciliopathy features followed by functional studies...
January 10, 2018: European Journal of Human Genetics: EJHG
Soichiro Nakahara, Mitsuyuki Matsumoto, Hiroyuki Ito, Katsunori Tajinda
Appropriate axonal pathfinding is a necessary step for the function of neuronal circuits. The mossy fibers (MFs) in the hippocampus of CaMKIIα heterozygous knockout (CaMKIIα-hKO) psychiatric model mice project onto not only the stratum lucidum but also the stratum oriens region in the CA3, which is a projection pattern distinct from that in normal mice. Thus, we examined the electrophysiological properties of the MF-CA3 connection in this mutant mouse on field recordings and found a lower synaptic connection...
2018: Biological & Pharmaceutical Bulletin
Hugo Ducuing, Thibault Gardette, Aurora Pignata, Servane Tauszig-Delamasure, Valérie Castellani
The navigation of commissural axons in the developing spinal cord has attracted multiple studies over the years. Many important concepts emerged from these studies which have enlighten the general mechanisms of axon guidance. The navigation of commissural axons is regulated by a series of cellular territories which provides the diverse guidance information necessary to ensure the successive steps of their pathfinding towards, across, and away from the ventral midline. In this review, we discuss how repulsive forces, by propelling, channelling, and confining commissural axon navigation, bring key contributions to the formation of this neuronal projection...
December 22, 2017: Seminars in Cell & Developmental Biology
Mithilesh Kumar Jha, Jong-Heon Kim, Gyun Jee Song, Won-Ha Lee, In-Kyu Lee, Ho-Won Lee, Seong Soo A An, SangYun Kim, Kyoungho Suk
Astrocytes, which are homeostatic cells of the central nervous system (CNS), display remarkable heterogeneity in their morphology and function. Besides their physical and metabolic support to neurons, astrocytes modulate the blood-brain barrier, regulate CNS synaptogenesis, guide axon pathfinding, maintain brain homeostasis, affect neuronal development and plasticity, and contribute to diverse neuropathologies via secreted proteins. The identification of astrocytic proteome and secretome profiles has provided new insights into the maintenance of neuronal health and survival, the pathogenesis of brain injury, and neurodegeneration...
March 2018: Progress in Neurobiology
Nadja Dinges, Violeta Morin, Nastasja Kreim, Tony D Southall, Jean-Yves Roignant
Longitudinals lacking (lola) is one of the most complex genes in Drosophila melanogaster, encoding up to 20 protein isoforms that include key transcription factors involved in axonal pathfinding and neural reprogramming. Most previous studies have employed loss-of-function alleles that disrupt lola common exons, making it difficult to delineate isoform-specific functions. To overcome this issue, we have generated isoform-specific mutants for all isoforms using CRISPR/Cas9. This enabled us to study specific isoforms with respect to previously characterized roles for Lola and to demonstrate a specific function for one variant in axon guidance via activation of the microtubule-associated factor Futsch...
December 5, 2017: Cell Reports
Tadashi Yokoi, Taku Tanaka, Emiko Matsuzaka, Fuminobu Tamalu, Shu-Ichi Watanabe, Sachiko Nishina, Noriyuki Azuma
We recently established a novel method for generating functional human retinal ganglion cells (RGCs) from human induced pluripotent cells (hiPSCs). Here, we confirmed that RGCs can also be generated from human embryonic stem cells (hESCs). We investigated the usefulness of human RGCs with long axons for assessing the effects of chemical agents, such as the neurotrophic factor, nerve growth factor (NGF), and the chemorepellent factors, semaphorin 3 A (SEMA3A) and SLIT1. The effects of direct and local administration of each agent on axonal projection were evaluated by immunohistochemistry, real-time polymerase chain reaction (PCR), and real-time imaging, in which the filopodia of the growth cone served as an excellent marker...
December 1, 2017: Scientific Reports
Jie Xie, Teng Zhao, Yaobo Liu
Previous studies have demonstrated that both Wnt5a and Sonic hedgehog (Shh) are involved in regulating the pathfinding of descending serotonergic (5-HT, 5-hydroxytryptamine) axons in an opposite manner in the brainstem. Shh and Wnt signaling pathways interact to guide post-crossing commissural axons, where Shh acts as a repellent directly and shaping the Wnt gradient indirectly by regulating the gradient expression of the frizzled-related protein 1 (Sfrp1). Whether such a mechanism functions in descending 5-HT axon guidance remains unknown...
November 28, 2017: International Journal of Developmental Neuroscience
Samuel Ojosnegros, Francesco Cutrale, Daniel Rodríguez, Jason J Otterstrom, Chi Li Chiu, Verónica Hortigüela, Carolina Tarantino, Anna Seriola, Stephen Mieruszynski, Elena Martínez, Melike Lakadamyali, Angel Raya, Scott E Fraser
Eph receptor signaling plays key roles in vertebrate tissue boundary formation, axonal pathfinding, and stem cell regeneration by steering cells to positions defined by its ligand ephrin. Some of the key events in Eph-ephrin signaling are understood: ephrin binding triggers the clustering of the Eph receptor, fostering transphosphorylation and signal transduction into the cell. However, a quantitative and mechanistic understanding of how the signal is processed by the recipient cell into precise and proportional responses is largely lacking...
December 12, 2017: Proceedings of the National Academy of Sciences of the United States of America
Eloísa Herrera, Lynda Erskine, Cruz Morenilla-Palao
In order to navigate through the surrounding environment many mammals, including humans, primarily rely on vision. The eye, composed of the choroid, sclera, retinal pigmented epithelium, cornea, lens, iris and retina, is the structure that receives the light and converts it into electrical impulses. The retina contains six major types of neurons involving in receiving and modifying visual information and passing it onto higher visual processing centres in the brain. Visual information is relayed to the brain via the axons of retinal ganglion cells (RGCs), a projection known as the optic pathway...
November 26, 2017: Seminars in Cell & Developmental Biology
Aref Arzan Zarin, Juan-Pablo Labrador
The Drosophila motor system starts to assemble during embryonic development. It is composed of 30 muscles per abdominal hemisegment and 36 motor neurons assembling into nerve branches to exit the CNS, navigate within the muscle field and finally establish specific connections with their target muscles. Several families of guidance molecules that play a role controlling this process as well as transcriptional regulators that program the behavior of specific motoneurons have been identified. In this review we summarize the role of both groups of molecules in the motor system as well as their relationship where known...
November 16, 2017: Seminars in Cell & Developmental Biology
Dario Bonanomi
Motor neurons of the spinal cord are responsible for the assembly of neuromuscular connections indispensable for basic locomotion and skilled movements. A precise spatial relationship exists between the position of motor neuron cell bodies in the spinal cord and the course of their axonal projections to peripheral muscle targets. Motor neuron innervation of the vertebrate limb is a prime example of this topographic organization and by virtue of its accessibility and predictability has provided access to fundamental principles of motor system development and neuronal guidance...
November 14, 2017: Seminars in Cell & Developmental Biology
Harald Hutter
The small number of neurons and the simple architecture of the Caenorhabditis elegans (C. elegans) nervous system enables researchers to study axonal pathfinding at the level of individually identified axons. Axons in C. elegans extend predominantly along one of the two major body axes, the anterior-posterior axis and the dorso-ventral axis. This review will focus on axon navigation along the anterior-posterior axis, leading to the establishment of the longitudinal axon tracts, with a focus on the largest longitudinal axon tract, the ventral nerve cord (VNC)...
November 12, 2017: Seminars in Cell & Developmental Biology
Evguenia Ivakhnitskaia, Ryan Weihsiang Lin, Kana Hamada, Chieh Chang
Molecular oscillators are well known for their roles in temporal control of some biological processes like cell proliferation, but molecular mechanisms that provide temporal control of differentiation and postdifferentiation events in cells are less understood. In the nervous system, establishment of neuronal connectivity during development and decline in neuronal plasticity during aging are regulated with temporal precision, but the timing mechanisms are largely unknown. Caenorhabditis elegans has been a preferred model for aging research and recently emerges as a new model for the study of developmental and postdevelopmental plasticity in neurons...
November 15, 2017: Wiley Interdisciplinary Reviews. Developmental Biology
Habib Bendella, Svenja Rink, Maria Grosheva, Levent Sarikcioglu, Tessa Gordon, Doychin N Angelov
It is well-known that, after nerve transection and surgical repair, misdirected regrowth of regenerating motor axons may occur in three ways. The first way is that the axons enter into endoneurial tubes that they did not previously occupy, regenerate through incorrect fascicles and reinnervate muscles that they did not formerly supply. Consequently the activation of these muscles results in inappropriate movements. The second way is that, in contrast with the precise target-directed pathfinding by elongating motor nerves during embryonic development, several axons rather than a single axon grow out from each transected nerve fiber...
February 2018: Experimental Neurology
Bo Wang, Rekha Iyengar, Xiujie Li-Harms, Joung Hyuck Joo, Christopher Wright, Alfonso Lavado, Linda Horner, Mao Yang, Jun-Lin Guan, Sharon Frase, Douglas R Green, Xinwei Cao, Mondira Kundu
Mammalian ULK1 (unc-51 like kinase 1) and ULK2, Caenorhabditis elegans UNC-51, and Drosophila melanogaster Atg1 are serine/threonine kinases that regulate flux through the autophagy pathway in response to various types of cellular stress. C. elegans UNC-51 and D. melanogaster Atg1 also promote axonal growth and defasciculation; disruption of these genes results in defective axon guidance in invertebrates. Although disrupting ULK1/2 function impairs normal neurite outgrowth in vitro, the role of ULK1 and ULK2 in the developing brain remains poorly characterized...
November 3, 2017: Autophagy
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