scholarly journals Pioneer interneurons instruct bilaterality in the Drosophila olfactory sensory map

2019 ◽  
Vol 5 (10) ◽  
pp. eaaw5537 ◽  
Author(s):  
Rashmit Kaur ◽  
Michael Surala ◽  
Sebastian Hoger ◽  
Nicole Grössmann ◽  
Alexandra Grimm ◽  
...  
Keyword(s):  
Cell Adhesion Molecule ◽  
Brain Evolution ◽  
Cellular Interaction ◽  
Synaptic Connections ◽  
Evolutionary Novelty ◽  
Unique Type ◽  
Sensory Axons ◽  
Brain Circuit ◽  
Sensory Map ◽  
Sequential Assembly

Interhemispheric synaptic connections, a prominent feature in animal nervous systems for the rapid exchange and integration of neuronal information, can appear quite suddenly during brain evolution, raising the question about the underlying developmental mechanism. Here, we show in the Drosophila olfactory system that the induction of a bilateral sensory map, an evolutionary novelty in dipteran flies, is mediated by a unique type of commissural pioneer interneurons (cPINs) via the localized activity of the cell adhesion molecule Neuroglian. Differential Neuroglian signaling in cPINs not only prepatterns the olfactory contralateral tracts but also prevents the targeting of ingrowing sensory axons to their ipsilateral synaptic partners. These results identified a sensitive cellular interaction to switch the sequential assembly of diverse neuron types from a unilateral to a bilateral brain circuit organization.

scholarly journals Exogenous hyalin and sea urchin gastrulation, Part II: hyalin, an interspecies cell adhesion molecule

Zygote ◽  
2008 ◽  
Vol 16 (1) ◽  
pp. 73-78 ◽  
Author(s):  
M. Alvarez ◽  
J. Nnoli ◽  
E.J. Carroll ◽  
V. Hutchins-Carroll ◽  
Z. Razinia ◽  
...  
Keyword(s):  
Sea Urchin ◽  
Cell Adhesion Molecule ◽  
Cellular Interaction ◽  
Adhesive Interaction ◽  
Lytechinus Pictus ◽  
Developmental Effects ◽  
Sea Urchin Embryo ◽  
Repeat Domain ◽  
Precise Quantification ◽  
Main Component

SummaryThe 330 kDa fibrillar glycoprotein hyalin is a well known component of the sea urchin embryo extracellular hyaline layer. Only recently, the main component of hyalin, the hyalin repeat domain, has been identified in organisms as widely divergent as bacteria and humans using the GenBank database and therefore its possible function has garnered a great deal of interest. In the sea urchin, hyalin serves as an adhesive substrate in the developing embryo and we have recently shown that exogenously added purified hyalin from Strongylocentrotus purpuratus embryos blocks a model cellular interaction in these embryos, archenteron elongation/attachment to the blastocoel roof. It is important to demonstrate the generality of this result by observing if hyalin from one species of sea urchin blocks archenteron elongation/attachment in another species. Here we show in three repeated experiments, with 30 replicate samples for each condition, that the same concentration of S. purpuratus hyalin (57 μg/ml) that blocked the interaction in living S. purpuratus embryos blocked the same interaction in living Lytechinus pictus embryos. These results correspond with the known crossreactivity of antibody against S. purpuratus hyalin with L. pictus hyalin. We propose that hyalin–hyalin receptor binding may mediate this adhesive interaction. The use of a microplate assay that allows precise quantification of developmental effects should help facilitate identification of the function of hyalin in organisms as divergent as bacteria and humans.

scholarly journals The role of muscle spindles in the development of the monosynaptic stretch reflex

2012 ◽  
Vol 108 (1) ◽  
pp. 83-90 ◽  
Author(s):  
Zhi Wang ◽  
LingYing Li ◽  
Eric Frank
Keyword(s):  
Muscle Fibers ◽  
Muscle Spindles ◽  
Synaptic Connections ◽  
Intrafusal Muscle ◽  
Intrafusal Fibers ◽  
Sensory Axons ◽  
Neurotrophin 3 ◽  
Erbb2 Receptor ◽  
Intrafusal Muscle Fibers

Muscle sensory axons induce the development of specialized intrafusal muscle fibers in muscle spindles during development, but the role that the intrafusal fibers may play in the development of the central projections of these Ia sensory axons is unclear. In the present study, we assessed the influence of intrafusal fibers in muscle spindles on the formation of monosynaptic connections between Ia (muscle spindle) sensory axons and motoneurons (MNs) using two transgenic strains of mice. Deletion of the ErbB2 receptor from developing myotubes disrupts the formation of intrafusal muscle fibers and causes a nearly complete absence of functional synaptic connections between Ia axons and MNs. Monosynaptic connectivity can be fully restored by postnatal administration of neurotrophin-3 (NT-3), and the synaptic connections in NT-3-treated mice are as specific as in wild-type mice. Deletion of the Egr3 transcription factor also impairs the development of intrafusal muscle fibers and disrupts synaptic connectivity between Ia axons and MNs. Postnatal injections of NT-3 restore the normal strengths and specificity of Ia–motoneuronal connections in these mice as well. Severe deficits in intrafusal fiber development, therefore, do not disrupt the establishment of normal, selective patterns of connections between Ia axons and MNs, although these connections require the presence of NT-3, normally supplied by intrafusal fibers, to be functional.

Late emigrating neural crest cells migrate specifically to the exit points of cranial branchiomotor nerves

Development ◽  
1996 ◽  
Vol 122 (8) ◽  
pp. 2367-2374 ◽  
Author(s):  
C. Niederlander ◽  
A. Lumsden
Keyword(s):  
Neural Crest ◽  
Motor Neurons ◽  
Cell Adhesion Molecule ◽  
Neural Crest Cells ◽  
Exit Point ◽  
Sensory Axons ◽  
Morphological Segmentation ◽  
Cranial Ganglia ◽  
Cranial Neural Crest Cells ◽  
Late Stages

Morphological segmentation of the avian hindbrain into rhombomeres is also reflected by the emergent organisation of branchiomotor nerves. In each case, the motor neurons of these nerves lie in two adjacent rhombomeres (e.g. of the Vth nerve in r2 and r3, VIIth in r4 and r5 etc.), and their outgrowing axons emerge into the periphery through defined exit points in rhombomeres r2, r4 and r6, respectively. Sensory axons of the cranial ganglia also enter the neuroepithelium at the same points. Motor axon outgrowth through experimentally rotated rhombomeres has suggested that a chemoattractive mechanism, involving the exit points, may form a component of their guidance. Yet so far, nothing is known about the establishment of the exit points or the identity of the cells that form them. In this study, we describe a group of late emigrating cranial neural crest cells which populate specifically the prospective exit points. Using chimaeras in which premigratory chick neural crest had been replaced orthotopically by quail cells, a population of neural crest was found to leave the cranial neural tube from about stage 10+ onwards and to migrate directly to the prospective exit points. These cells define the exit points by stage 12+, long before either motor or sensory axons have grown through them. The entire neural crest population of exit point cells expresses the recently described cell adhesion molecule c-cad7. Further, heterotopic grafting experiments show that midbrain and spinal cord crest, grafted at late stages in place of r4 crest, share the same migratory behaviour to the facial nerve exit points and express the same markers as cells contributed by the native r4 crest. It was not possible to generate new exit points in odd numbered rhombomeres simply by experimentally increasing their (normally insignificant) amount of crest production. Initiation of the exit point region probably lies, therefore, in the neuroepithelium.

scholarly journals The role of the odorant receptors in the formation of the sensory map

BMC Biology ◽  
2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Simona Francia ◽  
Claudia Lodovichi
Keyword(s):  
Olfactory System ◽  
Odorant Receptors ◽  
Axon Terminals ◽  
Sensory Axons ◽  
Sensory Maps ◽  
And Function ◽  
Sensory Map ◽  
Target Locations ◽  
The Brain

AbstractIn the olfactory system, odorant receptors (ORs) expressed at the cell membrane of olfactory sensory neurons detect odorants and direct sensory axons toward precise target locations in the brain, reflected in the presence of olfactory sensory maps. This dual role of ORs is corroborated by their subcellular expression both in cilia, where they bind odorants, and at axon terminals, a location suitable for axon guidance cues. Here, we provide an overview and discuss previous work on the role of ORs in establishing the topographic organization of the olfactory system and recent findings on the mechanisms of activation and function of axonal ORs.

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