Neural expression of the Xenopus homeobox gene Xhox3: evidence for a patterning neural signal that spreads through the ectoderm

Development ◽  
1990 ◽  
Vol 108 (4) ◽  
pp. 595-604 ◽  
Author(s):  
A. Ruiz i Altaba
Keyword(s):  
In Situ Hybridization ◽  
Neural Development ◽  
Organizer Region ◽  
Homeobox Gene ◽  
Neural Tissue ◽  
Neural Signal ◽  
Tailbud Stage ◽  
Neural Ectoderm ◽  
Anterior Posterior

The Xenopus laevis homeobox gene Xhox3 is expressed in the axial mesoderm of gastrula and neurula stage embryos. By the late neurula-early tailbud stage, mesodermal expression is no longer detectable and expression appears in the growing tailbud and in neural tissue. In situ hybridization analysis of the expression of Xhox3 in neural tissue shows that it is restricted within the neural tube and the cranial neural crest during the tailbud-early tadpole stages. In late tadpole stages, Xhox3 is only expressed in the mid/hindbrain area and can therefore be considered a marker of anterior neural development. To investigate the mechanism responsible for the anterior-posterior (A-P) regionalization of the neural tissue, the expression of Xhox3 has been analysed in total exogastrula. In situ hybridization analyses of exogastrulated embryos show that Xhox3 is expressed in the apical ectoderm of total exogastrulae, a region that develops in the absence of anterior axial mesoderm. The results provide further support for the existence of a neuralizing signal, which originates from the organizer region and spreads through the ectoderm. Moreover, the data suggest that this neural signal also has a role in A-P patterning the neural ectoderm.

Sequential silver staining and in situ hybridization reveal a direct association between rDNA levels and the expression of homologous nucleolar organizing regions: a hypothesis for NOR structure and function

1998 ◽  
Vol 111 (10) ◽  
pp. 1433-1439
Author(s):  
F. Zurita ◽  
R. Jimenez ◽  
M. Burgos ◽  
R.D. de la Guardia
Keyword(s):  
Transcription Factors ◽  
In Situ Hybridization ◽  
Silver Staining ◽  
Organizer Region ◽  
Nucleolar Organizer ◽  
Interindividual Variation ◽  
Nucleolar Organizer Regions ◽  
Single Pair ◽  
Ribosomal Cistrons

We have developed a procedure for sequential silver staining and in situ hybridization to analyze the relationship between the amount of rDNA present in nucleolar organizer regions, as estimated by in situ hybridization, and their level of expression, as estimated by the silver signal. For simplicity we used cells from the insectivorous mole Talpa occidentalis, which have a single pair of nucleolar organizer regions in chromosome pair 3. The relative content of ribosomal cistrons was also related to the hierarchy of activation of the nucleolar organizer regions present in this chromosomal pair. Statistical analyses demonstrated that both the relative level of expression and the activation hierarchy depended mainly on the number of ribosomal cistrons in nucleolar organizer regions. We propose a functional two-step hypothesis, which is consistent with most known data concerning interchromosomal, intercellular and interindividual variation in a number of plant and animal species, including Talpa occidentalis. In step one, the first available transcription factors bind randomly to the ribosomal promoters, such that larger nucleolar organizer regions are more likely to recruit them. In the second step the remaining transcription factors are recruited in a cooperative way, thus completing activation of one nucleolar organizer region, before the next one becomes active.

Ghox 4.7: a chick homeobox gene expressed primarily in limb buds with limb-type differences in expression

Development ◽  
1991 ◽  
Vol 112 (3) ◽  
pp. 791-806 ◽  
Author(s):  
S. Mackem ◽  
K.A. Mahon
Keyword(s):  
Expression Patterns ◽  
Homeobox Genes ◽  
Homeobox Gene ◽  
Limb Bud ◽  
Limb Buds ◽  
Limb Morphogenesis ◽  
Degenerate Oligonucleotide ◽  
Polymerase Chain ◽  
Anterior Posterior

Homeobox genes play a key role in specifying the segmented body plan of Drosophila, and recent work suggests that at least several homeobox genes may play a regulatory role during vertebrate limb morphogenesis. We have used degenerate oligonucleotide primers from highly conserved domains in the homeobox motif to amplify homeobox gene segments from chick embryo limb bud cDNAs using the polymerase chain reaction. Expression of a large number of homeobox genes (at least 17) is detected using this approach. One of these genes contains a novel homeobox loosely related to the Drosophila Abdominal B class, and was further analyzed by determining its complete coding sequence and evaluating its expression during embryogenesis by in situ hybridization. Based on sequence and expression patterns, we have designated this gene as Ghox 4.7 and believe that it is the chick homologue of the murine Hox 4.7 gene (formerly Hox 5.6). Ghox 4.7 is expressed primarily in limb buds during development and shows a striking spatial restriction to the posterior zone of the limb bud, suggesting a role in specifying anterior-posterior pattern formation. In chick, this gene also displays differences in expression between wing and leg buds, raising the possibility that it may participate in specifying limb-type identity.

Expression of Xenopus N-CAM RNA in ectoderm is an early response to neural induction

Development ◽  
1987 ◽  
Vol 99 (3) ◽  
pp. 311-325 ◽  
Author(s):  
C.R. Kintner ◽  
D.A. Melton
Keyword(s):  
Neural Development ◽  
Transcriptional Activation ◽  
Neural Induction ◽  
Early Response ◽  
Neural Plate ◽  
Cdna Clones ◽  
Epidermal Tissue ◽  
Early Expression ◽  
Neural Ectoderm

We have isolated Xenopus laevis N-CAM cDNA clones and used these to study the expression of N-CAM RNA during neural induction. The results show that the first marked increase in N-CAM RNA levels occurs during gastrulation when mesoderm comes in contact with ectoderm and induces neural development. In situ hybridization results show that the early expression of N-CAM RNA is localized to the neural plate and its later expression is confined to the neural tube. Induction experiments with explanted germ layers show that N-CAM RNA is not expressed in ectoderm unless there is contact with inducing tissue. Together these results suggest an approach to studying how ectoderm is committed to form neural rather than epidermal tissue. Specifically, the data suggest that neural commitment is marked and perhaps mediated by the transcriptional activation of genes, like N-CAM, in the neural ectoderm.

Ventral ectoderm of Xenopus forms neural tissue, including hindbrain, in response to activin

Development ◽  
1992 ◽  
Vol 115 (3) ◽  
pp. 681-688 ◽  
Author(s):  
M.E. Bolce ◽  
A. Hemmati-Brivanlou ◽  
P.D. Kushner ◽  
R.M. Harland
Keyword(s):  
In Situ Hybridization ◽  
Growth Factor ◽  
Normal Animal ◽  
Neural Tissue ◽  
Activin A ◽  
Peptide Growth Factor ◽  
Moderate Frequency ◽  
Whole Mount ◽  
Higher Doses

The peptide growth factor Activin A has been shown to induce complete axial structures in explanted blastula animal caps. However, it is not understood how much this response to activin depends upon early signals that prepattern the ectoderm. We have therefore asked what tissues can be induced in blastula animal caps by activin in the absence of early dorsal signals. Using whole-mount in situ hybridization, we compare the expression of three neural markers, N-CAM, En-2 and Krox-20 in activin-treated ectoderm from control and ventralized embryos. In response to activin, both normal and ventralized animal caps frequently form neural tissue (and express N-CAM) and express the hindbrain marker Krox-20. However, the more anterior marker, En-2, is expressed in only a small fraction of normal animal caps and rarely in ventralized animal caps; the frequency of expression does not increase with higher doses of activin. In all cases En-2 and Krox-20 are expressed in coherent patches or stripes in the induced caps. Although mesoderm is induced in both control and ventralized animal caps, notochord is found in response to activin at moderate frequency in control caps, but rarely in ventralized animal caps. These results support the idea that in the absence of other signals, activin treatment elicits hindbrain but not notochord or anterior neural tissue; and thus, the anterior and dorsal extent of tissues formed in response to activin depends on a prior prepatterning or previous inductions.

Expression of homeobox gene Hox 1.1 during mouse embryogenesis

Development ◽  
1988 ◽  
Vol 104 (Supplement) ◽  
pp. 187-195 ◽  
Author(s):  
Kathleen A. Mahon ◽  
Heiner Westphal ◽  
Peter Gruss
Keyword(s):  
In Situ Hybridization ◽  
Homeobox Genes ◽  
Homeobox Gene ◽  
Spinal Ganglia ◽  
Spatial And Temporal Patterns ◽  
Rna Transcripts ◽  
Positional Identity ◽  
Specific Manner ◽  
Dorsal Spinal

Many of the genes controlling segmentation and pattern formation in Drosophila contain a conserved 183 bp sequence known as the homeobox. Homeobox sequences have been found in a range of metazoan species, including the vertebrates mouse and man. This striking conservation suggests that homeobox genes may play a fundamental role in developmental processes. If this is the case then it might be expected that vertebrate homeobox genes will be differentially expressed during embryogenesis and that the timing of their expression will coincide with major morphogenetic events. Here the spatial and temporal patterns of expression of murine homeobox genes will be explored, concentrating on the Hox 1.1 gene as an example. Using in situ hybridization to localize RNA transcripts, it has been found that Hox 1.1 is expressed in a region-specific manner during the formation and differentiation of the embryonic anteroposterior axis. Although striking patterns of expression of Hox 1.1 and other homeobox genes are seen in overtly segmented structures of the embryo (i.e. somites, prevertebral elements, neural tube and dorsal spinal ganglia) expression is also seen in tissues with no obvious segmental origin. The results suggest that homeobox genes probably do not play an exclusive role in segmentation in vertebrates, but are consistent with a role in the assignment of positional identity along the axis of the embryo.

scholarly journals Region-specific expression in early chick and mouse embryos of Ghox-lab and Hox 1.6, vertebrate homeobox-containing genes related to Drosophila labial

Development ◽  
1990 ◽  
Vol 108 (1) ◽  
pp. 47-58
Author(s):  
O.H. Sundin ◽  
H.G. Busse ◽  
M.B. Rogers ◽  
L.J. Gudas ◽  
G. Eichele
Keyword(s):  
In Situ Hybridization ◽  
Homeobox Gene ◽  
Mouse Embryos ◽  
Mouse Development ◽  
Temporal And Spatial Distribution ◽  
Specific Expression ◽  
Early Embryos ◽  
Close Relationship ◽  
Additional Sequence

A chick gene homologous to the Drosophila homeobox gene labial has been cloned and sequenced. Regions of additional sequence identity outside of the homeobox reveal a close relationship to the mouse gene Hox 1.6. Northern blot analysis demonstrates that Ghox-lab and Hox 1.6 transcripts are both present at high levels during early stages of chick and mouse development, with a subsequent decline in abundance to very low levels by the time limb mesenchyme begins to differentiate. In situ hybridization analysis of chick embryos shows intense expression of Ghox-lab mRNA by Hamburger and Hamilton stage 4 (avian ‘mid gastrula’) and by stage 6 (pre-somitic neural plate) with expression decreasing shortly thereafter. The pattern of Ghox-lab RNA expression in these early embryos divides the embryo into an anterior and a posterior compartment. At stage 6, considerable signal is observed in the posterior two thirds of the embryo, while none is detected in the anterior third which is fated to become the head. This pattern is purely regional in nature, and does not follow boundaries defined by known tissue types. In situ hybridization of Hox 1.6 probes to mouse embryos of day 7.5 or 8.0 indicate that the Hox 1.6 transcript has a temporal and spatial distribution very similar to that of Ghox-lab in the chick embryo.

Lox10, a member of the NK-2 homeobox gene class, is expressed in a segmental pattern in the endoderm and in the cephalic nervous system of the leech Helobdella

Development ◽  
1993 ◽  
Vol 118 (3) ◽  
pp. 877-892 ◽  
Author(s):  
D. Nardelli-Haefliger ◽  
M. Shankland
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
In Situ Hybridization ◽  
Animal Species ◽  
Homeobox Gene ◽  
Endoderm Differentiation ◽  
Homeodomain Sequence ◽  
Supraesophageal Ganglion ◽  
The Central Nervous System

A novel leech homeobox gene, Lox10, is shown to encode a homeodomain sequence characteristic of a phyletically widespread NK-2 homeobox gene class. Lox10 expression was examined in leech embryos of various ages by in situ hybridization. In the unsegmented cephalic region, Lox10 RNA is expressed in a subset of the cells descended from the a' and b' micromeres, including a small cluster of cells, believed to be postmitotic neurons, within the supraesophageal ganglion of the central nervous system. Hybridization signal was not detected in either the mesoderm or ectoderm of the trunk segments, and the apparent restriction of Lox10 ectodermal expression to the nonsegmented cephalic domain resembles the restricted forebrain expression pattern of its mammalian homologues. Lox10 is also expressed within the endodermal tissues of the leech midgut, which arises by cellularization from a polynucleate syncytium. Endodermal expression is organized into a pattern of transverse stripes and spots which are aligned with the intersegmental septa, and which prefigure the pattern of gut wall constrictions observed at later stages of development. Lox10 is the first molecular marker of segmentally periodic endoderm differentiation reported for any animal species.

Homoeobox gene Hox-1.5 expression in mouse embryos: earliest detection by in situ hybridization is during gastrulation

Development ◽  
1987 ◽  
Vol 101 (1) ◽  
pp. 51-60 ◽  
Author(s):  
S.J. Gaunt
Keyword(s):  
Nervous System ◽  
In Situ Hybridization ◽  
Mouse Embryos ◽  
The Body ◽  
Body Axis ◽  
Hybridization Technique ◽  
Newborn Mice ◽  
Neural Ectoderm ◽  
Somitic Mesoderm

We showed earlier (Gaunt, Miller, Powell & Duboule, 1986) that the mouse homoeobox gene Hox-1.5 is expressed in posterior ectoderm and mesoderm of 7 1/2- and 7 3/4-day embryos, and in the 9 1/2-day nervous system posterior to a discrete boundary within the hindbrain. In further in situ hybridization experiments, it is now shown that restriction of Hox-1.5 expression to the posterior regions of the embryo can be detected at stages of development between 7 1/2 and 9 1/2 days. During this period, the intensity of transcription in presomitic and somitic mesoderm declines relative to that in the overlying neural ectoderm, and the transcription boundary within the presumptive hindbrain region sharpens. Hox-1.5 expression posterior to the hindbrain boundary is detected in the 10 1/2- and 12 1/2-day embryo, but this is no longer found in newborn mice. Embryos of ages 3 1/2, 6 1/2 and 7 1/4 days showed no evidence of Hox-1.5 transcripts. It is concluded that embryos undergoing gastrulation (at 7 1/2 days) are the earliest stage at which Hox-1.5 transcripts can be detected by the in situ hybridization technique. In discussion, it is shown how this lies within the period of development during which tissues become determined along the anteroposterior axis of the mouse. Since there may be anterior-to-posterior variation in the time of determination along the body axis, it is suggested that homoeobox genes expressed more posteriorly, such as Hox-3 (Awgulewitsch et al. 1986), might start expression at times later in development.

The chicken CdxA homeobox gene and axial positioning during gastrulation

Development ◽  
1993 ◽  
Vol 118 (2) ◽  
pp. 553-562 ◽  
Author(s):  
A. Frumkin ◽  
R. Haffner ◽  
E. Shapira ◽  
N. Tarcic ◽  
Y. Gruenbaum ◽  
...  
Keyword(s):  
Marginal Zone ◽  
Homeobox Gene ◽  
Primitive Streak ◽  
Immunohistochemical Localization ◽  
Tail Bud ◽  
E Coli ◽  
Tissue Sections ◽  
Whole Mount ◽  
Anterior Posterior

The chicken homebox containing gene, CdxA (formerly CHox-cad), was previously shown to be expressed during gastrulation. Localization of CdxA transcripts by in situ hybridization to tissue sections revealed that, during gastrulation, expression of this gene exhibits a posterior localization along the primitive streak. The transcripts are localized to epiblast cells in the vicinity of the primitive streak, to cells of the primitive streak itself and in the definitive endoderm as it replaces the hypoblast. In order to study in greater detail the pattern of expression of the CdxA gene during gastrulation, we expressed the full-length CdxA protein as a fusion protein in E. coli and generated monoclonal antibodies against it. Chicken embryos at different stages of gastrulation were processed for whole-mount immunohistochemical localization of the protein using anti-CdxA antibodies. Once the pattern of expression in the whole embryo was determined, the same embryos were sectioned to determine the identity of the cells expressing the CdxA protein. Detailed analysis of the CdxA protein in embryos, from the onset of primitive streak formation to the beginning of the tail bud stage (stages 2 to 10), has shown different patterns of expression during primitive streak elongation and regression. The CdxA protein is initially detected at the posterior marginal zone and the expression moves rostrally into the primitive streak during mid-streak stages. As the primitive streak elongates, the CdxA stripe of expression moves anteriorly. By definitive streak stages, the CdxA stripe of expression delineates a position along the anterior-posterior axis in the primitive streak. CdxA, like its Drosophila homologue cad, is expressed during gastrulation in a stripe localized to the posterior region of the embryo. These observations suggest that CdxA as a homebox gene may be part of a regulatory network coupled to axial determination during gastrulation in the early chick embryo.

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