![]() This provides information about specific neural circuits and how synaptic connectivity is associated with branching morphologies. Second, the entire nervous system structure and neural connectivity map (connectome) have been described in great detail in both sexes ( White et al., 1986 Jarrell et al., 2012 Cook et al., 2019). Branching patterns of these neurons are highly stereotyped throughout development ( Altun and Hall, 2011). elegans neurons have simple, unbranched morphologies, the few neurons with neurite branches can be observed with great specificity ( White et al., 1986). elegans nervous system make it a powerful model for studying molecular mechanisms of neurite branching. ![]() While the exact details of how extrinsic cues are transduced into intracellular signals through cell surface receptors to control actin dynamics during neurite branching remain poorly understood, recent findings in Caenorhabditis elegans begin to provide some insight. Subsequently, branch stabilization and outgrowth require intracellular reorganization of actin and microtubules, in which the actin cytoskeleton plays a role in an initial step of branch formation ( Jan and Jan, 2010 Kalil and Dent, 2014). Furthermore, these interactions are shown to control branch formation by stimulating or inhibiting nascent branch outgrowth. Evidence shows that the localization of neural cell surface receptors and their respective extracellular ligands is highly correlated with branch formation. Moreover, certain cell surface molecules can control various steps of circuit assembly ( Kim, 2019). Most neural cell surface molecules are evolutionarily conserved and play a critical role in neural circuit formation ( Kim, 2019). Of these molecules, cell surface proteins have been shown to modulate the precision of neural circuitry wiring via extracellular interactions ( De Wit and Ghosh, 2016). Numerous previous studies have identified molecules that regulate neurite morphogenesis, including transcription factors, cell surface molecules, and regulators of actin and microtubule dynamics ( Jan and Jan, 2010 Kalil and Dent, 2014). Growing evidence suggests that dysregulation of neurite branching could underlie various neurological and neurodevelopmental disorders such as autism, schizophrenia, and Down syndrome ( Kulkarni and Firestein, 2012 Copf, 2016). These neurite branch networks allow for the formation of highly complex neural circuits that integrate and process information, thereby coordinating specific nervous system functions. Dendrites have an extremely complex branching thereby producing a large dendritic field to receive synaptic or sensory inputs. For example, a single neuron can synapse onto multiple target neurons due to the extensive branching of the axonal shaft. Each axon and dendrite contain numerous neurite branches that enhance neural circuit complexity by allowing for interaction with a large number of target neurons and non-neuronal cells. elegans in an attempt to illustrate the importance of these studies in contributing to our understanding of conserved cell surface molecule regulation of neurite branch formation.Īn extensive neurite branching morphology is a fundamental aspect of neuronal structure. We also cover ectopic and sex-specific neurite branching in C. ![]() The mechanisms of neurite branching are often coupled with other neural circuit developmental processes, such as synapse formation and axon guidance, via the same cell-cell surface molecular interactions. We discuss how cell surface receptor complexes link to and modulate actin dynamics to regulate dendritic and axonal branch formation. Here, we review recent advances in understanding the molecular mechanisms of neurite branching in the nematode Caenorhabditis elegans. The underlying mechanisms of surface molecule activity have often been elucidated using invertebrates with simple nervous systems. Neuronal cell surface molecules play central roles during neurite branch formation. The high synaptic density in the nervous system results from the ability of neurites to branch. Department of Life Science, Dongguk University-Seoul, Goyang, South Korea.
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