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Rhombomere - Wikipedia, the free encyclopedia In the vertebrate embryo, a rhombomere is a segment of the developing rhombencephalon. The mature rhombencephalon is composed of the pons, cerebellum and medulla. The fate of a rhombomere is affected by differential expression of Hox genes. en.wikipedia.org /wiki/Rhombomere   (109 words)

Interactive Fly, Drosophila Moreover, the fate of the cells of caudally transplanted rhombomeres is modified: the rhombencephalic nuclei in the graft develop according to the new location as shown for an r5/6 to r8 transplantation. Thus posterior transposition of anterior rhombomeres to the r7/8 level results in the activation of Hox genes of the four first paralog groups and in homeotic transformations of the neuroepithelial fate according to cellular position along the anteroposterior axis. Rhombomeres transplanted to posterior truncal levels turn out to be able to express posterior genes of the first eight paralog groups to the exclusion of others located downstream in the Hox genes genomic clusters. www.sdbonline.org /fly/segment/deform2b.htm   (5136 words)

Interactive Fly, Drosophila This early disturbance in Hoxa-1 activation results in rhombomere and cranial nerve abnormalities, reminiscent of those obtained in the Hoxa-1 total knockout, although their severity and penetrance are lower, thus providing strong evidence for direct control of Hox gene function by retinoids during normal development. The patterning of rhombomeres 2 to 7 is lost, with a concurrent posterior expansion of the rhombomere 1 marker, Gbx2. In ventral rhombomere (r)4 of Hoxb1 and Hoxb2 mutant mouse embryos, Phox2b expression is not properly maintained in the visceral motoneuron progenitor domain (pMNv), resulting in a switch to serotonergic fate. www.sdbonline.org /fly/segment/labial2b.htm   (8057 words)

Rhombomeres Rhombomeres are sites of differential cell proliferation (cells at rhombomere boundaries divide faster than cells in the rest of the rhombomere), differential cell mobility (cells from any one rhombomere cannot easily cross into adjacent rhombomeres), and differential cell adhesion (cells prefer to stick to those of their own rhombomere). It is likely that problems in rhombomere formation are the underlying cause of congenital nervous system defects involving cranial nerves, ganglia, and peripheral structures derived from the cranial neural crest (the part of the neural crest that arises from the hindbrain). Rhombomeres in the developing chicken hindbrain and their relationship to the differentiation of the cranial nerves. www.ncbi.nlm.nih.gov /books/bv.fcgi?rid=neurosci.box.1478   (692 words)

Moens Lab Projects The appearance of rhombomere boundaries corresponds with the sharpening of rhombomere-specific domains of gene expression (Figure 5). Boundary sharpening can occur by a number of possible mechanisms: (1) cells on the "wrong" side of a boundary can move across it by a cell adhesion– or repulsion–based mechanism, (2) they can change their identity to match that of their neighbors, or (3) they can be eliminated by programmed cell death. Although cell sorting can contribute to rhombomere boundary formation, we have also observed that when cells are transplanted between rhombomeres they can sometimes change their identities to match that of their neighbors—so at the single-cell level, rhombomere identity is "plastic" and can change in response to environmental signals. www.fhcrc.org /science/labs/moens/projects.html?&&printfriendly=yes   (1072 words)

Induction of a Parafacial Rhythm Generator by Rhombomere 3 in the Chick Embryo -- Coutinho et al. 24 (42): 9383 -- ... Surgical isolation, shift, and grafting of rhombomeres do not interfere with the development of the EP in artificial rhombomere pairs in which the odd rhombomere is in contact with the anterior edge of the even rhombomere. A, B, Two examples of rhombomere islands (dorsal views) produced by heterotopic grafting in r3 position of r1 territories taken from donor embryos that had been submitted to unilateral electroporation of mixed GFP and Krox20 expression plasmids at the r1 level, before engraftment and isolation of the r1r4 island. Wizenmann A, Lumsden A (1997) Segregation of rhombomeres by differential chemoaffinity. www.jneurosci.org /cgi/content/full/24/42/9383   (5691 words)

Hoxa1 - homeo box A1 We examined in transgenic mice the DNA regulatory elements that determine the temporal and spatially restricted expression of two of the earliest and most anteriorly expressed murine genes, Hoxa-1 and Hoxa-2, which are homologues of the labial and proboscipedia genes of Drosophila. Hoxa1 mutations disrupt the rhombomeric organization of the hindbrain, whereas Hoxb1 mutations do not alter the rhombomeric pattern, but instead influence the fate of cells originating in rhombomere 4. In E8.0-8.5 Hoxa-1 mutants, cad6 expression was suppressed in the region of rhombomeres 4 to 6, although that in the other regions was not essentially affected. www.ihop-net.org /UniPub/iHOP/gg/121722.html   (2206 words)

Neural Crest Migration Neural crest cells from the 2nd and 4th rhombomeres migrate to the 1st and 2nd pharyngeal arches respectively, while cells from the 6th rhombomere travel into the 3rd and 4th pharyngeal arch. In the rhombomeres Hox gene expression boundaries coincide with the rhombomere borders. Cells that migrate from the 6th rhombomere have Hoxb-2 as well as Hoxb-3 expressed causing their migration to the 3rd pharyngeal arch. www.trinity.edu /rblyston/craftyMol/ncm.htm   (1166 words)

Krox-20 patterns the hindbrain through both cell-autonomous and non cell-autonomous mechanisms -- Giudicelli et al. 15 ... rhombomeres, or an inappropriate migration of odd-numbered rhombomere Graham, A. and Lumsden, A. Interactions between rhombomeres modulate Krox-20 and follistatin expression in the chick embryo hindbrain. Grapin-Botton, A., Bonnin, M.A., McNaughton, L.A., Krumlauf, R., and Le Douarin, N.M. Plasticity of transposed rhombomeres: Hox gene induction is correlated with phenotypic modifications. www.genesdev.org /cgi/content/full/15/5/567   (7387 words)

New insights into the evolution of the hindbrain Yasunori Murakami in the Kuratani lab labeled reticulospinal and branchial motor neurons (which derive from rhombomeres) to reveal the neuronal organization of the hindbrain of the Japanese lamprey, Lethenteron japonicum, and studies the expression patterns of rhombomere-specific genes. Rather, the trigeminal—facial nerve originates in the middle of rhombomere 4, in the region of expression of the lamprey Hox gene LjHox3. Based on their discoveries, Kuratani et al offer an alternate model in which the positional concurrence between Hox expression, rhombomere identity and specific subsets of hindbrain neurons is the result of a convergent process in which originally independent mechanisms became linked secondarily in the history of gnathostome evolution. www.eurekalert.org /pub_releases/2004-02/rcfd-nii022804.php   (432 words)

Contralateral efferent neurons can be detected in the hindbrain outside of rhombomere 4   (Site not responding. Last check: 2007-10-03) Abstract A group of efferent neurons whose bodies are located contralaterally and extend projections across the ventral midline of the hindbrain is considered as a rhombomere 4-specific characteristic. At the level of rhombomere 2 a similar kind of efferents have only been described as a result of several experimental manipulations and have been interpreted as being due to rhombomere 2 acquiring rhombomere 4 identity. They also imply that the formation of the contralateral efferents at different rostro-caudal levels might be under different genetic controls, because Hoxb-1, which is not expressed in rhombomere 2, seems to be essential for their proper formation in rhombomere 4. www.ijdb.ehu.es /abstract.octubre/41.5.10.htm   (166 words)

FGF3 and FGF8 mediate a rhombomere 4 signaling activity in the zebrafish hindbrain -- Maves et al. 129 (16): 3825 -- ... Rhombomere 4 differentiates earliest in the zebrafish hindbrain. Rhombomere boundaries are marked with arrowheads, and the r4/5 boundary arrowheads are labeled with a dot. mhb, midbrain-hindbrain boundary; r1-r7, rhombomeres 1-7; fb, forebrain. dev.biologists.org /cgi/content/full/129/16/3825   (8071 words)

Facial Visceral Motor Neurons Display Specific Rhombomere Origin and Axon Pathfinding Behavior in the Chick -- Jacob ...   (Site not responding. Last check: 2007-10-03) Kuratani SC, Eichele G (1993) Rhombomere transplantation repatterns the segmental organisation of cranial nerves and reveals cell-autonomous expression of a homeodomain protein. Marin F, Puelles L (1995) Morphological fate of rhombomeres in quail/chick chimaeras: a segmental analysis of hindbrain nuclei. Wingate RJ, Lumsden A (1996) Persistence of rhombomeric organisation in the postsegmental hindbrain. www.jneurosci.org /cgi/content/full/20/20/7664   (6528 words)

Segmental development of reticulospinal and branchiomotor neurons in lamprey: insights into the evolution of the ... rhombomere is instead identified in terms of the particular reticular to the morphological rhombomere boundaries and the trigeminal (B) Cranial nerve roots (arrowheads) and rhombomere boundaries (arrows) are visualized with the anti-acetylated tubulin antibody. dev.biologists.org /cgi/content/full/131/5/983   (7234 words)

Profile We have observed that a stereotyped caudal migration performed by motor neurons in the fourth rhombomere of the hindbrain is dependent on Pbx4 function, and that the Pbx4 protein interacts specifically with the Hoxb1a protein to control this process (Cooper et al., 2003). The appearance of rhombomere boundaries corresponds with the sharpening of rhombomere-specific domains of gene expression. Although cell sorting can contribute to rhombomere boundary formation, we have also observed that when cells are transplanted between rhombomeres they can sometimes change their identities to match that of their neighbors – so at the single cell level rhombomere identity is “plastic” and can change in response to environmental signals. myprofile.cos.com /cmoens   (1760 words)

HOXA1 - homeo box A1 Several DNA elements within the murine Hoxa-1 RA-inducible RAIDR5 enhancer, including the DR5 RARE, conserved element (CE) 1, and CE2, are conserved in the murine Hoxb-1 RAIDR5 enhancer, the human homolog of Hoxa-1, and in the chicken Hoxb-1 gene. In this study, genetic analysis of double mutants demonstrates that both Hoxa1 and Hoxb1 participate in the establishment and maintenance of Hoxb1 expression in rhombomere 4 through auto- and para-regulatory interactions. In immortalized bronchial epithelial cells, WNT7a was lost concomitantly with HOXA1, and a statistically significant correlation between the expression of both genes was observed in lung cancer cell lines. www.ihop-net.org /UniPub/iHOP/gg/89105.html   (2676 words)

RIKEN CDB - News archive In work published in the journal Development, Shigeru Kuratani and colleagues in the RIKEN CDB Laboratory for Evolutionary Morphology revealed discrete mechanisms for segmentation and neural cell specification in a one of the most primitive species known to possess a segmented hindbrain. In vertebrates, the hindbrain is a segmented structure, subdivided into clearly demarcated units called rhombomeres, which generate specific sets of neurons. Studies such as these underscore a pair of evo-devo precepts: that molecular designs capable of supporting viable ontogenies tend to act as magnets for convergent evolution, and that Nature is parsimonious with her creations, preferring to repurpose or tinker with existing genes rather than to introduce perfect novelties. www.cdb.riken.go.jp /en/04_news/articles/040130_new_insights_into.html   (459 words)

Lake Forest College > Eukaryon Vol 1 Jan 2005> News and Views> David Mann Thus, delta-signals seem to provide feedback to maintain wnt expression at rhombomere boundaries, and are thus important for metameric patterning of the hindbrain. Consequently, rhombomere boundaries act as signaling centers required for precise patterning of the hindbrain during development, and delta signals from flanking cells provide a feedback loop to maintain wnt expression at boundaries If rhombomere boundaries are not formed or maintained properly, various cell types including cranial nerves, ganglia, radial glia, commissural neurons, and reticulospinal neurons are mispatterned. www.lakeforest.edu /eukaryon/vol001/dmann.asp   (1637 words)

A homeo domain protein reveals the metameric nature of the developing chick hindbrain -- Sundin and Eichele 4 (8): 1267 ... rhombomeres, Ghox-lab is expressed within a single domain that extends formation of a distinct island of expression in rhombomere 4. Hoxa-2 expression in normal and transposed rhombomeres: independent regulation in the neural tube and neural crest www.genesdev.org /cgi/content/abstract/4/8/1267   (965 words)

Robb Krumlauf - Stowers Institute for Medical Research It serves as a higher order relay center that controls respiration, blood pressure, arousal and wakefulness and it contains the nuclei and fibers of the cranial nerves, which innervate the muscles of the head and neck, transmit sensory information on hearing, balance and taste and control the cardiovascular and gastrointestinal systems. The formation of regional diversity in the hindbrain is achieved through a process of segmentation, whereby neural tissue is transiently divided into seven segmental units, termed rhombomeres. Itasaki N, Sharpe J, Morrison A, Krumlauf R. Reprogramming Hox expression in the vertebrate hindbrain: influence of paraxial mesoderm and rhombomere transposition. www.stowers-institute.org /labs/KrumlaufLab.asp   (1982 words)

[No title] embryo.ectoderm.neural ectoderm.future brain.future rhombencephalon.hindbrain posterior to rhombomere 05.floor plate embryo.ectoderm.neural ectoderm.future brain.future rhombencephalon.hindbrain posterior to rhombomere 05.neural fold embryo.ectoderm.neural ectoderm.future brain.future rhombencephalon.hindbrain posterior to rhombomere 05.neural fold.neural crest genex.hgu.mrc.ac.uk /Databases/Anatomy/XML/TS13.xml   (84 words)

Publications Database - Gene Tools, LLC Transplantation studies have suggested that rhombomere boundaries form by the local sorting out of cells with different segmental identities []. Although a model for rhombomere-boundary formation based on repulsive Eph-ephrin signaling is well established in the literature, the predictions of this model have not been tested in loss-of-function experiments. We therefore propose that the well-known EphA4-dependent repulsion between rhombomeres operates in parallel with the EphA4-dependent adhesion within rhombomeres described here to drive the cell sorting that underlies rhombomere-boundary formation. www.gene-tools.com /Publications/Browse/Show?gtpubs_id=891   (252 words)

Cecilia Moens: Figure 3: Rhombomere identity in zebrafish embryos Figure 3: Rhombomere identity is homogenized in zebrafish embryos lacking Pbx function. Top: a wild-type embryo in dorsal view (anterior to the left) showing cranial motor neurons (green) clustered in rhombomere 2 (arrow) and rhombomeres 4-5 (arrowhead), and showing Engrailed-expressing neurons in rhombomeres 1-3 (red; asterisks). In contrast, embryos lacking Pbx activity (bottom panel) have a homogeneous string of motor neurons and Engrailed-expressing neurons that lack an overt segmental organization. www.fhcrc.org /science/labs/moens/projects/fig3.html   (125 words)

Hoxb1 Enhancer and Control of Rhombomere 4 Expression: Complex Interplay between PREP1-PBX1-HOXB1 Binding Sites -- ...   (Site not responding. Last check: 2007-10-03) The dashed vertical white lines indicate the border between the neural crest cells and the rhombomere or neural tube. Note in panels K to M that expression is greatly reduced or nearly absent in the r4 territory but is unaffected in the more lateral migrating cranial neural crest cells. Cross-regulation in the mouse HoxB complex: the expression of Hoxb2 in rhombomere 4 is regulated by Hoxb1. mcb.asm.org /cgi/content/full/25/19/8541   (8061 words)

TRANSFAC FACTOR TABLE, Release 6.0 - public - 2002-08-01, (C) Biobase GmbH   (Site not responding. Last check: 2007-10-03) RA Pellerin I., Schnabel C., Catron K. M., Abate C. Hox proteins have different affinities for a consensus DNA site that RT correlate with the positions of their genes on the hox cluster. RA Guthrie S., Muchamore I., Kuroiwa A., Marshall H., Krumlauf R., Lumsden A. Neuroectodermal autonomy of Hox-2.9 expression revealed by rhombomere RT transpositions. RA Murphy P., Hill R. Expression of the mouse labial-like homeobox-containing genes, Hox 2.9 and RT Hox 1.6, during segmentation of the hindbrain. www.biobase.de /cgi-bin/pub/databases/transfac/getTF.cgi?AC=T01720   (597 words)

Find in a Library: Analysis of transgenic mice with ectopic Hoxb-3 expression in rhombomere 4 Find in a Library: Analysis of transgenic mice with ectopic Hoxb-3 expression in rhombomere 4 Analysis of transgenic mice with ectopic Hoxb-3 expression in rhombomere 4 WorldCat is provided by OCLC Online Computer Library Center, Inc. on behalf of its member libraries. worldcatlibraries.org /wcpa/ow/1fcee34041a1be1ca19afeb4da09e526.html   (81 words)

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