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PubMed1997

Assessment of embryonic anatomy at 6-8 weeks of gestation by intrauterine and transvaginal sonography.

Our purpose was to compare the ultrasound visualization of the early first-trimester embryo using transvaginal and intrauterine sonography. In all, 32 women about to undergo therapeutic abortion at 6-8.9 weeks gestation were studied using a specially developed catheter-based, high-resolution, real-time miniature (2.4 mm outer diameter) ultrasonography transducer (20 MHz). Before the intrauterine sonographic procedure was performed, transvaginal sonographic assessment of the embryo was conducted. The parameters evaluated included the ability to visualize anatomical structures and a subjective assessment of the overall image clarity. The ability to view most organs was better with intrauterine sonography compared to transvaginal sonography, and this was especially true for the brain, spine, heart, liver, midgut herniation, extremities, and sacral tail. Moreover, it was possible to obtain finer image quality of very small embryonic structures with intrauterine sonography than with transvaginal sonography. Stomach, spleen, kidney, and bladder could not be depicted with both techniques. One cystic hygroma was diagnosed at 7 weeks 6 days using intrauterine sonography, but not with transvaginal sonography. Intrauterine sonography may provide additional information on the visualization of anatomical structures of the embryo in the early first trimester of pregnancy. In this limited series, one case of cystic hygroma was demonstrated and, thus, there is a potential for its use in the early detection of embryonic malformation. These results suggest that intrauterine sonography may be a valuable tool in imaging the early first-trimester embryo, complementing and not replacing transvaginal sonography in high-risk pregnancies.

Congenital Abnormalities↗
PubMed2006

Molecular genetic cascades for external genitalia formation: an emerging organogenesis program.

External genitalia are anatomical structures located at the posterior embryonic region as part of several urogenital/reproductive organs. The embryonic anlage of the external genitalia, the genital tubercle (GT) develops as a bud-shaped structure with an initial urethral plate and later urethra. Embryonic external genitalia are considered to be one of the appendages. Recent experiments suggest that essential regulatory genes possess similar functions for the outgrowth regulation of the GT and limb appendages. The transient embryonic epithelia located in the distal GT are called the distal urethral epithelium (DUE) regulating, at least in part, the (distal) GT development. This review covers the available data about early patterning of GT and discusses the molecular developmental similarities and points of divergence between the different appendages. Development of the male and female external genitalia is also reviewed.

Animals↗
PubMed1998

Drosophila coracle, a member of the protein 4.1 superfamily, has essential structural functions in the septate junctions and developmental functions in embryonic and adult epithelial cells.

Although extensively studied biochemically, members of the Protein 4. 1 superfamily have not been as well characterized genetically. Studies of coracle, a Drosophila Protein 4.1 homologue, provide an opportunity to examine the genetic functions of this gene family. coracle was originally identified as a dominant suppressor of EgfrElp, a hypermorphic form of the Drosophila Epidermal growth factor receptor gene. In this article, we present a phenotypic analysis of coracle, one of the first for a member of the Protein 4. 1 superfamily. Screens for new coracle alleles confirm the null coracle phenotype of embryonic lethality and failure in dorsal closure, and they identify additional defects in the embryonic epidermis and salivary glands. Hypomorphic coracle alleles reveal functions in many imaginal tissues. Analysis of coracle mutant cells indicates that Coracle is a necessary structural component of the septate junction required for the maintenance of the transepithelial barrier but is not necessary for apical-basal polarity, epithelial integrity, or cytoskeletal integrity. In addition, coracle phenotypes suggest a specific role in cell signaling events. Finally, complementation analysis provides information regarding the functional organization of Coracle and possibly other Protein 4.1 superfamily members. These studies provide insights into a range of in vivo functions for coracle in developing embryos and adults.

Alleles↗
PubMed1985

[Characteristics of cell structure and proliferative activity of organ cultures of normal embryonic lung tissue of mice resistant (C57BL) and predisposed (A) to lung blastomogenesis].

Linear differences were discovered in the quantitative ratio and proliferative activity of the cells of the epithelium and mesenchyma of organ cultures of the normal embryonal pulmonary tissue of mice resistant (C57BL) and predisposed (A) to lung blastomogenesis. In A mouse embryos, the index of the cell labels of the bronchiolar epithelium and fibroblast-like cells of the mesenchyma which migrate on the surface of the membrane filter was several times higher than that in C57BL mice. The number of the mesenchymal cells capable of migration in A mouse explants was essentially greater, that of the mesenchymal cells being in a direct contact with the epithelium of alveoloid and bronchiolar structures was, on the contrary, lower than in C57BL mouse explants. It is suggested that the differences described, particularly epithelial-mesenchymal interactions, are of importance for realization of the genetically determined sensitivity of these mice to spontaneous and induced lung blastomogenesis, which manifests as early as during prenatal ontogenesis.

Animals↗
PubMed1995

Gene structure and glial expression of the glycine transporter GlyT1 in embryonic and adult rodents.

Na+/Cl(-)-dependent glycine transporters are crucial for the termination of neurotransmission at glycinergic synapses. Two different glycine transporter genes, GlyT1 and GlyT2, have been described. Several isoforms differing in their 5' ends originate from the GlyT1 gene. We have determined the genomic structure of the murine GlyT1 gene to elucidate the genetic basis underlying the different isoforms. Analysis of cDNA 5'-ends revealed that the GlyT1a and 1b/1c mRNAs are transcribed from two different promoters. During murine embryonic development GlyT1 mRNAs were detectable by RNase protection assays as early as embryonic day E9 and reached maximal levels between E13 and E15. In situ hybridization revealed GlyT1 expression in the developing spinal cord mainly in the ventral part of the ventricular zone at E12. At later stages (E15) transcripts were also found in the lateral half of the basal and intermediate gray matter. In contrast, the second glycine transporter gene GlyT2 displayed a completely different expression pattern. At E11 it is expressed in the mantle zone, and at later stages throughout the ventral horns. In the adult rat brain and spinal cord, GlyT1 hybridization signals were found exclusively in glial cells. Our data indicate that GlyT1 is an early marker of neural development and encodes glia-specific transporter proteins.

Amino Acid Sequence↗
PubMedDate not supplied

Teratogenicity of the I(Kr)-blocker cisapride: relation to embryonic cardiac arrhythmia.

Cisapride and mosapride are structurally and pharmacologically related prokinetic agents. In contrast to mosapride, cisapride causes embryonic lethality in teratology studies, and has been related to fatal cardiac arrhythmia in the adult. The arrhythmogenic potential of cisapride is linked to its potential to inhibit a specific ion channel (I(Kr)) as a side effect. Mosapride lacks I(Kr)-blocking properties. The aims of this study were (1) to compare the effects of cisapride and mosapride on embryonic heart rhythm in vitro and (2) to investigate if cisapride in vivo, has potential to induce hypoxia-related teratogenic effects as has been shown for selective I(Kr)-blockers. Cisapride induced severe embryonic bradycardia (approximately 60% decrease), and arrhythmia in 94% of the cultured rat embryos at 1000 ng/ml. Mosapride did not induce any bradycardia or arrhythmia up to 2000 ng/ml. In vivo, single dose administration of cisapride to rats on gestational day (GD) 13 caused digital reductions (8/108 fetuses, 4/9 litters) at 75 mg/kg and high incidence of embryonic death (55-82%) at 100-200 mg/kg. Identical developmental toxic effects have been described after temporary interruption of oxygen supply, and after single dose administration of selective I(Kr)-blockers, on the same GD. The results support the idea that all potent I(Kr)-blocking agents have the potential to cause embryolethality and teratogenicity, and that the adverse effects are mediated via hypoxic episodes due to embryonic arrhythmia.

Abnormalities, Drug-Induced↗
PubMed1984

In vitro development of the embryonic mouse inner ear following exposure to trypsin.

Trypsin has been shown to disrupt normal in vitro morphogenesis of embryonic organ rudiments. Otic tissues derived from 11-, 12-, and 13-day-old mouse embryos were exposed to either Ca++- and Mg++-free PBS or 0.25% trypsin dissolved in Ca++- and Mg++-free PBS prior to explanation into organ culture. Trypsin treatment of otic explants disrupted the expression of the normal pattern of inner-ear development in vitro. There was a direct correlation between the embryonic age at time of exposure to trypsin and the severity of dysmorphogenesis of the inner ear. The younger explants showed abnormalities of both vestibular and auditory structures, whereas with increasing embryonic age, abnormalities were confined more to the auditory portion of the inner ear. The results suggest that integrity of the otocyst basal lamina and epitheliomesenchymal tissue interactions are important factors in early otic development. It is postulated that the major effect of trypsin on inner-ear morphogenesis is through disruption of these factors, which may act to regulate the progressive expression of early otic development.

Animals↗
PubMed1990

Molecular cloning and expression of sea urchin embryonic ciliary dynein beta heavy chain.

The determination of the structure and the expression of dynein during embryonic development are central to the understanding of dynein function. As an important first step toward these objectives, cDNAs encoding portions of sea urchin ciliary dynein were identified by antibody screening of a sea urchin cDNA expression library. Because of the complete lack of protein sequence data, it was first necessary to prove the identity of the dynein cDNAs. Of the five cDNA inserts initially cloned, one, designated P72A1, was characterized extensively. Four independent criteria demonstrated that P72A1 encoded a portion of a dynein heavy chain. (1) The beta-galactosidase-P72A1 fusion protein affinity-purified dynein-specific antibodies from crude antiserum. (2) Two other antisera to dynein, raised independently of the antiserum used to screen the cDNA library, reacted with the fusion protein. (3) A new antiserum raised against the fusion protein reacted with authentic dynein heavy chain on Western blots and stained embryonic cilia by indirect immunofluorescence microscopy. (4) Two new antisera, elicited against opposite ends of the P72A1 open reading frame, each reacted with authentic dynein heavy chain protein. Western blot analyses of dissociated dynein heavy chains revealed that P72A1 encoded a portion of the beta heavy chain. Epitope mapping experiments confirmed the identity of P72A1 as part of the beta heavy chain and also demonstrated that P72A1 encoded epitopes of the carboxyl-terminal fragment B domain of the dynein beta heavy chain. Northern blot analyses of poly(A)+ RNA revealed that P72A1 hybridized with a large RNA species ca. 12.5 kb in length. The dynein mRNA concentration increased during embryonic development. Dot blot analyses of RNA isolated at various times after embryo deciliation demonstrated that the dynein beta heavy chain mRNA accumulated rapidly in response to deciliation. The accumulation was similar to but not identical with the induction of tubulin mRNA in response to the same stimulus.

Adenosine Triphosphatases↗
PubMed1992

Analysis of glycosaminoglycan chains from different proteoglycan populations in human embryonic skin fibroblasts.

1. The structure of chondroitin/dermatan and heparan-sulphate chains from various proteoglycan populations derived from cultured human skin fibroblasts have been examined. Confluent cell cultures were biosynthetically labelled with [3H]-glucosamine and 35SO4(2-), and proteoglycans were purified according to buoyant density, size and charge density [Schmidtchen, A., Carlstedt, I., Malmström, A. & Fransson, L.-A. (1990) Biochem. J. 265, 289-300]. Some proteoglycan fractions were further fractionated according to hydrophobicity on octyl-Sepharose in Triton X-100 gradients. The glycosaminoglycan chains, intact or degraded by chemical or enzymic methods were then analysed by gel chromatography on Sepharose CL-6B, Bio-Gel P-6, ion exchange HPLC and gel electrophoresis. 2. Three types of dermatan-sulphate chains were identified on the basis of disaccharide composition and chain length. They were derived from the large proteoglycan, two small proteoglycans and a cell-associated proteoglycan with core proteins of 90 kDa and 45 kDa. Intracellular, free dermatan-sulphate chains were very similar to those of the small proteoglycans. 3. Heparan-sulphate chains from different proteoglycans had, in spite of small but distinct differences in size, strikingly similar compositional features. They contained similar amounts of D-glucuronate, L-iduronate (with or without sulphate) and N-sulphate groups. They all displayed heparin-lyase-resistant domains with average molecular mass of 10-15 kDa. The heparan-sulphate chains from proteoglycans with 250-kDa and 350-kDa cores were the largest greater than 50 kDa), containing an average of four or five domains, in contrast to heparan-sulphate chains from the small heparan-sulphate proteoglycans which had average molecular mass of 45 kDa and consisted of three or four such domains. Free, cell-associated heparan-sulphate chains were heterogeneous in size (5-45 kDa). 4. These results suggest that the core protein may have important regulatory functions with regard to dermatan-sulphate synthesis. On the other hand, synthesis of heparan sulphate may be largely controlled by the cell that expresses a particular proteoglycan core protein.

Cells, Cultured↗
PubMed1981

Structure of the human immunoglobulin mu locus: characterization of embryonic and rearranged J and D genes.

The variable portion of an immunoglobulin heavy chain gene is assembled from at least three discontinuous segments of DNA, the V, D and J regions. We have characterized a 30 kb segment of the human genome that plays a critical role in the formation of this variable region as well as in the expression of the two heavy chains that appear earliest in immunocyte ontogeny, the mu and delta chains. This region encodes nine J-like segments, an interspersed D segment, recombination signals and the genes responsible for the production of both mu and delta heavy chains. Six of the nine germline J-like genes appear to be active and easily account for most of the known human heavy chain amino acid sequences. Three of the J-like genes are pseudogenes. The large number of human J region genes and, hence, their greater potential for generating diversity as compared to the that of the mouse J region genes appears to result from recent genetic duplications. To assess this potential, we have analyzed two recombinant genes involving this region. One of these, a V-D-J recombinant, is likely to be an active gene; the other, an aberrant D-J recombinant. A comparison of the structures of these D regions raises the possibility that they are mosaics formed by recombination between D segments.

Amino Acid Sequence↗
PubMed1996

Grafts of the third branchial arch in chick embryos.

The parathyroid glands have been classically considered derivatives of the third and fourth pharyngeal pouches in most species, including humans. The presence of neural crest-derived cells in parathyroid glands connective tissue has apparently been established. However, our previous studies have provided a new hypothesis on the origin of these glands in human and chick embryos. To determine the true origin of the third parathyroid (parathyroid III) gland in the chick embryo, pieces of the third branchial arch from donor chick embryos at Hamburger and Hamilton's stage 19 (embryonic day 3) were grafted to host chick embryos at the same stage of development. Starting from Hamburger and Hamilton's stage 27 (embryonic day 5), a structure identified as the parathyroid III appeared in the ectodermal (epipharyngeal) placode of the third branchial arch graft, from which it subsequently became separated at Hamburger and Hamilton's stage 28 (embryonic day 5.5) and continued to develop and mature. Our findings suggest the conclusion that the parathyroid III gland begins to develop from the epipharyngeal placode, so that this gland, from our point of view, could be considered ectodermal in nature.

Animals↗
PubMed1986

Dysmorphogenesis of the inner ear: disruption of extracellular matrix (ECM) formation by an L-proline analog in otic explants.

L-azetidine-2-carboxylic acid (LACA), a l-proline analog, disrupts collagen secretion by cells and prevents normal morphogenesis of in vitro developing organ rudiments. Otic explants derived from 10.5-through 14-day-old mouse embryos were continuously exposed to LACA in the nutrient medium at concentrations of 75, 150, and 300 micrograms/ml. LACA disrupted normal in vitro otic morphogenesis in inner ears explanted from embryos of 10.5 through 13 days' gestation. Development of 14-day-old otic explants were not affected by LACA at the concentrations tested. There was a direct correlation between the embryonic age of the explant when exposed to LACA, and the severity of otic dysmorphogenesis. The younger explants (10.5-to 12-day-old) developed abnormalities of both vestibular and auditory structures, but with increasing embryonic age of the explants (12-to 13.5-day-old) abnormalities were confined more to the auditory portion of the inner ear. Disruption of collagen secretion of connective tissue cells of the otic explants are a major teratogenic action of LACA on inner ear development. Disrupted collagen secretion alters otic extracellular matrix production, which in turn affects the tissue interactions that regulate the progressive expression of otic morphogenesis and differentiation.

Abnormalities, Drug-Induced↗
PubMed1985

Structure of the Spec1 gene encoding a major calcium-binding protein in the embryonic ectoderm of the sea urchin, Strongylocentrotus purpuratus.

We have identified and characterized the structure of the Spec1 gene in the sea urchin Strongylocentrotus purpuratus. In earlier studies we demonstrated that a small family of messenger RNAs, termed Spec mRNAs for S. purpuratus ectodermal mRNAs, begins to accumulate 20 hours after fertilization in ectoderm cells of the sea urchin embryo. The Spec mRNAs code for a group of low molecular weight proteins belonging to the troponin C superfamily. Spec1 transcripts, the predominant mRNAs of the family, are heterogeneous in their 3' untranslated sequences but code for a single protein, recently shown to be a calcium-binding protein. Spec complementary DNA clones were used to isolate genomic clones from two lambda libraries. These genomic clones comprise a 41 kb (kb = 10(3) bases or base-pairs) region of the S. purpuratus genome and contain a Spec1 gene closely linked to another Spec gene, Spec2c. The Spec1 gene is 10.3 kb in length and contains six exons. The genomic clones containing the Spec1 gene can be placed into two groups based on restriction fragment length differences and differences in hybridization strengths using probes derived from Spec1 3' untranslated regions. Evidence that these groups probably correspond to two alleles of the Spec1 gene was obtained by probing genomic DNA blots of sperm DNA from different individuals with 3' untranslated sequences of Spec1 complementary DNA clones. These blots show that two of the Spec1 mRNAs we have characterized, and probably a third, are alleles of the Spec1 gene. Thus, there appears to be a single polymorphic Spec1 gene in the sea urchin genome. We used S1 protection and primer extension procedures to map the 5' end of the Spec1 gene. Results from these experiments indicate that the initiation of transcription of the Spec1 mRNA begins at an A residue 220 bases from the 3' end of the first exon. Adding support to this claim, cannonical T-A-T-A and C-A-A-T sequences, indicative of many eukaryotic promoters, are found 23 bases and 60 bases upstream from this site, respectively. Analysis of sequences within a few kb of the Spec1 gene show that there are five members of a repetitive sequence family near the gene, three upstream and two downstream. The 5' leader sequence of another Spec mRNA, Spec2a, also contains a member of this repeat family.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2003

Conservation of Sox4 gene structure and expression during chicken embryogenesis.

While mutations in Sox4, a member of the SRY-like HMG box gene family, have been associated with a variety of human disorders and embryonic defects in the mouse, the structure and developmental expression of Sox4 in the avian embryo has not been described. We have isolated and characterized the chicken Sox4 gene. The chicken Sox4 gene shows a high degree of sequence homology with the mouse and human Sox4 genes, particularly in the HMG-like DNA binding domain and at the carboxy terminus. Furthermore, our in situ hybridization studies document an expression pattern during embryonic development that is very similar to that described for the mouse, particularly with regards to expression in the developing heart. However, abundant expression was also detected in tissues of neural crest origin including pharyngeal arch and craniofacial mesoderm, supporting a potential primary role in neural crest cardiac pathology previously detected in Sox4 mutant mice. Furthermore, a reciprocal pattern of Sox4 and Sox11 expression in the developing neural tube was detected in the chicken compared to that seen in the mouse. These studies suggest that Sox4 plays an important and conserved role in the embryonic development of these structures in the chicken as well as in the mouse and lay the foundation for future studies of the role of Sox4 during critical events of organogenesis.

Amino Acid Sequence↗
PubMed1999

Cerebellar and brainstem development: an overview in relation to Joubert syndrome.

An overview of cerebellar and brainstem development is provided as a foundation for suggesting hypotheses about developmental defects in Joubert syndrome. Although neuropathologic studies of Joubert syndrome are rare, and the spectrum of brain pathology is not yet known, consistent findings include agenesis of the cerebellar vermis and hypoplasia or fragmentation of several brainstem nuclei (including dentate nuclei, inferior olives, and basis pontis), nuclei and tracts of cranial nerve V, solitary nuclei and tracts, and nuclei gracilis and cuneatus. Two aspects of cerebellar development might be important in the pathogenesis of Joubert syndrome: First, cerebellar development is regulated by a critical region of the embryo called the "midbrain-hindbrain organizer," and both mesencephalic and metencephalic elements take part in normal cerebellar development. While the metencephalon gives rise to the cerebellar hemispheres, the vermis is derived almost exclusively from the mesencephalon. This suggests that Joubert syndrome could involve an abnormality in formation of the pontomesencephalic junction (rhombomere 1). Second, the histogenesis of cranial nerve nuclei and brainstem structures derived from the embryonic rhombic lip (such as the inferior olives, neurons of the basis pontis, and arcuate nuclei) involves the formation, migration, and reorganization of nuclei and tracts during a critical period of development (6 to 8 weeks' gestation). Because these structures are abnormal in Joubert syndrome, an understanding of factors that regulate the proper formation and migration of cells that give rise to them could provide important clues about the pathogenesis of this disorder.

Animals↗
PubMed1995

An embryonic alternative transcription initiation site and the 5'-upstream structure of mouse cardiac troponin T gene.

By specific antibody screening of a lambda ZAPII expression library, we identified a class of cDNAs derived from mouse cardiac troponin T (TnT) mRNA with long 5'-ends containing the -30 TATA sequence of the promoter. These long mRNAs indicated the presence of a novel upstream transcription initiation site in the cardiac TnT gene. Primer extension mapping of the mouse cardiac TnT mRNA confirmed an alternative transcription initiation site 55-base pairs upstream of the major initiation site. The upstream initiation site was found significantly more active in the embryonic/neonatal hearts. Genomic cloning and sequencing further revealed an 1.5-kb 5'-upstream sequence of the mouse cardiac TnT gene and relationships between the promoter regulatory elements and the alternative transcription initiation sites.

Alternative Splicing↗