Making the connection: retinal axon guidance in the zebrafish

Culverwell, James; Karlstrom, Rolf O.

doi:10.1016/s1084952102001039

Cited by 26 publications

(24 citation statements)

References 81 publications

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“…1C-F). These axon phenotypes are similar to, but less severe than, those seen in other ipsilateral class mutants such as yot(gli2) and dtr(gli1) (Barresi et al, 2005;Culverwell and Karlstrom, 2002;Karlstrom et al, 1996).…”

Section: Axon Guidance and Forebrain Patterning Defects In Uml Mutantssupporting

confidence: 62%

brother of cdo (umleitung) is cell-autonomously required for Hedgehog-mediated ventral CNS patterning in the zebrafish

et al. 2011

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SUMMARYThe transmembrane protein Brother of Cdo (Boc) has been implicated in Shh-mediated commissural axon guidance, and can both positively and negatively regulate Hedgehog (Hh) target gene transcription, however, little is known about in vivo requirements for Boc during vertebrate embryogenesis. The zebrafish umleitung (uml ty54 ) mutant was identified by defects in retinotectal axon projections. Here, we show that the uml locus encodes Boc and that Boc function is cell-autonomously required for Hh-mediated neural patterning. Our phenotypic analysis suggests that Boc is required as a positive regulator of Hh signaling in the spinal cord, hypothalamus, pituitary, somites and upper jaw, but that Boc might negatively regulate Hh signals in the lower jaw. This study reveals a role for Boc in ventral CNS cells that receive high levels of Hh and uncovers previously unknown roles for Boc in vertebrate embryogenesis.

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Section: Axon Guidance and Forebrain Patterning Defects In Uml Mutantssupporting

confidence: 62%

brother of cdo (umleitung) is cell-autonomously required for Hedgehog-mediated ventral CNS patterning in the zebrafish

et al. 2011

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“…In zebrafish mutants in which components of the Hh signalling pathway are affected, RGC axons fail to cross the midline (Culverwell and Karlstrom, 2002). Detailed analysis of these mutants and the treatment of wild-type zebrafish embryos with cyclopamine demonstrated that axon guidance defects were secondary to the Shh-mediated specification of midline glial cells as well as to the control of Slit expression (Barresi et al, 2005;Culverwell and Karlstrom, 2002), a potent repellent for RGC axons (Erskine et al, 2000;Niclou et al, 2000;Ringstedt et al, 2000).…”

Section: C-rgc Axon Growth Depends On Two Shh Sources: the Rgc And Thmentioning

confidence: 99%

“…Detailed analysis of these mutants and the treatment of wild-type zebrafish embryos with cyclopamine demonstrated that axon guidance defects were secondary to the Shh-mediated specification of midline glial cells as well as to the control of Slit expression (Barresi et al, 2005;Culverwell and Karlstrom, 2002), a potent repellent for RGC axons (Erskine et al, 2000;Niclou et al, 2000;Ringstedt et al, 2000). Although in our experiments anti-Shh-producing cells were injected when Shh expression is already downregulated and no longer needed in the preoptic area (Manning et al, 2006;Trousse et al, 2001), we cannot entirely exclude the possibility that some of the observed defects might be secondary to subtle patterning alterations.…”

Section: C-rgc Axon Growth Depends On Two Shh Sources: the Rgc And Thmentioning

confidence: 99%

Autonomous and non-autonomous Shh signalling mediate the in vivo growth and guidance of mouse retinal ganglion cell axons

2008

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In non-mammalian vertebrates, the relatively homogeneous population of retinal ganglion cells (RGCs) differentiates and projects entirely to the contralateral side of the brain under the influence of sonic hedgehog (Shh). In mammals, by contrast, there are two different RGC types: the Zic2-positive ipsilateral projecting and the Isl2-positive contralateral projecting. We asked whether the axons of these two populations respond to Shh and if their response differs. We have also analysed whether midline-and RGCderived Shh contributes to the growth of the axons in the proximal visual pathway. We show that these two RGC types are characterised by a differential expression of Shh signalling components and that they respond differently to Shh when challenged in vitro. In vivo blockade of Shh activity, however, alters the path and distribution mostly of the contralateral projecting RGC axons at the chiasm, indicating that midline-derived Shh participates in funnelling contralateral visual fibres in this region. Furthermore, interference with Shh signalling in the RGCs themselves causes abnormal growth and navigation of contralateral projecting axons in the proximal portion of the pathway, highlighting a novel cell-autonomous mechanism by which Shh can influence growth cone behaviour.

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“…This large-scale screen uncovered 114 mutations, in about 35 genes, disrupting either the pathfinding of axons from the eye to the tectum or the retinotopic map. Although some of the more specific mutations, such as gna, woe and nev, still await molecular identification, most of the genes have now been cloned (Culverwell and Karlstrom, 2002). Unsurprisingly, retinotectal pathfinding was found to depend on proper brain patterning (Hedgehog signaling, syu, igu, con, dtr, uml and yot; Nodal signaling, cyc; homeodomain transcription factors, noi) and on components of the extracellular matrix (bal, gpy and sly).…”

Section: Introductionmentioning

confidence: 99%

A GFP-based genetic screen reveals mutations that disrupt the architecture of the zebrafish retinotectal projection

et al. 2005

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for anatomical phenotypes. Thirteen recessive mutations in 12 genes were discovered. In one mutant, ddl, the majority of RGCs fail to differentiate. Three of the mutations, vrt, late and tard, delay the orderly ingrowth of retinal axons into the tectum. Two alleles of drg disrupt the layer-specific targeting of retinal axons. Three genes, fuzz, beyo and brek, are required for confinement of the tectal neuropil. Fasciculation within the optic tract and adhesion within the tectal neuropil are regulated by vrt, coma, bluk, clew and blin. The mutated genes are predicted to encode molecules essential for building the intricate neural architecture of the visual system.

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Making the connection: retinal axon guidance in the zebrafish

Cited by 26 publications

References 81 publications

brother of cdo (umleitung) is cell-autonomously required for Hedgehog-mediated ventral CNS patterning in the zebrafish

brother of cdo (umleitung) is cell-autonomously required for Hedgehog-mediated ventral CNS patterning in the zebrafish

Autonomous and non-autonomous Shh signalling mediate the in vivo growth and guidance of mouse retinal ganglion cell axons

A GFP-based genetic screen reveals mutations that disrupt the architecture of the zebrafish retinotectal projection

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