The eed mutation disrupts anterior mesoderm production in mice

Mouse embryos homozygous for the mutation embryonic ectoderm development (eed) exhibit a growth defect and fail to gastrulate normally. While extraembryonic mesoderm is produced extensively, very little embryonic mesoderm is detected in eed mutant embryos, and there is no subsequent organization of mesoderm into node, notochord, or somites. The phenotype is consistent with a defect in the distal primitive streak. Here we report additional phenotypic analyses that include mRNA in situ hybridization of genes whose expression reflects the function of different regions of the primitive streak and their derivatives. These studies have confirmed that mesoderm derived from the proximal primitive streak is specified appropriately. Despite the absence of a morphologically distinct node, sparse axial mesoderm cells in eed mutant embryos are specified, as reflected by expression of Brachyury (T), Sonic hedgehog, and Tcf3b/HNF-3 beta, and definitive endoderm is produced. Specification of these cell types is also independent of correct expression of nodal, Fgf4, and gsc. Finally, T and Evx1 display ectopic expression in cells not normally fated to ingress through the primitive streak. The data presented are discussed in terms of mechanisms for establishment of the eed phenotype, and are consistent with the eed gene product playing an early role in primitive streak formation and/or organization.

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Pattern of the insulin-like growth factor II gene expression during early mouse embryogenesis

Development ◽

10.1242/dev.110.1.151 ◽

1990 ◽

Vol 110 (1) ◽

pp. 151-159 ◽

Cited By ~ 6

Author(s):

J.E. Lee ◽

J. Pintar ◽

A. Efstratiadis

Keyword(s):

Growth Factor ◽

Immunohistochemical Analysis ◽

Primitive Streak ◽

Insulin Like Growth Factor ◽

Surface Ectoderm ◽

Factor Ii ◽

Extraembryonic Mesoderm ◽

Early Mouse ◽

Lateral Mesoderm

The mouse insulin-like growth factor II (IGF-II) gene encodes a polypeptide that plays a role in embryonic growth. We have examined the temporal and spatial pattern of expression of this gene in sections of the mouse conceptus between embryonic days 4.0 and 8.5 by in situ hybridization. Abundant IGF-II transcripts were detected in all the trophectodermal derivatives, after implantation. Labeling was then observed in primitive endoderm, but was transient and disappeared after formation of the yolk sac. Expression was next detected in extraembryonic mesoderm at the early primitive streak stage. Labeling in the embryo proper appeared first at the late primitive streak/neural plate stage in lateral mesoderm and in anterior-proximal cells located between the visceral endoderm and the most cranial region of the embryonic ectoderm. The position of the latter cells suggests that their descendants are likely to participate in the formation of the heart and the epithelium of the ventral and lateral walls of the foregut, where intense labeling was observed at the neural fold stage. Hybridization was also detected in cranial mesenchyme, including neural crest cells. The intensity of hybridization signal increased progressively in paraxial (presomitic and somitic) mesoderm, while declining in the ectoplacental cone. The neuroectoderm and surface ectoderm did not exhibit hybridization at any stage. Immunohistochemical analysis indicated co-localization of IGF-II transcripts, translated pre-pro-IGF-II, and the cognate IGF-II/mannose-6-phosphate receptor. These correlations are consistent with the hypothesis that IGF-II has an autocrine function.

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Primordial germ cells in the mouse embryo during gastrulation

Development ◽

10.1242/dev.110.2.521 ◽

1990 ◽

Vol 110 (2) ◽

pp. 521-528 ◽

Cited By ~ 14

Author(s):

M. Ginsburg ◽

M.H. Snow ◽

A. McLaren

Keyword(s):

Germ Cells ◽

Primordial Germ Cells ◽

Primitive Streak ◽

Cell Types ◽

Mesodermal Cell ◽

Alp Activity ◽

Cluster Area ◽

Extraembryonic Mesoderm ◽

Excised Tissue ◽

Number Of Cells

With the aid of a whole-mount technique, we have detected a small cluster of alkaline phosphatase (ALP)-positive cells in whole mounts of mid-primitive-streak-stage embryos, 7–7 1/4 days post coitum (dpc). Within the cluster, about 8 cells contain a small cytoplasmic spot, intensely stained for ALP activity and possibly associated with an active Golgi complex. The cluster lies just posterior to the definitive primitive streak in the extraembryonic mesoderm, separated from the embryo by the amniotic fold. Towards the end of gastrulation, the number of cells containing the ALP-positive spot rises to between 50 and 80. Thereafter the number of cells in the extraembryonic cluster declines, and similar cells start to be seen in the mesoderm of the primitive streak and then in the endoderm. At 8 dpc, about 125 ALP-stained cells are found, mainly in the hindgut endoderm and also at the base of the allantois, their appearance and location at this stage agreeing closely with previous reports on primordial germ cells (PGCs). Embryos from which the cluster area has been removed at the 7-day stage are devoid of PGCs after culture for 48 h, whereas the excised tissue is rich in PGCs. We argue that the cells in the cluster are indeed primordial germ cells, at a stage significantly earlier than any reported previously. This would indicate that the PGC lineage in the mouse is set aside at least as early as 7 dpc, possibly as one of the first ‘mesodermal’ cell types to emerge, and that its differentiation, as expressed by ALP activity, is gradual.

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Deletion of the selection cassette, but not cis-acting elements, in targeted Flk1-lacZ allele reveals Flk1 expression in multipotent mesodermal progenitors

Blood ◽

10.1182/blood-2005-05-1970 ◽

2006 ◽

Vol 107 (1) ◽

pp. 111-117 ◽

Cited By ~ 197

Author(s):

Masatsugu Ema ◽

Satoru Takahashi ◽

Janet Rossant

Keyword(s):

Growth Factor Receptor ◽

Primitive Streak ◽

Cell Types ◽

Gene Encoding ◽

Mesodermal Cell ◽

Selection Cassette ◽

Cis Acting ◽

Endogenous Expression ◽

Extraembryonic Mesoderm ◽

Early Mouse

Abstract Flk1, the gene encoding the vascular endothelial growth factor receptor 2 (VEGFR-2), is a well-known marker for vascular and hematopoietic progenitors and is indispensable for normal hematopoiesis and vasculogenesis. Here we show that Flk1 expression in the early mouse embryo marks a broad spectrum of mesodermal progenitors exiting the primitive streak as well as later mesodermal cell types including some cardiomyocytes, portions of the somites, and all extraembryonic mesoderm cells. These findings made use of an Flk1-lacZ knock-in allele in which the neomycin selection cassette was removed, which resulted in full replication of the endogenous expression of Flk1. Targeted deletion of a region in intron 1 that has been proposed to direct endothelial expression produced no alteration in either endothelial or broader mesodermal expression of the Flk1-lacZ allele. Examination of lacZ expression in homozygotes for the Flk1lacZ neo-out allele revealed that lacZ-expressing mesodermal cells persisted in nonvascular regions. Thus, Flk1 expression marks progenitors with broad mesodermal potential but is not absolutely required for the development of all mesodermal lineages in which it is expressed.

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Pbx-dependent regulation of lbx gene expression in developing zebrafish embryos

Genome ◽

10.1139/g11-061 ◽

2011 ◽

Vol 54 (12) ◽

pp. 973-985 ◽

Cited By ~ 3

Author(s):

Chris M. Lukowski ◽

Danna Lynne Drummond ◽

Andrew J. Waskiewicz

Keyword(s):

Transcription Factors ◽

Neural Tube ◽

Muscle Development ◽

Cell Types ◽

Regulatory Elements ◽

Transgenic Zebrafish ◽

Zebrafish Embryos ◽

Regulatory Interaction ◽

Mrna In Situ Hybridization

Ladybird (Lbx) homeodomain transcription factors function in neural and muscle development—roles conserved from Drosophila to vertebrates. Lbx expression in mice specifies neural cell types, including dorsally located interneurons and association neurons, within the neural tube. Little, however, is known about the regulation of vertebrate lbx family genes. Here we describe the expression pattern of three zebrafish ladybird genes via mRNA in situ hybridization. Zebrafish lbx genes are expressed in distinct but overlapping regions within the developing neural tube, with strong expression within the hindbrain and spinal cord. The Hox family of transcription factors, in cooperation with cofactors such as Pbx and Meis, regulate hindbrain segmentation during embryogenesis. We have identified a novel regulatory interaction in which lbx1 genes are strongly downregulated in Pbx-depleted embryos. Further, we have produced a transgenic zebrafish line expressing dTomato and EGFP under the control of an lbx1b enhancer—a useful tool to acertain neuron location, migration, and morphology. Using this transgenic strain, we have identified a minimal neural lbx1b enhancer that contains key regulatory elements for expression of this transcription factor.

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Initiation of Murine Embryonic Erythropoiesis: A Spatial Analysis

Blood ◽

10.1182/blood.v89.4.1154 ◽

1997 ◽

Vol 89 (4) ◽

pp. 1154-1164 ◽

Cited By ~ 92

Author(s):

Louise Silver ◽

James Palis

Keyword(s):

Expression Patterns ◽

Erythroid Differentiation ◽

Primitive Streak ◽

Neural Plate ◽

Temporal Expression ◽

Targeted Disruption ◽

Mesoderm Cell ◽

Temporal And Spatial ◽

Extraembryonic Mesoderm

Abstract Hematopoiesis in the mouse conceptus begins in the visceral yolk (VYS), with primitive erythroblasts first evident in blood islands at the headfold stage (E8.0). VYS erythropoiesis is decreased or abrogated by targeted disruption of the hematopoietic transcription factors tal-1, rbtn2, GATA-1, and GATA-2. To better understand the potential roles of these genes, and to trace the initial temporal and spatial development of mammalian embryonic hematopoiesis, we examined their expression patterns, and that of βH1-globin, in normal mouse conceptuses by means of in situ hybridization. Attention was focused on the 36-hour period from mid-primitive streak to early somite stages (E7.25 to E8.5), when the conceptus undergoes rapid morphologic changes with formation of the yolk sac and blood islands. Each of these genes was expressed in extraembryonic mesoderm, from which blood islands are derived. This VYS expression occurred in a defined temporal sequence: tal-1 and rbtn2 transcripts were detected earlier than the others, followed by GATA-2 and GATA-1, and then by βH1-globin. Transcripts for all of these genes were present in VYS mesoderm cell masses at the neural plate stage (E7.5), indicating commitment of these cells to the erythroid lineage before the appearance of morphologically recognizable erythroblasts. By early somite stages (E8.5), GATA-2 mRNA expression is downregulated in VYS blood islands as terminal primitive erythroid differentiation proceeds. We conclude that primitive mammalian erythropoiesis arises during gastrulation through the ordered temporal expression of tal-1, rbtn2, GATA2, and GATA-1 in a subset of extraembryonic mesoderm cells. During the stages analyzed, tal-1 and rbtn2 expression was also present in posterior embryonic mesoderm, while GATA-1 and GATA-2 expression was evident in extraembryonic tissues of ectodermal origin.

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In situ differentiation of iridophore crystallotypes underlies zebrafish stripe patterning

Nature Communications ◽

10.1038/s41467-020-20088-1 ◽

2020 ◽

Vol 11 (1) ◽

Author(s):

Dvir Gur ◽

Emily J. Bain ◽

Kory R. Johnson ◽

Andy J. Aman ◽

H. Amalia Pasoili ◽

...

Keyword(s):

Skin Color ◽

Cell Types ◽

Color Pattern ◽

Single Type ◽

Sequencing Analysis ◽

X Ray Diffraction ◽

X Ray ◽

Cryogenic Scanning Electron Microscopy ◽

Different Cell Types

AbstractSkin color patterns are ubiquitous in nature, impact social behavior, predator avoidance, and protection from ultraviolet irradiation. A leading model system for vertebrate skin patterning is the zebrafish; its alternating blue stripes and yellow interstripes depend on light-reflecting cells called iridophores. It was suggested that the zebrafish’s color pattern arises from a single type of iridophore migrating differentially to stripes and interstripes. However, here we find that iridophores do not migrate between stripes and interstripes but instead differentiate and proliferate in-place, based on their micro-environment. RNA-sequencing analysis further reveals that stripe and interstripe iridophores have different transcriptomic states, while cryogenic-scanning-electron-microscopy and micro-X-ray diffraction identify different crystal-arrays architectures, indicating that stripe and interstripe iridophores are different cell types. Based on these results, we present an alternative model of skin patterning in zebrafish in which distinct iridophore crystallotypes containing specialized, physiologically responsive, organelles arise in stripe and interstripe by in-situ differentiation.

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Pituitary adenoma producing growth hormone and adrenocorticotropin: a histological, immunocytochemical, electron microscopic, and in situ hybridization study

Journal of Neurosurgery ◽

10.3171/jns.1998.88.6.1111 ◽

1998 ◽

Vol 88 (6) ◽

pp. 1111-1115 ◽

Cited By ~ 27

Author(s):

Kalman Kovacs ◽

Eva Horvath ◽

Lucia Stefaneanu ◽

Juan Bilbao ◽

William Singer ◽

...

Keyword(s):

Growth Hormone ◽

In Situ Hybridization ◽

Pituitary Adenoma ◽

Immunoelectron Microscopy ◽

Secretory Granules ◽

Cell Types ◽

Content Type ◽

Separate Cell ◽

Fine Print

✓ The authors report on the morphological features of a pituitary adenoma that produced growth hormone (GH) and adrenocorticotropic hormone (ACTH). This hormone combination produced by a single adenoma is extremely rare; a review of the available literature showed that only one previous case has been published. The tumor, which was removed from a 62-year-old man with acromegaly, was studied by histological and immunocytochemical analyses, transmission electron microscopy, immunoelectron microscopy, and in situ hybridization. When the authors used light microscopy, the tumor appeared to be a bimorphous mixed pituitary adenoma composed of two separate cell types: one cell population synthesized GH and the other ACTH. The cytogenesis of pituitary adenomas that produce more than one hormone is obscure. It may be that two separate cells—one somatotroph and one corticotroph—transformed into neoplastic cells, or that the adenoma arose in a common stem cell that differentiated into two separate cell types. In this case immunoelectron microscopy conclusively demonstrated ACTH in the secretory granules of several somatotrophs. This was associated with a change in the morphological characteristics of secretory granules. Thus it is possible that the tumor was originally a somatotropic adenoma that began to produce ACTH as a result of mutations that occurred during tumor progression.

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Chromatin fibers observed in situ in frozen hydrated sections. Native fiber diameter is not correlated with nucleosome repeat length.

The Journal of Cell Biology ◽

10.1083/jcb.125.1.11 ◽

1994 ◽

Vol 125 (1) ◽

pp. 11-19 ◽

Cited By ~ 81

Author(s):

C L Woodcock

Keyword(s):

Cell Types ◽

Repeat Length ◽

Strong Positive Correlation ◽

Whole Cells ◽

Chromosome Architecture ◽

Chromatin Fibers ◽

The Moment ◽

Chicken Erythrocytes ◽

Patiria Miniata

Chromatin fibers have been observed and measured in frozen hydrated sections of three types of cell (chicken erythrocytes and sperm of Patiria miniata and Thyone briareus) representing an approximately 20-bp range of nucleosomal repeat lengths. For sperm of the starfish P. miniata, it was possible to obtain images of chromatin fibers from cells that were swimming in seawater up to the moment of cryo-immobilization, thus providing a record of the native morphology of the chromatin of these cells. Glutaraldehyde fixation produced no significant changes in the ultrastructure or diameter of chromatin fibers, and fiber diameters observed in cryosections were similar to those recorded after low temperature embedding in Lowicryl K11M. Chromatin fiber diameters measured from cryosections of the three types of nuclei were similar, a striking contrast to the situation for chromatin isolated from these cell types, where a strong positive correlation between diameter and nucleosomal repeat length has been established. The demonstration of chromatin fibers in unfixed whole cells establishes an unequivocal baseline for the study of native chromatin and chromosome architecture. The significant differences between chromatin fibers in nucleo and after isolation supports a previous observation (P. J. Giannasca, R. A. Horowitz, and C. L. Woodcock. 1993. J. Cell Sci. 105:551-561), and suggests that structural studies on isolated material should be interpreted with caution until the changes that accompany chromatin isolation are understood.

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Enzymatic Degradation of Phenazines Can Generate Energy and Protect Sensitive Organisms from Toxicity

mBio ◽

10.1128/mbio.01520-15 ◽

2015 ◽

Vol 6 (6) ◽

Cited By ~ 26

Author(s):

Kyle C. Costa ◽

Megan Bergkessel ◽

Scott Saunders ◽

Jonas Korlach ◽

Dianne K. Newman

Keyword(s):

Microbial Communities ◽

Pathogenic Fungi ◽

Cell Types ◽

Redox Activity ◽

Mycobacterium Fortuitum ◽

Active Metabolites ◽

Content Type ◽

Phenazine Production ◽

Physiological Benefits

ABSTRACTDiverse bacteria, including severalPseudomonasspecies, produce a class of redox-active metabolites called phenazines that impact different cell types in nature and disease. Phenazines can affect microbial communities in both positive and negative ways, where their presence is correlated with decreased species richness and diversity. However, little is known about how the concentration of phenazines is modulatedin situand what this may mean for the fitness of members of the community. Through culturing of phenazine-degrading mycobacteria, genome sequencing, comparative genomics, and molecular analysis, we identified several conserved genes that are important for the degradation of threePseudomonas-derived phenazines: phenazine-1-carboxylic acid (PCA), phenazine-1-carboxamide (PCN), and pyocyanin (PYO). PCA can be used as the sole carbon source for growth by these organisms. Deletion of several genes inMycobacterium fortuitumabolishes the degradation phenotype, and expression of two genes in a heterologous host confers the ability to degrade PCN and PYO. In cocultures with phenazine producers, phenazine degraders alter the abundance of different phenazine types. Not only does degradation support mycobacterial catabolism, but also it provides protection to bacteria that would otherwise be inhibited by the toxicity of PYO. Collectively, these results serve as a reminder that microbial metabolites can be actively modified and degraded and that these turnover processes must be considered when the fate and impact of such compounds in any environment are being assessed.IMPORTANCEPhenazine production byPseudomonasspp. can shape microbial communities in a variety of environments ranging from the cystic fibrosis lung to the rhizosphere of dryland crops. For example, in the rhizosphere, phenazines can protect plants from infection by pathogenic fungi. The redox activity of phenazines underpins their antibiotic activity, as well as providing pseudomonads with important physiological benefits. Our discovery that soil mycobacteria can catabolize phenazines and thereby protect other organisms against phenazine toxicity suggests that phenazine degradation may influence turnoverin situ. The identification of genes involved in the degradation of phenazines opens the door to monitoring turnover in diverse environments, an essential process to consider when one is attempting to understand or control communities influenced by phenazines.

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Misexpression of chick Vg1 in the marginal zone induces primitive streak formation

Development ◽

10.1242/dev.124.24.5127 ◽

1997 ◽

Vol 124 (24) ◽

pp. 5127-5138 ◽

Cited By ~ 8

Author(s):

S.B. Shah ◽

I. Skromne ◽

C.R. Hume ◽

D.S. Kessler ◽

K.J. Lee ◽

...

Keyword(s):

Marginal Zone ◽

Ectopic Expression ◽

Primitive Streak ◽

Axis Formation ◽

Mesoderm Induction ◽

Cell Fates ◽

Signalling Molecules ◽

Posterior Area ◽

Area Pellucida

In the chick embryo, the primitive streak is the first axial structure to develop. The initiation of primitive streak formation in the posterior area pellucida is influenced by the adjacent posterior marginal zone (PMZ). We show here that chick Vg1 (cVg1), a member of the TGFbeta family of signalling molecules whose homolog in Xenopus is implicated in mesoderm induction, is expressed in the PMZ of prestreak embryos. Ectopic expression of cVg1 protein in the marginal zone chick blastoderms directs the formation of a secondary primitive streak, which subsequently develops into an ectopic embryo. We have used cell marking techniques to show that cells that contribute to the ectopic primitive streak change fate, acquiring two distinct properties of primitive streak cells, defined by gene expression and cell movements. Furthermore, naive epiblast explants exposed to cVg1 protein in vitro acquire axial mesodermal properties. Together, these results show that cVg1 can mediate ectopic axis formation in the chick by inducing new cell fates and they permit the analysis of distinct events that occur during primitive streak formation.

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