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At least 721 records · Page 40Linked to original sources
PubMed1996

Transient expression of CD44 variant isoforms in the ontogeny of the rat: ectoderm-, endoderm- and mesoderm-derived cells express different exon combinations.

Expression on rat tumor cells of CD44 variant isoforms containing exons v4-v7 or v6-v7 has been described as sufficient for initiation of the metastatic cascade. The question arose as to whether physiological programs may be reactivated by particular CD44 isoforms. With this in mind, expression of mRNAs for the CD44 isoforms was surveyed during ontogeny of the rat. Using available monoclonal antibodies, expression of the CD44 standard isoform (CD44s) and of an epitope of CD44 exon v6 (CD44v6) were evaluated by immunohistology also. While CD44s was expressed in cells of all three germ layers, CD44v6 expression was restricted to distinct epithelial layers and cells of the hematopoietic system. During ontogeny, expression of CD44v6 was first noted in the neural tube and the leading epithelial layer of the limb buds. Later, anti-CD44v6 (1.1ASML) stained basal layers of the epidermis, the epithelium of the gut, and the acini of the submandibular gland. Strong, but transient expression of CD44v6 was seen during lung development, in hematopoietic stem cells of the liver, in thymic epithelia and early thymic immigrants. Expression in these organs was downregulated shortly before or after birth. As revealed by Southern blotting after use of the reverse transcriptase polymerase chain reaction (RT-PCR), most CD44v6-positive organs contained more than one CD44 variant isoform, and the expression patterns differed between individual organs. Hematopoietic cells preferentially expressed exons v4-v7, endodermal tissue exons v4-v10 and only in the epidermis were exons v1-v10 detected. The temporally regulated expression during ontogeny and the different exon compositions suggest a pivotal role of CD44 isoforms particularly in hematopoesis and in pattern formation by instructive epithelia.

Animals↗
PubMed1997

Glucocorticoid receptor gene expression during rat embryogenesis. An in situ hybridization study.

Glucocorticoids play an important role in embryonic development. The existence of sufficient amounts of their receptors during rodent embryogenesis has proved to be an absolute necessity for the physiological growth of the animal. We have analyzed the pattern of glucocorticoid receptor gene expression in the rat embryo through embryonic days 12 to 17, by using in situ hybridization histochemistry. Glucocorticoid receptor mRNA is present in the rat liver on embryonic day (E) 12, and by E13 the signal can also be detected in several other tissues, such as the lung, the heart, the mesonephros, the sclerotomes, the thymus and Rathke's pouch. Glucocorticoid receptor gene expression was quite ubiquitous in tissue derivatives of all three germ layers and appeared to vary in intensity within the same tissue during embryogenesis. These variations in the level of receptor gene expression paralleled the developmental stage of each tissue: Intense labelling was detected just prior to the final differentiation step of a structure. Upon differentiation, cell populations highly expressing glucocorticoid receptor gene in the previous stage were found to have reduced amounts of the receptor mRNA. Our results support a morphogenetic role for glucocorticoids during embryogenesis.

Animals↗
PubMed1997

Molecular cloning from neurulating Ambystoma mexicanum embryos of the cDNA encoding an orphan nuclear receptor (aDOR1) closely related to TR2-11.

We have isolated a cDNA encoding a novel orphan nuclear receptor, aDOR1, closely related to testicular receptor-2 (TR2) orphan receptor family members, from neurulating Ambystoma mexicanum embryos. The cDNA sequence predicts a protein primary sequence of 416 amino acids with a calculated molecular weight of 45.8 kDa. While the DNA-binding domains of aDOR1 and hTR2-11 share 96% identity, considerable divergence is observed at both extremities of the peptides. At the N-terminus, aDOR1 is 66% identical to hTR2-11 and longer by 37 amino acids. At the C-terminus, despite a greater similarity (69%), aDOR1 is much shorter than the hTR2 isoforms and seems to encode a distinct ligand-binding domain. Expression of aDOR1 was studied by the reverse transcription polymerase chain reaction assay (RT-PCR). High mRNA levels were detected during oogenesis, they remained high during the cleavage stage, and decreased at the mid-blastula transition (MBT). Transcripts increased again at the end of gastrulation, reached a peak level during neurulation, and leveled off after closure of the neural tube. In neurulas dissected along the anteroposterior axis, aDOR1 mRNA was enriched at both extremities of the embryo, while no particular distribution was favored along the dorsoventral axis. Retinoic acid (RA) treatments at the beginning of gastrulation did not affect overall mRNA levels in the neurula nor its distribution along both axes. In the adult, expression was predominant in the brain; lower levels (about 15%) were detectable in all germ layer derivatives, except muscle. These results suggest that aDOR1 may be required for the early determination events occurring during the cleavage stages of development, and may be involved in embryogenesis and in brain function.

Ambystoma↗
PubMed2002

Ectoderm gene activation in sea urchin embryos mediated by the CCAAT-binding factor.

Transcriptional enhancers are short stretches of DNA that function to achieve highly specific patterns of gene expression. To identify the mechanisms by which enhancers achieve their specificity, we made use of an enhancer from the aboral ectoderm-specific spec2a gene of the sea urchin Strongylocentrotus purpuratus. The spec2a enhancer contains five cis-regulatory elements within 78 base pairs that interact with five distinct DNA-binding proteins to confer aboral ectoderm expression. Here, we present an analysis of the sea urchin CCAAT binding factor (CBF), which binds to a CCAAT motif within the spec2a enhancer. S. purpuratus CBF and SpOtx, a ubiquitously expressed factor, act together at closely placed cis-regulatory elements to mediate spec2a transcription in the ectoderm. SpCBF was the sole factor that bound to the spec2a CCAAT element, and two of the three subunits that make up the CBF holoprotein were cloned and shown to have high sequence conservation with their vertebrate orthologs. Based on its involvement in the regulation of several other sea urchin genes, SpCBF appears to be a major transcription factor in the sea urchin embryo for positive regulation of ectoderm gene expression. In addition to its role in vertebrate cell growth and proliferation, our results indicate that CBF also functions at the early stages of germ layer formation, namely ectoderm differentiation.

Amino Acid Sequence↗
PubMed2003

In vitro differentiation of embryonic stem cells into mineralized osteoblasts.

Embryonic stem cells are pluripotent cells derived from the inner cell mass of mouse blastocysts that have been shown to differentiate spontaneously into cell types representing all three germ layers. This study shows that ES cells were induced to differentiate in vitro into mineralized osteoblasts under the influence of ascorbic acid, beta-glycerophosphate and 1alpha,25-OH vitamin D3. The activity of alkaline phosphatase, an early osteoblast marker, was found to be increased around day 12 of culture. Mineralized cells were clearly identified by histochemical staining, which detects mineralized calcium. The major noncollagenous component of bone matrix, osteocalcin, was localized to the mineralized cells by immunofluorescence. The expression of bone-specific genes was analyzed by real-time quantitative PCR. Osteocalcin and bone sialoprotein (BSP) were identified as early as in the fourth week of embryonic stem cell culture, both being characteristic for late stages of osteoblastic differentiation, indicating that at this time of culture the identified cells represent "mature" osteoblasts. The osteoblast-specific transcription factor Cbfa1 was induced a few days earlier. The expression of osteopontin and osteonectin, both being involved in binding calcium ions and hydroxyapatite during mineralization processes, as well as of collagen type I, representing by far the most predominant collagen in vertebrate organisms, is enhanced at the beginning of the second culture week upon addition of supplements. In the third week of culture, treated cells showed a second peak of osteopontin, osteonectin and collagen type I expression, osteopontin and osteonectin being stimulated 3-4-fold and collagen type I being induced 6-fold over control values. Alkaline phosphatase (ALP) expression was enhanced at the beginning of the third week of culture and was found to be increased again at later stages of culture at days 27-34. The in vitro differentiation of mouse embryonic stem cells into osteoblasts may provide a suitable model for studying the molecular processes of osteoblastic development in vivo.

Animals↗
PubMed1997

Oral-aboral ectoderm differentiation of sea urchin embryos is disrupted in response to calcium ionophore.

Intracellular signaling mediated by calcium ions has been implicated as important in controlling cell activity. The ability of calcium ionophore (A23187), which causes an increase in calcium ion concentration in the cytoplasm, to alter the pattern of differentiation of cells during sea urchin development was examined. The addition of A23187 to embryos for 3 h during early cleavage causes dramatic changes in their development during gastrulation. Using tissue-specific cDNA probes and antibodies, it was shown that A23187 causes the disruption of oral-aboral ectoderm differentiation of sea urchin embryos. The critical period for A23187 to disturb the oral-aboral ectoderm differentiation is during the cleavage stage, and treatment of embryos with A23187 after that time has little effect. The A23187 does not affect the formation of the three germ layers. These results indicate that intracellular signals mediated by calcium ions may play a key role in establishment of the oral-aboral axis during sea urchin development.

Animals↗
PubMedDate not supplied

Expression of Distal-less in molluscan eggs, embryos, and larvae.

Distal-less (Dll) is best known as a transcription factor involved with "limb patterning" in Drosophila melanogaster. Observations of both deuterostome and protostome phyla have led to the suggestion that some aspect of this gene's function in "appendage" or proximal-distal "outgrowth" development is conserved. Here we explore the possibility of other conserved roles operating earlier in development. We examine the expression of DLL protein during the early development of two molluscan classes, Polyplacophora (chiton) and Gastropoda (snail). Using an antibody approach, we find DLL expression in the oocytes of a chiton (Mopalia muscosa) and in the pregastrulae through early veliger larvae of a marine snail (Kelletia kelletii). We observe antibody localization in the oocyte, nuclear expression in all cells of the pregastrulae, and predominant expression in the ectoderm of postgastrulae and early veliger larvae. Comparison of our observations on spiralian taxa, thought to have conservative development with previous work, primarily on deuterostomes, suggests the possibility of an ancient role(s) for DLL in early development. Possible functions appear to include maternal and zygotic involvement in the establishment of embryonic polarity, involvement in the process of germ layer formation, and a role in the specification and/or differentiation of ectoderm/epithelia. We note that the exploration of conserved gene function in early development may be clarified by examining taxa whose early development has putatively not been subject to dramatic evolutionary change.

Animals↗
PubMedDate not supplied

Localization of RNAs in oocytes of Eleutherodactylus coqui, a direct developing frog, differs from Xenopus laevis.

Eleutherodactylus coqui develops directly on land to a frog. The large 3.5-mm oocyte of E. coqui has enough yolk to allow development without a feeding tadpole. In the smaller Xenopus laevis oocyte, 1.3 mm in diameter, mRNAs involved in germ layer formation, such as VegT and Vg1, are localized to the vegetal cortex of the oocyte. We hypothesized that an animal shift has occurred in the localization of the E. coqui Orthologs of VegT and Vg1 due to the large egg size. Through a combination of degenerate reverse transcriptase polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE), we cloned 1634 bp of EcVegT and 1377 bp of EcVg1. Northern blot analysis shows that the lengths of these transcripts are 2.5 kb and 1.3 kb, respectively. This result suggests that we have obtained the complete Vg1 transcript, although this transcript has an extremely short 3' untranslated region compared with X. laevis, 256 bp and 1268 bp, respectively. Zygotic expression of EcVegT closely resembles that of VegT, supporting their orthology. Radioactive RT-PCR and in situ hybridization demonstrated the presence of EcVegT and EcVg1 predominantly near the animal pole of the oocyte. RT-PCR showed that the animal blastomeres, formed from the first horizontal cleavage, inherit half of the EcVegT and EcVg1 transcripts, although they contain only about 1% of the embryo volume. Our results indicate major differences between the molecular organization of the eggs of X. laevis and E. coqui.

Animals↗
PubMedDate not supplied

Spontaneous thyroid-containing teratoma associated with impaired development in the African clawed frog, Xenopus laevis.

Teratomas are rare in amphibians and the neoplasm described here, which had a significant thyroid carcinoma component, is the first tumour of this type to be reported in Xenopus laevis. The thyroid component contained moderately to well-differentiated acinar glands showing much hyperplasia, dysplasia, and reduced and distorted colloid reservoirs. Cartilaginous, neural, muscular, mesenchymal and gut-like epithelial components were also observed in this ventral mediastinal neoplasm, indicating aberrant proliferation from all three germ layers. This teratoma was only one abnormality in a complex of developmental changes, followed for 28 months, which appeared in a single generation of sibling 2-week-old Xenopus larvae. Two hundred larvae produced by an apparently normal adult pair initially showed ocular defects, including microphthalmia, anophthalmia and tumours projecting near the eyes. During further development up to 28 months, mediastinal tumours developed in nine frogs; these tumours were associated with reduced growth, the frogs reaching only 13-20% of normal weight, and greatly enhanced ventral pigmentation.

Animals↗
PubMed2002

Paediatric gastric teratoma.

AIM: This paper reviews our experience with patients presenting with gastric teratoma treated over an eighteen-year period. This rare paediatric tumour has an excellent prognosis after curative resection. METHODS: There were seven patients, all males. Investigations included a haematological profile, plain radiography and ultrasound of the abdomen. All patients were operated and the specimens subjected to histopathological examination. RESULTS: The age at presentation ranged from 1 month to 7 years. Two patients presented with melaena and the rest with progressively increasing abdominal mass. Our oldest patient had a massive tumour occupying nearly the whole abdomen. None of the children had metastases and none of the lesions had invaded adjacent structures. The tumours could be completely resected and all patients had an uneventful recovery. Histology of the tumours showed mature elements arising from the three germ layers in 6 children, one child had an immature teratoma. The average follow-up was 3 years (range 2 - 6 years). None of the patients has had a recurrence or any other problem. CONCLUSIONS: Gastric teratoma is a rare tumour but amenable to curative resection with an excellent prognosis.

Child, Preschool↗
PubMed2003

Severe anemia in a 25-day-old infant due to gastric teratoma with focal neuroblastoma.

Gastric teratoma is an extremely rare embryonic neoplasm containing tissue from all three germ layers (ectoderm, endoderm, and mesoderm). A 25-day-old infant presented with anemia and a palpable abdominal mass. Computed tomography (CT) scanning showed a solid and cystic multiloculated tumor of mixed echogenicity and calcifications. An encapsulated bleeding tumor localized to the posterior wall of the stomach with extension to a bowel segment was promptly excised. Histology revealed a grade III immature teratoma with small foci of neuroblastoma. To the best of our knowledge, this is the first infant with gastric teratoma containing foci of neuroblastoma causing bleeding and anemia as presentation symptoms at neonatal age.

Anemia↗
PubMed1989

The hairy polyp: a benign teratoma of the colon.

A 76-year-old female presented with bright red rectal bleeding. Endoscopic evaluation revealed a polypoid lesion sprouting hair in the sigmoid colon. Histologically the resected polyp was composed of elements of all three germ layers, fulfilling the criteria for a teratoma. The differential diagnosis of this benign polyp and its significance are discussed.

Aged↗
PubMedDate not supplied

[Primary observation of a congenital intracranial teratoma in a twin with a healthy brother].

Primary intracranial teratomas are rare germ cell tumors arising from embryonic tissues, which contain cellular or tissue derivates from all three germ layers. Today the early intrauterine diagnosis by ultrasound is possible. We first describe a patient with such a tumor which was diagnosed by routine ultrasound in the 33rd week of gestational age in a twin-pregnancy, of which the 2nd twin developed normally. This must be considered in the obstetrical situation. In such a case the parents should be advised accordingly.

Brain Neoplasms↗
PubMed1986

[Oral teratoma (epignathus), a rare congenital abnormality].

We report on 2 newborn girls with congenital oropharyngeal teratoma (Epignathus). In both children the tumour was totally resected on the first days of life. The histopathological investigation shows tissue from all three germ layers. 11 and 19 months after excision there is no evidence of recurrence. Frequency, prognosis and therapy of oral teratomas are discussed.

Female↗
PubMed1982

[Yolk-sac tumours of the mediastinum (author's transl)].

Three patients with yolk-sac tumours of the mediastinum have been described. This is a rare primary germ layer tumour of the thorax. Most commonly it is situated anteriorly in the mediastinum. Only rarely is it found in the posterior mediastinum. Only males are affected. In most patients the prognosis, despite intensive radiation and chemotherapy, is extremely poor.

Adult↗
PubMed1999

Exercise intolerance due to mutations in the cytochrome b gene of mitochondrial DNA.

BACKGROUND: The mitochondrial myopathies typically affect many organ systems and are associated with mutations in mitochondrial DNA (mtDNA) that are maternally inherited. However, there is also a sporadic form of mitochondrial myopathy in which exercise intolerance is the predominant symptom. We studied the biochemical and molecular characteristics of this sporadic myopathy. METHODS: We sequenced the mtDNA cytochrome b gene in blood and muscle specimens from five patients with severe exercise intolerance, lactic acidosis in the resting state (in four patients), and biochemical evidence of complex III deficiency. We compared the clinical and molecular features of these patients with those previously described in four other patients with mutations in the cytochrome b gene. RESULTS: We found a total of three different nonsense mutations (G15084A, G15168A, and G15723A), one missense mutation (G14846A), and a 24-bp deletion (from nucleotide 15498 to 15521) in the cytochrome b gene in the five patients. Each of these mutations impairs the enzymatic function of the cytochrome b protein. In these patients and those previously described, the clinical manifestations included progressive exercise intolerance, proximal limb weakness, and in some cases, attacks of myoglobinuria. There was no maternal inheritance and there were no mutations in tissues other than muscle. The absence of these findings suggests that the disorder is due to somatic mutations in myogenic stem cells after germ-layer differentiation. All the point mutations involved the substitution of adenine for guanine, but all were in different locations. CONCLUSIONS: The sporadic form of mitochondrial myopathy is associated with somatic mutations in the cytochrome b gene of mtDNA. This myopathy is one cause of the common and often elusive syndrome of exercise intolerance.

Adult↗
PubMed2001

Lineage specific differentiation of pluripotent cells in vitro: a role for extraembryonic cell types.

The controlled differentiation of pluripotent cells will be a prerequisite for many cell therapies. We have previously reported homogeneous conversion of embryonic stem (ES) cells in vitro to early primitive ectoderm-like (EPL) cells, equivalent to early primitive ectoderm, an obligatory differentiation intermediate between ES cells and somatic cell populations. Early primitive ectoderm-like cells differentiated within aggregates form mesodermal lineages at the expense of ectoderm. In this work we demonstrate that the failure of EPL cells to form ectodermal cell types does not reflect an inherent restriction in developmental potential. Early primitive ectoderm-like cells form ectodermal derivatives such as neurons in response to neural inducers such as retinoic acid, or when differentiated in the environment provided by ES cell embryoid bodies. This could be explained by signals from the extraembryonic cell type visceral endoderm which forms in differentiating ES cell but not EPL cell aggregates. Consistent with this possibility, culture of EPL cell aggregates in the presence of visceral endoderm-like signals did not prevent differentiation of the pluripotent cells, but resulted in suppression of mesoderm formation. These results suggest a role for visceral endoderm in regulation of germ layer specification from pluripotent cells, and can be integrated into a model for cell differentiation in vitro and in vivo.

Blotting, Northern↗
PubMed2005

Comparison of neurosphere cells with cumulus cells after fusion with embryonic stem cells: reprogramming potential.

Embryonic stem cells (ESCs) are the pluripotent cells that also have the capacity to induce the genomic reprogramming of differentiated somatic cells. The progressively restricted genomic potential of somatic cells observed during embryonic development can be reverted to a pluripotent state by the formation of cell hybrids with ESCs. To assess the reprogramming potential of ESCs, we investigated the reprogramming of one of two different somatic cell populations, neurosphere cells (NSCs) and cumulus cells (CCs), after fusion with ESCs. Specifically, hybrid cells were produced by cell fusion of E14 ESCs with either NSCs or CCs containing the neo/lacZ and Oct4-GFP transgenes. The first reprogramming event, observed by the presence of Oct4-GFP in the hybrid cells, could be identified on Day 2, at approximately 45 h after fusion in both ESC-NSC and ESC-CC hybrids. In addition, the two ESC-somatic cell hybrids exhibit a similar reprogramming rate and share characteristics with the E14 ESC line: (1) expression of pluripotent markers (Oct4, Rex-1 and nanog); (2) inactivation of differentiated tissue-specific gene expression; and (3) the capacity to differentiate into all three germ layers. Taken together, our results suggest that the ESC-somatic cell hybrids have fully acquired ESC characteristics and that somatic cells of different tissue origin have the same potential to be reprogrammed after fusion with ESCs.

Animals↗