Netrin-1 directs dendritic growth and connectivity of vertebrate central neurons in vivo

Abstract

BackgroundNetrins are a family of extracellular proteins that function as chemotropic guidance cues for migrating cells and axons during neural development. In the visual system, netrin-1 has been shown to play a key role in retinal ganglion cell (RGC) axon growth and branching at the target, where presynaptic RGC axons form partnerships with the dendrites of tectal neurons. However, the signals that guide the connections between RGC axons and their postsynaptic partners are yet unknown. Here, we explored dynamic cellular mechanisms by which netrin-1 influences visual circuit formation, particularly those that impact postsynaptic neuronal morphology and connectivity during retinotectal wiring.ResultsTime-lapse in vivo imaging of individual Xenopus laevis optic tectal neurons co-expressing tdTomato and PSD95-GFP revealed rapid remodeling and reorganization of dendritic arbors following acute manipulations in netrin-1 levels. Effects of altered netrin signaling on developing dendritic arbors of tectal neurons were distinct from its effects on presynaptic RGC axons. Within 4 h of treatment, tectal injection of recombinant netrin-1 or sequestration of endogenous netrin with an UNC-5 receptor ectodomain induced significant changes in the directionality and orientation of dendrite growth and in the maintenance of already established dendrites, demonstrating that relative levels of netrin are important for these functions. In contrast, altering DCC-mediated netrin signaling with function-blocking antibodies induced postsynaptic specialization remodeling and changed growth directionality of already established dendrites. Reducing netrin signaling also decreased avoidance behavior in a visually guided task, suggesting that netrin is essential for emergent visual system function.ConclusionsThese in vivo findings together with the patterns of expression of netrin and its receptors reveal an important role for netrin in the early growth and guidance of vertebrate central neuron dendritic arbors. Collectively, our studies indicate that netrin shapes both pre- and postsynaptic arbor morphology directly and in multiple ways at stages critical for functional visual system development.

Genome-Wide Association Analysis Identifies Dcc as an Essential Factor in the Innervation of the Peripheral Vestibular System in Inbred Mice

“…In the adult, Dcc expression was seen on neuronal cell bodies at the base of the utricle and on the projections of neurons to the crista ampullaris and utricle. This staining pattern is similar to that described in the neuronal cell bodies and projections in the optic tectum of Xenopus embryos and rat central nervous system (CNS) (Nagel et al 2015;Keino-Masu et al 1996;Horn et al 2013). These findings suggested a potential role for Dcc in the process of innervation during development and potentially of maintenance of innervation into adulthood as seen in the mouse retinal ganglion and in CNS development (Mehlen and Mazelin 2003;Shi et al 2010).…”

“…Complaints of dizziness or disequilibrium are common in the elderly, with an estimated lifetime prevalence of 35 % in people over age 60 (Neuhauser et al 2005). In a recent survey of emergency room visits over a 10-year interval, 26 million visits were recorded for dizziness with an average of over three diagnostic tests per patient, including imaging of the brain in 17 % (Kerber et al 2008).…”

NOVA regulates Dcc alternative splicing during neuronal migration and axon guidance in the spinal cord

“…It remains to be seen if altered Dcc alternative splicing accounts for additional cases of colorectal cancers and other cancers. Furthermore, Dcc plays additional roles in the nervous system, such as in dendritic growth and guidance ( Furrer et al, 2003 ; Nagel et al, 2015 ; Suli et al, 2006 ; Teichmann and Shen, 2011 ), and in synapse formation and function ( Colon-Ramos et al, 2007 ; Goldman et al, 2013 ; Horn et al, 2013 ). Therefore, it is important to determine if Dcc alternative splicing is also important for other biological processes.…”

Dependence receptor involvement in subtilisin-induced long-term depression and in long-term potentiation

“…The anti-Unc-5C antibody corresponds to an epitope on the intracellular domain of the receptor while the anti-DCC antibody (monoclonal ab 16793 [AF5], Abcam, Cambridge, UK) interacts with a sequence in the extracellular domain. The DCC antibody used here has been clearly identified as a function-blocking antibody (Keino-masu et al, 1996;Deiner et al, 1997;Forcet et al, 2002;Powell et al, 2008;Tsai et al, 2003;Nagel et al 2015;Huang et al 2015;Lee et al, 2014;Son et al 2013;Qu et al 2013;Manitt et al, 2009). Unc-5 antibodies have been used less often as function-blocking agents, but were successfully used by Koch et al, 2011).…”