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At least 1,639 records · Page 91Linked to original sources
PubMed2005

Loss of the extraembryonic ectoderm in Elf5 mutants leads to defects in embryonic patterning.

The extraembryonic ectoderm (ExE) is essential for mammalian placental formation and survival of the embryo in utero. We have obtained a mouse model lacking the ExE, by targeted deletion of the transcription factor Elf5. Although Elf5 mutant embryos implant and form an ectoplacental cone, no trophoblast stem (TS) cells can be derived, indicating that the absence of ExE is a result of the lack of TS cell maintenance. Embryos without ExE tissue are able to form the anterior visceral endoderm but fail to undergo gastrulation, demonstrating an essential role for the ExE in embryonic patterning during a defined window of development.

Animals↗
PubMed2006

The Notch-effector HRT1 gene plays a role in glomerular development and patterning of the Xenopus pronephros anlagen.

Notch signaling has been shown to play a role in cell fate decisions in the Xenopus pronephros anlagen. Here, we show that the Xenopus Hairy-related transcription factor (HRT) gene XHRT1, and the Hairy/Enhancer of split (HES) genes Xhairy1, Xhairy2b, esr9 and esr10, have distinct restricted dynamic expression patterns during pronephros development, and that their expression is regulated by Notch. XHRT1, which is the earliest and strongest gene expressed in the pronephric region, is initially transcribed predominantly in the forming glomus, where it is downregulated by antisense morpholino oligonucleotide inhibition of xWT1. Later, it is activated in the most dorsoanterior part of the pronephros anlagen that gives rise to the proximal tubules. In agreement with this dynamic expression profile, we found that early activation of Notch favors glomus, whereas only later activation promotes proximal tubule formation. We show that, among the bHLH-O factors tested, only XHRT1 efficiently inhibits distal tubule and duct formation, and that only its translational inhibition causes a reduction of the expression of proximal tubule and glomus markers. Using domain swap experiments, we found that the XHRT1 C-terminal region is crucial for its activity. Together, our results provide evidence that XHRT1 plays an important role in glomerular development and early proximodistal patterning that is distinct from those of the other pronephric bHLH repressors.

Animals↗
PubMed2000

Correlation of diversity of leg morphology in Gryllus bimaculatus (cricket) with divergence in dpp expression pattern during leg development.

Insects can be grouped into mainly two categories, holometabolous and hemimetabolous, according to the extent of their morphological change during metamorphosis. The three thoracic legs, for example, are known to develop through two overtly different pathways: holometabolous insects make legs through their imaginal discs, while hemimetabolous legs develop from their leg buds. Thus, how the molecular mechanisms of leg development differ from each other is an intriguing question. In the holometabolous long-germ insect, these mechanisms have been extensively studied using Drosophila melanogaster. However, little is known about the mechanism in the hemimetabolous insect. Thus, we studied leg development of the hemimetabolous short-germ insect, Gryllus bimaculatus (cricket), focusing on expression patterns of the three key signaling molecules, hedgehog (hh), wingless (wg) and decapentaplegic (dpp), which are essential during leg development in Drosophila. In Gryllus embryos, expression of hh is restricted in the posterior half of each leg bud, while dpp and wg are expressed in the dorsal and ventral sides of its anteroposterior (A/P) boundary, respectively. Their expression patterns are essentially comparable with those of the three genes in Drosophila leg imaginal discs, suggesting the existence of the common mechanism for leg pattern formation. However, we found that expression pattern of dpp was significantly divergent among Gryllus, Schistocerca (grasshopper) and Drosophila embryos, while expression patterns of hh and wg are conserved. Furthermore, the divergence was found between the pro/mesothoracic and metathoracic Gryllus leg buds. These observations imply that the divergence in the dpp expression pattern may correlate with diversity of leg morphology.

Animals↗
PubMed2001

Genetic dissection of nodal function in patterning the mouse embryo.

Loss-of-function analysis has shown that the transforming growth factor-like signaling molecule nodal is essential for mouse mesoderm development. However, definitive proof of nodal function in other developmental processes in the mouse embryo has been lacking because the null mutation blocks gastrulation. We describe the generation and analysis of a hypomorphic nodal allele. Mouse embryos heterozygous for the hypomorphic allele and a null allele undergo gastrulation but then display abnormalities that fall into three distinct mutant phenotypic classes, which may result from expression levels falling below critical thresholds in one or more domains of nodal expression. Our analysis of each of these classes provides conclusive evidence for nodal-mediated regulation of several developmental processes in the mouse embryo, beyond its role in mesoderm formation. We find that nodal signaling is required for correct positioning of the anteroposterior axis, normal anterior and midline patterning, and the left-right asymmetric development of the heart, vasculature, lungs and stomach.

Alleles↗
PubMed2001

Pre-pattern in the pronephric kidney field of zebrafish.

Vertebrate embryos use a series of transient kidneys to regulate fluid balance, osmolarity and metabolic waste during development. The first kidney to form in the embryo is the pronephros. This kidney is composed of several cell types with very different functions and is organized into discrete segments: glomerulus, tubules and nephric duct. The site of origin of these cells is poorly understood, as are their lineage relationships. We have defined regions of the intermediate mesoderm as candidates for the pronephric field by expression patterns of the Wilms' Tumor suppressor gene (wt1), single-minded 1 (sim1) and pax2.1. All of these potential kidney markers are expressed in a stripe of intermediate mesoderm, with distinct, overlapping antero-posterior borders. We labeled small groups of cells in this area by laser uncaging of a fluorescent dextran, and then tracked their fates. We found that there was a bounded contiguous region of the intermediate mesoderm that provides pronephric progenitors. As is true for other organ fields, the pronephric field regulates after focal destruction, such that a normal pronephros forms after laser-mediated removal of the wt1 domain. The progenitors for podocytes, tubular cells and duct are restricted to subdomains within the pronephric field. The most anterior cells in the pronephric field give rise to podocytes. This corresponds to the wt1-expressing region. The next more posterior cells contribute to the tubule, and express both wt1 and pax2.1. The most posterior cells contribute to the nephric duct, and these express pax2.1 and sim1, but not wt1. Thus, there is a field for the pronephric kidney with classical attributes of defined border, pre-pattern and regulation. The pattern of the fate map reflects particular combinations of transcription factors.

Animals↗
PubMed2002

Distinct roles for Fgf, Wnt and retinoic acid in posteriorizing the neural ectoderm.

Early neural patterning in vertebrates involves signals that inhibit anterior (A) and promote posterior (P) positional values within the nascent neural plate. In this study, we have investigated the contributions of, and interactions between, retinoic acid (RA), Fgf and Wnt signals in the promotion of posterior fates in the ectoderm. We analyze expression and function of cyp26/P450RAI, a gene that encodes retinoic acid 4-hydroxylase, as a tool for investigating these events. Cyp26 is first expressed in the presumptive anterior neural ectoderm and the blastoderm margin at the late blastula. When the posterior neural gene hoxb1b is expressed during gastrulation, it shows a strikingly complementary pattern to cyp26. Using these two genes, as well as otx2 and meis3 as anterior and posterior markers, we show that Fgf and Wnt signals suppress expression of anterior genes, including cyp26. Overexpression of cyp26 suppresses posterior genes, suggesting that the anterior expression of cyp26 is important for restricting the expression of posterior genes. Consistent with this, knock-down of cyp26 by morpholino oligonucleotides leads to the anterior expansion of posterior genes. We further show that Fgf- and Wnt-dependent activation of posterior genes is mediated by RA, whereas suppression of anterior genes does not depend on RA signaling. Fgf and Wnt signals suppress cyp26 expression, while Cyp26 suppresses the RA signal. Thus, cyp26 has an important role in linking the Fgf, Wnt and RA signals to regulate AP patterning of the neural ectoderm in the late blastula to gastrula embryo in zebrafish.

Animals↗
PubMed2002

Colinearity and non-colinearity in the expression of Hox genes in developing chick skin.

Hox genes are usually expressed temporally and spatially in a colinear manner with respect to their positions in the Hox complex. We found that these characteristics apply to several Hox genes expressed in developing chick skin (Hoxb-4, Hoxa-7 and Hoxc-8), and we classed this group of genes as regionally restricted. To our surprise, we found that most of the Hox genes we examined are regionally unrestricted in their expression in the embryonic chick skin. This second group includes the Hoxd genes, Hoxd-4 to Hoxd-13, Hoxa-11 and Hoxc-6. Temporally, the expression of the regionally restricted genes can be observed by E5 within the epidermis, whereas the spatially unrestricted genes are not expressed in the epidermis until E6.25. Unexpectedly, we found that all the unrestricted genes are expressed concomitantly and therefore do not conform to temporal colinearity. Moreover, the dermal expression for both groups occurs later, but maintains the same anteroposterior patterning to that seen previously in the epidermis. During embryonic day 7-8, expression for all genes is up-regulated within the dense dermis whilst being reduced within the inter-bud regions. Later expression within the bud mesenchyme is down-regulated whilst high levels of transcriptional activity are detectable within the epidermal sheath of each feather bud. These results indicate that the transcriptional activity of Hox genes in the developing chick skin could be important during embryonic skin patterning both by providing regionally restricted positional cues, and also by imparting generic signals necessary for feather morphology.

Animals↗
PubMed2000

The caenorhabditis elegans fate-determining gene mab-9 encodes a T-box protein required to pattern the posterior hindgut.

Caenorhabditis elegans mab-9 mutants are defective in hindgut and male tail development because of cell fate transformations in two posterior blast cells, B and F. We have cloned mab-9 and show that it encodes a member of the T-box family of transcriptional regulators. MAB-9 localizes to the nucleus of B and F and their descendents during development, suggesting that it acts cell autonomously in the posterior hindgut to direct cell fate. T-box genes related to brachyury have also been implicated in hindgut patterning, and our results support models for an evolutionarily ancient role for these genes in hindgut formation.

Amino Acid Sequence↗
PubMed2000

Intestinal fatty acid binding protein gene expression reveals the cephalocaudal patterning during zebrafish gut morphogenesis.

Intracellular fatty acid-binding proteins (FABPs) are small and highly conserved cytoplasmic proteins that bind long-chain fatty acids and other hydrophobic ligands. We have examined, as a model for studying intestinal epithelial cell differentiation, the cell-specific and spatio-temporal expression of intestinal fatty acid-binding protein (i-fabp) gene during zebrafish larval development. After molecular cloning of zebrafish I-FABP cDNA, whole-mount in situ hybridization analysis revealed that i-fabp is expressed in the intestinal tube around day 3 postfertilization. By day 4, highest level of i-fabp transcript is encountered in the proximal columnar epithelium. From day 5 onwards, i-fabp is strongly expressed in the anterior intestine and its rostral expansion, slightly expressed in the esophagus mucosa and rectum, while no mRNA could be detected in the posterior intestine. Therefore, the regional differentiation of the intestine precedes first feeding and complete yolk resorption. I-fabp expression in the anterior intestine of the fed larvae is correlated with an intracellular storage of lipid droplets in the enterocytes and the massive synthesis of very low-density lipoprotein particles. In conclusion, the cephalocaudal expression pattern of i-fabp demarcates early during zebrafish gut morphogenesis the anterior fat absorbing to posterior cells of the intestine. This gene could be used as a marker for screening for mutations that affect the events of intestinal epithelial differentiation, cephalocaudal patterning, and asymmetric gut looping morphogenesis.

Amino Acid Sequence↗
PubMed2003

Effects of gravity on early embryogenesis [correction of embryogeneis] in Caenorhabditis elegans.

The embryonic development of the nematode Caenorhabditis elegans was examined under different gravitational conditions. The embryos after fertilization normally hatched under hypergravity (200 G) or 3D-clinorotation, whereas the number of eggs laid from an adult hermaphrodite decreased and their hatching rate was reduced under the hypergravity condition. The first cleavage plane in the 1-cell embryo was slid to some extent by re-orientation of liquid culture vessel, but the pattern and timing of cleavages were not affected.

Animals↗
PubMed1998

[Signaling molecules involved in induction and early patterning of limb buds].

Soluble signaling factors are involved in morphogenetic events during vertebrate limb development. They belong to the Hedgehog family, the bone morphogenetic protein (BMP) family, the fibroblast growth factor (FGF) family and the Wnt family. FGF-8 and FGF-10 play central roles to specify the limb field and promote initial outgrowth. In the established limb bud, FGF-4, FGF-8 and BMP-2 are secreted in the apical ectodermal ridge and control proximal-distal pattern formation. In the zone of polarizing activity Sonic hedgehog is produced and pattern along the anterior-posterior axis. Members of the BMP family may be the secondary signals in this patterning. Wnt-7a from the dorsal ectoderm dorsalizes limb mesenchyme and controls dorsal-ventral patterning. These factors expressed in the signaling centers in limb buds influence gene expression each other and coordinate limb morphogenesis.

Animals↗
PubMed2000

Tracking of body mass index from childhood to adolescence: a 6-y follow-up study in China.

BACKGROUND: Although extensive descriptive research shows that childhood obesity predisposes a person to adult obesity, little is understood about the dynamics of weight during childhood and the predictors of weight tracking. OBJECTIVE: Our objective was to examine tracking patterns of body mass index (BMI) as well as their predictors between childhood and adolescence. DESIGN: A cohort of 975 Chinese children aged 6-13 y was followed for 6 y (1991-1997). Tracking of BMI was defined as an individual maintaining a certain status (overweight or underweight) or relative position (relative BMI quartile) over time. Relative BMI related BMI to age- and sex-specific BMI cutoffs. RESULTS: After 6 y, approximately 40% of the subjects had maintained their relative positions, but 30% had moved into a lower or higher quartile. The BMIs of thin and fat children were more likely to track: 51% and 46% remained in the bottom and upper quartiles, respectively. Nearly one-third of the underweight children remained underweight in 1997. Overweight children were 2.8 times as likely as all other children to become overweight adolescents; underweight children were 3.6 times as likely to remain underweight as adolescents. Parental obesity and underweight, individuals' initial BMIs, dietary fat intake, and family income helped predict tracking and changes in BMI. CONCLUSION: In a society undergoing enormous changes in diet and activity, BMI tracking is still very important between childhood and adolescence in China.

Adolescent↗
PubMed1975

On the role of the interstitial volume in the response of the rat to blood volume expansion.

Patterns of body fluid distribution and selected cardiovascular and renal responses were studied following vascular expansion in normal rats and in rats with altered interstitial fluid volume produced by dehydration, prehydration or hyperoncotic albumin infusion. In all four groups the patterns of the renal excretory response and the accompanying change in central venous pressure (CVP) were closely parallel and the disturbance in CVP was finally corrected in the presence of a considerable residual vascular expansion. During the diuresis and saluresis following iso-oncotic vascular expansion in prehydrated and dehydrated rats, both groups removed fluid chiefly from the interstitium; this fluid removal was attributable mainly to urinary excretion in prehydrated rats but mainly to redistribution into the cellsin dehydrated rats. In the latter series, preferential renal excretion of sodium over water was observed. Hyperoncotic vascular expansion led to a peak renal excretory response only 70% of that following iso-oncotic expansion. The excreted volume was accounted for by a similar depletion of interstitial fluid after the iso-oncotic load. These findings are consistent with the hypothesis that the renal response to volume expansion regulates some parameter which is more closely related to the mean central venous pressure than to the vascular volume. This regulation was associated with incomplete correction of the vascular expansion and absolute decrease in interstitial fluid volume compared to the initial size of that compartment. This provides support for a functionally important influence of the interstitial volume on venous compliance.

Animals↗
PubMed2005

Anthropoecological investigations in Central Asia.

The results of anthropoecological investigations in Central Asia are described. From 1976 to 1991 about 6,000 individuals of both sexes were examined. 2,500 of them were children from 7 to 17 years. The program included the study of body build, metabolic rates, genetic markers and demographic structures. Different groups of Tuvins, Khakass, Mountain and Abakan Shortsys, Altai-kijis, Telengits, Teleuts, Kazakhs, and several groups of Mongols and Khotons were studied. It was shown that some patterns of body build and physiological traits of native populations of Central Asia partly reflect the influence of the geographical environment. The differences observed between various populations of the region may be explained by ecological reasons and not only by ethnic differentiation.

Adult↗
PubMed1999

Growth pattern and carcase development in male ducks selected for growth rate.

1. Growth patterns of the whole body, eviscerated carcases, breast muscle, leg and thigh muscles and abdominal fat pads were compared in 4 lines (Lines A, B, C, and D) of male ducks selected for market weight (n = 1305) using growth curve analysis, allometric growth analysis and repeated measure analysis. At 49 d of age, Line A was heaviest, followed by Line B, Line C and Line D. 2. Ducks were fed ad libitum under 24-h lighting and 12 or 24 ducks were killed to determine body, carcase, breast-muscle, leg and thigh-muscle, and abdominal fat weights at time points from hatching until 53 d of age. 3. The Weibull function was chosen for growth curve analysis. The asymptote and inflection point from the Weibull growth curves identified 3 lines (Lines B, C, and D) with discrete body and carcase growth patterns but did not distinguish Line A from Line B. In all 4 lines the asymptote ranged from 4437 g to 3008 g for body weight and from 3334 g to 2098 g for carcase weight; the inflection point ranged from 22.5 d to 25.3 d for body weight and from 25.4 d to 29.6 d for carcase weight. 4. The allometric growth coefficient, relative to whole-body growth, was higher than 1.00 for breast muscle and lower than 1.00 for leg and thigh muscles during from 4 d to 53 d of age. 5. Body fat accumulation was estimated by abdominal fat. Line D accumulated more abdominal fat than other lines. The pattern of fat accumulation in Line D was different from Lines A, B and C and there were no differences between Lines A, B and C.

Abdomen↗
PubMed2002

Development of the zebrafish inner ear.

Abstract Recent years have seen a renaissance of investigation into the mechanisms of inner ear development. Genetic analysis of zebrafish has contributed significantly to this endeavour, with several dramatic advances reported over the past year or two. Here, we review the major findings from recent work in zebrafish. Several cellular and molecular mechanisms have been elucidated, including the signaling pathways controlling induction of the otic placode, morphogenesis and patterning of the otic vesicle, and elaboration of functional attributes of inner ear.

Animals↗
PubMed2003

Transitions in the model of epithelial patterning.

We analyze pattern formation in the model of cell communication in Drosophila egg development. The model describes the regulatory network formed by the epidermal growth factor receptor (EGFR) and its ligands. The network is activated by the oocyte-derived input that is modulated by feedback loops within the follicular epithelium. We analyze these dynamics within the framework of a recently proposed mathematical model of EGFR signaling (Shvartsman et al. [2002] Development 129:2577-2589). The emphasis is on the large-amplitude solutions of the model that can be correlated with the experimentally observed patterns of protein and gene expression. Our analysis of transitions between the major classes of patterns in the model can be used to interpret the experimentally observed phenotypic transitions in eggshell morphology in Drosophila melanogaster. The existence of complex patterns in the model can be used to account for complex eggshell morphologies in related fly species.

Animals↗
PubMed2006

Sema3D, Sema3F, and Sema5A are expressed in overlapping and distinct patterns in chick embryonic heart.

An increasing number of axon guidance cues have been shown recently to play important roles in the development of non-neural tissues. Semaphorins comprise one of the largest conserved families of axon guidance factors. We analyzed the expression patterns of Sema3D, Sema3F, and Sema5A genes in the chick embryonic heart by in situ hybridization. All three genes are expressed in the cardiac cushion regions, both in the mesenchymal cells, and epithelial cells in the endocardial layer, during the period of cardiac remodeling. In addition to the overlapping expression patterns in the cardiac cushion regions, these genes also exhibit distinct expression patterns in the developing heart: Sema3D is additionally expressed in the tips of the ventricular trabeculae; Sema3F is expressed in a subset of cells scattered throughout the ventricles; and Sema5A is expressed in the newly formed atrioventricular valves. The overlapping and distinct expression patterns of these genes suggest that they may play important roles in heart development.

Animals↗