Disproportionate neuroanatomical effects of haploinsufficiency in adolescence compared with adulthood: links to dopamine, connectivity, covariance, and gene expression brain maps in mice.

Background: Critical adolescent neural refinement is controlled by the DCC (deleted in colorectal cancer) protein, a receptor for the netrin-1 guidance cue. We sought to describe the effects of reduced on neuroanatomy in the adolescent and adult mouse brain.

Methods: We examined neuronal connectivity, structural covariance, and molecular processes in a -haploinsufficient mouse model, compared with wild-type mice, using new, custom analytical tools designed to leverage publicly available databases from the Allen Institute.

High molecular weight Intraarticular hyaluronic acid for the treatment of knee osteoarthritis: a network meta-analysis.

Background: The 2013 American Academy of Orthopaedic Surgeons (AAOS) guidelines made strong recommendations against intraarticular hyaluronic acid (IAHA) for patients with knee osteoarthritis (OA), as evidence supporting improvements in pain did not meet the minimal clinically important improvement (MCII) threshold. However, there may be important distinctions based on IAHA molecular weight (MW). Hence our objective was to evaluate the efficacy of IAHAs in knee OA based on molecular weight.

Mesocorticolimbic Connectivity and Volumetric Alterations in Mutation Carriers.

The axon guidance cue receptor DCC (deleted in colorectal cancer) plays a critical role in the organization of mesocorticolimbic pathways in rodents. To investigate whether this occurs in humans, we measured (1) anatomical connectivity between the substantia nigra/ventral tegmental area (SN/VTA) and forebrain targets, (2) striatal and cortical volumes, and (3) putatively associated traits and behaviors. To assess translatability, morphometric data were also collected in -haploinsufficient mice.

DCC Receptors Drive Prefrontal Cortex Maturation by Determining Dopamine Axon Targeting in Adolescence.

Background: Dopaminergic input to the prefrontal cortex (PFC) increases throughout adolescence and, by establishing precisely localized synapses, calibrates cognitive function. However, why and how mesocortical dopamine axon density increases across adolescence remains unknown.

Methods: We used a developmental application of axon-initiated recombination to label and track the growth of dopamine axons across adolescence in mice.

Dcc haploinsufficiency regulates dopamine receptor expression across postnatal lifespan.

Adolescence is a period during which the medial prefrontal cortex (mPFC) undergoes significant remodeling. The netrin-1 receptor, deleted in colorectal cancer (DCC), controls the extent and organization of mPFC dopamine connectivity during adolescence and in turn directs mPFC functional and structural maturation. Dcc haploinsufficiency leads to increased mPFC dopamine input, which causes improved cognitive processing and resilience to behavioral effects of stimulant drugs of abuse.

DCC Confers Susceptibility to Depression-like Behaviors in Humans and Mice and Is Regulated by miR-218.

Backgroud: Variations in the expression of the Netrin-1 guidance cue receptor DCC (deleted in colorectal cancer) appear to confer resilience or susceptibility to psychopathologies involving prefrontal cortex (PFC) dysfunction.

Methods: With the use of postmortem brain tissue, mouse models of defeat stress, and in vitro analysis, we assessed microRNA (miRNA) regulation of DCC and whether changes in DCC levels in the PFC lead to vulnerability to depression-like behaviors.

Results: We identified miR-218 as a posttranscriptional repressor of DCC and detected coexpression of DCC and miR-218 in pyramidal neurons of human and mouse PFC.

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

Background: Netrins 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.

Haloperidol treatment downregulates DCC expression in the ventral tegmental area.

A core feature in the pathophysiology of schizophrenia is abnormal development and function of mesocorticolimbic dopamine (DA) circuitry. We have previously shown that variations in the function of the netrin-1 receptor, deleted in colorectal cancer (DCC), result in changes to the development, organization and ongoing plasticity of DA circuitry. In rodents, repeated exposure to the indirect DA-agonist, amphetamine upregulates DCC expression in the ventral tegmental area (VTA), but not in DA terminal regions.

unc5c haploinsufficient phenotype: striking similarities with the dcc haploinsufficiency model.

DCC and UNC5 homologs (UNC5H) are guidance cue receptors highly expressed by mesocorticolimbic dopamine neurons. We have shown that dcc heterozygous mice exhibit increased dopamine, but not norepinephrine, innervation and function in medial prefrontal cortex. Concomitantly, dcc heterozygotes show blunted mesolimbic dopamine release and behavioral responses to stimulant drugs.

Dynamic responses of Xenopus retinal ganglion cell axon growth cones to netrin-1 as they innervate their in vivo target.

Netrin-1 influences retinal ganglion cell (RGC) axon pathfinding and also participates in the branching and synaptic differentiation of mature RGC axons at their target. To investigate whether netrin also serves as an early target recognition signal in the brain, we examined the dynamic behavior of Xenopus RGC axons soon after they innervate the optic tectum. Time-lapse confocal microscopy imaging of RGC axons expressing enhanced yellow fluorescent protein demonstrated that netrin-1 is involved in early axon branching, as recombinant netrin-1 halted further advancement of growth cones into the tectum and induced back branching.

The netrin receptor DCC is required in the pubertal organization of mesocortical dopamine circuitry.

Netrins are guidance cues involved in neural connectivity. We have shown that the netrin-1 receptor DCC (deleted in colorectal cancer) is involved in the functional organization of the mesocorticolimbic dopamine (DA) system. Adult mice with a heterozygous loss-of-function mutation in dcc exhibit changes in indexes of DA function, including DA-related behaviors.

Peri-pubertal emergence of UNC-5 homologue expression by dopamine neurons in rodents.

Puberty is a critical period in mesocorticolimbic dopamine (DA) system development, particularly for the medial prefrontal cortex (mPFC) projection which achieves maturity in early adulthood. The guidance cue netrin-1 organizes neuronal networks by attracting or repelling cellular processes through DCC (deleted in colorectal cancer) and UNC-5 homologue (UNC5H) receptors, respectively. We have shown that variations in netrin-1 receptor levels lead to selective reorganization of mPFC DA circuitry, and changes in DA-related behaviors, in transgenic mice and in rats.

Netrin participates in the development of retinotectal synaptic connectivity by modulating axon arborization and synapse formation in the developing brain.

Netrin has been implicated in retinal ganglion cell (RGC) axon pathfinding in a number of species. In Xenopus laevis, RGC axons reaching their target in the optic tectum can be repelled by a netrin-1 gradient in vitro, suggesting that netrin may also function in wiring events that follow successful axon pathfinding. Here, we examined the contribution of netrin to RGC axon arborization and synapse formation at the target.

Positioned to inhibit: netrin-1 and netrin receptor expression after spinal cord injury.

Netrin-1 regulates axon extension during embryonic development and is expressed by neurons and myelinating oligodendrocytes in the adult CNS. To investigate the potential role of netrin-1 after spinal cord injury, we examined the expression of netrin-1 and netrin receptors after sagittal myelotomy in adult rats. This lesion targets spinal commissural projections, which respond to netrin-1 during development.

Effects of pelvic, pudendal, or hypogastric nerve cuts on Fos induction in the rat brain following vaginocervical stimulation.

In the female rat, genitosensory input is conveyed to the central nervous system predominantly through the pelvic, pudendal, and hypogastric nerves. The present study examined the relative contribution of those three nerves in the expression of Fos immunoreactivity within brain regions previously shown to be activated by vaginocervical stimulation (VCS). Bilateral transection of those nerves, or sham neurectomy, was conducted in separate groups of ovariectomized, sexually-experienced females.

Developmental shift in expression of netrin receptors in the rat spinal cord: predominance of UNC-5 homologues in adulthood.

Netrins are a family of secreted proteins required for normal neural development. Netrin-1 is expressed at similar levels in the adult rat spinal cord and the embryonic CNS, suggesting that it contributes to adult CNS function. Here we show that the netrin receptors dcc, neogenin, unc5h1, unc5h2, and unc5h3 are also expressed in the adult rat spinal cord.

Netrin-1 is a chemorepellent for oligodendrocyte precursor cells in the embryonic spinal cord.

Netrin-1, secreted by floor plate cells, orients axon extension in relation to the ventral midline of the embryonic spinal cord. Oligodendrocyte precursor (OP) cells are born close to the ventral midline and migrate away from the floor plate. Here we show that OP cells, identified by expression of the platelet-derived growth factor alpha receptor, express the netrin receptors dcc and unc5h1 but do not express netrin-1.

Where the rubber meets the road: netrin expression and function in developing and adult nervous systems.

Netrins are a family of secreted proteins that direct the migration of cells and axonal growth cones during neural development. They are bifunctional cues, attracting some cell types and repelling others. Netrins function as either short- or long-range cues, in some circumstances acting close to the surface of the cells that produce them and in other cases at a distance.