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PubMed2006

Beta-catenin function is required for cerebellar morphogenesis.

Because of the failure to form embryonic mid-hindbrain structures in conventional Wnt1 knockout animals, ongoing roles for Wnt signaling at later stages have been difficult to resolve. Here, we used Nestin-cre to ablate beta-catenin at midgestation in developing CNS precursors to investigate beta-catenin-dependent Wnt signaling in the development of late-derived structures such as the cerebellum. At 14.5 dpc, we found evidence for premature neural precursor cell fate commitment. At P0, we observed vermian hypoplasia and failure to fuse the cerebellar hemispheres and caudal midbrain, a phenotype reminiscent of the swaying (Wnt1(sw/sw)) mouse mutant. Our findings indicate general functions for beta-catenin beyond the neural plate stage during brain development and a particular role for beta-catenin-dependent Wnt signaling during morphogenesis of the caudal midbrain and the cerebellum. We discuss our results with respect to genetic pathways that regulate formation of derivatives of the embryonic midbrain-hindbrain region.

Animals↗

PubMed1999

Development of immunocompetence of broiler chickens.

Subpopulations of T-cells, B-cells, macrophages and ellipsoid-associated reticular cells (EARC) could be demonstrated by immunohistochemical staining early in the development of chicken spleen. However, the typical structures of the spleen, such as the peri-arteriolar lymphoid sheath (PALS) and the ellipsoids with their surrounding ring of macrophages, were only formed around embryonic day (ED) 20. These structures and especially the B-cell compartment, i.e., the peri-ellipsoid lymphoid sheath (PELS) gradually matured during the first week posthatch. Therefore, we analysed at what age broiler chickens could generate a humoral response against the thymus-dependent antigen bovine serum albumin (BSA). Chickens were immunised in ovo (ED16 and ED18) and at 1, 7 and 12 days of age and subsequent BSA-specific immunoglobulin (Ig) M and IgG responses were measured up to 10 days postimmunisation (DPI). No major differences were observed in the relative growth rates, while hatchability was only slightly reduced. Only in chicks immunised on 12 days of age, IgM and IgG responses were high with a normal kinetic pattern. In chicks immunised on 7 days of age, responses were just detectable, but they were absent in chicks immunised in ovo and on the day of hatching (Day 1). In a subsequent experiment, 1-, 7- and 12-day-old chicks were BSA-immunised and Ig responses were measured for a longer period up to the age of 28 days. The IgG response of chicks immunised at 1 day of age was lower and occurred later (from 28 DPI) than the response of chicks immunised at 7 and 14 days of age (from 14 DPI). It was not increased by a booster immunisation on 29 days of age, in contrast to the response of chicks immunised at 7 and 14 days of age. These findings indicate that vaccination at 1 day of age does not activate the B-cell response resulting in antibody production and support the idea that the immune function of the late embryonic and neonatal chickens is not entirely developed due to the incomplete structural organisation of their secondary immune organs.

Aging↗

PubMed1991

In vivo and in vitro structure-dosimetry-activity relationships of substituted phenols in developmental toxicity assays.

Structure-dosimetry-activity relationships (SDARs) of a series of substituted phenols were evaluated following exposure of gestation day 11 rats in vivo and in comparable stage embryos in vitro. In the in vivo study, 27 congeners were assayed and log P (a term used synomously with lipophilicity in this paper) and Hammett sigma values (a measure of the electronic withdrawing ability of the substituent) were shown to correlate with maternal toxicity; however, no relationships between these parameters and developmental effects were observed. In the in vitro system, 13 congeners were evaluated and molar refractivity and/or lipophilicity were shown to correlate with the ability of the phenols to induce embryonic growth retardation and structural defects in the absence of the hepatocytes. In contrast, when a metabolic activating system (primary hepatocytes) was present in the in vitro system, the potential to induce growth retardation was inversely related to lipophilicity, although the relationships were weaker than the positive relationship seen without the hepatocytes. The binding of the phenols to macromolecules in the culture medium was highly correlated with log P. Correcting the in vitro potency data for the variable amount of binding improved the predictiveness of the quantitative structure-activity relationships (QSARs). The potential to induce embryotoxicity in vitro was not well correlated with the potential to induce developmental toxicity in vivo: whereas the in vitro data demonstrates that the phenols are intrinsically embryotoxic, few of them actually produced significant developmental toxicity in the in vivo system, and there were few positive correlations between effects observed in the two systems.(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormalities, Drug-Induced↗

PubMed1991

A multivariate analysis of cardiac growth in human embryos: endocardial cushions and ventricular myocardium.

STUDY OBJECTIVE: In view of the controversy about the morphological significance of the endocardial cushion tissue and ventricular myocardium during cardiac development, the aim was to carry out quantitative studies of these structures. DESIGN: Endocardial cushion tissue and ventricular myocardium were quantified by point count planimetry. The relative growth of the volume of these structures, and also the embryonic crown-rump length, was studied by multivariate allometry (principal components analysis) with the covariance matrix calculated from natural logarithms of the data. EXPERIMENTAL MATERIAL: 27 serially sectioned human embryos were studied, ranging from stage 15 to stage 23 (Paris collection). MEASUREMENTS AND MAIN RESULTS: The relative growth of endocardial cushion tissue, ventricular myocardium, and crown-rump length was discontinuous during the postsomitic period. The first component in principal components analysis measures overall size and, in the present analysis, accounts for 88.6% of the total variance. The growth vector isometry hypothesis was checked with the chi 2 test. This showed that differences in growth between cardiac structures and crown-rump length were allometric (p less than 0.01). Endocardial cushion tissue volume and crown-rump length grew with negative allometry during the second month of gestation, while ventricular myocardium volume grew with positive allometry. CONCLUSIONS: The results agree with those researchers who consider that endocardial cushion tissue functions only in causing initial cardiac fusion and partitioning, with little influence on the formation of definitive cardiac structures.

Heart↗

PubMed1985

The complete sequence of the chicken delta 1 crystallin gene and its 5' flanking region.

delta-Crystallin is the principal structural protein of the embryonic chicken lens. In the chicken, there are two linked delta-crystallin genes arranged in the same transcriptional polarity (5'-delta 1-delta 2-3'). Here we have sequenced the delta 1 crystallin gene and almost 4.3 kilobases of its 5' flanking region. The delta 1 gene is 7766 base pairs in length and has 17 exons. At least one lariat branch consensus sequence has been identified in each intron. Analysis of the deduced delta-crystallin protein using a program which accounts for conservative amino acid changes shows regions of similarity within the delta 1 amino acid sequence. These suggest a rough 2-fold repeat in the protein structure.

Amino Acid Sequence↗

PubMed1992

Dolichos biflorus agglutinin binding to intracranial germ-cell tumors: detection of embryonal components in germinomas.

Dolichos biflorus agglutinin (DBA) binding was examined in 32 cases of intracranial human germ-cell tumors. In embryonal carcinomas, intense DBA binding sites were found on the free surface and cytoplasm of embryonal cells. In teratomas, glandular structures often had positive DBA binding sites. Yolk sac carcinomas and choriocarcinomas showed negative DBA affinity. Of 19 cases of germinomas, 10 showed no DBA-positive cells, while sporadically and/or collectively distributed-DBA positive cells were found in the other 9 cases. Common brain tumors such as gliomas, neurinomas and meningiomas were negative for DBA staining. Considering the cellular carbohydrate structure, these findings suggest that DBA-positive cells in germinoma might be evidence of differentiation into embryonal or some somatic components. In addition, because of the absence of DBA binding sites in the common brain tumors, the identification of such binding sites in brain tumors might act as a marker for embryonal or somatic components, especially among germ-cell tumors.

Alkaline Phosphatase↗

PubMed1982

[The structure of the vitreous body in vivo and after fixation ].

The condensations of the vitreous consist of parallel, in some cases of horse's tail like structures of the vitreous body. These tractus according to their position are equivalent to the funnel shaped embryonic blood vessels which run from the optic disc to the ora serrata, and are thus determined by the embryonic development. The always parallel structures produced by the vitreous cells appear as multiple beginning and ending fibers. The reticular "fibers" appearing after fixation or equally well in liquefaction of the vitreous can be produced in the watery filtrate of the vitreous, for instance by addition of acetone. They might be regarded, therefore, mainly as fiberlike artificial precipitation products.

Adult↗

PubMed2002

The glycobiology of implantation.

Embryo implantation involves complex, coordinated interactions of cell surface components of embryonic (trophectoderm/trophoblast) and uterine cells. Oligosaccharides are common constituents of cell surface molecules. A variety of oligosaccharide structures have been identified at embryonic and uterine cell surfaces and change dynamically during progression of the implantation reaction. In many cases, the oligosaccharides have been shown to have biological activities with great relevance to the implantation process. This review summarizes the available information on glycoconjugates as it relates to the implantation process. It is suggested that carbohydrate bearing molecules at embryonic and uterine cell surfaces play diverse roles during the implantation process that are similar to the roles suggested for these molecules in other biological contexts.

Animals↗

PubMed2001

LEAFY COTYLEDON2 encodes a B3 domain transcription factor that induces embryo development.

The Arabidopsis LEAFY COTYLEDON2 (LEC2) gene is a central embryonic regulator that serves critical roles both early and late during embryo development. LEC2 is required for the maintenance of suspensor morphology, specification of cotyledon identity, progression through the maturation phase, and suppression of premature germination. We cloned the LEC2 gene on the basis of its chromosomal position and showed that the predicted polypeptide contains a B3 domain, a DNA-binding motif unique to plants that is characteristic of several transcription factors. We showed that LEC2 RNA accumulates primarily during seed development, consistent with our finding that LEC2 shares greatest similarity with the B3 domain transcription factors that act primarily in developing seeds, VIVIPAROUS1/ABA INSENSITIVE3 and FUSCA3. Ectopic, postembryonic expression of LEC2 in transgenic plants induces the formation of somatic embryos and other organ-like structures and often confers embryonic characteristics to seedlings. Together, these results suggest that LEC2 is a transcriptional regulator that establishes a cellular environment sufficient to initiate embryo development.

Amino Acid Sequence↗

PubMed1986

Spatial pattern of catalase (Cat2) gene activation in scutella during postgerminative development in maize.

The scutellum of maize is a fully differentiated, nondividing, diploid embryonic tissue. Two distinct structural genes (Cat1 and Cat2) encoding the enzyme catalase (CAT) are differentially expressed in this tissue during postgerminative development. As development proceeds, the expression of Cat1 diminishes, while that of Cat2 is enhanced, leading to the disappearance of the CAT-1 protein and the gradual accumulation of the CAT-2 protein. The present investigation was undertaken to determine whether all scutellar cells may be genetically programmed to activate expression of Cat2 synchronously or whether there is an asynchronous spatial gradient of Cat2 activation. By using immunofluorescence microscopy and anti-CAT-2 IgG, we have found that a gradient of Cat2 activation occurs within the scutellar cell mass during postgerminative development. The gradient of Cat2 activation occurs from the outer perimeter of the tissue inward toward the embryonic axis. To determine a potential site of origin for any putative "triggering signal" for Cat2 activation, we demonstrated that Cat2 is expressed in the single layer of aleurone cells prior to its expression in any other tissue during kernel development. To our knowledge, this is the first observation of a gradient-type spatial pattern of a eukaryote gene activation occurring in a stable, virtually nondividing tissue such as the maize scutellum. The significance of these results with respect to developmental gene regulation is discussed.

Catalase↗

PubMed2004

Stem-cell-based tissue engineering of murine teeth.

Teeth develop from reciprocal interactions between mesenchyme cells and epithelium, where the epithelium provides the instructive information for initiation. Based on these initial tissue interactions, we have replaced the mesenchyme cells with mesenchyme created by aggregation of cultured non-dental stem cells in mice. Recombinations between non-dental cell-derived mesenchyme and embryonic oral epithelium stimulate an odontogenic response in the stem cells. Embryonic stem cells, neural stem cells, and adult bone-marrow-derived cells all responded by expressing odontogenic genes. Transfer of recombinations into adult renal capsules resulted in the development of tooth structures and associated bone. Moreover, transfer of embryonic tooth primordia into the adult jaw resulted in development of tooth structures, showing that an embryonic primordium can develop in its adult environment. These results thus provide a significant advance toward the creation of artificial embryonic tooth primordia from cultured cells that can be used to replace missing teeth following transplantation into the adult mouth.

3T3 Cells↗

PubMed1987

Neurotomes and birth defects: a neuroanatomic method of interpretation of multiple congenital malformations.

It has been suggested that complexes of multiple congenital malformations, involving limbs and viscera, may be caused by embryonic neural crest injury. Structures supplied by the sensory and autonomic nerves derived from the injured zone of crest would suffer defective development through presumed impairment of neurotrophic influence. Our study aimed to examine this concept by a retrospective analysis of autopsy findings in 27 babies who died of multiple congenital malformations associated with longitudinal limb defects. Sclerotome maps of the segmental sensory innervation of the skeleton were used to analyse the limb defects in terms of their nerve supply. From a review of the literature, the approximate segmental contribution of neural crest to the autonomic innervation of internal organs was ascertained, and thus "viscerotome" diagrams were constructed. Application of sclerotomes and viscerotomes to the data derived from the autopsy reports showed a neuroanatomic correlation in 89% of cases. Interpretation of multiple malformation syndromes is proposed on the basis of neurotomes, or embryonic developmental fields with common regional innervation.

Abnormalities, Multiple↗

PubMed1987

Mutants of embryonal carcinoma cells defective in the expression of embryoglycan.

Embryonal carcinoma cells defective in the expression of developmentally regulated carbohydrate epitope of teratocarcinoma cells (TEC-1) were isolated from mutagenized P19X1 and P19S1801A1 cells by a single-step selection technique using monoclonal antibody TEC-01 conjugated to plant toxin ricin. Three independently isolated mutant cell lines were characterized in detail. Analysis of the expression of the TEC-1 epitope in somatic cell hybrids constructed between wild-type and mutant cells and between two mutant cell types revealed that the mutant phenotypes are recessive and that the mutants belong to, at least, two complementation groups. Each mutant cell line exhibited a unique binding pattern of four monoclonal antibodies and five lectins, and different properties of large glycopeptides were distinguished by Sephadex G-50 column chromatography. The combined data suggest that our mutants identify three genes involved in the synthesis of embryoglycan, one of which appears to be the regulatory or structural gene for fucosyltransferase. One mutant cell line was completely deprived of embryoglycan and several carbohydrate structures typical of early embryonic and embryonal carcinoma cells; however, the cells were similar to parental cells in their morphology, their ability to form aggregates when cultured in suspension, their ability to differentiate into neuron-like cells after treatment with retinoic acid, and their ability to form tumors composed of embryonal carcinoma cells. Thus, embryoglycan is not required for the expression of a number of properties of the embryonal carcinoma phenotype.

Animals↗

PubMed1988

[Variants of pathological immaturity of the placenta and their role in fetal development].

Morphologic evaluation of 125 placentas in various pregnancy and neonatal disturbances versus 46 normal placentas of different gestation provided the basis for recognition of 4 basic variants of the villous tree immaturity. Variant I is marked by embryonal villi close in structure to the villi of normal placentas (8-12 weeks gestation). Variant II presents intermediate immature and mature branches demonstrating the morphology of mean-caliber placental villi (13-28 weeks gestation). Variant III involves irregular sclerosed villi (23-24 weeks gestation). These variants are concerned with pathologic placental immaturity. There is also another variant which is confirmed by the evidence gained and can be related to a borderline condition between health and pathology--dissociated placentation. A favourable neonatal prognosis depends on a large amount of terminal special villi and compensatory placental angiomatosis.

Abortion, Spontaneous↗

PubMed1999

A role for the extraembryonic yolk syncytial layer in patterning the zebrafish embryo suggested by properties of the hex gene.

Recent studies in mouse suggest that the extraembryonic endoderm has an important role in early embryonic patterning [1]. To analyze whether similar mechanisms operate in other vertebrates, we cloned the zebrafish homologue of Hex, a homeobox gene that is expressed asymmetrically in the mouse visceral endoderm [2]. Early expression of zebrafish hex is restricted to the dorsal portion of the yolk syncytial layer (YSL), an extraembryonic tissue. By the onset of gastrulation, hex is expressed in the entire dorsal half of the YSL, which directly underlies the cells fated to form the neural plate. We show that hex expression is initially regulated by the maternal Wnt pathway and later by a Bmp-mediated pathway. Overexpression experiments of wild-type and chimeric Hex constructs indicate that Hex functions as a transcriptional repressor and its overexpression led to the downregulation of bmp2b and wnt8 expression and the expansion of chordin expression. These findings provide further evidence that the zebrafish YSL is the functional equivalent of the mouse visceral endoderm and that extraembryonic structures may regulate early embryonic patterning in many vertebrates.

Animals↗

PubMed1998

The nature of the 'nucleolus precursor body' in early preimplantation embryos: a review of fine-structure cytochemical, immunocytochemical and autoradiographic data related to nucleolar function.

In mammals, the restoration of rRNA transcription after fertilisation is accompanied by a gradual differentiation of the nucleolar structure by a process called embryonic nucleogenesis. During cleavage, the nucleolar components appear sterically related to a class of nuclear bodies already detectable in pronuclei. These structures, due to their apparent function as centres of nucleolus formation, have been designated nucleolus precursor bodies (NPBs). It was found recently not only that the size and morphology of the NPBs differ among mammalian species, but that the pattern of embryonic nucleologenesis and even the molecular composition of different NPB compartments vary from one species to another. Accordingly we assumed that at least two definitely different types of NPBs exist, namely the mouse-type NPB and cow-type NPB. In the mouse-type NPB, the original compact material of the NPB remains detectable in the early functional nucleolus. This NPB core does not contain DNA or typical Ag-NOR nucleolar proteins. At the onset of rRNA transcription, the nucleolonema is formed at the periphery of the NPB. The cow-type NPB shows a homogeneous distribution of typical nucleolar proteins throughout its body from the pronucleolar to the early 8-cell stage. At the beginning of rRNA transcription, the cow-type NPB is penetrated by perinucleolar DNA and rRNA synthesis is detectable deep inside the nucleolus. In this case, the entire NPB is readily transformed into a typical nucleolus. These processes are recognisable using fine-structure analysis of preimplantation mammalian embryos. For this reason this approach is often used as a method of evaluating the state of experimental embryos; in such studies, the species differences must be taken into account.

Animals↗

PubMed2003

The keratocan gene is expressed in both ocular and non-ocular tissues during early chick development.

Extracellular matrix (ECM) keratan sulfate proteoglycans (KSPGs) are core proteins with sulfated polylactosamine side chains (KS). The KSPG core protein keratocan gene (Kera) is expressed almost exclusively in adult vertebrate cornea, but its embryonic expression is little known. Embryonic chick in situ hybridization reveals Kera mRNA expression in corneal endothelium from embryonic day (E) 4.5, Hamburger-Hamilton (HH) 25, in stromal keratocytes from E6.5, HH30, and in iris distal surface cells from E8, HH34. As highly sulfated, antibody I22-positive KS increases extracellularly from posterior to anterior across the stroma, nerves enter and populate only anterior stroma and epithelium. RT-PCR and in situ hybridization demonstrate that developmentally regulated Kera mRNA expression initiates in midbrain and dorsolateral mesenchyme at E1, HH7, then spreads caudally in hindbrain and cranial and trunk mesenchyme flanking the neural tube through E2, HH20. Cranial expression extends ventrally through the developing head, and concentrates in mesenchyme surrounding eye anterior regions and cranial ganglia, and in subepidermal pharyngeal arch mesenchyme by E3.5, HH22. Kera expression in the trunk at E3.5, HH22 and E4.5, HH25, is strong in dorsolateral subepidermal, sclerotomal and nephrogenic mesenchymes, but absent in neural tube, dorsal root ganglia, nerve outgrowths, notochord, heart and gut. Early limb buds express Kera mRNA throughout their mesenchyme, then in restricted proximal and distal mesenchymes. I22-positive KS appears only in notochord in E3.5, HH22 and E4.5, HH25, embryos. Results suggest the hypothesis that keratocan, or keratocan with minimally sulfated KS chains, may play a role in structuring ECM for early embryonic cell and neuronal migrations.

Amino Acid Sequence↗

PubMed1993

A role for regulated secretion of apical extracellular matrix during epithelial invagination in the sea urchin.

Epithelial invagination, a basic morphogenetic process reiterated throughout embryonic development, generates tubular structures such as the neural tube, or pit-like structures such as the optic cup. The 'purse-string' hypothesis, which proposes that circumferential bands of actin microfilaments at the apical end of epithelial cells constrict to yield a curved epithelial sheet, has been widely invoked to explain invaginations during embryogenesis. We have reevaluated this hypothesis in two species of sea urchin by examining both natural invagination of the vegetal plate at the beginning of gastrulation and invagination induced precociously by Ca2+ ionophore. Neither type of invagination is prevented by cytochalasin D. In one species, treatment with A23187 three hours before the initiation of invagination resulted in the deposition of apical extracellular matrix at the vegetal plate, rather than invagination. This apical matrix contains chondroitin sulfate, as does the lumen of the archenteron in normal gastrulae. When the expansion of this secreted matrix was resisted by an agarose gel, the vegetal plate buckled inward, creating an archenteron that appeared 3-4 hours prematurely. Pretreatment with monensin, which blocks secretion, inhibits both Ca2+ ionophore-stimulated folding and natural invagination, demonstrating that secretion is probably required for this morphogenetic event. These results indicate that alternatives to the purse-string hypothesis must be considered, and that the directed deposition of extracellular matrix may be a key Ca(2+)-regulated event in some embryonic invaginations. A bending bilayer model for matrix-driven epithelial invagination is proposed in which the deposition of hygroscopic material into a complex, stratified extra-cellular matrix results in the folding of an epithelial sheet in a manner analagous to thermal bending in a bimetallic strip.

Animals↗