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Query: UMLS:C0009402 (colorectal cancer)
 53,228 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The mammalian striatum arises in the basal telencephalon and contains morphologically homogenous neurons that can be divided into two distinct compartments, patches and the matrix. During development, patch neurons are generated first to form a striatal primordium. After a large influx of later-born matrix neurons into this region, the unique mosaic arrangement of these two neuronal phenotypes is established. The massive migration of matrix neurons continues during the embryonic period, and they eventually comprise 80-85% of the mature striatum. To elucidate the cellular mechanism or mechanisms underlying this critical event in striatal histogenesis, we examined the migration characteristics of striatal subventricular zone (SVZ) cells at embryonic day 18 when neurogenesis peaks for matrix neurons. Using gel cultures, we show that netrin-1, one of the diffusible guidance cues expressed in the striatal ventricular zone (VZ), exerts a repulsive action on migrating SVZ cells. This effect is blocked in the presence of antibodies against Deleted in colorectal cancer (DCC), a putative receptor for netrin-1. The expression patterns of netrin-1 and DCC strongly suggest the involvement of this effect in the outward migration of SVZ cells into the striatal postmitotic region. Our cell tracing study using living brain slices demonstrates that striatal SVZ cells migrate toward and disperse throughout the striatum, in which they differentiate into phenotypes of striatal projection neurons. We suggest that netrin-1 expressed in the striatal VZ serves to guide the large influx of striatal matrix neurons into the striatal primordium and is thereby involved in the initial formation of fundamental striatal structures.
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PMID:A role of netrin-1 in the formation of the subcortical structure striatum: repulsive action on the migration of late-born striatal neurons. 1140 12

Netrins are a family of secreted proteins that function as tropic cues directing cell and axon migration during neural development. We show that the netrin-1 receptor, deleted in colorectal cancer (DCC), is present at filopodia tips in growth cones of embryonic rat spinal commissural neurons. To further investigate DCC function, we characterized the expression of netrins and netrin receptors in HEK293T cells and NG108-15 cells and found that they express netrin-1 but do not express DCC. Ectopic expression of DCC produced a netrin-1-dependent increase in the number of filopodia and in cell surface area. Coexpression of DCC and dominant negative Cdc42 or dominant negative Rac1 blocked the increase in filopodia number and cell surface area, respectively. Furthermore, addition of netrin-1 to cells expressing DCC caused a persistent activation of Cdc42 and Rac1. These findings suggest that netrin-1, via DCC, influences cellular motility by regulating actin-based membrane extension through the activation of Cdc42 and Rac1.
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PMID:The netrin-1 receptor DCC promotes filopodia formation and cell spreading by activating Cdc42 and Rac1. 1181 94

Netrins are chemotropic guidance cues that attract or repel growing axons during development. DCC (deleted in colorectal cancer), a transmembrane protein that is a receptor for netrin-1, is implicated in mediating both responses. However, the mechanism by which this is achieved remains unclear. Here we report that Rho GTPases are required for embryonic spinal commissural axon outgrowth induced by netrin-1. Using N1E-115 neuroblastoma cells, we found that both Rac1 and Cdc42 activities are required for DCC-induced neurite outgrowth. In contrast, down-regulation of RhoA and its effector Rho kinase stimulates the ability of DCC to induce neurite outgrowth. In Swiss 3T3 fibroblasts, DCC was found to trigger actin reorganization through activation of Rac1 but not Cdc42 or RhoA. We detected that stimulation of DCC receptors with netrin-1 resulted in a 4-fold increase in Rac1 activation. These results implicate the small GTPases Rac1, Cdc42, and RhoA as essential components that participate in signaling the response of axons to netrin-1 during neural development.
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PMID:Rac1 and Cdc42 but not RhoA or Rho kinase activities are required for neurite outgrowth induced by the Netrin-1 receptor DCC (deleted in colorectal cancer) in N1E-115 neuroblastoma cells. 1184 89

Netrin-1 is a bifunctional secreted protein that directs axon extension in various groups of developing axonal tracts. The transmembrane DCC (deleted in colorectal cancer) receptor is described as netrin-1 receptor and is involved in the attractive effects of netrin-1. In this study, we examined the spatio-temporal expression patterns of both netrin-1 and DCC in the rat olfactory system at different stages of development and during axonal regeneration following unilateral bulbectomy. High DCC expression was detected on the pioneer olfactory axons as they are extending toward the telencephalon. This expression was transient since from embryonic day 16 onwards, DCC was no longer detected along the olfactory nerve path. From embryonic day 14 until birth, DCC was also expressed within the mesenchyme surrounding the olfactory epithelium. During the same period, netrin-1 protein was detected along the trajectory of olfactory axons up to the olfactory bulb and its expression pattern in the nasal mesenchyme largely overlapped that of DCC. Moreover, netrin-1 continued to be present during the two first post-natal weeks, and a weak protein expression still persisted in the dorso-medial region of the olfactory epithelium in adult rats. While unilateral bulbectomy induced a transient up-regulation of netrin-1 in the lamina propria, particularly in the dorso-medial region of the neuroepithelium, no DCC expression was detected on the regenerating olfactory axons. In the developing olfactory bulb, the extension of mitral cell axons was associated with DCC presence while netrin-1 was absent along this axonal path. DCC was also highly expressed in the newly formed glomeruli after birth, and a weak DCC expression was still detected in the glomerular layer in adult rats. Taken together, these data support the notion that netrin-1, via DCC expressed on axons, may play a role in promoting outgrowth and/or guidance of pioneering olfactory axons toward the olfactory bulb primordium. Moreover, association of netrin-1 with mesenchymal DCC may provide a permissive environment to the growth of both pioneer and later-growing axons. The maintenance of netrin-1 expression in the nasal mesenchyme of adult rats as well as its regional up-regulation following unilateral bulbectomy infer that netrin-1, even in the absence of DCC, may be involved in the process of axonal growth of newly differentiated olfactory receptor neurons probably through the use of other receptors.
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PMID:Expression of netrin-1 and netrin-1 receptor, DCC, in the rat olfactory nerve pathway during development and axonal regeneration. 1192 47

Precursors of the olfactory interneurons migrate from the subventricular zone via the rostral migratory stream (RMS). To investigate the molecular mechanisms by which RMS cells migrate, we used a slice preparation, which allows the migrating cells to be imaged at very high temporal and spatial resolution in the presence of added inhibitors. Using immunohistochemistry, we first determined that the alpha1-, beta8-, and beta1-integrin subunits and the alpha5- and gamma1-laminin subunits are expressed during embryonic day 16 to the early postnatal stage. During early postnatal days, alpha(v)- and beta6-integrins appeared, and their expression persisted throughout adulthood. The migrating cells also expressed the netrin receptors neogenin and Deleted in Colorectal Carcinoma (DCC). Netrin-1 is expressed in olfactory mitral cells. Anti-integrin antibodies inhibited the production of protrusions as well as cellular translocation. In contrast, anti-DCC antibodies primarily altered the direction of the protrusions; consequently, the migration was no longer unidirectional, and the speed was reduced. Thus, the interaction of DCC, possibly through an interaction with netrin-1, contributes to the direction of migration by regulating the formation of directed protrusions. In contrast, the integrins function in production of protrusions and cellular translocation, with different integrins participating at different developmental stages.
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PMID:Deleted in colorectal carcinoma and differentially expressed integrins mediate the directional migration of neural precursors in the rostral migratory stream. 1197 33

Neuronal growth cones are guided to their targets by attractive and repulsive guidance cues. In mammals, netrin-1 is a bifunctional cue, attracting some axons and repelling others. Deleted in colorectal cancer (Dcc) is a receptor for netrin-1 that mediates its chemoattractive effect on commissural axons, but the signalling mechanisms that transduce this effect are poorly understood. Here we show that Dcc activates mitogen-activated protein kinase (MAPK) signalling, by means of extracellular signal-regulated kinase (ERK)-1 and -2, on netrin-1 binding in both transfected cells and commissural neurons. This activation is associated with recruitment of ERK-1/2 to a Dcc receptor complex. Inhibition of ERK-1/2 antagonizes netrin-dependent axon outgrowth and orientation. Thus, activation of MAPK signalling through Dcc contributes to netrin signalling in axon growth and guidance.
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PMID:Netrin-1-mediated axon outgrowth requires deleted in colorectal cancer-dependent MAPK activation. 1198 22

Oligodendrocytes, the myelin-forming cells of the CNS, are generated from multiple foci distributed along the developing neural tube. Little is known about the endogenous guidance cues controlling the migration of oligodendrocyte precursor cells (OPCs) from their site of emergence toward their final destination, mainly the future white matter tracts. During embryonic development, the optic nerve is populated by OPCs originating in the diencephalon that migrate from the chiasm toward the retina. Here we show that OPCs migrating into the embryonic optic nerve express the semaphorin receptors neuropilin-1 and -2, as well as deleted in colorectal cancer (DCC) and, to a lesser extend unc5H1, two of the netrin-1 receptors. Using a functional migration assay, we provide evidence that Sema 3A and netrin-1 exert opposite chemotactic effects, repulsive or attractive, respectively, on embryonic OPCs. In addition, we show that Sema 3F has a dual effect, chemoattractive and mitogenic on embryonic OPCs. The localization of cells expressing Sema 3A, Sema 3F, and netrin-1 is consistent with a role for these ligands in the migration of OPCs in the embryonic optic nerve. Altogether, our results suggest that the migration of OPCs in the embryonic optic nerve is modulated by a balance of effects mediated by members of the semaphorin and netrin families.
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PMID:Directional guidance of oligodendroglial migration by class 3 semaphorins and netrin-1. 1212 61

Netrins are a family of secreted proteins that guide the migration of cells and axonal growth cones during development. DCC (deleted in colorectal cancer) is a receptor for netrin-1 implicated in mediating these responses. Here, we show that DCC interacts constitutively with the SH3/SH2 adaptor Nck in commissural neurons. This interaction is direct and requires the SH3 but not SH2 domains of Nck-1. Moreover, both DCC and Nck-1 associate with the actin cytoskeleton, and this association is mediated by DCC. A dominant negative Nck-1 inhibits the ability of DCC to induce neurite outgrowth in N1E-115 cells and to activate Rac1 in fibroblasts in response to netrin-1. These studies provide evidence for an important role of mammalian Nck-1 in a novel signaling pathway from an extracellular guidance cue to changes in the actin-based cytoskeleton responsible for axonal guidance.
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PMID:The adaptor protein Nck-1 couples the netrin-1 receptor DCC (deleted in colorectal cancer) to the activation of the small GTPase Rac1 through an atypical mechanism. 1214 62

Netrin-1 and its receptors deleted in colorectal cancer (DCC) and neogenin are expressed within the developing visual system and have been implicated in mediating axon guidance and cell migration. However, the expression of the netrin-1 receptor UNC-5 has not yet been addressed. Here we clone Xenopus UNC-5 (XUNC-5) and describe its expression within the developing visual system. Xunc-5 transcripts are expressed within the developing optic vesicles and later become restricted to the dorsal ciliary marginal zone, a site of retinoblast proliferation and differentiation. This highly restricted expression pattern could make XUNC-5 an excellent marker of dorsal retinal precursor cells.
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PMID:Expression of UNC-5 in the developing Xenopus visual system. 1235 Nov 79

The Caenorhabditis elegans gene unc-5 and it's vertebrate homologues are Netrin receptors. In this study, I report the cloning of three mouse Unc5 family members, namely, Unc5h1, Unc5h2 and Unc5h4. Furthermore, a comparative expression analysis is presented with Unc5h3, deleted in colorectal cancer and Netrin-1. Transcript distribution is studied during early eye development, mammary bud formation, vascularisation, and limb development. The most widely expressed Unc5 family member is Unc5h2 and it's mRNA is observed during early blood vessel formation, in the semicircular canal and in a dorsal to ventral gradient in the retina. Unc5h1 expression is restricted to the central nervous system, whereas, sites of Unc5h4 expression are in the developing limb and mammary gland.
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PMID:Cloning of three mouse Unc5 genes and their expression patterns at mid-gestation. 1235 Nov 86


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