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Results for “Embryonic Development”

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PubMed1989

[Role of c-myc protein in the early embryonic development of Xenopus].

Microinjections of antibodies directed against the protein encoded by the c-myc protooncogene strongly inhibit or arrest the early cell cleavage stage of Xenopus laevis embryos. Injections in one blastomere of a two cell stage embryo inhibit the segmentation of this blastomere. The cleavage of the uninjected blastomere behaves normally. Injections of control rabbit immunoglobulins do not alter the embryonic development.

Animals↗

PubMed1975

Cholinesterase in embryonic development.

I. Cholinesterase (ChE) activity was studied histochemically during early development of the sea urchin, the amphibian, the chick and the rat embryo. After formalin fixation and embedding in water-soluble carbowax, the enzyme reaction was carried out in serial section. 2. Independent from innervation ChE appears in every embryonic blastema in a very early stage of development. It disappears from the embryonic cells after they have assembled into definite organ structures. Thus, ChE plays a role in embryonic development which is different from its known function in the adult. Therefore, ChE activity present in differentiating cells during a limited phase of development, is termed "embryonic cholinesterase". 3. Embryonic ChE was invariably found in cells engaged in morphogenetic movements. This observation has led us to suppose that the enzyme in involved in the regulation of cellular movements during development. 4. In particular, embryonic ChE is described in the following locations: a) During sea urchin gastrulation ChE is present in the primary mesenchymal cells emigrating from the blastula wall and in the archenteron cells which are known to bring about the invagination movement by contraction of their pseudopods. b) In the early chick blastoderm ChE active "droplet cells" are described which are supposed to emigrate from the epiblast layer in order to form the hypoblast. c) During development of notochord and somites, during closure of the neural tube and development of the head anlage, the close correlation of ChE activity with various morphogenetic movements is demonstrated: ChE appears during aggregation and desaggregation of epithelial compounds. The active bending of preexisting epithelial sheets, such as the neural plate, is also accompanied by ChE activity in epithelial cells...

Acetylcholinesterase↗

PubMed2006

Unique and redundant functions of C. elegans HP1 proteins in post-embryonic development.

HP1 proteins are essential components of heterochromatin and contribute to the transcriptional repression of euchromatic genes. Although most species contain more than one HP1 family member which differ in their chromosomal distribution, it is not known to what extent the activity of these different family members is redundant or specific in a developmental context. C. elegans has two HP1 homologues, HPL-1 and HPL-2. While HPL-2 functions in vulval and germline development, no function has so far been attributed to HPL-1. Here we report the characterization of an hpl-1 null allele. We show that while the absence of hpl-1 alone results in no obvious phenotype, hpl-1;hpl-2 double mutants show synthetic, temperature sensitive phenotypes including larval lethality and severe defects in the development of the somatic gonad. Furthermore, we find that hpl-1 has an unexpected role in vulval development by acting redundantly with hpl-2, but not other genes previously implicated in vulval development. Localization studies show that like HPL-2, HPL-1 is a ubiquitously expressed nuclear protein. However, HPL-1 and HPL-2 localization does not completely overlap. Our results show that HPL-1 and HPL-2 play both unique and redundant functions in post-embryonic development.

Alleles↗

PubMedDate not supplied

Analyzing evolutionary patterns in amniote embryonic development.

Heterochrony (differences in developmental timing between species) is a major mechanism of evolutionary change. However, the dynamic nature of development and the lack of a universal time frame makes heterochrony difficult to analyze. This has important repercussions in any developmental study that compares patterns of morphogenesis and gene expression across species. We describe a method that makes it possible to quantify timing shifts in embryonic development and to map their evolutionary history. By removing a direct dependence on traditional staging series, through the use of a relative time frame, it allows the analysis of developmental sequences across species boundaries. Applying our method to published data on vertebrate development, we identified clear patterns of heterochrony. For example, an early onset of various heart characters occurs throughout amniote evolution. This suggests that advanced (precocious) heart development arose in evolutionary history before endothermy. Our approach can be adapted to analyze other forms of comparative dynamic data, including patterns of developmental gene expression.

Age Factors↗

PubMed1999

Choline availability alters embryonic development of the hippocampus and septum in the rat.

Choline availability in the diet during pregnancy alters fetal brain biochemistry with resulting behavioral changes that persist throughout the lifetime of the offspring. In the present study, the effects of dietary choline on cell proliferation, migration, and apoptosis in neuronal progenitor cells in the hippocampus and septum were analyzed in fetal brains at different stages of embryonic development. Timed-pregnant rats on day E12 were fed AIN-76 diet with varying levels of dietary choline for 6 days, and, on days E18 or E20, fetal brain sections were collected. We found that choline deficiency (CD) significantly decreased the rate of mitosis in the neuroepithelium adjacent to the hippocampus. An increased number of apoptotic cells were found in the region of the dentate gyrus of CD hippocampus compared to controls (5.5+/-0.7 vs. 1.9+/-0.3 apoptotic cells per section; p<0.01). Using a combination of bromodeoxyuridine (BrdU) labeling and an unbiased computer-assisted image analysis method, we found that modulation of dietary choline availability changed the distribution and migration of precursor cells born on E16 in the fimbria, primordial dentate gyrus, and Ammon's horn of the fetal hippocampus. CD also decreased the migration of newly born cells from the neuroepithelium into the lateral septum, thus indicating that the sensitivity of fetal brain to choline availability is not restricted to the hippocampus. We found an increase in the expression of TOAD-64 protein, an early neuronal differentiation marker, in the hippocampus of CD day E18 fetal brains compared to controls. These results show that dietary choline availability alters the timing of the genesis, migration, and commitment to differentiation of progenitor neuronal-type cells in fetal brain hippocampal regions known to be associated with learning and memory processes in adult brain.

Animals↗

PubMed2002

Rhodnius heme-binding protein (RHBP) is a heme source for embryonic development in the blood-sucking bug Rhodnius prolixus (Hemiptera, Reduviidae).

We have previously shown that Rhodnius prolixus' eggs and hemolymph are pink due to the presence of the hemeprotein Rhodnius heme-binding protein (RHBP). In the hemolymph it functions as an antioxidant. Nevertheless, its function in eggs has not been determined. Here we present evidence that RHBP is a source of heme for embryonic development. RHBP content decreases during embryogenesis, but the total heme content of eggs remains unchanged. Biliverdin, the product of heme degradation, is not detectable in late embryos. The activity of the heme-synthesizing pathway is low throughout embryogenesis and rises sharply after nymphs' hatching. Heme-radiolabeled eggs were produced and, at the day of hatching, nymphs were dissected. The presence of radiolabeled heme in their carcass is an indication that heme reutilization is occurring. The only animal known to reutilize heme in significant levels is the cattle tick Boophilus microplus, which cannot synthesize its own heme. Diversely, Rhodnius can synthesize its own heme but, in the context of embryogenesis, heme demand seems to be supplied by the programmed release of heme form RHBP. This behavior indicates that in Rhodnius, we might have a highly unusual profile: heme is both synthesized and reutilized.

Animals↗

PubMed2002

Pluripotent stem cells--model of embryonic development, tool for gene targeting, and basis of cell therapy.

Embryonic stem (ES) cells are pluripotent cell lines with the capacity of self-renewal and a broad differentiation plasticity. They are derived from pre-implantation embryos and can be propagated as a homogeneous, uncommitted cell population for an almost unlimited period of time without losing their pluripotency and their stable karyotype. Murine ES cells are able to reintegrate fully into embryogenesis when returned into an early embryo, even after extensive genetic manipulation. In the resulting chimeric offspring produced by blastocyst injection or morula aggregation, ES cell descendants are represented among all cell types, including functional gametes. Therefore, mouse ES cells represent an important tool for genetic engineering, in particular via homologous recombination, to introduce gene knock-outs and other precise genomic modifications into the mouse germ line. Because of these properties ES cell technology is of high interest for other model organisms and for livestock species like cattle and pigs. However, in spite of tremendous research activities, no proven ES cells colonizing the germ line have yet been established for vertebrate species other than the mouse (Evans and Kaufman, 1981; Martin, 1981) and chicken (Pain et al., 1996). The in vitro differentiation capacity of ES cells provides unique opportunities for experimental analysis of gene regulation and function during cell commitment and differentiation in early embryogenesis. Recently, pluripotent stem cells were established from human embryos (Thomson et al., 1998) and early fetuses (Shamblott et al., 1998), opening new scenarios both for research in human developmental biology and for medical applications, i.e. cell replacement strategies. At about the same time, research activities focused on characteristics and differentiation potential of somatic stem cells, unravelling an unexpected plasticity of these cell types. Somatic stem cells are found in differentiated tissues and can renew themselves in addition to generating the specialized cell types of the tissue from which they originate. Additional to discoveries of somatic stem cells in tissues that were previously not thought to contain these kinds of cells, they also appear to be capable of developing into cell types of other tissues, but have a reduced differentiation potential as compared to embryo-derived stem cells. Therefore, somatic stem cells are referred to as multipotent rather than pluripotent. This review summarizes characteristics of pluripotent stem cells in the mouse and in selected livestock species, explains their use for genetic engineering and basic research on embryonic development, and evaluates their potential for cell therapy as compared to somatic stem cells.

Animals↗

PubMed1987

Parental DNA strands segregate randomly during embryonic development of Caenorhabditis elegans.

The fate of gamete DNA was followed in the next generation embryos of the nematode C. elegans. Either male worms or spermless hermaphrodites were grown on bromodeoxyuridine-containing E. coli in order to label germ-line DNA. Matings then produced embryos in which only the DNA strands provided by the gametes contained label. This original gamete DNA could be detected during embryonic development by using a fluorescently labeled monoclonal antibody specific to bromodeoxyuridine. Both the number and position of fluorescent spots in the embryo indicate that gamete DNA strands segregate randomly during development. Random segregation of parental DNA strands rules out models of development that invoke chromosome imprinting or immortal DNA strands.

Animals↗

PubMed2002

Comparative immunolocalization of the plasma membrane calcium pump and calbindin D28K in chicken retina during embryonic development.

The immunolocalization of the plasma membrane calcium pump (PMCA) was studied in 4-week-old chick retina in comparison with calbindin D28K (CaBP) immunostaining. We have demonstrated that the monoclonal anti-PMCA antibody SF10 from human erythrocyte plasma membrane cross-reacts with a Ca2+ pump epitope of the cells from the neural retina. The immunolocalization of both proteins was also studied during the embryonic development of the chicken retina. At age 4.5 days, the cells of the retina were faintly immunoreactive to PMCA and CaBP antibodies, but the lack of cellular aggregation and differentiation did not allow discrimination between the two proteins. A clear difference in the localization was seen from the tenth day of development through post-hatching with slight variation. PMCA localized mainly in the outer and inner plexiform layers, in some cells in the ganglion layer, in the nerve fiber layer and slightly in the photoreceptor cells. CaBP was intensely stained in cones, cone pedicles and some amacrine cells. The number of CaBP positive amacrine cells declined after hatching. A few ganglion cells and several nerve fibers were CaBP immunoreactive. The role of these proteins in the early stages of retinal development is unknown, but the results suggest that Ca2+ homeostasis in the retina is well regulated, probably to avoid excessive accumulation of Ca2+, which often leads to neurodegeneration.

Animals↗

PubMed2001

The protein 4.1, ezrin, radixin, moesin (FERM) domain of Drosophila Coracle, a cytoplasmic component of the septate junction, provides functions essential for embryonic development and imaginal cell proliferation.

Coracle is a member of the Protein 4.1 superfamily of proteins, whose members include Protein 4.1, the Neurofibromatosis 2 tumor suppressor Merlin, Expanded, the ERM proteins, protein tyrosine phosphatases, and unconventional myosins. Recent evidence suggests that members of this family participate in cell signaling events, including those that regulate cell proliferation and the cytoskeleton. Previously, we demonstrated that Coracle protein is localized to the septate junction in epithelial cells and is required for septate junction integrity. Loss of coracle function leads to defects in embryonic development, including failure in dorsal closure, and to proliferation defects. In addition, we determined that the N-terminal 383 amino acids define an essential functional domain possessing membrane-organizing properties. Here we investigate the full range of functions provided by this highly conserved domain and find that it is sufficient to rescue all embryonic defects associated with loss of coracle function. In addition, this domain is sufficient to rescue the reduced cell proliferation defect in imaginal discs, although it is incapable of rescuing null mutants to the adult stage. This result suggests the presence of a second functional domain within Coracle, a notion supported by molecular characterization of a series of coracle alleles.

Alleles↗

PubMed2026

Phosphorylation of BigH1 regulates its expression pattern and promotes embryonic development.

Metazoan genomes typically encode several linker histone variants, often expressed in a tissue- or developmental stage-specific manner. The Drosophila melanogaster genome contains only two linker histone variants: H1 is present in somatic cells, while BigH1 substitutes H1 in the germline and early embryos. In the early stages of embryogenesis, BigH1 is replaced by H1 in the chromatin of somatic cells, contributing to the initiation and maintenance of the zygotic gene expression program. Nevertheless, the molecular mechanism of this exchange and the possible functions of post-translational modifications of BigH1 in this process remain elusive. Here, we identify phosphorylation as a key post-translational regulator of BigH1 dynamics. Using proteomics and targeted mutagenesis of the endogenous BigH1 locus, we show that the loss of N-terminal phosphorylation results in persistent retention of BigH1 in somatic nuclei throughout embryogenesis, indicating a failure in BigH1 turnover. In contrast, disruption of C-terminal phosphorylation does not markedly affect BigH1 clearance but increases defects during early nuclear divisions and compromises embryonic development, particularly under suboptimal conditions. Together, these findings demonstrate that domain-specific phosphorylation differentially regulates BigH1 function, coordinating its early embryonic role with its subsequent removal from the chromatin.

BigH1↗

PubMed1989

An increase in the intracellular pH of fertilized eggs of Xenopus laevis is associated with inhibition of protein and DNA syntheses and followed by an arrest of embryonic development.

In many systems, events participating in cell division are controlled by intracellular pH (pHi). In Xenopus eggs, fertilization is accompanied by an increase in pHi which occurs concomitantly with an increase in protein synthesis and a reinitiation of DNA synthesis, leading the embryo to cell division. In this paper, we have shown that increasing pHi of fertilized eggs from 7.8 to 8.2 by using weak bases produced an arrest in embryonic development. Such a change in pHi was accompanied by a severe inhibition of both protein and DNA syntheses. In order to discriminate between a direct effect of pHi and a pH-independent effect of weak bases on these biosyntheses, the situation was studied in vitro. For this purpose, cytoplasmic extracts were used in which weak base addition did not produce any change in pH. Under these conditions, protein synthesis was not inhibited, suggesting that pH is probably one of the events implicated in the regulation of protein synthesis. On the other hand, DNA synthesis was inhibited by weak bases in vitro, without any change in pH intervening.

Animals↗

PubMed1983

The embryonic development of the cortical plate in reptiles: a comparative study in Emys orbicularis and Lacerta agilis.

From the earliest stage of its ontogenesis, the mammalian cerebral cortex displays a remarkable cytoarchitectonic organization, with its neurons oriented radially within the cortical plate (CP). It is not known whether this radial organization of cortical neurons is characteristic of every cerebral cortex or whether it reflects a progressive phylogenetic acquisition. In order to study this question, the embryonic development of the cortex has been examined in reptiles, where it is the most primitive. Two species, Emys orbicularis and Lacerta agilis, representative of the two principal reptilian orders (chelonians and squamates), have been studied with histological methods. Golgi impregnation, and electron microscopy. Very similar patterns of cell proliferation, migration, maturation, and synaptogenesis have been observed. However, important species differences are present in the cellular organization of the cortical plate. Whereas in Emys the structure of the cortical plate is rudimentary, in Lacerta it appears well developed and quite reminiscent of its mammalian counterpart. Preliminary comparisons with embryological preparations of Sphenodon and Crocodilus niloticus show that the organization of the cortical plate displays significant variations among the different reptilian groups. The present results suggest that the radial organization of cortical neurons is not an all or nothing phenomenon but has been acquired independently and is thus a case of homoplasy, probably due to convergence (Northcutt, 81). Several possible implications of these findings are discussed and a working hypothesis based on the role of radial glial cells in the formation of cytoarchitectonic patterns (Rakic, '80) is presented.

Animals↗

PubMed1995

Embryonic development of central nervous system myelination in a reptilian species, Eumeces fasciatus.

The myelin proteolipid proteins are a vital component of the vertebrate central nervous system (CNS), contributing essential functions to the development of the myelinating cells of the CNS and to the structure of CNS myelin. Alternative splicing of the proteolipid protein (PLP) gene to produce two related isoforms occurs in Mammalia, Aves, and Reptilia, but not Amphibia. As part of a long-term investigation into the function of the different isoforms of PLP, embryonic development, myelination, and PLP gene expression in reptilian CNS were examined. PLP gene expression was already substantial by day 19 (stage 39) of the 27-day Eumeces fasciatus egg incubation period. By day 21 of incubation, also stage 39, PLP mRNA was at peak levels; there was a significant amount of CNS myelination as demonstrated by electron microscopy of the spinal cord; and the reflexive motor response was evident. Although most axons were myelinated by the time of hatching, myelin sheaths continued to increase in size and compactness after hatching. The correlation of physiological development, CNS myelination, and expression of the PLP gene in the lizard corresponded well with the developmental pattern seen in mammals.

Animals↗

PubMed2004

TBP2, a vertebrate-specific member of the TBP family, is required in embryonic development of zebrafish.

TATA binding protein (TBP) is a key regulator of RNA polymerase transcription. It binds to core promoters, often in large multiprotein complexes, and nucleates RNA polymerase II (Pol II) transcription initiation. In addition to the previously described TBP-like factor present in metazoans (TLF/TRF2/TRP/TLP), we describe a third, vertebrate-specific member of the TBP protein family from zebrafish, called TBP2. Evolutionary conserved TBP2 homologs were also found in human, mouse, frog, and pufferfish. The N-terminal domains of TBP2s are divergent amongst themselves and different from those of TBPs; however, the core domain of TBP2s and TBPs are almost identical. TBP2 binds the TATA box, interacts with TFIIA and TFIIB (similarly to TBP), and can mediate Pol II transcription initiation. However, TBP2 shows contrasting expression patterns in the gonads and during embryonic development in comparison to TBP, suggesting differential function. Knockdown of zebrafish TBP2 results in specific reduction of the protein level, leading to a phenotype, which indicates the requirement of TBP2 for embryonic patterning. The presence of three different TBP family members in vertebrates suggests the existence of developmental stage- and tissue-specific preinitiation complexes with specific requirements for different TBP family members.

Animals↗

PubMed1988

A close look at early embryonic development with the high-frequency transvaginal transducer.

Transabdominal sonography has been, for the past two decades, used as an effective diagnostic and research tool in obstetrics. It is predominantly used in the second and third trimesters of gestation. Its use in the first trimester is relatively limited and mostly diagnostic in nature. The introduction of the higher frequency transvaginal transducer probe, with its higher resolution of the images, opens new possibilities to study early gestation. We studied embryonic development in 38 well-dated and normal pregnancies. A well-defined intrauterine gestational sac could be seen at 4 weeks and 1 to 4 days of menstrual age. The beta-subunit of human chorionic gonadotropin level at this time was 450 to 750 mlU/ml. Structures such as the yolk sac, membranes, ventricular system in the brain, musculoskeletal system, and cord were described and illustrated. Textbooks and atlases were used for comparative purposes. High-resolution transvaginal sonography will facilitate first-trimester perinatology.

Embryo, Mammalian↗

PubMed2006

Expression of avian C-terminal binding proteins (Ctbp1 and Ctbp2) during embryonic development.

C-terminal binding proteins (CtBPs) are transcriptional corepressors of mediators of Notch, Wnt, and other signalling pathways. Thus, they are potential players in the control of several developmentally important processes, including segmentation, somitogenesis, and neural tube and limb patterning. We have cloned the avian orthologues of Ctbp1 and Ctbp2 and examined their expression pattern by whole-mount in situ hybridization between Hamburger and Hamilton (HH) stages 3 and 24. Both Ctbp genes show similar expression patterns during embryonic development, and both are detected from HH stage 3 in the developing central nervous system, by HH stage 7 in the paraxial mesoderm and later in the limb bud. In most places, Ctbp1 and Ctbp2 are expressed in overlapping domains. However, there are interesting domains and/or temporal expression patterns that are specific to each Ctbp gene. For instance, Ctbp1 is predominantly expressed in the epiblast, whereas Ctbp2 is in the primitive streak at HH stage 3. However, by HH stage 4, both genes are found in the primitive streak and in the ectoderm. Similarly, although both genes display similar expression patterns in early somitogenesis, in mature somites, Ctbp1 transcripts are located in myotomal cells, whereas Ctbp2 transcripts are observed in dermomyotomal cells. Finally, we found that emigrating neural crest cells express Ctbp2, whereas dorsal root ganglia express Ctbp1. These data suggest that Ctbp1 and Ctbp2 may be functionally redundant in some tissues and have unique functions in other tissues.

Alcohol Oxidoreductases↗

PubMed2005

RacGap50C negatively regulates wingless pathway activity during Drosophila embryonic development.

The Wingless (Wg)/Wnt signal transduction pathway directs a variety of cell fate decisions in developing animal embryos. Despite the identification of many Wg pathway components to date, it is still not clear how these elements work together to generate cellular identities. In the ventral epidermis of Drosophila embryos, Wg specifies cells to secrete a characteristic pattern of denticles and naked cuticle that decorate the larval cuticle at the end of embryonic development. We have used the Drosophila ventral epidermis as our assay system in a series of genetic screens to identify new components involved in Wg signaling. Two mutant lines that modify wg-mediated epidermal patterning represent the first loss-of-function mutations in the RacGap50C gene. These mutations on their own cause increased stabilization of Armadillo and cuticle pattern disruptions that include replacement of ventral denticles with naked cuticle, which suggests that the mutant embryos suffer from ectopic Wg pathway activation. In addition, RacGap50C mutations interact genetically with naked cuticle and Axin, known negative regulators of the Wg pathway. These phenotypes suggest that the RacGap50C gene product participates in the negative regulation of Wg pathway activity.

Alleles↗