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PubMed2006

calderón encodes an organic cation transporter of the major facilitator superfamily required for cell growth and proliferation of Drosophila tissues.

The adaptation of growth in response to dietary changes is essential for the normal development of all organisms. The insulin receptor (InR) signalling pathway controls growth and metabolism in response to nutrient availability. The elements of this pathway have been described, although little is known about the downstream elements regulated by this cascade. We identified calderón, a gene that encodes a protein with highest homology with organic cation transporters of the major facilitator superfamily, as a new transcriptional target of the InR pathway. These transporters are believed to function mainly in the uptake of sugars, as well as other organic metabolites. Genetic experiments demonstrate that calderón is required cell autonomously and downstream of the InR pathway for normal growth and proliferation of larval tissues. Our results indicate that growth of imaginal cells may be modulated by two distinct, but coordinated, nutrient-sensing mechanisms: one cell-autonomous and the other humoral.

Amino Acid Sequence↗
PubMed2006

Induction and prepatterning of the zebrafish pectoral fin bud requires axial retinoic acid signaling.

Vertebrate forelimbs arise as bilateral appendages from the lateral plate mesoderm (LPM). Mutants in aldh1a2 (raldh2), an embryonically expressed gene encoding a retinoic acid (RA)-synthesizing enzyme, have been used to show that limb development and patterning of the limb bud are crucially dependent on RA signaling. However, the timing and cellular origin of RA signaling in these processes have remained poorly resolved. We have used genetics and chemical modulators of RA signaling to resolve these issues in the zebrafish. By rescuing pectoral fin induction in the aldh1a2/neckless mutant with exogenous RA and by blocking RA signaling in wild-type embryos, we find that RA acts as a permissive signal that is required during the six- to eight-somite stages for pectoral fin induction. Cell-transplantation experiments show that RA production is not only crucially required from flanking somites, but is sufficient to permit fin bud initiation when the trunk mesoderm is genetically ablated. Under the latter condition, intermediate mesoderm alone cannot induce the pectoral fin field in the LPM. We further show that induction of the fin field is directly followed by a continued requirement for somite-derived RA signaling to establish a prepattern of anteroposterior fates in the condensing fin mesenchyme. This process is mediated by the maintained expression of the transcription factor hand2, through which the fin field is continuously posteriorized, and lasts up to several hours prior to limb-budding. Thus, RA signaling from flanking somites plays a dual early role in the condensing limb bud mesenchyme.

Animals↗
PubMed2006

Repression of mesodermal fate by foxa, a key endoderm regulator of the sea urchin embryo.

The foxa gene is an integral component of the endoderm specification subcircuit of the endomesoderm gene regulatory network in the Strongylocentrotus purpuratus embryo. Its transcripts become confined to veg2, then veg1 endodermal territories, and, following gastrulation, throughout the gut. It is also expressed in the stomodeal ectoderm. gatae and otx genes provide input into the pregastrular regulatory system of foxa, and Foxa represses its own transcription, resulting in an oscillatory temporal expression profile. Here, we report three separate essential functions of the foxa gene: it represses mesodermal fate in the veg2 endomesoderm; it is required in postgastrular development for the expression of gut-specific genes; and it is necessary for stomodaeum formation. If its expression is reduced by a morpholino, more endomesoderm cells become pigment and other mesenchymal cell types, less gut is specified, and the larva has no mouth. Experiments in which blastomere transplantation is combined with foxa MASO treatment demonstrate that, in the normal endoderm, a crucial role of Foxa is to repress gcm expression in response to a Notch signal, and hence to repress mesodermal fate. Chimeric recombination experiments in which veg2, veg1 or ectoderm cells contained foxa MASO show which region of foxa expression controls each of the three functions. These experiments show that the foxa gene is a component of three distinct embryonic gene regulatory networks.

Animals↗
PubMed2006

Odd-skipped genes specify the signaling center that triggers retinogenesis in Drosophila.

Although many of the factors responsible for conferring identity to the eye field in Drosophila have been identified, much less is known about how the expression of the retinal ;trigger', the signaling molecule Hedgehog, is controlled. Here, we show that the co-expression of the conserved odd-skipped family genes at the posterior margin of the eye field is required to activate hedgehog expression and thereby the onset of retinogenesis. The fly Wnt1 homologue wingless represses the odd-skipped genes drm and odd along the anterior margin and, in this manner, spatially restricts the extent of retinal differentiation within the eye field.

Animals↗
PubMed2001

Identification of pleiotrophin as a mesenchymal factor involved in ureteric bud branching morphogenesis.

Branching morphogenesis is central to epithelial organogenesis. In the developing kidney, the epithelial ureteric bud invades the metanephric mesenchyme, which directs the ureteric bud to undergo repeated branching. A soluble factor(s) in the conditioned medium of a metanephric mesenchyme cell line is essential for multiple branching morphogenesis of the isolated ureteric bud. The identity of this factor had proved elusive, but it appeared distinct from factors such as HGF and EGF receptor ligands that have been previously implicated in branching morphogenesis of mature epithelial cell lines. Using sequential column chromatography, we have now purified to apparent homogeneity an 18 kDa protein, pleiotrophin, from the conditioned medium of a metanephric mesenchyme cell line that induces isolated ureteric bud branching morphogenesis in the presence of glial cell-derived neurotrophic factor. Pleiotrophin alone was also found to induce the formation of branching tubules in an immortalized ureteric bud cell line cultured three-dimensionally in an extracellular matrix gel. Consistent with an important role in ureteric bud morphogenesis during kidney development, pleiotrophin was found to localize to the basement membrane of the developing ureteric bud in the embryonic kidney. We suggest that pleiotrophin could act as a key mesenchymally derived factor regulating branching morphogenesis of the ureteric bud and perhaps other embryonic epithelial structures.

Animals↗
PubMed2001

Hindbrain patterning: Krox20 couples segmentation and specification of regional identity.

We have previously demonstrated that inactivation of the Krox20 gene led to the disappearance of its segmental expression territories in the hindbrain, the rhombomeres (r) 3 and 5. We now performed a detailed analysis of the fate of prospective r3 and r5 cells in Krox20 mutant embryos. Genetic fate mapping indicates that at least some of these cells persist in the absence of a functional Krox20 protein and uncovers the requirement for autoregulatory mechanisms in the expansion and maintenance of Krox20-expressing territories. Analysis of even-numbered rhombomere molecular markers demonstrates that in Krox20-null embryos, r3 cells acquire r2 or r4 identity, and r5 cells acquire r6 identity. Finally, study of embryonic chimaeras between Krox20 homozygous mutant and wild-type cells shows that the mingling properties of r3/r5 mutant cells are changed towards those of even-numbered rhombomere cells. Together, these data demonstrate that Krox20 is essential to the generation of alternating odd- and even-numbered territories in the hindbrain and that it acts by coupling the processes of segment formation, cell segregation and specification of regional identity.

Animals↗
PubMed1990

Modulation of native chondroitin sulphate structure in tissue development and in disease.

Chondroitin sulphate proteoglycans are synthesised by different tissues and cell types, and the chondroitin sulphate chains are variably sulphated. Three monoclonal antibodies 3B3, 7D4 and 6C3 that recognise different native chondroitin sulphate epitopes have been used to investigate changes in structure during embryonic tissue development in the chick and in the response of mature canine articular cartilage during experimental osteoarthritis. Strong focal expression of the epitopes was seen during development of chick bursa, which was different for the three epitopes and which changed during 5 days of development. In embryonic chick limb, although chondroitin sulphate is present throughout the cartilage, the 3B3 epitope, which is at the non-reducing terminus of chains, was only expressed on chondroitin sulphate within one region of the sub-articular cartilage. In mature canine articular cartilage the expression of this epitope on proteoglycans was very low, but when determined 3 or 6 months after induction of experimental osteoarthritis the level was greatly increased in all joints tested (23/23). The abundance of the other two native chondroitin sulphate epitopes was also increased in this experimental disease. The results show that expression of the chondroitin sulphate epitopes detected by the monoclonal antibodies changes during cellular differentiation and development and suggests that it is closely controlled by the cells synthesising chondroitin sulphate chains.

Animals↗
PubMed1978

Chromosomal aberrations and congenital heart diseases.

The incidence of chromosomal aberration with CHD is 10.5% in the autopsy cases. 2. The characteristic major cardiac malformations associated with chromosomal aberration are conal abnormality, abnormal septation and cardiac valve abnormalities. 3. The characteristic association of chromosomal aberration and CHD is CAVO in Down syndrome, triple shunts and multivalvular disease in 18 trisomy, shunts in delition syndrome and coarctation of the aorta in Turner syndrome. 4. Minor cardiac anomalies associated with chromosomal aberration are valve dysplasia such as bicuspid semilunar cusps, parachute A-V valve, thickning, deformity and insufficient differentiation of valve and of chordae tendinae and hypoplastic or immature papillary muscles. 5. Primary target in cardiovascular involvement by chromosomal aberration might be a cement property of the connective tissue which is expected to conseal the foramens and shunts and to develop valve structures in embryonic heart.

Chordae Tendineae↗
PubMed2005

Evaluation of the quality of porcine somatic cell nuclear transfer embryo by gene transcription profiles.

This study aimed to evaluate the quality of porcine somatic cell nuclear transfer (SCNT) embryos by examining its gene transcription patterns. Embryos were produced by SCNT, intracytoplasmic sperm injection (ICSI) or under different conditions, and transcripts of genes for fibroblast growth factor receptor (FGFr) 2IIIc, FGFr72IIIb, X inactive-specific transcript (Xist), interleukin 6 (IL6), IL6 receptor (IL6r) alpha and c-kit ligand, were detected by real-time RT-PCR. The percentages of embryos in which these transcripts were detected were similar in SCNT and ICSI embryos. On the other hand, the transcriptional levels of the FGFr72IIIb and IL6ralpha genes were 0.5 times less and 2 times more, respectively, in SCNT blastocysts than those of ICSI blastocysts (p<0.05). When nuclear transfer was performed before or after activation of oocytes, embryos in the latter case showed significantly lower frequencies of having FGFr72IIIb (74% vs. 90%) and Xist (3% vs. 33%) transcripts compared to the former case embryos (p<0.05). When two lines of nuclear donor cells with different developmental potencies were used, the transcriptional profiles in the reconstructed embryos did not show any significant differences. Our study suggests that expression profiles of FGFr72IIIb, IL6ralpha, and Xist can be used as markers for the diagnosis of the developmental potency of porcine nuclear transfer embryos.

Animals↗
PubMed2006

Generation of chondrocytes from embryonic stem cells.

Pluripotent embryonic stem (ES) cells have complete potential for all the primary germ layers, such as ectoderm, mesoderm, and endoderm. However, the cellular and molecular mechanisms that control their lineage-restricted differentiation are not understood. Although embryoid bodies, which are formed because of the spontaneous differentiation of ES cells, have been used to study the differentiation into different cell types, including neurons, chondrocytes, insulin-producing cells, bone-forming cells, hematopoietic cells, and so on, this system has limitations for investigating the upstream events that lead to commitment of cells that occur during the inaccessible period of development. Recent developments in human ES cells have offered a challenge to develop strategies for understanding the basic mechanisms that play a key role in differentiation of stem cell into specific cell types for their applications in regenerative medicine and cell-based therapies. A micromass culture system was developed to induce the differentiation of ES cells into chondrocytes, the cartilage-producing cells, as a model to investigate the upstream events of stem cell differentiation. ES cells were co-cultured with limb bud progenitor cells. A high percentage of differentiated cells exhibit typical morphological characteristics of chondrocytes and express cartilage matrix genes such as collagen type II and proteoglycans, suggesting that signals from the progenitor cells are sufficient to induce ES cells into the chondrogenic lineage. Degeneration of cartilage in the joints is associated with osteoarthritis, which affects the quality of life of human patients. Therefore, the quantitative production of chondrocytes can be a powerful resource to alleviate the suffering of those patients.

Animals↗
PubMed2004

Embryogenesis of GABAergic elements in the nervous system of Eisenia fetida (Annelida, Oligochaeta).

The appearance and development of the GABA-immunoreactive nervous elements in the central nervous system of Eisenia fetida were studied by immunocytochemistry. The nervous system originates from the neuroectoderm situated on the ventral side of the embryo. The organization of the circumpharyngeal ring starts earlier than that of the ventral cord. In the elementary ring the first GABA-immunopositive neurons can be observed (E1 stage) around the mouth. Later the cell number gradually increases and parallel to this process the elementary ring is separeted into a superficial and a deeper portion. The brain and the subesophageal ganglion will be organized from the superficial ring, while the nervous elements of the deeper ring will give rise for the first GABA-immunoreactive elements of the stomatogastric nervous system. In the early stages of the embryogenesis the immunoreactive cells of the developing brain appear solitary, while from the stage E4 they gradually are observed in groups. According to their position, these cell groups are similar to those observed in the brain of the adult earthworms. During embryogenesis the level of the ventral cord ganglia depends on their position in the ectodermal germ bands. It means, that the more organized ganglia are near the circumpharyngeal ring, mean while less developed ganglia are situated caudally from them. By the end of the embryogenesis all ganglia of the ventral cord will be equally well organized. The nerve tracts of the ganglia are built up from contra- and ipsilateral by projected fibres. From E3 stage the medial tracts, mean while from the E4 stage the lateral tracts begin to be formed. During the next stages, more and more fibres connect to the both tracts. At hatching, the development of the central nervous system of Eisenia fetida is not completed, the process is continued during the postembryonic development.

Animals↗
PubMed2004

Enhancement of oligodendrocyte differentiation from murine embryonic stem cells by an activator of gp130 signaling.

Embryonic stem (ES) cells derived from the inner cell mass of blastocyst-stage embryos are a potential large scale source of oligodendrocytes and of their progenitors for transplantation into the central nervous system for the repair of demyelinating lesions. We found previously that interleukin-6 (IL-6) fused to its soluble receptor (IL-6R), a potent activator of the gp130 receptor, induces myelin gene expression in Schwann cells of embryonic dorsal root ganglia. Like leukemia inhibitory factor, IL-6R/IL-6 inhibits the differentiation of murine ES cells into embryoid bodies. In the present study, we show that this recombinant cytokine may be efficiently used to stimulate the differentiation of oligodendrocytes if added to ES cell-derived neural precursors. IL-6R/IL-6 leads to an increase in early chondroitin sulfate proteoglycan positive and late O4 positive progenitors and to a stimulation of maturation into O1 and myelin basic protein expressing oligodendrocytes. Expression of the genes for transcription factor genes Olig-1 and Sox10, which appear early in the oligodendrocyte lineage, was stimulated by IL-6R/IL-6 addition. We conclude that this cytokine can significantly enhance the derivation of oligodendrocytes from ES cells.

Animals↗
PubMed2005

Kidney development and disease in the zebrafish.

Unraveling the molecular pathogenesis of human disease presents many experimental challenges, not the least of which is that experiments on humans are generally frowned upon. Model organisms, including the zebrafish, allow for experimental analysis of gene function and the detailed characterization of disease processes. Zebrafish have matured as a vertebrate model organism now that genetic tools for targeted "knockdowns" and unbiased mutagenesis approaches are in hand. The fish larval pronephros is a relevant kidney in which to pursue many aspects of human kidney development and disease. This short review outlines recent progress in applying the zebrafish pronephros to issues of human health and development.

Animals↗
PubMed1989

Wilms tumor (nephroblastoma) in the adult patient: clinical and radiologic manifestations.

Wilms tumor (nephroblastoma), a primary renal neoplasm containing primitive blastema and embryonic glomerulotubular structures, is seen rarely in adults. To identify clinical and radiologic criteria for preoperative diagnosis of adult Wilms tumor, we studied 29 cases reported in the literature from 1975 to 1987 (all patients were 15 years old or older) and four newly diagnosed cases. The mean age of patients was 30 years; 80% were less than 35 years old. Each patient presented with a large, rapidly growing, abdominal mass (average duration of symptoms, less than 2 months), had no constitutional symptoms (e.g., weight loss, fever), and otherwise were healthy (80%). Twenty-six patients had IV or retrograde pyelograms. Twenty-three showed a nonspecific mass effect. In seven (78%) of nine patients, abdominal CT scans showed a large, inhomogeneous mass with large areas of low density and increased enhancement of the compressed remaining normal renal parenchyma, which resembled a pseudocapsule. In five (63%) of eight patients, sonograms showed a complex mass with large cystic components. In 18 (82%) of 22 patients, arteriograms showed a hypovascular mass with fine wavy or zigzag (creeping-vine) neovascularity. We conclude that a rapidly growing renal mass in a young patient (less than 35 years old) that is shown to be complex and cystic by CT or sonography and that is hypovascular with fine, wavy neovascularity on arteriography is suggestive of adult Wilms tumor (75-80%). An awareness of this constellation of findings may be helpful in diagnosing this unusual tumor before surgery.

Adolescent↗
PubMed1978

Changes in membrane structure and function during chick embryonic erythropoiesis.

We found considerable differences in the pattern of membrane proteins as well as in the relative amounts of individual components in isolated chick red blood cell membranes during the course of embryonic development. Of special interest in the increase in the relative amounts of two major polypeptides, band 3 and 3.1 (MW 100,000 daltons) with increasing age of the cells. With respect to functional studies, we found that the magnitude of sulfate influx decreases with increasing age of the embryo. Furthermore, the activity of ouabain-sensitive ATPase increases with increasing age (2.5-day embryo to adult). In addition, both the basal and the fluoride-stimulated adenylate cyclase activities decrease as the embryo age increases, whereas the enzyme sensitivity to epinephrine increases with increasing age of the embryo.

Adenosine Triphosphatases↗
PubMed2000

[On embryotropic action of XTS-1 plant growth stimulator].

XTC-1 level near 10.1 mg/m3 appeared to approximate to embryotropic activity threshold, but that near 1.3 mg/m3 is inactive. The embryotropic activity occurred on the background of general toxic effects, so the substance does not posses specific embryotropic activity.

Animals↗