Misexpression of Cwnt8C in the mouse induces an ectopic embryonic axis and causes a truncation of the anterior neuroectoderm

Development ◽  
1997 ◽  
Vol 124 (15) ◽  
pp. 2997-3005 ◽  
Author(s):  
H. Popperl ◽  
C. Schmidt ◽  
V. Wilson ◽  
C.R. Hume ◽  
J. Dodd ◽  
...  
Keyword(s):  
Mouse Embryo ◽  
Primitive Streak ◽  
Primitive Endoderm ◽  
Morphological Examination ◽  
Expression Domain ◽  
Anterior Aspect ◽  
Beta Actin ◽  
Early Expression ◽  
Actin Promoter ◽  
Transgenic Embryos

Transgenic embryos expressing Cwnt8C under the control of the human beta-actin promoter exhibit duplicated axes or a severely dorsalised phenotype. Although the transgene was introduced into fertilised eggs all duplications occurred within a single amnion and, therefore, arose from the production of more than one primitive streak at the time of gastrulation. Morphological examination and the expression of diagnostic markers in transgenic embryos suggested that ectopic Cwnt8C expression produced only incomplete axis duplication: axes were always fused anteriorly, there was a reduction in tissue rostral to the anterior limit of the notochord, and no duplicated expression domain of the forebrain marker Hesx1 was observed. Anterior truncations were evident in dorsalised transgenic embryos containing a single axis. These results are discussed in the light of the effects of ectopic Xwnt8 in Xenopus embryos, where its early expression leads to complete axis duplication but expression after the mid-blastula transition causes anterior truncation. It is proposed that while ectopic Cwnt8C in the mouse embryo can duplicate the primitive streak and node this only produces incomplete axis duplication because specification of the anterior aspect of the axis, as opposed to maintenance of anterior character, is established by interaction with anterior primitive endoderm rather than primitive streak derivatives.

Hex: a homeobox gene revealing peri-implantation asymmetry in the mouse embryo and an early transient marker of endothelial cell precursors

Development ◽  
1998 ◽  
Vol 125 (1) ◽  
pp. 85-94 ◽  
Author(s):  
P.Q. Thomas ◽  
A. Brown ◽  
R.S. Beddington
Keyword(s):  
Endothelial Cell ◽  
Mouse Embryo ◽  
Expression Patterns ◽  
Homeobox Gene ◽  
Definitive Endoderm ◽  
Visceral Endoderm ◽  
Primitive Endoderm ◽  
Mouse Development ◽  
Expression Domain ◽  
Early Marker

The divergent homeobox gene Hex exhibits three notable expression patterns during early mouse development. Initially Hex is expressed in the primitive endoderm of the implanting blastocyst but by 5.5 dpc its transcripts are present only in a small patch of visceral endoderm at the distal tip of the egg cylinder. Lineage analysis shows that these cells move unilaterally to assume an anterior position while continuing to express Hex. The primitive streak forms on the opposite side of the egg cylinder from this anterior Hex expression domain approximately 24 hours after the initial anterior movement of the distal visceral endoderm. Thus, Hex expression marks the earliest unequivocal molecular anteroposterior asymmetry in the mouse embryo and indicates that the anteroposterior axis of the embryo develops from conversion of a proximodistal asymmetry established in the primitive endoderm lineage. Subsequently, Hex is expressed in the earliest definitive endoderm to emerge from the streak and its expression within the gut strongly suggests that the ventral foregut is derived from the most anterior definitive endoderm and that the liver is probably the most anterior gut derivative. Hex is also an early marker of the thyroid primordium. Within the mesoderm, Hex is transiently expressed in the nascent blood islands of the visceral yolk sac and later in embryonic angioblasts and endocardium. Comparison with flk-1 (T. P. Yamaguchi et al., Development 118, 489–498, 1993) expression indicates that Hex is also an early marker of endothelial precursors but its expression in this progenitor population is much more transient than that of flk-1, being downregulated once endothelial cell differentiation commences.

Hematopoietic induction and respecification of A-P identity by visceral endoderm signaling in the mouse embryo

Development ◽  
1998 ◽  
Vol 125 (24) ◽  
pp. 5009-5018 ◽  
Author(s):  
M. Belaoussoff ◽  
S.M. Farrington ◽  
M.H. Baron
Keyword(s):  
Mouse Embryo ◽  
Decisive Role ◽  
Primitive Streak ◽  
Explant Culture ◽  
Cell Contact ◽  
Primitive Endoderm ◽  
Cell Fates ◽  
Posterior Aspect ◽  
Anterior Posterior

The anteroposterior axis of the developing embryo becomes morphologically apparent at the onset of gastrulation with the formation of the primitive streak. This structure, where the first mesodermal cells arise, marks the posterior aspect of the embryo. To examine the potential role of non-mesodermal signals in specifying posterior (hematopoietic and endothelial) cell fates in the mouse embryo, we have devised a transgenic explant culture system. We show that interactions between primitive endoderm and adjacent embryonic ectoderm or nascent mesoderm are required early in gastrulation for initiation of hematopoiesis and vasculogenesis. Surprisingly, primitive endoderm signals can respecify anterior (prospective neural) ectoderm to a posterior mesodermal fate, resulting in formation of blood and activation of endothelial markers. Reprogramming of anterior ectoderm does not require cell contact and is effected by stage-dependent, short-range, diffusible signal(s). Therefore, primitive endoderm signaling is a critical early determinant of hematopoietic and vascular development and plays a decisive role in anterior-posterior patterning during mouse embryogenesis.

scholarly journals Spatiotemporal sequence of mesoderm and endoderm lineage segregation during mouse gastrulation

2020 ◽  
Author(s):  
Simone Probst ◽  
Sagar ◽  
Jelena Tosic ◽  
Carsten Schwan ◽  
Dominic Grün ◽  
...  
Keyword(s):  
Mouse Embryo ◽  
Primitive Streak ◽  
Cell Types ◽  
Complete Separation ◽  
Embryonic Cell ◽  
Spatiotemporal Pattern ◽  
Cell Lineages ◽  
Dependent Cell ◽  
Summary Statement ◽  
Germ Layer Formation

AbstractAnterior mesoderm (AM) and definitive endoderm (DE) progenitors represent the earliest embryonic cell types that are specified during germ layer formation at the primitive streak (PS) of the mouse embryo. Genetic experiments indicate that both lineages segregate from Eomes expressing progenitors in response to different NODAL signaling levels. However, the precise spatiotemporal pattern of the emergence of these cell types and molecular details of lineage segregation remain unexplored. We combined genetic fate labeling and imaging approaches with scRNA-seq to follow the transcriptional identities and define lineage trajectories of Eomes dependent cell types. All cells moving through the PS during the first day of gastrulation express Eomes. AM and DE specification occurs before cells leave the PS from discrete progenitor populations that are generated in distinct spatiotemporal patterns. Importantly, we don’t find evidence for the existence of progenitors that co-express markers of both cell lineages suggesting an immediate and complete separation of AM and DE lineages.Summary statementCells lineages are specified in the mouse embryo already within the primitive streak where Mesp1+ mesoderm and Foxa2+ endoderm are generated in a spatial and temporal sequence from unbiased progenitors.

Modular long-range regulation of Myf5 reveals unexpected heterogeneity between skeletal muscles in the mouse embryo

Development ◽  
2000 ◽  
Vol 127 (20) ◽  
pp. 4455-4467 ◽  
Author(s):  
J. Hadchouel ◽  
S. Tajbakhsh ◽  
M. Primig ◽  
T.H. Chang ◽  
P. Daubas ◽  
...  
Keyword(s):  
Mouse Embryo ◽  
Transgene Expression ◽  
Distal Region ◽  
Trunk Muscles ◽  
Regulatory Sequences ◽  
Spatiotemporal Expression ◽  
Branchial Arches ◽  
Early Expression ◽  
Myogenic Factor ◽  
The Brain

The myogenic factor Myf5 plays a key role in muscle cell determination, in response to signalling cascades that lead to the specification of muscle progenitor cells. We have adopted a YAC transgenic approach to identify regulatory sequences that direct the complex spatiotemporal expression of this gene during myogenesis in the mouse embryo. Important regulatory regions with distinct properties are distributed over 96 kb upstream of the Myf5 gene. The proximal 23 kb region directs early expression in the branchial arches, epaxial dermomyotome and in a central part of the myotome, the epaxial intercalated domain. Robust expression at most sites in the embryo where skeletal muscle forms depends on an enhancer-like sequence located between −58 and −48 kb from the Myf5 gene. This element is active in the epaxial and hypaxial myotome, in limb muscles, in the hypoglossal chord and also at the sites of Myf5 transcription in prosomeres p1 and p4 of the brain. However later expression of Myf5 depends on a more distal region between −96 and −63 kb, which does not behave as an enhancer. This element is necessary for expression in head muscles but strikingly only plays a role in a subset of trunk muscles, notably the hypaxially derived ventral body muscles and also those of the diaphragm and tongue. Transgene expression in limb muscle masses is not affected by removal of the −96/-63 region. Epaxially derived muscles and some hypaxial muscles, such as the intercostals and those of the limb girdles, are also unaffected. This region therefore reveals unexpected heterogeneity between muscle masses, which may be related to different facets of myogenesis at these sites. Such regulatory heterogeneity may underlie the observed restriction of myopathies to particular muscle subgroups.

Embryonic axis orientation in the mouse and its correlation with blastocyst relationships to the uterus

Development ◽  
1985 ◽  
Vol 89 (1) ◽  
pp. 15-35
Author(s):  
L. J. Smith
Keyword(s):  
Mouse Embryo ◽  
Three Dimensional ◽  
Primitive Streak ◽  
Positional Information ◽  
Uterine Horn ◽  
The Other ◽  
Dimensional System ◽  
Fate Map ◽  
Axis Orientation ◽  
Three Dimensional System

Each of the three primary axes of the primitive streak (6¾ days p.c.) to C-shaped (9½ days) stage mouse embryo has a specific relationship to the uterine horn axes. By a retrograde analysis of younger sectioned embryos it has been possible to construct an axis fate map for the implanting 4¼-day blastocyst and to show how its implantation in one or the other of two specific orientations to the ends and walls of the horn leads to these embryo-horn relationships. The implanting blastocyst axis fate map can be related to an axis fate map of the attached blastocyst (Smith, 1980) since these too are in one or the other of two orientations to the ends and walls of the horn. It is suggested that the asymmetries of the attached and implanting blastocysts that allowed the distinctive attachment and implantation orientations to be recognized, are the initial expressions of a three-dimensional system of positional information that is present in the attached blastocyst.

scholarly journals Intermediate filaments formed de novo from tail-less cytokeratins in the cytoplasm and in the nucleus.

1991 ◽  
Vol 115 (5) ◽  
pp. 1293-1307 ◽  
Author(s):  
B L Bader ◽  
T M Magin ◽  
M Freudenmann ◽  
S Stumpp ◽  
W W Franke
Keyword(s):  
De Novo ◽  
Light And Electron Microscopy ◽  
Type I ◽  
Gene Products ◽  
Tail Domain ◽  
Specific Domain ◽  
Transfected Cells ◽  
Beta Actin ◽  
Actin Promoter ◽  
Nucleocytoplasmic Distribution

The roles of the different molecular domains of intermediate filament (IF) proteins in the assembly and higher order organization of IF structures have recently been studied by various groups but with partially controversial results. To examine the requirement of the aminoterminal (head) and the carboxyterminal (tail) domain of cytokeratins (CKs) for de novo IF formation in the living cell, we have constructed cDNAs coding for intact as well as head- and/or tail-less human CKs 8 and 18 and the naturally tail-less human CK 19, all under the control of the human beta-actin promoter. After transient and stable transfections of mouse 3T3-L1 cells, which are devoid of any CKs, we have studied, with such constructs, the resulting gene products by gel electrophoresis and immunolocalization techniques. By light and electron microscopy we show that extended cytoplasmic IF meshworks are formed from pairs of the type II CK 8 with the type I CKs 18 or 19 as well as from pairs of tail-less CK 8 with tail-less CKs 18 or 19 in the transfected cells, proving that the absence of the tail domain in both types of CKs does not prevent the de novo formation of regular IFs. Most surprisingly, however, we have observed spectacular alterations in the nucleocytoplasmic distribution of the IFs formed from tail-less CKs. In many of the transfected cells, a large part, or all, of the detectable CKs was found to occur in extensive IF bundles in the nucleoplasm. Intranuclear accumulations of CK deposits, however mostly nonfibrillar, were also observed when the cells had been transfected with cDNAs encoding tail-less CKs also lacking their head domains, whereas CKs deleted only in the head domain were found exclusively in the cytoplasm. The specific domain requirements for the assembly of cytoplasmic IF bundles are discussed and possible mechanisms of intranuclear accumulation of IFs are proposed.

Large Ionic Currents Leave the Primitive Streak of the 7.5-Day Mouse Embryo

1989 ◽  
Vol 176 (2S) ◽  
pp. 110-117 ◽  
Author(s):  
GLEN K. WINKEL ◽  
RICHARD NUCCITELLI
Keyword(s):  
Mouse Embryo ◽  
Ionic Currents ◽  
Primitive Streak

Expression of green fluorescent protein under beta-actin promoter in living spermatogenic cells of the mouse: stage-specific regulation by FSH

2000 ◽  
Vol 23 (4) ◽  
pp. 236-242 ◽  
Author(s):  
Sami Ventela ◽  
Masaru Okabe ◽  
Hiromitsu Tanaka ◽  
Yoshitake Nishimune ◽  
Jorma Toppari ◽  
...  
Keyword(s):  
Green Fluorescent Protein ◽  
Fluorescent Protein ◽  
Spermatogenic Cells ◽  
Beta Actin ◽  
Actin Promoter ◽  
Specific Regulation ◽  
Green Fluorescent
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