共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
3.
When Xenopus embryos from mid-tailbud to early tadpole stages were exposed to retinoic acid (RA), the gut developed with an uncoiled,
straight intestinal tube, morphogenesis of the liver and stomach was affected and intestinal epithelial cells developed without
a brush border and alkaline phosphatase activity. However, the temporal and spatial expression pattern of XlHbox 8, the only
homeobox gene expressed in the endoderm was unaffected. In lateral plate mesodermal cells the expression of α-smooth muscle
(SM) actin was delayed. A similar syndrome has been reported in a study of embryos lacking functional FGF receptors in which
it was proposed that the uncoiled intestinal tube and the delayed differentiation of the intestinal muscle cells are causally
related. Our results support this proposition and further suggest that mesenchymal-epithelial interactions concerned with
regional specification of the endoderm may be impaired resulting in other defects in the gut.
Received: 3 October 1997 / Accepted: 3 February 1998 相似文献
4.
The HOX-like gene Cnox2-Pc is expressed at the anterior region in all life cycle stages of the jellyfish Podocoryne carnea 总被引:3,自引:0,他引:3
The marine jellyfish Podocoryne carnea (Cnidaria, Hydrozoa) has a metagenic life cycle consisting of a larva, a colonial polyp and a free-swimming jellyfish (medusa).
To study the function of HOX genes in primitive diploblastic animals we screened a library of P. carnea cDNA using PCR primers derived from the most conserved regions in helix 1 and helix 3 of the homeobox. A novel gene, Cnox2-Pc, has been isolated and characterized. Cnox2-Pc is a HOX cluster-like gene, and its homeodomain shows similarity to the Deformed subfamily of HOM-C/HOX genes. In situ hybridization revealed that Cnox2-Pc is expressed in the anterior region of the larva, the polyp head, and the most apical ectoderm of the differentiating bud
during medusa development. In adult medusa expression is restricted to the gastrovascular entoderm. The results suggest that
Cnox2-Pc is involved in establishment of an anterior-posterior axis during development in primitive metazoans.
Received: 23 February 1999 / Accepted: 27 July 1999 相似文献
5.
Onuma Y Nishihara R Takahashi S Tanegashima K Fukui A Asashima M 《Development genes and evolution》2000,210(6):325-327
The Ran gene family encodes small GTP binding proteins that are associated with a variety of nuclear processes. We isolated a Xenopus Ran cDNA and analyzed the pattern of expression of this gene during embryogenesis. Ran is expressed maternally and later in the CNS, neural crest, mesenchyme, eyes, and otic vesicles. However, expression is not
detected in the somites or the notochord.
Received: 22 November 1999 / Accepted: 22 December 1999 相似文献
6.
A. D. Deshpande W. Ramakrishna G. P. Mulay V. S. Gupta P. K. Ranjekar 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,97(1-2):135-140
Homeobox genes are the master control genes harbouring the homeobox which is crucial for developmental associated functions.
One homeobox gene, knotted1, which has a role in leaf development, is conserved in plants and might have arisen from a single ancestral gene. Using PCR,
we identified multiple kn1 homeoboxes in diverse cereals and showed a cereal/ species-specific organization correlating them to evolutionary changes.
We postulate the insertion of a large intron preceded by duplication of the kn1 homeobox in the lineage leading to rice.
Received: 17 October 1997 / Accepted: 9 December 1997 相似文献
7.
8.
9.
10.
11.
H. W. J. Stroband Marcus P. S. Dekens Geertruy te Kronnie Henk Schipper Johannis Samallo 《Development genes and evolution》1998,208(1):56-59
The homeobox gene Carp-Ovx1 shows similarity to vertebrate and invertebrate Ovx genes and to Drosophila unplugged. Its expression pattern was studied by in situ hybridization in carp embryos and juveniles. During segmentation, expression
becomes gradually limited to the neural tube. In juveniles up to 9 weeks old, cells in the ventral telencephalon, the facial
lobe and the vagal lobe show Ovx1 expression, confining expression to parts with chemosensory projections.
Received: 29 October 1997 / Accepted: 12 November 1997 相似文献
12.
13.
The genes belonging to the Paired class exert primary developmental functions. They are characterized by six invariant amino
acid residues in the homeodomain, while the residue at position 50 can be a serine, glutamine or lysine as in the Pax-type,
Q50 Paired-like or the K50 Paired-like homeodomains respectively. Genes in this class emerged early in animal evolution: three distinct Pax genes and
two Q50 Paired-like genes have recently been characterised from cnidarians. Phylogenetic molecular reconstructions taking into account
homeodomain and paired-domain sequences provide some new perspectives on the evolution of the Paired-class genes. Analysis
of 146 Paired-class homeodomains from a wide range of metazoan taxa allowed us to identify 18 families among the three sub-classes
from which the aristaless family displays the least diverged position. Both Pax-type and K50 families branch within the Q50 Paired-like sequences implying that these are the most ancestral. Consequently, most Pax genes arose from a Paired-like ancestor,
via fusion of a Paired-like homebox gene with a gene encoding only a paired domain; the Cnidaria appear to contain genes representing
the ’before’ and ’after’ fusion events.
Received: 16 September 1998 / Accepted: 27 October 1998 相似文献
14.
15.
16.
Soares ML Torres-Padilla ME Zernicka-Goetz M 《Development, growth & differentiation》2008,50(7):615-621
The extraembryonic ectoderm (ExE) of the mouse conceptus is known to play a role in embryo patterning by signaling to the underlying epiblast and surrounding visceral endoderm. Bmp4 is one of the key ExE signaling molecules and has been recently implicated to participate in regulating development and migration of the anterior visceral endoderm (AVE). However, it remains unclear when exactly BMP4 signaling starts to regulate AVE positioning. To examine this, we have chosen to affect BMP4 function at two different time points, at embryonic day 5.25 (E5.25), thus before AVE migration, and E5.75, just after AVE migration. To this end, an RNAi technique was used, which consisted of the injection of Bmp4 dsRNA into the proamniotic cavity of the egg cylinder followed by its targeted electroporation into the ExE. This resulted in specific knockdown of Bmp4 . It was found that Bmp4 RNAi at E5.25, but not at E5.75, led to an abnormal pattern of expression of the AVE marker Cerberus-like . Thus, BMP4 signaling appears to affect the expression of Cer1 at a specific time window. This RNAi approach provides a convenient means to study spatial and temporal function of genes shortly after embryo implantation. 相似文献
17.
Distinct structural domains in the planarian brain defined by the expression of evolutionarily conserved homeobox genes 总被引:4,自引:4,他引:0
Homeobox genes such as orthodenticle in Drosophila and its mouse homologues, Otx1 and Otx2, are known to be essential for rostral brain development. To investigate the molecular basis of brain evolution, we searched
for otd/Otx-related homeobox genes in the planarian Dugesia japonica, and identified two genes, DjotxA and B, whose expression appears to be restricted to the cephalic ganglion (brain). DjotxA was expressed more medially, in the region containing the termini of the visual axons, and in the visual cells, suggesting
involvement in establishment of the visual system. DjotxB was expressed in a discrete region just lateral to the DjotxA-positive domain, but not in the more lateral branch structures, which in turn are characterized by the expression of Djotp, a planarian homeobox gene related to mouse Orthopedia (Otp). In transverse sections of planarians, DjotxA and B expression were observed only at the anterior ends of the stumps, corresponding to the regional pattern of the regenerating
brain. Our findings suggest that the planarian brain is composed of structurally distinct and functionally diverse domains
which are defined by the discrete expression of the three evolutionarily conserved homeobox genes.
Received: 17 June 1998 / Accepted: 20 August 1998 相似文献
18.
The anterior visceral endoderm (AVE) plays an important role in anterior-posterior axis formation in the mouse. The AVE functions in part by expressing secreted factors that antagonize growth factor signaling in the proximal epiblast. Here we report that the Secreted frizzled-related protein 5 (Sfrp5) gene, which encodes a secreted factor that can antagonize Wnt signaling, is expressed in the AVE and foregut endoderm during early mouse development. At embryonic day (E) 5.5, Sfrp5 is expressed in the visceral endoderm at the distal tip region of the embryo and at E6.5 in the AVE opposite the primitive streak. In Lim1 embryos, which lack anterior neural tissue and sometimes form a secondary body axis, Sfrp5-expressing cells fail to move towards the anterior and remain at the distal tip of E6.5 embryos. When compared with Dkk1, which encodes another secreted Wnt antagonist molecule present in the visceral endoderm, Sfrp5 and Dkk1 expression overlap but Sfrp5 is expressed more broadly in the AVE. Between E7.5 and 8, Sfrp5 is expressed in the foregut endoderm underlying the cardiac mesoderm. At E8.5, Sfrp5 is expressed in the ventral foregut endoderm that gives rise to the liver. Additional domains of Sfrp5 expression occur in the dorsal neural tube and in the forebrain anterior to the optic placode. These findings identify a gene encoding a secreted Wnt antagonist that is expressed in the extraembryonic visceral endoderm and anterior definitive endoderm during axis formation and organogenesis in the mouse. 相似文献
19.
We have used two complementary cell labeling techniques to investigate dorsal mesoderm formation in Xenopus laevis and Hymenochirus boettgeri. Epithelial grafts from fluorescently labeled donors into unlabeled hosts demonstrate that in Xenopus, as previously shown for Hymenochirus, superficial cells of the dorsal marginal zone have the ability to invade the notochord and somite and participate in their
normal morphogenesis, in a stage-specific and region-specific manner. A new method for superficial fate mapping using cell
surface biotinylation confirms this result for Hymenochirus and demonstrates that in Xenopus as well, even in normal development in the absence of surgical disruption, notochord and the most posterior somitic mesoderm
originate partly in the superficial epithelial layer. This finding is contrary to the widespread belief that Xenopus mesoderm originates solely in the deep mesenchymal layer. In Xenopus (but not in Hymenochirus), the amount of superficial contribution to mesoderm varies, such that in some spawnings it appears not to be present, while
in others it is evident in all or most embryos.
Received: 13 May 1997 / Accepted: 17 July 1997 相似文献
20.
Manuel Viotti Ann C. Foley Anna-Katerina Hadjantonakis 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2014,369(1657)
Despite the importance of the gut and its accessory organs, our understanding of early endoderm development is still incomplete. Traditionally, endoderm has been difficult to study because of its small size and relative fragility. However, recent advances in live cell imaging technologies have dramatically expanded our understanding of this tissue, adding a new appreciation for the complex molecular and morphogenetic processes that mediate gut formation. Several spatially and molecularly distinct subpopulations have been shown to exist within the endoderm before the onset of gastrulation. Here, we review findings that have uncovered complex cell movements within the endodermal layer, before and during gastrulation, leading to the conclusion that cells from primitive endoderm contribute descendants directly to gut. 相似文献