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At least 361 records · Page 20Linked to original sources

PubMed2005

Somatic embryogenesis in Solanum tuberosum from cell suspension cultures: histological analysis and extracellular protein patterns.

An embryogenic cell suspension, continuously grown in Murashige and Skoog (MS) medium with 0.5 mg/L of 2,4-dichlorophenoxyacetic acid, was established from friable callus of Solanum tuberosum internode sections. The cell suspension was predominantly composed of cell masses and free embryogenic cells. When transferred to an auxin-free medium with zeatin, somatic embryos (SEs) developed and converted to complete plants when cultured on solid MS medium without growth regulators. The system produced approximately 600 SEs per 50 mL of medium. In this investigation, accumulation of extracellular proteins (EPs) of different molecular weights were found associated to different phases of the embryogenic process. At the initiation of the cell suspension, cell clusters and free cells present in the culture (phase "A") secreted a 78kDa EP, unique to this phase. In phase "B", which is related to embryonic cell determination process, proteins (7-14kDa) were secreted mainly by embryogenic cells. In phase "C", SEs in different developmental stages secreted protein of 32 kDa, which appeared as a particular feature of the phase. EPs of phase "D", secreted by torpedo and mature embryos, had molecular weights between 20 and 50 kDa. Further studies will be necessary to identify these proteins and link them to previously identified somatic embryogenesis-related proteins. Histological analysis of the potato embryogenesis in liquid media showed unicellular origin of the SE.

Cell Culture Techniques↗

PubMed2006

The lysyl hydroxylase isoforms are widely expressed during mouse embryogenesis, but obtain tissue- and cell-specific patterns in the adult.

Lysyl hydroxylase catalyzes the hydroxylation of lysine residues in collagenous sequences. Three isoforms (LH1, LH2 and LH3) of lysyl hydroxylase have been characterized, and LH2 is present as two alternatively spliced forms. In order to better understand the functional differences between the isoforms in vivo, the expression of the different isoforms was studied in mouse embryos and adult tissues. Our data indicate a widespread expression of all isoforms during embryogenesis, whereas the expression profiles become more specialized in adult tissues. The expression of LH2 was more tissue-specific, whereas a uniform and housekeeping like behavior was observed for LH3. Some cells express both LH2 and LH3, while a clear cell specificity was seen in some tissues. Moreover, immunoelectron microscopy revealed differences in the localization of LH2 and LH3. LH2 was localized intracellularly in the ER in all tissues studied, whereas the localization of LH3 was either intracellular or extracellular or both, depending on the tissue. Furthermore, our data indicate that the alternative splicing of LH2 is developmentally regulated. The short form of LH2 (LH2a) is the predominant form until E11.5; the long form (LH2b) dominates thereafter and is the major form in many adult tissues. Interestingly, however, adult mouse kidney and testis express exclusively the short form, LH2a. The results reveal a specific regulation for the expression of LH isoforms as well as for alternative splicing of LH2 during embryogenesis and in different tissues.

Animals↗

PubMed2004

Ce-Y14 and MAG-1, components of the exon-exon junction complex, are required for embryogenesis and germline sexual switching in Caenorhabditis elegans.

Y14 is a component of the splicing-dependent exon-exon junction complex (EJC) and is involved in the mRNA quality control system called nonsense-mediated mRNA decay. It has recently been shown that together with another EJC component, Mago, the Drosophila homologue DmY14/Tsunagi is required for proper localization of oskar mRNA during oogenesis, a process critical for posterior formation in Drosophila development. Here we show that the nematode Caenorhabditis elegans Ce-Y14 and MAG-1 (Mago homologue) are required for late embryogenesis and proper germline sexual differentiation. Like in other organisms, Ce-Y14 preferentially binds to spliced mRNA and specifically interacts with MAG-1. Consistent with the evolutionarily conserved interaction between Y14 and Mago homologues, suppression of Ce-Y14 by RNAi resulted in the same phenotypes as those caused by RNAi of mag-1 lethality during late embryogenesis and masculinization of the adult hermaphrodite germline. Our results demonstrate that the evolutionarily conserved interaction between two EJC components, Ce-Y14 and MAG-1, has critical developmental roles in C. elegans.

Animals↗

PubMed2004

Drosophila p24 homologues eclair and baiser are necessary for the activity of the maternally expressed Tkv receptor during early embryogenesis.

p24 proteins are assumed to play an important role in the transport of secreted and transmembrane proteins into membranes. However, only few cargo proteins are known that partially, but in no case completely require p24 proteins for membrane transport. Here, we show that two p24 proteins are essential for dorsoventral patterning of Drosophila melanogaster embryo. Mutations in the genes, eclair (eca) and baiser (bai), encoding two p24 proteins reduce signalling by the TGF-beta homologue, Dpp, in early embryos. This effect is strictly maternal and specific to early embryogenesis, as Dpp signalling in other contexts is not notably affected. We provide genetic evidence that in the absence of eca or bai function in the oocyte, the maternally expressed type I TGF-beta receptor Tkv is not active. We propose that during early embryogenesis eca and bai are specifically required for the activity of the maternal Tkv, while the zygotic Tkv is not affected in the mutant embryos. Mutations in either eca or bai are sufficient for the depletion of Tkv activity and no enhancement of the phenotypes was observed in embryos derived from oocytes mutant for both genes. The dependence of maternal Tkv protein on the products of p24 genes may serve as an in vivo model for studying p24 proteins.

Amino Acid Sequence↗

PubMed2005

FGF signalling controls expression of vomeronasal receptors during embryogenesis.

Fibroblast growth factors (FGFs) have been shown to control formation and differentiation of multiple organ systems in the developing vertebrate embryo. The analysis of differential gene expression during embryogenesis is, therefore, a potent tool to identify novel target genes regulated by FGF signalling. Here, we have applied microarray analysis to identify differentially regulated genes in FGF mutant mouse embryos. Surprisingly, transcripts corresponding to vomeronasal receptors (VRs), which so far have been only detected in the vomeronasal organ (VNO), were found to be downregulated in FGF mutant embryos. VR expression was detected in the developing olfactory pit and the anlage of the VNO. Interestingly, several FGFs can be detected in the developing olfactory pit during mouse embryogenesis [Bachler, M., Neubuser, A. 2001. Expression of members of the Fgf family and their receptors during midfacial development. Mech. Dev. 100, 313-316]. FGF signalling may thus control expression of VRs in the olfactory pit and formation of the VNO. Moreover, VR expression was detected in unexpected locations within the developing embryo including retina, dorsal root ganglia and neural tube. The relevance of VR expression in these structures and for formation of the VNO is discussed.

Animals↗

PubMed2005

Expression patterns of the homeotic genes Scr, Antp, Ubx, and abd-A during embryogenesis of the cricket Gryllus bimaculatus.

We have studied embryogenesis of the two-spotted cricket Gryllus bimaculatus as an example of a hemimetabolous, intermediate germ insect, which is a phylogenetically basal insect and may retain primitive features. We observed expression patterns of the orthologs of the Drosophila homeotic genes, Sex combs reduced (Scr), Antennapedia (Antp), Ultrabithorax (Ubx) and abdominal-A (abd-A) during embryogenesis and compared the expression patterns of these genes with the more basal thysanuran insect, Thermobia domestica (the firebrat), and the derived higher dipteran insect, Drosophila melanogaster. Although Scr is expressed commonly in the presumptive posterior maxillary and labial segment in all three insects, the thoracic expression domains vary. Antp is expressed similarly in the three thoracic segments, the limbs, and the anterior abdominal region among these three insects. The early Antp expression in the firebrat and cricket obeys a segmental register in all three thoracic segments, while in Drosophila its initial expression appears in parasegments 4 and 6. Ubx is expressed in the metathoracic (T3) and abdominal segments similarly in the three insects, whereas the expression pattern in the T3 leg differs among them. abd-A is expressed in the posterior compartment of the first abdominal segment and the remaining abdominal segments in all three insects, although its posterior border varies among them.

Amino Acid Sequence↗

PubMed2006

Cloning and expression of medaka dazl during embryogenesis and gametogenesis.

The Deleted in azoospermia family consists of RNA-binding proteins Boule, Daz, and Daz-like (Dazl) that are expressed in the germline. Here, we report the cloning and expression of the medakafish (Oryzias latipes) dazl gene (odazl). Interestingly, although the predicted medaka Dazl protein (oDazl) contains a RRM motif and a DAZ repeat characteristic of its mammalian homologs, it lacks 80 aa at the C-terminus. By RT-PCR, RNA in situ hybridization, Western blotting and fluorescent immunohistochemistry using a rabbit anti-Dazl antibody (alphaDazl), we analyzed the expression patterns of odazl and its protein. The odazl transcript persists throughout embryogenesis and delineates with primordial germ cells. In adults, the expression of odazl RNA and its protein is restricted to germ cells of both the testis and ovary. We observed differential expression of RNA and protein at critical stages of gametogenesis. In the testis, the odazl RNA is low at premeiotic stages, abundant at meiotic stages, but absent in postmeiotic stages; whereas the oDazl protein is rich in premeiotic stages, reduced at meiotic stages, becomes barely detectable or absent in postmeiotic round spermatids or sperm, respectively. This is in sharp contrast to the human situation where the Dazl transcript and protein are present in mature spermatozoa. In the ovary, the odazl RNA and protein persist throughout oogenesis and also show differential expression at premeiotic, meiotic and postmeiotic stages. Thus, the odazl or its protein is a marker for germ cells during embryogenesis and at critical stages of gametogenesis in both sexes of medaka.

Amino Acid Sequence↗

PubMed2004

Embryogenesis of the peripheral nervous system.

Embryogenesis is a complex, wide-ranging event. Key processes may proceed simultaneously in different portions of the embryo, or sequentially, with phase offsets as waves of maturation pass outward from an initial point toward the periphery. The molecular signals used to pattern the body commonly serve multiple functions and reiterate as the body plan progresses. This article therefore presents first the anatomic model of the peripheral nervous system, so that the final goal is clear. It then reviews the terminology needed to describe embryogenesis. The article's first section reviews neural development. The main portion of the article addresses the maturation of the fetal nervous system in terms of the evolving gross morphology and the molecular signals that pattern these changes.

Embryonic and Fetal Development↗

PubMed2025

3D chromatin structures precede genome activation in Drosophila embryogenesis.

3D chromatin structure is critical for the regulation of gene expression during development. Here we used Micro-C assays at 100-bp resolution to map genome organization in Drosophila melanogaster throughout the first half of embryogenesis. These high-resolution contact maps reveal fine-scale features such as loops and boundaries delineating topologically associating domains. Notably, we observe that 3D chromatin structures form prior to zygotic genome activation and persist during successive mitotic cycles. Integrative analysis with 149 public chromatin immunoprecipitation sequencing (ChIP-seq) datasets identifies four classes of chromatin structuring elements, including a distinct group enriched for GAGA-associated factor (GAF) and Zelda binding, associated with developmental-gene regulation. These elements are mitotically retained and exhibit sequence and structure similarity between D. melanogaster and D. virilis. We propose that 3D chromatin organization in the pre-cellular embryo facilitates deployment of developmentally regulated genes during Drosophila embryogenesis.

Animals↗

PubMed2004

HRP-2, a heterogeneous nuclear ribonucleoprotein, is essential for embryogenesis and oogenesis in Caenorhabditis elegans.

Heterogeneous nuclear ribonucleoproteins (hnRNPs) have fundamental roles in the posttranscriptional control of gene expression. Here, we describe an hnRNP from Caenorhabditis elegans(HRP-2), which shares significant homology with mammalian hnRNP R, hnRNP Q and ACF, the essential complementation factor in ApoB mRNA editing. All four proteins possess a similar molecular architecture, with three closely linked RNA-binding domains and a C-terminus that contains RG/RGG repeat motifs. An HRP-2::GFP fusion protein was ubiquitously expressed in C. elegans during embryogenesis and subsequent larval development. Expression was also detected in the hermaphrodite gonad using a specific antibody, suggesting that HRP-2 is provided maternally. HRP-2 was predominantly localised to nuclei and analysis of transgenic lines expressing C-terminal deletions of HRP-2 defined a functional nuclear localisation signal. Analysis by RNAi demonstrated that HRP-2 was essential for embryogenesis and fertility. Cell divisions were slower in hrp-2(RNAi) embryos and the majority showed an early embryonic arrest phenotype. Shorter exposure to dsRNA allowed development to the twofold stage and the few embryos that hatched were abnormal. Adult worms that developed from embryos exposed to RNAi were completely sterile due to a failure in oocyte formation. These results demonstrate that HRP-2 or its RNA targets are essential for normal embryonic development and oogenesis in C. elegans.

Animals↗

PubMed2002

Caenorhabditis elegans reticulon interacts with RME-1 during embryogenesis.

Reticulon (RTN) family proteins are localized in the endoplasmic reticulum (ER). At least four different RTN genes have been identified in mammals, but in most cases, the functions of the encoded proteins except mammalian RTN4-A and RTN4-B are unknown. Each RTN gene produces 1-3 proteins by different promoters and alternative splicing. In Caenorhabditis elegans, there is a single gene (rtn gene) encoding three reticulon proteins, nRTN-A, B, and C. mRNA of nRTN-C is expressed in germ cells and embryos. However, nRTN-C protein is only expressed during embryogenesis and rapidly disappears after hatch. By yeast two-hybrid screening, two clones encoding the same C-terminal region of RME-1, a protein functioning in the endocytic recycling, were isolated. These findings suggest that nRTN-C functions in the endocytic pathway during embryogenesis.

Animals↗

PubMed1983

Changes in deoxyribonucleoside triphosphate pools in the starfish oocyte during maturation and early embryogenesis.

dNTP pools are quite low in immature oocytes of the starfish, expand during the 1-methyladenine-induced maturational process and thereafter reach a maximal level (approx. 35, 20, 15 and 5 fmoles/egg for dTTP, dCTP, dATP and dGTP, respectively) which is maintained in overmatured eggs. Maturing oocytes were inseminated at the stage just before extrusion of the first polar body and determination of dNTP pools during early embryogenesis showed the same expansion pattern as that of the 1-methyladenine-treated oocytes. Therefore, the increase in dNTP pools during early embryogenesis is dependent on 1-methyladenine (1-MA) but independent of fertilization. Aphidicolin, a specific inhibitor of eukaryotic DNA polymerase alpha, has no effect on dNTP pool size in 1-methyladenine-treated oocytes, but causes considerable expansion of dNTP pools in fertilized eggs which cleave achromosomally in the presence of the drug.

Animals↗

PubMed1997

Integrins and reproductive physiology: expression and modulation in fertilization, embryogenesis, and implantation.

OBJECTIVE: To review the available information regarding the role of integrins in reproductive physiology and to discuss their potential clinical implications. DESIGN: Studies that specifically relate to the expression and modulation of integrins in fertilization, embryogenesis, and implantation were identified through the literature and Medline searches. RESULT(S): Integrins are a class of adhesion molecules that participate in cell-to-cell and cell-to-substratum interactions and are present on essentially all human cells. All mammalian eggs express integrins at their surface, and the integrin alpha 6 beta 1 serves as a sperm receptor that mediates sperm-egg binding. In addition, certain integrin moieties appear to be regulated within the cycling endometrium. Specifically, the expression of beta 1 integrins in the early proliferative phase is restricted to the glandular epithelium, whereas stromal cells also express beta 1 integrins in the midsecretory phase. The expression of beta 1 integrins increases at the time of implantation and remains elevated in the decidua during early pregnancy. A disruption of integrin expression is associated with certain types of infertility in women. The apical surface of the mural trophectoderm does indeed possess functional integrins, and trophoblast interactions with extracellular matrix proteins largely depend on the integrin family of adhesion receptors. CONCLUSION(S): Integrins play particularly important roles in both fertilization and embryogenesis, including the process of implantation.

Animals↗

PubMed1998

Expression of the RNA component of telomerase in Wilms tumor and nephrogenic rest recapitulates renal embryogenesis.

Telomerase is a ribonucleoprotein enzyme associated with cellular immortality and has been detected in the vast majority of adult tumors. Wilms tumor is a histologically diverse embryonal malignancy of childhood, and the histological features of Wilms tumor and its precursor lesion, the nephrogenic rest, recapitulate the components of normal renal embryogenesis. Both the epithelial and the stromal components of Wilms tumor arise by differentiation of primitive mesodermal blastema. We compared expression of the RNA component of human telomerase (hTR) in normal developing kidneys, Wilms tumors, and nephrogenic rests and correlated expression of hTR with cell proliferation. Using a radioactive in situ hybridization method, we examined archival material from 17 Wilms tumors (including nine with nephrogenic rests), four therapeutically aborted embryos (37 to 56 days), three fetuses on whom autopsies had been performed, and one neonate for expression of hTR. Proliferative index was measured by immunohistochemical staining for MIB1. In the embryonic kidney, Wilms tumors, and nephrogenic rests, the patterns of hTR expression were similar: expression was usually maximal within the immature epithelial elements followed by the poorly differentiated blastema, but was weak or absent in the immature stroma. Mature tubules, glomeruli, and stroma were negative for hTR expression, as were differentiated heterologous elements present in post-therapy Wilms tumors. There was only a partial relationship between proliferative index and hTR expression. In the embryonic kidney, Wilms tumors, and nephrogenic rests, blastema had the highest proliferative index, whereas the indices were significantly lower in the immature epithelium and stroma. The proliferative index in mature and heterologous elements was low or zero. Thus, the pattern of hTR expression in Wilms tumor and its precursor lesion recapitulates embryogenesis precisely and may represent that aspect of the persistent fetal phenotype which predisposes to the development of malignancy.

Child, Preschool↗

PubMed2005

Programmed cell death in plant embryogenesis.

Successful embryonic development in plants, as in animals, requires a strict coordination of cell proliferation, cell differentiation, and cell-death programs. The role of cell death is especially critical for the establishment of polarity at early stages of plant embryogenesis, when the differentiation of the temporary structure, the suspensor, is followed by its programmed elimination. Here, we review the emerging knowledge of this and other functions of programmed cell death during plant embryogenesis, as revealed by developmental analyses of Arabidopsis embryo-specific mutants and gymnosperm (spruce and pine) model embryonic systems. Cell biological studies in these model systems have helped to identify and order the cellular processes occurring during self-destruction of the embryonic cells. While metazoan embryos can recruit both apoptotic and autophagic cell deaths, the ultimate choice depending on the developmental task and conditions, plant embryos use autophagic cell disassembly as a single universal cell-death pathway. Dysregulation of this pathway leads to aberrant or arrested embryo development. We address the role of distinct cellular components in the execution of the autophagic cell death, and outline an overall mechanistic view of how cells are eliminated during plant embryonic pattern formation. Finally, we discuss the possible roles of some of the candidate plant cell-death proteins in the regulation of developmental cell death.

Apoptosis↗

PubMed1989

Generation of cell diversity during early embryogenesis in the nematode Caenorhabditis elegans.

Caenorhabditis elegans zygotes undergo a series of four differentiative divisions to generate 5 somatic founder cells and a germ-line progenitor cell by the 16- to 24-cell stage of embryogenesis. The pattern of divisions, cell positions, and development of the embryonic cells are invariant from embryo to embryo. Through a combination of embryo manipulation, treatment of embryos with pharmacologic agents, and genetic analysis of maternal-effect embryonic-lethal mutants, researchers in several laboratories have investigated when and how cell differences are generated and cell fates are specified during embryogenesis: 1. Most blastomeres develop in a cell-autonomous manner. They do not need to undergo cell division and they do not require their normal neighbors to express differentiation products characteristic of their lineage. In embryos in which specific cells have been ablated, the fates of neighboring cells do not change to compensate for the missing cells. These observations suggest that most embryonic cells are determined by lineally transmitted internally segregated information. 2. There is at least one clear-cut example of inductive interactions during early development. The anterior daughter of AB gives rise to hypodermis, neurons, pharyngeal muscles, and body wall muscles. Interactions between ABa cells and P1-derived blastomeres are required between the 4- and 28-cell stage for ABa to generate pharyngeal and body wall muscles. ABa appears to be directed to generate hypodermis by internally segregated cues and directed to generate muscle by external cues. 3. Certain of the early internal segregation events require the participation of microfilaments. Disruption of the microfilament array leads to the missegregation of germ granules and of the potential of cells to undergo unequal germ-line-like divisions. Microfilaments may be involved in many other segregation events as well. 4. Several maternal-effect lethal mutants also perturb zygotic segregation events. These par mutants, which divide symmetrically and fail to segregate germ granules, may identify genes whose products interact with microfilaments or otherwise participate in cytoplasmic localization during the early divisions.

Animals↗

PubMed1997

Distribution and functions of platelet-derived growth factors and their receptors during embryogenesis.

Platelet-derived growth factors (PDGFs) are soluble proteins that mediate intercellular signaling via receptor tyrosine kinases. The patterns of PDGF and PDGF receptor expression during embryogenesis are complex and dynamic and suggest that signaling can be autocrine or paracrine, depending on the particular tissue and the stage of development. Mesenchymal cells throughout the embryo and within some developing organs produce PDGF receptors, whereas their ligands are often produced by adjacent epithelial or endothelial cells. Disruption of PDGF signaling in the embryo leads to morphogenetic defects and embryonic or perinatal lethality. Tissues that are particularly susceptible to the absence of PDGF signaling are migrating mesoderm cells during gastrulation, nonneuronal neural crest cell derivatives, and kidney mesangial cells. These tissues share the common feature of undergoing epithelial-mesenchymal transitions. We review current knowledge of the distribution of PDGF ligands and receptors and discuss how this distribution may relate to several roles for PDGF during embryogenesis, particularly the regulation of mesenchymal cell behavior.

Animals↗

PubMed2003

Adverse effects of (surface water pollutants) Cd, Cr and Pb on the embryogenesis of the mallard.

The effects of chromium, lead and cadmium were studied on the embryogenesis, hatching success and viability of the mallard. Eggs were exposed to relatively low environmental concentrations that are characteristic to the level in polluted Hungarian surface waters. Eggs were treated by injection or immersion--prior to incubation. In study I, effects on early embryogenesis (first 10 days of incubation) were examined. Eggs were opened daily, mortality was determined and permanent slides of the embryos were made to help further external examinations. Each metal proved to be toxic to the developing mallard embryo, causing an increase in mortality and developmental anomalies. Chromium was the most teratogenic of the three heavy metals increasing the rate of malformations by 30% (P<0.001) after immersion, and 17% (P<0.01) after injection of the eggs. Cadmium proved to cause the highest rate of mortality. Embryonic death was increased by 27% (P<0.01) and 40% (P<0.001) after Cd immersion and injection, respectively. In study II, effects on hatching and viability of the ducklings were studied. The eggs were hatched, hatching and mortality rates were established, the liver of animals was histopathologically examined. However each heavy metal decreased hatching success, cadmium was found the most toxic compound, causing a 21% (P<0.01) and 47% (P<0.001) reduction in hatching success after immersion and injection, respectively. The liver of hatched ducklings showed significant lesions, dystrophy in the form of hepatic necrosis was detected in each treated animal. Each heavy metal (Cr, Pb, Cd) proved to have adverse effects on the embryonic development, hatching and viability of the mallard.

Analysis of Variance↗