scholarly journals The Xenopus homologue of Otx2 is a maternal homeobox gene that demarcates and specifies anterior body regions

Development ◽  
1995 ◽  
Vol 121 (3) ◽  
pp. 707-720 ◽  
Author(s):  
M. Pannese ◽  
C. Polo ◽  
M. Andreazzoli ◽  
R. Vignali ◽  
B. Kablar ◽  
...  
Keyword(s):  
Marginal Zone ◽  
Homeobox Gene ◽  
Cell Stage ◽  
Rnase Protection ◽  
Glutamic Acid Residue ◽  
Body Regions ◽  
Early Embryos ◽  
Anterior Body ◽  
Low Levels

In this paper we study Xotx2, a Xenopus homeobox gene related to orthodenticle, a gene expressed in the developing head of Drosophila. The murine cognate, Otx2, is first expressed in the entire epiblast of prestreak embryos and later in very anterior regions of late-gastrulae, including the neuroectoderm of presumptive fore- and mid-brain. In Xenopus, RNase protection experiments reveal that Xotx2 is expressed at low levels throughout early development from unfertilized egg to late blastula, when its expression level significantly increases. Whole-mount in situ hybridization shows a localized expression in the dorsal region of the marginal zone at stage 9.5. At stage 10.25 Xotx2 is expressed in dorsal bottle cells and in cells of the dorsal deep zone fated to give rise to prechordal mesendoderm, suggesting a role in the specification of very anterior structures. In stage 10.5 gastrulae, Xotx2 transcripts start to be detectable also in presumptive anterior neuroectoderm, where they persist in subsequent stages. Various treatments of early embryos cause a general reorganization of Xotx2 expression. In particular, retinoic acid treatment essentially abolishes Xotx2 expression in neuroectoderm. Microinjection of Xotx2 mRNA in 1-, 2- and 4-cell stage embryos causes the appearance of secondary cement glands and partial secondary axes in embryos with reduced trunk and tail structures. The presence of the Xotx2 homeodomain is required to produce these effects. In particular, this homeodomain contains a specific lysine residue at position 9 of the recognition helix. Microinjected transcripts of Xotx2 constructs containing a homeodomain where this lysine is substituted by a glutamine or a glutamic acid residue fail to cause these effects.

Integrin alpha subunit mRNAs are differentially expressed in early Xenopus embryos

Development ◽  
1993 ◽  
Vol 117 (4) ◽  
pp. 1239-1249 ◽  
Author(s):  
C.A. Whittaker ◽  
D.W. DeSimone
Keyword(s):  
In Situ Hybridization ◽  
Rnase Protection Assay ◽  
Early Embryo ◽  
Mrna Levels ◽  
Rnase Protection ◽  
Dorsal Midline ◽  
Transmembrane Receptors ◽  
Early Embryos ◽  
Whole Mount

Adhesion of cells to extracellular matrix proteins is mediated, in large part, by transmembrane receptors of the integrin family. The identification of specific integrins expressed in early embryos is an important first step to understanding the roles of these receptors in developmental processes. We have used polymerase chain reaction methods and degenerate oligodeoxynucleotide primers to identify and clone Xenopus integrin alpha subunits from neurula-stage (stage 17) cDNA. Partial cDNAs encoding integrin subunits alpha 2, alpha 3, alpha 4, alpha 5, alpha 6 and an alpha IIb-related subunit were cloned and used to investigate integrin mRNA expression in early embryos by RNase protection assay and whole-mount in situ hybridization methods. Considerable integrin diversity is apparent early in development with integrins alpha 2, alpha 3, alpha 4, alpha 5 and alpha 6 each expressed by the end of gastrulation. Both alpha 3 and alpha 5 are expressed as maternal mRNAs. Zygotic expression of alpha 2, alpha 3, alpha 4 and alpha 6 transcripts begins during gastrulation. Integrin alpha 5 is expressed at relatively high levels during cleavage, blastula and gastrula stages suggesting that it may represent the major integrin expressed in the early embryo. We demonstrated previously that integrin beta 1 protein synthesis remains constant following induction of stage 8 animal cap cells with activin (Smith, J. C., Symes, K., Hynes, R. O. and DeSimone, D. W. (1990) Development 108, 289–298.). Here we report that integrin alpha 3, alpha 4 and alpha 6 mRNA levels increase following induction with 10 U/ml activin-A whereas alpha 5, beta 1 and beta 3 mRNA levels remain unchanged. Whole-mount in situ hybridization reveals that alpha 3 mRNAs are expressed by cells of the involuting mesoderm in the dorsal lip region of early gastrulae. As gastrulation proceeds, alpha 3 expression is localized to a stripe of presumptive notochordal cells along the dorsal midline. In neurulae, alpha 3 mRNA is highly expressed in the notochord but becomes progressively more restricted to the caudalmost portion of this tissue as development proceeds from tailbud to tadpole stages. In addition, alpha 3 is expressed in the forebrain region of later stage embryos. These data suggest that integrin-mediated adhesion may be involved in the process of mesoderm involution at gastrulation and the organization of tissues during embryogenesis.

Regional specification within the mesoderm of early embryos of Xenopus laevis

Development ◽  
1987 ◽  
Vol 100 (2) ◽  
pp. 279-295 ◽  
Author(s):  
L. Dale ◽  
J.M. Slack
Keyword(s):  
Xenopus Laevis ◽  
Marginal Zone ◽  
Mesoderm Induction ◽  
Intermediate Type ◽  
Cell Stage ◽  
Early Embryos ◽  
Significant Difference ◽  
Cell Embryo ◽  
Single Blastomeres

We have further analysed the roles of mesoderm induction and dorsalization in the formation of a regionally specified mesoderm in early embryos of Xenopus laevis. First, we have examined the regional specificity of mesoderm induction by isolating single blastomeres from the vegetalmost tier of the 32-cell embryo and combining each with a lineage-labelled (FDA) animal blastomere tier. Whereas dorsovegetal (D1) blastomeres induce ‘dorsal-type’ mesoderm (notochord and muscle), laterovegetal and ventrovegetal blastomeres (D2–4) induce either ‘intermediate-type’ (muscle, mesothelium, mesenchyme and blood) or ‘ventral-type’ (mesothelium, mesenchyme and blood) mesoderm. No significant difference in inductive specificity between blastomeres D2, 3 and 4 could be detected. We also show that laterovegetal and ventrovegetal blastomeres from early cleavage stages can have a dorsal inductive potency partially activated by operative procedures, resulting in the induction of intermediate-type mesoderm. Second, we have determined the state of specification of ventral blastomeres by isolating and culturing them in vitro between the 4-cell stage and the early gastrula stage. The majority of isolates from the ventral half of the embryo gave extreme ventral types of differentiation at all stages tested. Although a minority of cases formed intermediate-type and dorsal-type mesoderms we believe these to result from either errors in our assessment of the prospective DV axis or from an enhancement, provoked by microsurgery, of some dorsal inductive specificity. The results of induction and isolation experiments suggest that only two states of specification exist in the mesoderm of the pregastrula embryo, a dorsal type and a ventral type. Finally we have made a comprehensive series of combinations between different regions of the marginal zone using FDA to distinguish the components. We show that, in combination with dorsal-type mesoderm, ventral-type mesoderm becomes dorsalized to the level of intermediate-type mesoderm. Dorsal-type mesoderm is not ventralized in these combinations. Dorsalizing activity is confined to a restricted sector of the dorsal marginal zone, it is wider than the prospective notochord and seems to be graded from a high point at the dorsal midline. The results of these experiments strengthen the case for the three-signal model proposed previously, i.e. dorsal and ventral mesoderm inductions followed by dorsalization, as the simplest explanation capable of accounting for regional specification within the mesoderm of early Xenopus embryos.

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.

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.

scholarly journals Sea urchin maternal and embryonic U1 RNAs are spatially segregated in early embryos.

1987 ◽  
Vol 104 (5) ◽  
pp. 1133-1142 ◽  
Author(s):  
M A Nash ◽  
S E Kozak ◽  
L M Angerer ◽  
R C Angerer ◽  
H Schatten ◽  
...  
Keyword(s):  
Sea Urchin ◽  
Oocyte Maturation ◽  
Immunofluorescence Microscopy ◽  
Cell Fractionation ◽  
Early Cleavage ◽  
Cell Stage ◽  
Early Embryos ◽  
Nuclear Species ◽  
Germinal Vesicles

We have used in situ hybridization and cell fractionation methods to follow the distribution of U1 RNA and immunofluorescence microscopy to follow the distribution of snRNP proteins in oocytes, eggs, and embryos of several sea urchin species. U1 RNA and U1-specific snRNP antigens are concentrated in germinal vesicles of oocytes. Both appear to relocate after oocyte maturation because they are found primarily, if not exclusively, in the cytoplasm of mature unfertilized eggs. This cytoplasmic residence is maintained during early cleavage and U1 RNA is first detectable in nuclei of micromeres at the 16-cell stage. Between morula and gastrula stages the steady-state concentrations of both RNA and antigens gradually increase in nuclei and decrease in cytoplasm. Surprisingly, analysis of the distribution of newly synthesized U1 RNA shows that it does not equilibrate with the maternal pool. Instead new transcripts are confined to nuclei, while cytoplasmic U1 RNAs are of maternal origin. This lack of equilibration and the conversion of maternal U1 RNAs from nuclear species in oocytes to cytoplasmic in embryos suggests that these RNPs (or RNAs) are structurally altered when released to the cytoplasm at oocyte maturation.

Chromatin modifications during oogenesis in the mouse: removal of somatic subtypes of histone H1 from oocyte chromatin occurs post-natally through a post-transcriptional mechanism

1997 ◽  
Vol 110 (4) ◽  
pp. 477-487 ◽  
Author(s):  
H.J. Clarke ◽  
M. Bustin ◽  
C. Oblin
Keyword(s):  
Cell Types ◽  
Histone H1 ◽  
Early Embryo ◽  
Rt Pcr ◽  
Cell Stage ◽  
Embryonic Genome ◽  
Early Embryos ◽  
Before And After ◽  
Subtype H1

We examined the distribution of the somatic subtypes of histone H1 and the variant subtype, H1(0), and their encoding mRNAs during oogenesis and early embryogenesis in the mouse. As detected using immunocytochemistry, somatic H1 was present in the nuclei of oocytes of 18-day embryos. Following birth, however, somatic H1 became less abundant in both growing and non-growing oocytes, beginning as early as 4 days of age in the growing oocytes, and was scarcely detectable by 19 days. Together with previous results, this defines a period of time when somatic H1 is depleted in oocytes, namely, from shortly after birth when the oocytes are at prophase I until the 4-cell stage following fertilization. At the stages when somatic H1 was undetectable, oocyte nuclei could be stained using an antibody raised against histone H1(0), which suggests that this may be a major linker histone in these cells. In contrast to the post-natal loss of somatic H1 protein, mRNAs encoding four (H1a, H1b, H1d, H1e) of the five somatic subtypes were present, as detected using RT-PCR in growing oocytes of 9-day pups, and all five subtypes including H1c were present in fully grown oocytes of adults. All five subtypes were also present in embryos, both before and after activation of the embryonic genome. mRNA encoding H1(0) was also detected in oocytes and early embryos. Whole-mount in situ hybridization using cloned H1c and H1e cDNAs revealed that the mRNAs were present in the cytoplasm of oocytes and 1-cell embryos, in contrast to the sea urchin early embryo where they are sequestered in the cell nucleus. We suggest that, as in many somatic cell types, the chromatin of mouse oocytes becomes depleted of somatic H1 and relatively enriched in histone H1(0) postnatally, and that somatic H1 is reassembled onto chromatin in cleavage-stage embryos. The post-natal loss of somatic H1 appears to be regulated post-transcriptionally by a mechanism not involving nuclear localization.

Isolation and expression of a new mouse homeobox gene

Development ◽  
1988 ◽  
Vol 102 (2) ◽  
pp. 397-407 ◽  
Author(s):  
P.T. Sharpe ◽  
J.R. Miller ◽  
E.P. Evans ◽  
M.D. Burtenshaw ◽  
S.J. Gaunt
Keyword(s):  
In Situ Hybridization ◽  
Dna Sequence ◽  
Southern Blotting ◽  
Homeobox Gene ◽  
Single Copy ◽  
Northern Blotting ◽  
Metaphase Chromosomes ◽  
Rnase Protection ◽  
Sequence Encoding

A homeobox-containing clone has been isolated from an adult mouse kidney cDNA library and shown by DNA sequence analysis to be a new isolate, Hox-6.1. A genomic clone containing Hox-6.1 has been isolated and found to contain another putative homeobox sequence (Hox-6.2), within 7 kb of Hox-6.1. In situ hybridization of mouse metaphase chromosomes shows this Hox-6 locus to be located on chromosome 14 (14E2). Hox-6.1 has been studied in detail and the predicted protein sequence of the homeobox is 100% homologous to the Xenopus Xeb1 (formally AC1) homeobox and the human c8 homeobox (Carrasco et al. 1984; Boncinelli et al. 1985; Simeone et al. 1987). Southern blotting shows that the DNA sequence encoding Hox-6.1 is single copy. Expression of Hox-6.1 has been studied in adult tissues and embryos by RNase protection assays, Northern blotting analysis and in situ hybridization. RNase protection assays show that Hox-6.1 transcripts are present in embryos between days 9 1/2 and 13 1/2 of gestation and in extraembryonic tissues at day 9 1/2. Adult expression is detectable in kidney and testis but not in liver, spleen and brain. One major transcript is detectable on Northern blots of kidney and day-13 1/2 embryo RNA. In kidney, this transcript is 2.7 kb whereas in embryos the major transcript is smaller at 1.9 kb, a much fainter band being visible at 2.7 kb. Localized expression of Hox-6.1 is observed in the spinal cord and prevertebral column of day-12 1/2 embryos, and in the posterior mesoderm and ectoderm of day-8 1/4 embryos. An anterior boundary of expression is located just behind the hindbrain whereas the boundary in the mesoderm is located at the level of the 7th prevertebra.

scholarly journals Retinoic acid signaling is critical during the totipotency window in early mammalian development

2021 ◽  
Author(s):  
Ane Iturbide ◽  
Mayra L. Ruiz Tejeda Segura ◽  
Camille Noll ◽  
Kenji Schorpp ◽  
Ina Rothenaigner ◽  
...  
Keyword(s):  
Retinoic Acid ◽  
Regulatory Networks ◽  
Es Cells ◽  
Embryonic Stem ◽  
Mammalian Development ◽  
Cell Stage ◽  
Cell Potential ◽  
Cellular Models ◽  
Early Embryos ◽  
Genome Activation

AbstractTotipotent cells hold enormous potential for regenerative medicine. Thus, the development of cellular models recapitulating totipotent-like features is of paramount importance. Cells resembling the totipotent cells of early embryos arise spontaneously in mouse embryonic stem (ES) cell cultures. Such ‘2-cell-like-cells’ (2CLCs) recapitulate 2-cell-stage features and display expanded cell potential. Here, we used 2CLCs to perform a small-molecule screen to identify new pathways regulating the 2-cell-stage program. We identified retinoids as robust inducers of 2CLCs and the retinoic acid (RA)-signaling pathway as a key component of the regulatory circuitry of totipotent cells in embryos. Using single-cell RNA-seq, we reveal the transcriptional dynamics of 2CLC reprogramming and show that ES cells undergo distinct cellular trajectories in response to RA. Importantly, endogenous RA activity in early embryos is essential for zygotic genome activation and developmental progression. Overall, our data shed light on the gene regulatory networks controlling cellular plasticity and the totipotency program.

scholarly journals Extended expression of MaKN1 contributes to the leaf morphology in aquatic forms of Myriophyllum aquaticum

Botany ◽  
2015 ◽  
Vol 93 (9) ◽  
pp. 611-621
Author(s):  
M.D. Shafiullah ◽  
Christian R. Lacroix
Keyword(s):  
Apical Meristem ◽  
Leaf Morphology ◽  
Expression Patterns ◽  
Homeobox Gene ◽  
Leaf Primordia ◽  
Leaf Primordium ◽  
Myriophyllum Aquaticum ◽  
Knox Gene ◽  
Leaf Morphogenesis

Myriophyllum aquaticum (Vell.) Verdc. is heterophyllous in nature with highly dissected simple leaves consisting of several lobes. KNOX (KNOTTED1-LIKE HOMEOBOX) genes are believed to have played an important role in the evolution of leaf diversity. Up-regulation of KNOX during leaf primordium initiation can lead to leaf dissection in plants with simple leaves and, if overexpressed, can produce ectopic meristems on leaves. A previous study on KNOX gene expression in the aerial form of this species showed that this gene is expressed in the shoot apical meristem (SAM), as well as in leaf primordia P0 to P8. Based on these results, it was hypothesized that the prolonged expression of the MaKN1 (Myriophyllum aquaticum Knotted1-like homeobox) gene beyond P8, might play an important role in the generation of more lobes, longer lobes, and hydathode formation in the aquatic leaves of M. aquaticum. The technique of in situ hybridization was carried out using a previously sequenced 300 bp fragment of MaKN1 to determine the expression patterns of this gene in the shoot of aquatic forms of the plant. Expression patterns of MaKN1 revealed that the SAM and leaf primordia of aquatic forms of M. aquaticum at levels P0 (youngest) to P4 were distributed throughout these structures. The level of expression of this MaKN1 gene progressively became more localized to lobes in older leaf primordia (levels P5 to P12). Previous studies of aerial forms of this plant showed MaKN1 expression until P8. Our results with aquatic forms show that the highly dissected leaf morphology in aquatic forms was the result of the prolonged expression of MaKN1 beyond P8. This resulted in the formation of elongated and slightly more numerous lobes, and hydathodes in aquatic forms. These findings support the view that KNOX genes are important developmental regulators of leaf morphogenesis and have played an important role in the evolution of leaf forms in the plant kingdom.

Expression of a novel FGF in the Xenopus embryo. A new candidate inducing factor for mesoderm formation and anteroposterior specification

Development ◽  
1992 ◽  
Vol 114 (3) ◽  
pp. 711-720 ◽  
Author(s):  
H.V. Isaacs ◽  
D. Tannahill ◽  
J.M. Slack
Keyword(s):  
Specific Activity ◽  
Biological Properties ◽  
The Body ◽  
Mesoderm Induction ◽  
Gastrula Stage ◽  
Blastula Stage ◽  
Mesoderm Formation ◽  
Low Levels

We have cloned and sequenced a new member of the fibroblast growth factor family from Xenopus laevis embryo cDNA. It is most closely related to both mammalian kFGF (FGF-4) and FGF-6 but as it is not clear whether it is a true homologue of either of these genes we provisionally refer to it as XeFGF (Xenopus embryonic FGF). Two sequences were obtained, differing by 11% in derived amino acid sequence, which probably represent pseudotetraploid variants. Both the sequence and the behaviour of in vitro translated protein indicates that, unlike bFGF (FGF-2), XeFGF is a secreted molecule. Recombinant XeFGF protein has mesoderm-inducing activity with a specific activity similar to bFGF. XeFGF mRNA is expressed maternally and zygotically with a peak during the gastrula stage. Both probe protection and in situ hybridization showed that the zygotic expression is concentrated in the posterior of the body axis and later in the tailbud. Later domains of expression were found near the midbrain/hindbrain boundary and at low levels in the myotomes. Because of its biological properties and expression pattern, XeFGF is a good candidate for an inducing factor with possible roles both in mesoderm induction at the blastula stage and in the formation of the anteroposterior axis at the gastrula stage.

Sign in / Sign up

Export Citation Format

Share Document