her1, a zebrafish pair-rule like gene, acts downstream of notch signalling to control somite development

Development ◽  
1999 ◽  
Vol 126 (13) ◽  
pp. 3005-3014 ◽  
Author(s):  
C. Takke ◽  
J.A. Campos-Ortega
Keyword(s):  
Active Form ◽  
Notch Signalling ◽  
Paraxial Mesoderm ◽  
Presomitic Mesoderm ◽  
Essentially Normal ◽  
Early Embryos ◽  
Somite Formation ◽  
Genes Encoding ◽  
Ectopic Activation ◽  
Pair Rule

During vertebrate embryonic development, the paraxial mesoderm becomes subdivided into metameric units known as somites. In the zebrafish embryo, genes encoding homologues of the proteins of the Drosophila Notch signalling pathway are expressed in the presomitic mesoderm and expression is maintained in a segmental pattern during somitogenesis. This expression pattern suggests a role for these genes during somite development. We misexpressed various zebrafish genes of this group by injecting mRNA into early embryos. RNA encoding a constitutively active form of notch1a (notch1a-intra) and a truncated variant of deltaD [deltaD(Pst)], as well as transcripts of deltaC and deltaD, the hairy-E(spl) homologues her1 and her4, and groucho2 were tested for their effects on somite formation, myogenesis and on the pattern of transcription of putative downstream genes. In embryos injected with any of these RNAs, with the exception of groucho2 RNA, the paraxial mesoderm differentiated normally into somitic tissue, but failed to segment correctly. Activation of notch results in ectopic activation of her1 and her4. This misregulation of the expression of her genes might be causally related to the observed mesodermal defects, as her1 and her4 mRNA injections led to effects similar to those seen with notch1a-intra. deltaC and deltaD seem to function after subdivision of the presomitic mesoderm, since the her gene transcription pattern in the presomitic mesoderm remains essentially normal after misexpression of delta genes. Whereas notch signalling alone apparently does not affect myogenesis, zebrafish groucho2 is involved in differentiation of mesodermal derivatives.

The Notch ligand, X-Delta-2, mediates segmentation of the paraxial mesoderm in Xenopus embryos

Development ◽  
1997 ◽  
Vol 124 (6) ◽  
pp. 1169-1178 ◽  
Author(s):  
W.C. Jen ◽  
D. Wettstein ◽  
D. Turner ◽  
A. Chitnis ◽  
C. Kintner
Keyword(s):  
Paraxial Mesoderm ◽  
Bhlh Gene ◽  
Presomitic Mesoderm ◽  
Notch 1 ◽  
Notch Ligand ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
Vertebrate Embryo ◽  
Somite Formation ◽  
Segmental Expression

Segmentation of the vertebrate embryo begins when the paraxial mesoderm is subdivided into somites, through a process that remains poorly understood. To study this process, we have characterized X-Delta-2, which encodes the second Xenopus homolog of Drosophila Delta. Strikingly, X-Delta-2 is expressed within the presomitic mesoderm in a set of stripes that corresponds to prospective somitic boundaries, suggesting that Notch signaling within this region establishes a segmental prepattern prior to somitogenesis. To test this idea, we introduced antimorphic forms of X-Delta-2 and Xenopus Suppressor of Hairless (X-Su(H)) into embryos, and assayed the effects of these antimorphs on somite formation. In embryos expressing these antimorphs, the paraxial mesoderm differentiated normally into somitic tissue, but failed to segment properly. Both antimorphs also disrupted the segmental expression of X-Delta-2 and Hairy2A, a basic helix-loop-helix (bHLH) gene, within the presomitic mesoderm. These observations suggest that X-Delta-2, via X-Notch-1, plays a role in segmentation, by mediating cell-cell interactions that underlie the formation of a segmental prepattern prior to somitogenesis.

Thylacine 1 is expressed segmentally within the paraxial mesoderm of the Xenopus embryo and interacts with the Notch pathway

Development ◽  
1998 ◽  
Vol 125 (11) ◽  
pp. 2041-2051 ◽  
Author(s):  
D.B. Sparrow ◽  
W.C. Jen ◽  
S. Kotecha ◽  
N. Towers ◽  
C. Kintner ◽  
...  
Keyword(s):  
Expression Patterns ◽  
Ectopic Expression ◽  
Notch Pathway ◽  
Notch Signalling ◽  
Xenopus Embryo ◽  
Paraxial Mesoderm ◽  
Marker Genes ◽  
Transcription Activator ◽  
Presomitic Mesoderm ◽  
Helix Loop Helix

The presomitic mesoderm of vertebrates undergoes a process of segmentation in which cell-cell interactions mediated by the Notch family of receptors and their associated ligands are involved. The vertebrate homologues of Drosophila Δ are expressed in a dynamic, segmental pattern within the presomitic mesoderm, and alterations in the function of these genes leads to a perturbed pattern of somite segmentation. In this study we have characterised Thylacine 1 which encodes a basic helix-loop-helix class transcription activator. Expression of Thylacine is restricted to the presomitic mesoderm, localising to the anterior half of several somitomeres in register with domains of X-Delta-2 expression. Ectopic expression of Thylacine in embryos causes segmentation defects similar to those seen in embryos in which Notch signalling is altered, and these embryos also show severe disruption in the expression patterns of the marker genes X-Delta-2 and X-ESR5 within the presomitic mesoderm. Finally, the expression of Thylacine is altered in embryos when Notch signalling is perturbed. These observations suggest strongly that Thylacine 1 has a role in the segmentation pathway of the Xenopus embryo, by interacting with the Notch signalling pathway.

Expression domains of a zebrafish homologue of the Drosophila pair-rule gene hairy correspond to primordia of alternating somites

Development ◽  
1996 ◽  
Vol 122 (7) ◽  
pp. 2071-2078 ◽  
Author(s):  
M. Muller ◽  
E. Weizsacker ◽  
J.A. Campos-Ortega
Keyword(s):  
Expression Pattern ◽  
Bhlh Protein ◽  
Presomitic Mesoderm ◽  
Tail Bud ◽  
Expression Domain ◽  
Somite Formation ◽  
Pair Rule Gene ◽  
Pair Rule ◽  
Time Point

her1 is a zebrafish cDNA encoding a bHLH protein with all features characteristic of members of the Drosophila HAIRY-E(SPL) family. During late gastrulation stages, her1 is expressed in the epibolic margin and in two distinct transverse bands of hypoblastic cells behind the epibolic front. After completion of epiboly, this pattern persists essentially unchanged through postgastrulation stages; the marginal domain is incorporated in the tail bud and, depending on the time point, either two or three paired bands of expressing cells are present within the paraxial presomitic mesoderm separated by regions devoid of transcripts. Labelling of cells within the her1 expression domains with fluorescein-dextran shows that the cells in the epibolic margin and the tail bud are not allocated to particular somites. However, allocation of cells to somites occurs between the marginal expression domain and the first expression band, anterior to it. Moreover, the her1 bands, and the intervening non-expressing zones, each represents the primordium of a somite. This expression pattern is highly reminiscent of that of Drosophila pair-rule genes. A possible participation of her1 in functions related to somite formation is discussed.

The role of presenilin 1 during somite segmentation

Development ◽  
2001 ◽  
Vol 128 (8) ◽  
pp. 1391-1402 ◽  
Author(s):  
K.i. Koizumi ◽  
M. Nakajima ◽  
S. Yuasa ◽  
Y. Saga ◽  
T. Sakai ◽  
...  
Keyword(s):  
Notch Pathway ◽  
Notch Signalling ◽  
Signalling Pathway ◽  
Paraxial Mesoderm ◽  
Presenilin 1 ◽  
Wild Type ◽  
Presomitic Mesoderm ◽  
Notch Signalling Pathway ◽  
Deficient Mice

The Notch signalling pathway plays essential roles during the specification of the rostral and caudal somite halves and subsequent segmentation of the paraxial mesoderm. We have re-investigated the role of presenilin 1 (Ps1; encoded by Psen1) during segmentation using newly generated alleles of the Psen1 mutation. In Psen1-deficient mice, proteolytic activation of Notch1 was significantly affected and the expression of several genes involved in the Notch signalling pathway was altered, including Δ-like3, Hes5, lunatic fringe (Lfng) and Mesp2. Thus, Ps1-dependent activation of the Notch pathway is essential for caudal half somite development. We observed defects in Notch signalling in both the caudal and rostral region of the presomitic mesoderm. In the caudal presomitic mesoderm, Ps1 was involved in maintaining the amplitude of cyclic activation of the Notch pathway, as represented by significant reduction of Lfng expression in Psen1-deficient mice. In the rostral presomitic mesoderm, rapid downregulation of the Mesp2 expression in the presumptive caudal half somite depends on Ps1 and is a prerequisite for caudal somite half specification. Chimaera analysis between Psen1-deficient and wild-type cells revealed that condensation of the wild-type cells in the caudal half somite was concordant with the formation of segment boundaries, while mutant and wild-type cells intermingled in the presomitic mesoderm. This implies that periodic activation of the Notch pathway in the presomitic mesoderm is still latent to segregate the presumptive rostral and caudal somite. A transient episode of Mesp2 expression might be needed for Notch activation by Ps1 to confer rostral or caudal properties. In summary, we propose that Ps1 is involved in the functional manifestation of the segmentation clock in the presomitic mesoderm.

Anteroposterior patterning is required within segments for somite boundary formation in developing zebrafish

Development ◽  
2000 ◽  
Vol 127 (8) ◽  
pp. 1703-1713 ◽  
Author(s):  
L. Durbin ◽  
P. Sordino ◽  
A. Barrios ◽  
M. Gering ◽  
C. Thisse ◽  
...  
Keyword(s):  
Anterior Segment ◽  
Ectopic Expression ◽  
Paraxial Mesoderm ◽  
Study Analysis ◽  
Presomitic Mesoderm ◽  
Anteroposterior Patterning ◽  
Boundary Formation ◽  
Hox Gene ◽  
Somite Formation ◽  
Adjacent Segments

Somite formation involves the establishment of a segmental prepattern in the presomitic mesoderm, anteroposterior patterning of each segmental primordium and formation of boundaries between adjacent segments. How these events are co-ordinated remains uncertain. In this study, analysis of expression of zebrafish mesp-a reveals that each segment acquires anteroposterior regionalisation when located in the anterior presomitic mesoderm. Thus anteroposterior patterning is occurring after the establishment of a segmental prepattern in the paraxial mesoderm and prior to somite boundary formation. Zebrafish fss(−), bea(−), des(−) and aei(−) embryos all fail to form somites, yet we demonstrate that a segmental prepattern is established in the presomitic mesoderm of all these mutants and hox gene expression shows that overall anteroposterior patterning of the mesoderm is also normal. However, analysis of various molecular markers reveals that anteroposterior regionalisation within each segment is disturbed in the mutants. In fss(−), there is a loss of anterior segment markers, such that all segments appear posteriorized, whereas in bea(−), des(−) and aei(−), anterior and posterior markers are expressed throughout each segment. Since somite formation is disrupted in these mutants, correct anteroposterior patterning within segments may be a prerequisite for somite boundary formation. In support of this hypothesis, we show that it is possible to rescue boundary formation in fss(−) through the ectopic expression of EphA4, an anterior segment marker, in the paraxial mesoderm. These observations indicate that a key consequence of the anteroposterior regionalisation of segments may be the induction of Eph and ephrin expression at segment interfaces and that Eph/ephrin signalling subsequently contributes to the formation of somite boundaries.

The allocation of cells in the presomitic mesoderm during somite segmentation in the mouse embryo

Development ◽  
1988 ◽  
Vol 103 (2) ◽  
pp. 379-390 ◽  
Author(s):  
P.P. Tam
Keyword(s):  
Mouse Embryo ◽  
Colloidal Gold ◽  
Wheat Germ ◽  
Mouse Embryos ◽  
Middle Region ◽  
Presomitic Mesoderm ◽  
Posterior Displacement ◽  
Somite Formation ◽  
Gold Conjugate

Orthotopic grafts of wheat germ agglutinin-colloidal gold conjugate (WGA-gold) labelled cells were used to demonstrate differences in the segmental fate of cells in the presomitic mesoderm of the early-somite-stage mouse embryos developing in vitro. Labelled cells in the anterior region of the presomitic mesoderm colonized the first three somites formed after grafting, while those grafted to the middle region of this tissue were found mostly in the 4th-7th newly formed somites. Labelled cells grafted to the posterior region were incorporated into somites whose somitomeres were not yet present in the presomitic mesoderm at the time of grafting. There was therefore an apparent posterior displacement of the grafted cells in the presomitic mesoderm. Colonization of somites by WGA-gold labelled cells was usually limited to two to three consecutive somites in the chimaera. The distribution of cells derived from a single graft to two somites was most likely due to the segregation of the labelled population when cells were allocated to adjacent meristic units during somite formation. Further spreading of the labelled cells to several somites in some cases was probably the result of a more extensive mixing of mesodermal cells among the somitomeres prior to somite segmentation.

sry h-1, a new Drosophila melanogaster multifingered protein gene showing maternal and zygotic expression

1988 ◽  
Vol 8 (10) ◽  
pp. 4459-4468
Author(s):  
A Vincent ◽  
J Kejzlarovà-Lepesant ◽  
L Segalat ◽  
C Yanicostas ◽  
J A Lepesant
Keyword(s):  
Dna Sequences ◽  
Subsequent Development ◽  
Initiation Site ◽  
Protein Product ◽  
Protein Coding ◽  
Finger Protein ◽  
Early Embryos ◽  
The Family ◽  
Genes Encoding ◽  
Internal Initiation

Low-stringency hybridization of the Drosophila serendipity (sry) finger-coding sequences revealed copies of homologous DNA sequences in the genomes of members of the family Drosophilidae and higher vertebrates. sry h-1, a new Drosophila finger protein-coding gene isolated on the basis of this homology, encodes a 3.2-kilobase (kb) mRNA accumulating in eggs and abundant in early embryos. The predicted sry h-1 protein product, starting at an internal initiation site of translation, is a 868-amino-acid basic polypeptide containing eight TFIIIA-like fingers encoded by three separate exons. Links separating individual fingers in the sry h-1 protein are variable in length and sequence, in contrast with the invariant H/C link found in most multi-fingered proteins. The similarity of the developmental pattern of transcription of sry h-1 with that of several other Drosophila finger protein genes suggests the existence of a complex set of such genes encoding an information which is, at least partly, maternally provided to the embryo and required for activation of gene transcription in early embryos or maintenance of gene activity during subsequent development.

259. Pluripotency genes in a marsupial, the tammar wallaby

2008 ◽  
Vol 20 (9) ◽  
pp. 59
Author(s):  
S. Frankenberg ◽  
A. J. Pask ◽  
M. B. Renfree
Keyword(s):  
Expression Profiles ◽  
Genomic Analysis ◽  
Tammar Wallaby ◽  
Early Embryo ◽  
Lineage Specification ◽  
Signalling Molecules ◽  
Early Embryos ◽  
Genes Encoding ◽  
Morphological Differences ◽  
Pluripotency Genes

Markers of pluripotency and early differentiation in the early embryo have been extensively characterised in eutherian species, most notably the mouse. By comparison, mechanisms controlling pluripotency and early lineage specification have received surprisingly little attention in marsupials, which represent the second major infraclass of mammals. Early marsupial embryogenesis exhibits overt morphological differences to that of eutherians, however the underlying developmental mechanisms may be conserved. In order to characterise early marsupial development at the molecular level, we have identified, cloned and analysed expression of orthologueues of several eutherian genes encoding transcription factors and signalling molecules involved in regulating pluripotency and early lineage specification. These genes include POU5F1 (OCT4), SOX2, NANOG, FGF4, FGFR2, CDX2, EOMES, TEAD4, GATA6 and KITL and are all expressed at early stages of development in the tammar. In addition, we have identified and cloned tammar POU2, which has orthologueues in non-mammalian vertebrates. POU2 is a paralogue of POU5F1 – a master regulator of pluripotency in eutherians. Genomic analysis indicates that POU5F1 arose via gene duplication of POU2 before the monotreme-therian divergence. Both genes have persisted in marsupials and monotremes, while POU2 was lost early during eutherian evolution. Similar expression profiles of tammar POU5F1 and POU2 in early embryos and gonadal tissues suggest possible overlapping roles in the maintenance of pluripotency.

scholarly journals NDT80 and the Meiotic Recombination Checkpoint Regulate Expression of Middle Sporulation-Specific Genes in Saccharomyces cerevisiae

1998 ◽  
Vol 18 (10) ◽  
pp. 5750-5761 ◽  
Author(s):  
Shelley R. Hepworth ◽  
Helena Friesen ◽  
Jacqueline Segall
Keyword(s):  
Gene Expression ◽  
Saccharomyces Cerevisiae ◽  
Meiotic Recombination ◽  
Active Form ◽  
Specific Gene ◽  
Subsequent Generation ◽  
Genes Encoding ◽  
Recombination Checkpoint ◽  
Sporulation Genes ◽  
Meiosis I

ABSTRACT Distinct classes of sporulation-specific genes are sequentially expressed during the process of spore formation in Saccharomyces cerevisiae. The transition from expression of early meiotic genes to expression of middle sporulation-specific genes occurs at about the time that cells exit from pachytene and form the meiosis I spindle. To identify genes encoding potential regulators of middle sporulation-specific gene expression, we screened for mutants that expressed early meiotic genes but failed to express middle sporulation-specific genes. We identified mutant alleles ofRPD3, SIN3, and NDT80 in this screen. Rpd3p, a histone deacetylase, and Sin3p are global modulators of gene expression. Ndt80p promotes entry into the meiotic divisions. We found that entry into the meiotic divisions was not required for activation of middle sporulation genes; these genes were efficiently expressed in a clb1 clb3 clb4 strain, which fails to enter the meiotic divisions due to reduced Clb-dependent activation of Cdc28p kinase. In contrast, middle sporulation genes were not expressed in a dmc1 strain, which fails to enter the meiotic divisions because a defect in meiotic recombination leads to aRAD17-dependent checkpoint arrest. Expression of middle sporulation genes, as well as entry into the meiotic divisions, was restored to a dmc1 strain by mutation of RAD17. Our studies also revealed that NDT80 was a temporally distinct, pre-middle sporulation gene and that its expression was reduced, but not abolished, on mutation of DMC1,RPD3, SIN3, or NDT80 itself. In summary, our data indicate that Ndt80p is required for expression of middle sporulation genes and that the activity of Ndt80p is controlled by the meiotic recombination checkpoint. Thus, middle genes are expressed only on completion of meiotic recombination and subsequent generation of an active form of Ndt80p.

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