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PubMed2001

Expression of evolutionarily conserved eye specification genes during Drosophila embryogenesis.

Eye specification in Drosophila is thought be controlled by a set of seven nuclear factors that includes the Pax6 homolog, Eyeless. This group of genes is conserved throughout evolution and has been repeatedly recruited for eye specification. Several of these genes are expressed within the developing eyes of vertebrates and mutations in several mouse and human orthologs are the underlying causes of retinal disease syndromes. Ectopic expression in Drosophila of any one of these genes is capable of inducing retinal development, while loss-of-function mutations delete the developing eye. These nuclear factors comprise a complex regulatory network and it is thought that their combined activities are required for the formation of the eye. We examined the expression patterns of four eye specification genes, eyeless (ey), sine oculis (so), eyes absent (eya), and dachshund (dac) throughout all time points of embryogenesis and show that only eyeless is expressed within the embryonic eye anlagen. This is consistent with a recently proposed model in which the eye primordium acquires its competence to become retinal tissue over several time points of development. We also compare the expression of Ey with that of a putative antennal specifying gene Distal-less (Dll). The expression patterns described here are quite intriguing and raise the possibility that these genes have even earlier and wide ranging roles in establishing the head and visual field.

Animals↗

PubMed2003

Major components of the insulin-like growth factor axis are expressed early in chicken embryogenesis, with IGF binding protein ( IGFBP) -5 expression subject to regulation by Sonic Hedgehog.

Using whole-mount in situ hybridisation techniques, we have examined the expression of major components of the insulin-like growth factor (IGF) axis in early development of the chicken embryo, including both IGF-I and -II, the type 1 IGF receptor ( IGFR), and two of the IGF binding proteins, ( IGFBP) -2 and -5. We report that these genes fall into two distinct groups with respect to expression pattern, with IGFBP-2 displaying broad overlap of mRNA expression with IGFR and IGF-I during early development, whereas the expression profile of IGFBP-5 most closely resembled that of IGF-II. Comparison between different stages revealed IGFBP-2 mRNA was detected as early as stage 3, whereas IGFBP-5 was first seen at stage 4. In addition, we detected expression domains of IGFBP-5, and to a lesser extent IGFBP-2, which did not overlap with either IGFR or IGF expression patterns. This could indicate IGF independent actions of the IGFBPs during early embryonic development. A striking observation concerning the expression profiles of both IGF-II and IGFBP-5 at early stages of chick embryogenesis is that both these genes are expressed asymmetrically in a pattern similar to that of Sonic Hedgehog (Shh). Furthermore, using cyclopamine, we have demonstrated that IGFBP-5 expression in the early embryo is regulated by Shh. Taken together, these results describe an important role for the IGF system in the very early stages of the developing chicken embryo, and imply that IGFBP-2 and -5 are fundamental developmental factors, with the latter involved in Shh signalling pathways.

Animals↗

PubMed2005

Expression pattern of cytosolic glutathione peroxidase (cGPx) mRNA during mouse embryogenesis.

The selenoprotein cytosolic glutathione peroxidase (cGPx) is ubiquitously distributed in a variety of organs, and its primary function is to protect oxidative damage. To investigate the spatial and temporal expression pattern of cGPx mRNA in embryogenesis, as this has not been studied before, reverse transcription-polymerase chain reaction (RT-PCR) was carried out in a thermal cycler using mouse-specific cGPx primers, and in situ hybridization was performed in whole embryos or embryonic tissues using digoxigenin-labeled mouse cGPx riboprobes. Expression of cGPx mRNA was detected in all the embryos retrieved from embryonic days (EDs) 7.5 to 18.5. On EDs 10.5-12.5, cGPx mRNA was highly expressed in the margin of forelimb and hindlimb buds and dorsally in the cranial neural tube, including the telencephalon, diencephalon, and hindbrain neural tube. On ED 13.5, cGPx mRNA was accumulated especially in vibrissae, forelimb and hindlimb plates, tail, and spinal cord. On EDs 14.5-16.5, cGPx mRNA was found in the developing brain, Rathke's pouch, thymus, lung, and liver. On ED 17.5, the expression of cGPx mRNA was apparent in various tissues such as brain, submandibular gland, vibrissae, heart, lung, liver, stomach, intestine, pancreas, skin, and kidney. In particular, cGPx mRNA was greatly expressed in epithelial linings and metabolically active sites such as whisker follicles, alveolar epithelium of lung, surface epithelium and glandular region of stomach, skin epithelium, and cortex and tubules of kidney. Overall results indicate that cGPx mRNA is expressed in developing embryos, cell-specifically and tissue-specifically, suggesting that cGPx may function to protect the embryo against reactive oxygen species and/or hydroperoxides massively produced by the intracellular or extracellular environment.

Animals↗

PubMed2002

Involvement of Toll-like receptor 4 in the embryogenesis of the rodent filaria Litomosoides sigmodontis.

To examine the role that lipopolysaccharide (LPS)-like molecules from the filarial intracellular endobacteria Wolbachia might play in the development of filarial infections, a natural infection in the LPS-nonresponsive C3H/HeJ mouse strain was compared to that of the LPS-responsive C3H/HeN mouse strain. C3H/HeN mice have been shown to be susceptible to the rodent filarial nematode Litomosoides sigmodontis, with the development of adult worms including females containing mature microfilariae (first stage larvae) in the uterine tubes. However, free microfilariae are not detected. In this study the worm burden and worm length were not significantly different between the C3H/HeN and C3H/HeJ mice. However, the fertility of worms from CeH/HeJ mice was found to be higher than those from C3H/HeN mice. Significantly, mature microfilariae were found at the site of infection only in C3H/HeJ mice. These results indicate a role for TLR4 signaling in the immune response that inhibits worm embryogenesis and prevents the release of microfilariae or directly kills released microfilariae.

Animals↗

PubMed2004

Morphohistological analysis and histochemistry of Feijoa sellowiana somatic embryogenesis.

Morphohistological analysis and histochemical studies were carried out during the induction and development of Feijoa sellowiana somatic embryos. Zygotic embryos were cultured on LPm medium containing 2,4-dichlorophenoxyacetic acid (20 microM) and glutamine (8 mM). Somatic embryogenesis could be induced from embryogenic cells that originated in meristematic centers or from clusters of cells. The presence of few starch grains and abundant protein bodies was observed in the globular and early torpedo stages, while in torpedo and cotyledonary-stage somatic embryos an enhanced synthesis of starch grains was associated with the accumulation of reserves to be used in the conversion of the embryos to plantlets. Proteins were predominantly observed in protoderm cells, as well as in the meristematic apical region of torpedo and cotyledonary-stage somatic embryos.

Feijoa↗

PubMed2002

Central nervous system embryogenesis and its failures.

The well-orchestrated development of the central nervous system (CNS) requires highly integrated regulatory processes to ensure its precise spatial organization that provides the foundation for proper function. As emphasized in this review, the type, timing, and location of regulatory molecules influence the different stages of development from neuronal induction, regional specification, neuronal specification, and neuronal migration to axonal growth and guidance, neuronal survival, and synapse formation. The known molecular mechanisms are summarized from studies of invertebrates and lower vertebrates, in which we have learned more about the different ligands, receptors, transcription factors, and the intracellular signaling pathways that play specific roles in the different stages of development. Despite known molecular mechanisms of some disturbances, most of the clinical entities that arise from failures of CNS embryogenesis remain unexplained. As more novel genes and their functions are discovered, existing mechanisms will be refined and tenable explanations will be made. With these limitations, two specific clinical entities that have been relatively well studied, holoprosencephaly and neuronal migration defects, are discussed in more detail to illustrate the complexity of regulatory mechanisms that govern well-defined stages of CNS development.

Animals↗

PubMed1992

Modulation of calmodulin levels, calmodulin methylation, and calmodulin binding proteins during carrot cell growth and embryogenesis.

Carrot cell cultures were used to study the dynamics of calmodulin protein levels, calmodulin methylation, and calmodulin-binding proteins during plant growth and development. Comparisons of proliferating and nonproliferating wild carrot cells show that, while calmodulin protein levels does not vary significantly, substantial variation in post-translational methylation of calmodulin on lysine-115 is observed. Calmodulin methylation is low during the lag and early exponential stages, but increases substantially as exponential growth proceeds and becomes maximal in the postexponential phase. Unmethylated calmodulin quickly reappears within 12 h of reinoculation of cells into fresh media, suggesting that the process is regulated according to the cell growth state. Calmodulin and calmodulin-binding proteins were also analyzed during the formation and germination of domestic carrot embryos in culture. Neither calmodulin methylation nor calmodulin protein levels varied significantly during somatic embryogenesis. However, upon germination of embryos, the level of calmodulin protein doubled. By calmodulin overlay analysis, we have detected a major 54,000 M(r) calmodulin-binding protein that also increased during embryo germination. This protein was purified from carrot embryo extracts by calmodulin-Sepharose chromatography. Overall, the data suggest that calmodulin methylation is regulated depending upon the state of cell growth and that calmodulin and its target proteins are modulated during early plant development.

Calmodulin↗

PubMed1989

A role of carbohydrate-carbohydrate interaction in the process of specific cell recognition during embryogenesis and organogenesis: a preliminary note.

A possible role of cell surface glycoconjugates in cell recognition has been envisioned based on recognition of carbohydrates by cell surface proteins such as endogenous lectins, glycosyltransferases, and hydrolases (refs. 18-22 in text). A new possibility that a specific carbohydrate at the cell surface could be recognized by the same or similar carbohydrate on the counterpart cell surface is now suggested by specific interaction between Lex and Lex, but not between Lex and sialylated or non-substituted type 2 chain. A new hypothesis is hereby proposed for carbohydrate-carbohydrate interactions as recognition signals during embryogenesis and organogenesis.

Antigens, Surface↗

PubMed1991

Activin receptor mRNA is expressed early in Xenopus embryogenesis and the level of the expression affects the body axis formation.

Activin is a member of the transforming growth factor beta (TGF-beta) and possesses various activities in cellular control phenomena. During Xenopus embryonic development, activin is thought to act as a natural mesoderm-inducing factor. We isolated here the Xenopus activin receptor cDNA from Xenopus tadpole cDNA library and examined the expression of the Xenopus activin receptor gene during the course of early embryonic development. The Xenopus activin receptor has an 87% homology at the level of deduced amino acid sequence with the mouse activin receptor, and using the cDNA obtained, three bands of mRNA with different lengths were detected in Xenopus embryos throughout early embryogenesis. We synthesized activin receptor mRNA in vitro and tested the effect of the injection of the mRNA into Xenopus fertilized eggs on subsequent development. When the synthetic mRNA was injected into uncleaved fertilized eggs, embryos with reduced trunk structure were formed. However, when the mRNA was injected into the ventral blastomeres at the 16-cell stage, embryos with a secondary body axis were formed. These results indicate the importance of the function of activin receptor in the regulatory mechanism for body axis formation.

Activin Receptors↗

PubMed1983

Immunohistochemical localization of two monoclonal antibody-defined carbohydrate antigens during early murine embryogenesis.

Monoclonal antibodies designated "C6" and "A5" identify cell surface carbohydrates shared by embryonal carcinoma cells and early mouse embryos. The binding of both antibodies to F9 embryonal carcinoma cells was inhibited by N-acetyllactosamine. While antibody C6 did not agglutinate human erythrocytes, antibody A5 agglutinated adult, but not fetal, erythrocytes of both type A and O, suggesting partial specificity for branched polylactosamine structures. Antibodies C6 and A5 did not label preimplantation stage embryos; however, labeling with both antibodies was observed following treatment of embryos with neuraminidase. In paraffin sections of postimplantation stage embryos, C6 and A5 exhibited similar yet distinct patterns of labeling, restricted primarily to the luminal surfaces of ectodermal and visceral endodermal epithelia. Neuraminidase treatment was found to expose additional patterns of C6 and A5 labeling within the ectoderm and mesoderm of the postimplantation embryo, not restricted to periluminal surfaces. These results suggest that cell surface carbohydrates are modified during early embryogenesis, in part, by selective patterns of sialylation.

Animals↗

PubMed1986

Ammonium ion as a possible regulator of the commencement of rRNA synthesis in Xenopus laevis embryogenesis.

Recently, we have shown that ammonium salts and amines at an external concentration of 3 mM selectively inhibit rRNA synthesis in Xenopus disaggregated neurula cells. We studied here the change in the amount of ammonia within the embryo and its inhibitory action on the commencement of rRNA synthesis which normally occurs at the blastula stage of development. Ammonia exists at ca. 50 ng/egg (or ca. 3.0 mM at an intra-egg concentration) in the unfertilized egg. This level was maintained during cleavage and then sharply decreased during the blastula stage to the level of ca. 20 ng/embryo (or 1.2 mM) in postblastular stages. Ammonia was extracted from cleavage embryos in a form of ammonium chloride and confirmed to selectively inhibit rRNA synthesis in neurula cells. With authentic ammonium chloride, ammonia was found to be promptly incorporated into cells and to inhibit rRNA synthesis within 1 hr after treatment. In blastula cells, ammonium salts reversibly inhibited the commencement of the synthesis of rRNA, but not hnRNA, 5 S RNA and U1, U2, and U5 snRNAs. The inhibition was at the step of transcription of 40 S pre-rRNA but not the processing or degradation of the processed rRNA. Ammonium salts did not inhibit DNA synthesis, protein synthesis, cell division, and cellular reaggregation. These observations suggest that ammonium ion may be involved in the regulation of the commencement of rRNA synthesis in Xenopus embryogenesis, although it is not yet clear if the ammonium ion exerts its effect directly upon the rDNA transcription system.

Ammonium Chloride↗

PubMed1986

Translational activation of maternal mRNA encoding the heat-shock protein hsp90 during sea urchin embryogenesis.

Changes in protein synthesis induced by heat shock of Strongylocentrotus purpuratus gastrulae were analyzed bt two-dimensional electrophoresis. Hyperthermia induces the synthesis of polypeptides having molecular masses of 90, 70, 50, 40, and 38 kDa. One of these, hsp90, appears as a pair of polypeptides which comigrates with proteins synthesized at normal temperature in eggs and embryos; these comigrating spots produce indistinguishable patterns upon electrophoretic analysis of partial V8 protease digests, indicating that hsp90 is synthesized throughout embryogenesis. The relative rate of incorporation of methionine into hsp90 is low in eggs and zygotes, but increases abruptly in morulae, constituting a rare and striking change in protein synthesis during early development. Cell-free translation analyses indicate that most of the mRNA encoding hsp90 resides in the pool of free ribonucleoprotein particles in eggs and early embryos, but shifts to polysomes by the 64-cell stage while remaining constant in mass. Thus the increase in synthesis of hsp90 appears to be via the selective activation of translation of a stored maternal mRNA. The shift of hsp90 mRNA to polysomes is accompanied by polyadenylation. Heat shock of eggs or zygotes did not result in translational activation of hsp90 mRNA. The sea urchin hsp90 doublet of spots comigrates with hsp90 induced by heat shock of chicken embryo fibroblasts, a conserved protein abundant in many cells of a variety of species.

Animals↗

PubMed1986

Coordinate expression of X and Y haptens during murine embryogenesis.

The X hapten (Gal beta 1----4[Fuc alpha 1----3]GlcNAc) may play an important role in the adhesion of blastomeres during compaction. Therefore, we have investigated more thoroughly developmental changes in the fucosylation of lactoseries carbohydrate chains and the enzymatic basis of these fucosylation changes using well-characterized monoclonal antibodies. The Y hapten (Fuc alpha 1----2Gal beta 1----4[Fuc alpha 1----3]GlcNAc) and polymeric X haptens were detected by fluorescence-activated flow cytometry on murine embryonal carcinoma cells. In paraffin sections of postimplantation mouse embryos, the Y hapten was detected in the embryonic ectoderm and visceral endoderm on Days 5.5-7.5; this pattern of antigen expression is identical to that previously reported for the X hapten (SSEA-1). Thus, the Gal:alpha 1----2 (H) and GlcNAc:alpha 1----3 (X) fucosyltransferases appear to be co-regulated during embryogenesis. Reciprocal changes in X and Y hapten expression were observed, however, during preimplantation development. Unlike the X hapten, the Y hapten is expressed maximally on 16-cell morulae and 32- to 64-cell blastocysts. Eight-cell embryos cultured to the blastocyst stage in vitro did not acquire the Y hapten, however, suggesting a role for the uterine environment in carbohydrate antigen expression. Homogenates of F9 embryonal carcinoma cells were found to possess a potent GlcNAc:alpha 1----3 fucosyltransferase activity, as well as a weaker Gal:alpha 1----2 fucosyltransferase activity, using paragloboside as a substrate. The results suggest that embryonic cell surface carbohydrate phenotypes represent a balance in the competition between glycosyltransferases for available substrates. Rapid changes in carbohydrate expression during development may reflect intermediate states of cellular commitment and determination that are critical for lineage formation and morphogenesis.

Animals↗

PubMed1986

Spectrin in mouse gametogenesis and embryogenesis.

Antibodies to nonerythroid alpha spectrin (p 230) were used to study the distribution of this polypeptide in mouse germ cells, zygote, and early embryonic cells. In the primordial germ cells, fetal oocytes, and spermatogonia, spectrin was found predominantly in the form of a narrow condensed subplasmalemmal band, as in all other somatic cells. During spermatogenesis, spectrin is condensed into the supraacrosomal cytoplasm and is lost during the reduction of the cytoplasm of the maturing spermatozoa. The postnatal growth of the oocyte is accompanied by a loss of the dense cortical band of spectrin and its redistribution in the cytoplasm. Zygotes also contain granular dispersed spectrin. Cortical condensation of spectrin filaments gradually reappears in the blastomeres at the two-cell stage and in the secondary polar body. Cortically condensed filaments represent thereafter the predominant form of spectrin in all preimplantation stage embryonic cells. Trophoblastic cells spreading out from explanted blastocysts are devoid of the cortically condensed spectrin and contain, instead, spectrin arrays in the cytoplasm. Trophoblastic cells, which surround the implanted embryo in vivo, also show diffuse cytoplasmic spectrin which subsequently undergoes subplasmalemmal condensation. These data show that spectrin is present in all stages of gametogenesis and embryogenesis, except in mature spermatozoa; and that it undergoes cytoplasmic redistribution during morphogenesis.

Animals↗

PubMed1987

Cell-lineage-specific expression of the mouse hsp68 gene during embryogenesis.

Transcription of the mouse hsp68 and hsc70 genes in embryonal carcinoma cells, various embryonic and extraembryonic tissues, and some adult tissues has been assessed using cloned probes to the mouse hsp68 gene. The results from Northern blots showed that both F9 and P19 cells respond in the expected manner to a heat shock. Hsp68 expression was only detected in heat-induced F9 and P19 cells. Hsc70 transcripts were present in uninduced cells and their levels increased after induction. In adult tissues, the hsp68 gene was expressed constitutively in the kidney. A different hsp68-like transcript was detected at significant levels in adult testes. Constitutive expression of hsp68 was observed in both the placenta (beginning at Day 8.5) and yolk sac (beginning at Day 11.5). No hsp68 expression was detected in embryonic tissues until Day 15.5. Expression of the mouse hsp68 gene during embryogenesis suggests that it may play some role in development.

Animals↗

PubMed1987

Expression of epidermis-specific antigens during embryogenesis of the ascidian, Halocynthia roretzi.

We have produced two monoclonal antibodies (Epi-1 and Epi-2) which specifically recognize epidermal cells and their derivative, the larval tunic, of developing embryos of the ascidian Halocynthia roretzi. The antigens, examined by indirect immunofluorescence staining, first appear at the early tailbud stage and are present until at least the swimming larval stage. There were distinct and separate puromycin and actinomycin D sensitivity periods for each antigen. Aphidicolin, a specific inhibitor of DNA synthesis, prevented the appearance of each antigen when embryos were exposed to the drug continuously from cleavage stages. These results suggest that the antigens are synthesized during embryogenesis by developing epidermal cells and that several rounds of DNA replication are required for the antigen expression. Early cleavage stage embryos, including fertilized but unsegmented eggs, in which cytokinesis had been blocked with cytochalasin B expressed the antigens, and blastomeres exhibiting the antigens were always of the epidermis lineage. In partial embryos produced by four separated blastomere pairs of the 8-cell embryos, the expression of antigens was seen only in those developed from the animal blastomere pairs, which are progenitors of epidermal cells. These observations indicate that differentiation of epidermal cells in ascidian embryos takes place in a typical "mosaic" fashion.

Animals↗

PubMed1987

Expression of the murine homeo box gene Hox 1.5 during embryogenesis.

The spatial pattern of expression of the murine homeo box-containing gene Hox 1.5 was studied during embryogenesis. In situ hybridization of single-stranded RNA probes to mouse embryo sections revealed a specific spatial distribution of the Hox 1.5 transcripts in mouse embryos 8.5 to 12.5 days postcoitum (p.c.). Analysis of mouse embryos 8.5 days p.c. showed that the gene is expressed in a spatially restricted manner. Expression appears to be limited to the central nervous system with an anterior boundary in the hindbrain and extending posteriorly through caudal regions of the spinal cord. The same spatial pattern of expression was observed in embryos 9.5 to 12.5 days p.c. These results show that the murine Hox 1.5 gene is expressed in a spatially restricted manner during embryonic development similar to the patterns observed in Drosophila homeotic genes.

Animals↗

PubMed1988

Accumulation and decay of DG42 gene products follow a gradient pattern during Xenopus embryogenesis.

The DG42 gene is expressed during a short window during embryogenesis of Xenopus laevis. The mRNA for this gene can be first detected just after midblastula, peaks at late gastrula, and decays by the end of neurulation. The sequence of the DG42 cDNA and genomic DNA predicts a 70,000-Da protein that is not related to any other known protein. Antibodies prepared against portions of the DG42 open reading frame that had been expressed in bacteria detected a 70,000-Da protein in the embryo with a temporal course of appearance and decay that follows that of the RNA by several hours. Localization of the mRNA in dissected embryos and immunohistochemical detection of the protein showed that DG42 expression moves as a wave or gradient through the embryo. The RNA is first detected in the animal region of the blastula, and by early gastrula is found everywhere except in the outer layer of the dorsal blastopore lip. By midgastrula DG42 protein is present in the inner ectodermal layer and the endoderm; it disappears from dorsal ectoderm as the neural plate is induced and later decays in a dorsoventral direction. The last remnants of DG42 protein are seen in ventral regions of the gut at the tailbud stage.

Animals↗