Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “ECTODERMAL DEFECT”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 829 records · Page 46Linked to original sources
PubMed1989

Coordinately and differentially mutable activities of torpedo, the Drosophila melanogaster homolog of the vertebrate EGF receptor gene.

The torpedo (top) locus of Drosophila encodes the fruitfly homolog of the vertebrate epidermal growth factor receptor gene and the neu proto-oncogene. We have isolated 13 top alleles in a screen for mutations failing to complement the female sterility of top, a recessive maternal effect allele that disrupts the establishment of the dorsoventral pattern of the egg shell and embryo. Several alleles recovered in this screen are zygotic lethal mutations; genetic analysis of these alleles has demonstrated that top is allelic to the embryonic lethal locus faint little ball. The 13 mutations recovered in our screens and 19 previously isolated top alleles have been genetically characterized through complementation tests with a series of hypomorphic and amorphic alleles. Nearly every top allele fails to complement the maternal effect sterility of top. Complementation tests show that the gene is required not only for oogenesis and embryogenesis, but also for pupal viability, for the growth of certain imaginal discs and for the patterning of specific ectodermal derivatives of the imaginal discs. Complementation analysis further demonstrates that the top lesions can be divided into general phenotypic categories: alleles affecting all gene activities in a coordinate manner, alleles preferentially affecting embryogenesis, alleles preferentially retaining oogenesis activity and alleles differentially affecting the development of specific imaginal disc derivatives. Correlations observed between the various developmental defects produced by top lesions suggest that the gene possesses several differentially, though not independently, mutable activities.

Alleles↗
PubMed1995

A four generation hidrotic ectodermal dysplasia family: an allelic variant of Clouston syndrome?

A four generation Scottish family with hidrotic ectodermal dysplasia affecting predominantly teeth, skin and hair is described. Hypo- or oligodontia of the secondary dentition by late adolescence was characteristic and two individuals had multiple natal teeth. Flexural acanthosis nigricans during childhood and early adolescence is a feature in some of the women. All affected individuals produced sweat, but heat tolerance was variable. Hypoplasia of the pilosebaceous units was found on light microscopy in one subject. Scalp hair was thin and slow growing (but adult females described much improved quality during pregnancy) and body hair was scanty. Scanning electron microscopy of hair samples showed abnormal cuticular appearances consistent with a primary defect affecting keratin structure. The nails were normal. Relative macrocephaly due to hyperostosis of the cranial vault was variably present. Short stature (5-10th centile) present in some cases is possibly a separate familial trait. The family demonstrates overlapping features with Clouston syndrome. In Clouston syndrome, however, alopecia can be severe, palmarplantar hyperkeratosis is usually present, and hypo/oligodontia is not a prominent feature.

Adult↗
PubMed2004

BMP controls nitric oxide-mediated regulation of cell numbers in the developing neural tube.

Balanced cell proliferation and cell death determines neural precursor cell numbers in early stages of neural tube (NT) development. We have previously shown that nitric oxide (NO) regulates cell numbers locally in the NT of eight to 12 somite embryos. Here, we demonstrate that bone morphogenetic protein-4 (BMP-4), which is expressed in the ectoderm and dorsal NT at these developmental stages, induces programmed cell death (PCD) and promotes entry into the S-phase, via nitric oxide synthase (NOS) activity. These effects can be reversed by BMP-4 antagonists, such as follistatin and noggin, or by specific NOS inhibitors, resulting in low NO levels that facilitate mitosis and reduce PCD. Ectopic BMP-4 induction of PCD is restricted to the dorsal NT, whereas promotion of the S-phase is evenly observed across the dorsal-ventral (D-V) axis. Prolonged exposure to either BMP-4 or NOS inhibitors, which results in high or low NO levels, respectively, causes NT defects. The results presented here throw new light on the BMP signaling pathway. The local presence of BMP-4 helps to regulate cell numbers in the developing NT by a NO-mediated pathway, which is essential for normal NT formation.

Animals↗
PubMed1997

Development of the thymus.

Proper development of the thymus is critical for an individual to acquire full immune capability. A full complement of the components that participate in thymic development, interacting with each other at the correct time, is required for maturation. In order to establish the microenvironment necessary for T-cell differentiation, the epithelial primordium of the thymus must expand from pharyngeal endoderm with the aid of contributions from the ectoderm. Experimental studies have established the importance of mesenchymal derivatives from the neural crest in functional development of the epithelial primordium. Interfering with this process inhibits thymic development in a manner similar to that observed in congenital conditions such as the DiGeorge syndrome and the fetal alcohol syndrome. These observations provide clues to understanding the origin of defects in thymus-dependent immunity, and point the way to studies that will expand our understanding of the controls that are involved in genetic and environmental factors impacting on this process.

Animals↗
PubMed2006

Development of the upper lip: morphogenetic and molecular mechanisms.

The vertebrate upper lip forms from initially freely projecting maxillary, medial nasal, and lateral nasal prominences at the rostral and lateral boundaries of the primitive oral cavity. These facial prominences arise during early embryogenesis from ventrally migrating neural crest cells in combination with the head ectoderm and mesoderm and undergo directed growth and expansion around the nasal pits to actively fuse with each other. Initial fusion is between lateral and medial nasal processes and is followed by fusion between maxillary and medial nasal processes. Fusion between these prominences involves active epithelial filopodial and adhering interactions as well as programmed cell death. Slight defects in growth and patterning of the facial mesenchyme or epithelial fusion result in cleft lip with or without cleft palate, the most common and disfiguring craniofacial birth defect. Recent studies of craniofacial development in animal models have identified components of several major signaling pathways, including Bmp, Fgf, Shh, and Wnt signaling, that are critical for proper midfacial morphogenesis and/or lip fusion. There is also accumulating evidence that these signaling pathways cross-regulate genetically as well as crosstalk intracellularly to control cell proliferation and tissue patterning. This review will summarize the current understanding of the basic morphogenetic processes and molecular mechanisms underlying upper lip development and discuss the complex interactions of the various signaling pathways and challenges for understanding cleft lip pathogenesis.

Animals↗
PubMed1997

Xwnt-8 and lithium can act upon either dorsal mesodermal or neurectodermal cells to cause a loss of forebrain in Xenopus embryos.

When Xenopus gastrulae are made to misexpress Xwnt-8, or are exposed to lithium ions, they develop with a loss of anterior structures. In the current study, we have characterized the neural defects produced by either Xwnt-8 or lithium and have examined potential cellular mechanisms underlying this anterior truncation. We find that the primary defect in embryos exposed to lithium at successively earlier stages during gastrulation is a progressive rostral to caudal deletion of the forebrain, while hindbrain and spinal regions of the CNS remain intact. Misexpression of Xwnt-8 during gastrulation produces an identical loss of forebrain. Our results demonstrate that lithium and Wnts can act upon either prospective neural ectodermal cells, or upon dorsal mesodermal cells, to cause a loss of anterior pattern. Specifically, ectodermal cells isolated from lithium- or Wnt-exposed embryos are unable to form anterior neural tissue in response to inductive signals from normal dorsal mesoderm. In addition, although dorsal mesodermal cells from lithium- or Wnt-exposed embryos are specified properly, and produce normal levels of the anterior neural inducing molecules noggin and chordin, they show a greatly reduced capacity to induce anterior neural tissue in conjugated ectoderm. Taken together, our results are consistent with a model in which Wnt- or lithium-mediated signals can induce either mesodermal or ectodermal cells to produce a dominant posteriorizing morphogen which respecifies anterior neural tissue as posterior.

Animals↗
PubMed1999

HNF3beta and Lim1 interact in the visceral endoderm to regulate primitive streak formation and anterior-posterior polarity in the mouse embryo.

Recent embryological and genetic experiments have suggested that the anterior visceral endoderm and the anterior primitive streak of the early mouse gastrula function as head- and trunk-organising centers, respectively. Here, we report that HNF3beta and Lim1 are coexpressed in both organising centers suggesting synergistic roles of these genes in regulating organiser functions and hence axis development in the mouse embryo. To investigate this possibility, we generated compound HNF3beta and Lim1 mutant embryos. An enlarged primitive streak and a lack of axis formation were observed in HNF3beta (-)(/)(-);Lim1(-)(/)(-), but not in single homozygous mutant embryos. Chimera experiments indicate that the primary defect in these double homozygous mutants is due to loss of activity of HNF3beta and Lim1 in the visceral endoderm. Altogether, these data provide evidence that these genes function synergistically to regulate organiser activity of the anterior visceral endoderm. Moreover, HNF3beta (-)(/)(-);Lim1(-)(/)(-) mutant embryos also exhibit defects in mesoderm patterning that are likely due to lack of specification of anterior primitive streak cells.

Animals↗
PubMed1995

A molecular approach to the pathophysiology of the X chromosome-linked Kallmann's syndrome.

The human KAL gene is responsible for the X chromosome-linked Kallmann's syndrome, which consists of an association between hypogonadotropic hypogonadism and anosmia (or hyposmia). Additional symptoms are occasionally observed. The olfactory defect is associated with hypoplasia of the olfactory bulbs and tracts. The hypogonadism may be due to a defect in the embryonic migratory process of GnRH-synthesizing neurones from the olfactory pits up to the brain. The human and chicken KAL genes have been isolated. From the amino acid sequences deduced, it has been postulated that the KAL protein is an extracellular matrix component, with putative antiprotease activity and adhesion function. Various point mutations and, in a few cases, deletions of KAL have been detected in patients. By in situ hybridization, KAL expression has been studied during embryonic development in the chick. From embryonic day 2 (ED2) to ED8, the KAL gene is expressed in various endodermal, mesodermal and ectodermal derivatives, whereas the expression from ED8 is almost entirely restricted to definite neuronal populations in the central nervous system, most of which still express the gene after hatching. According to such a spatiotemporal pattern of expression, we suggest that the KAL gene is involved both in morphogenetic events and in late neuronal differentiation and/or neuronal trophicity. With respect to the olfactory system, the KAL gene is expressed in the mitral cells of the olfactory bulbs from ED8 onwards. In contrast, no expression of the KAL gene is detected at any stage in either the embryonic olfactory epithelium or the surrounding nasal mesenchyme. Therefore, assuming that similar conditions are found in the human embryo, we suggest that the olfactory anomaly in X-linked Kallmann's syndrome results from a central target cell defect. Current hypotheses regarding the pathophysiology of the GnRH deficiency are also discussed. In situ hybridization experiments in the human embryo, as well as characterization of the KAL protein, are in progress.

Animals↗
PubMed2002

Stripe provides cues synergizing with branchless to direct tracheal cell migration.

The Drosophila tracheal system is an interconnected tubular respiratory network, which is formed by directed stereotypic migration and fusion of branches. Cell migration and specification are determined by combinatorial signaling of several morphogens secreted from the ectoderm. We report the discovery of a group of ectodermal cells, marked by Stripe (Sr) expression, that coordinates tracheal cell migration in the dorsoventral axis. Sr, an EGR family transcription factor, is known to regulate muscle migration. In this study, we show that Sr ectodermal cells also provide signals that are utilized for tracheal migration. These cues are separated in the time course of embryonic development. Initially, tendon-precursor cells are in close proximity to the tracheal cells, and later, when tracheal migration is complete, the muscles displace the trachea and attach to the tendon cells. sr-mutant embryos exhibit defects in migration of all tracheal branches. Although the FGF ligand Branchless (Bnl) is expressed in a subset of tendon-precursor cells independently of Sr, Bnl functions cooperatively with proteins induced by Sr in attraction of tracheal branches.

Animals↗
PubMed2005

Pax6-dependence of Six3, Eya1 and Dach1 expression during lens and nasal placode induction.

The Drosophila eyeless gene plays a central role in fly eye development and controls a subordinate regulatory network consisting of the so, eya and dac genes. All three genes have highly conserved mammalian homologs, suggesting possible conservation of this eye forming regulatory network. sine oculis (so) belongs to the so/Six gene family, and Six3 is prominently expressed in the developing mammalian eye. Eya1 and Dach1 are mammalian homologs of eya and dac, respectively, and although neither Eya1 nor Dach1 knockout mice express prenatal eye defects, possibilities exist for postnatal ocular phenotypes or for functional redundancy between related family members. To examine whether expression relationships analogous to those between ey, so, eya and dac exist in early mammalian oculogenesis, we investigated Pax6, Six3, Eya1 and Dach1 protein expression in murine lens and nasal placode development. Six3 expression in the pre-placode lens ectoderm is initially Pax6-independent, but subsequently both its expression and nuclear localization become Pax6-dependent. Six3, Dach1 and Eya1 nasal expression in pre-placode ectoderm are also initially Pax6-independent, but thereafter become Pax6-dependent. Pax6, Six3, Dach1 and Eya1 are all co-expressed in the developing ciliary marginal zone, a source of retinal stem cells in some vertebrates. An in vitro protein-protein interaction is detected between Six3 and Eya1. Collectively, these findings suggest that the Pax-Eya-Six-Dach network is at best only partly conserved during lens and nasal placode development. However, the findings do not rule out the possibility that such a regulatory network acts at later stages of oculogenesis.

Animals↗
PubMed1991

Abdominal wall defect associated with persistent cloaca. The embryologic clues in autopsy.

Three stillborn fetuses are reported in which an abdominal wall defect was associated with defects in the urogenital and anal region. Autopsy of these fetuses provided clues indicative of how and where the embryonic development went wrong. The malformation involved a disturbance of the cell deposition process, occurring in the caudal part of the embryo. During the cell deposition process, which takes place in the neural crest and the body wall placode, ectodermal cells are added to the mesodermal compartment of the embryo, thus contributing to the anlagen of several structures, including the ventral body wall. In addition, a change in the shape of the embryo is generated. The sequence of events resulting from a disturbance of the cell deposition process is explained.

Abdominal Muscles↗
PubMed2005

Congenital brachydactyly and nail hypoplasia: clue to bone-dependent nail formation.

Congenital hyponychia and anonychia are rare malformations which may form part of syndromes such as nail-patella syndrome, ectodermal dysplasias and brachydactylies, or may occur as an isolated finding. Congenital hyponychia and anonychia are frequently accompanied by underlying skeletal abnormalities. A 20-year-old woman showed congenital bilateral hypoplasia or aplasia of the second, third and fourth toenails with corresponding phalanx dysplasia or aplasia of the affected toes. Malformations of the hands or other congenital defects were absent. The findings in this patient do not exactly fit any known entities. Our clinical observation prompted us to review the literature on congenital hyponychia/anonychia and to summarize recent advances in understanding molecular events in nail development. In conclusion, the association of nail anomalies with aplasia and/or hypoplasia of corresponding middle and/or distal phalanges supports the hypothesis of bone-dependent nail formation.

Adult↗
PubMedDate not supplied

Keratolenticular dysgenesis (Peters' anomaly) as a result of acute embryonic insult during gastrulation.

Keratolenticular dysgenesis (Peters' anomaly) was induced in mice by exposure to the human teratogens, ethanol or 13-cis retinoic acid (isotretinoin, Accutane). Acute teratogen exposure on the seventh day of gestation (corresponding to the third week of human gestation) resulted in an eye malformation incidence of 46% to 100% in day 14 fetuses. Of the abnormal eyes, 10% to 29% demonstrated failure of detachment of the lens from the surface ectoderm. Delayed lens detachment was seen as anterior lenticonus in 33% to 35% of the abnormal eyes. Abnormal lens detachment appeared to result in mechanical interference with neural crest migration to form the corneal stroma and endothelium, and iris stroma. This secondary effect on neural crest derivatives is exhibited in the adult animals as corneal opacities associated with defects in Descemet's membrane and endothelium, and anterior polar cataracts.

Animals↗
PubMed2000

Spinal neurenteric cysts without associated malformations. Are they the same as those presenting in spinal dysraphism?

Spinal neurenteric cysts are rare intradural developmental lesions, usually composed of a thin-walled cyst whose lining mimicks gastro-intestinal or respiratory epithelium. A detailed review of the literature revealed 80 cases of solitary spinal neurenteric cysts (including a new case of ours), which were analysed and compared, regarding clinical and pathological aspects, with 56 such cases of those with concomitant evidence of dysraphism. Older age and cervical location were found to be statistically characteristic of the solitary cysts in contrast to younger age and lumbosarcal location for the 'dysraphic' cases. Magnetic resonance imaging is the diagnostic modality of choice. Good evidence of the developmental origin of incomplete separation of notochord and endoderm was given by the fact that histologically solitary cysts were mainly composed by endodermal derivatives, while 'dysraphic' had also mesenchymal and ectodermal elements. Thus, it seems that additional spinal dysraphic changes are more likely to be found when ectodermal and mesenchymal elements co-exist with endodermal ones, possibly indicating an earlier error in development than in other cases containing only endodermal elements.

Humans↗
PubMed2005

Congenital scalp and calvarial deficiencies: principles for classification and surgical management.

Congenital defects of the scalp and skull present a challenge for care providers because of a combination of their rarity and the magnitude of potential morbidity. Recent advancements in autogenous and alloplastic cranioplasty and scalp reconstruction techniques argue for a comprehensive consideration of this problem. This article (1) reviews the causes of congenital scalp and calvarial defects; (2) proposes a classification system based on defect type, similar to the tumor-node-metastasis classification, in that defect location, defect size, and extent of neuromeningeal involvement are the critical variables; and (3) presents algorithms for care based on the defect classification. A set of management principles on which treatment plans can be based for these unique problems is provided.

Algorithms↗
PubMed2006

Expression of Wnt9b and activation of canonical Wnt signaling during midfacial morphogenesis in mice.

Cleft lip with or without cleft palate (CLP) is the most common craniofacial birth defect in humans. Recently, mutations in the WNT3 and Wnt9b genes, encoding two members of the Wnt family of signaling molecules, were found associated with CLP in human and mice, respectively. To investigate whether Wnt3 and Wnt9b directly regulate facial development, we analyzed their developmental expression patterns and found that both Wnt3 and Wnt9b are expressed in the facial ectoderm at critical stages of midfacial morphogenesis during mouse embryogenesis. Whereas Wnt3 mRNA is mainly expressed in the maxillary and medial nasal ectoderm, Wnt9b mRNA is expressed in maxillary, medial nasal, and lateral nasal ectoderm. During lip fusion, Wnt9b, but not Wnt3, is expressed in the epithelial seam between the fusing medial and lateral nasal processes. Furthermore, we found that expression of TOPGAL, a transgenic reporter of activation of canonical Wnt signaling pathway, is specifically activated in the distal regions of the medial nasal, lateral nasal, and maxillary processes prior to lip fusion. During lip fusion, the epithelial seam between the medial and lateral nasal processes as well as the facial mesenchyme directly beneath the fusing epithelia strongly expresses TOPGAL. These data, together with the CLP lip phenotype in WNT3-/- humans and Wnt9b-/- mutant mice, indicate that Wnt3 and Wnt9b signal through the canonical Wnt signaling pathway to regulate midfacial development and lip fusion.

Animals↗
PubMed1975

Regeneration of the tail bud in Xenopus embryos.

In an attempt to solve some aspect of the long-standing controversy about the regenerative ability of appendages in vertebrate embryos, the tail bud of Xenopus laevis embryos has beenamputated at stage sranging from St. 26 to St. 32 and its ability to regenerate duringa culture period of 2-3 days has been studied. At amputation stages 26-28,the tail bud consisted only undifferentialted mesoderm and ectoderm, but at stage 32 it had afully differentiated neural tube, a vaculotaed notochord and segmented somites. A total of 137amputations at differnt stages gace consistent results: a tail formed in all the operated larvacand it had normal, well-developed axial tissues in most cases. The relatively few cases with abnormal tail struture were stunted, oedematour larvae with defects in the trunk region as well. It is concluded from these experiments that cells near the original tail budare able to differentiate into tialbud tissues and to replace the amputated regoin, even at these late embryoic stages. The implications of these findings for comparative studies on regeneration in vertebrates are discussed.

Amputation, Surgical↗
PubMed1996

A mammalian patched homolog is expressed in target tissues of sonic hedgehog and maps to a region associated with developmental abnormalities.

Drosophila patched is a segment polarity gene required for the correct patterning of larval segments and imaginal discs during fly development and has a close functional relationship with hedgehog. We have isolated a complete human PATCHED cDNA sequence, which encodes a putative protein of 1296 amino acids, and displays 39% identity and 60% similarity to the Drosophila PATCHED protein. Hydropathy analysis suggests that human PATCHED is an integral membrane protein with a pattern of hydrophobic and hydrophilic stretches nearly identical to that of Drosophila patched. In the developing mouse embryo, patched is initially detected within the ventral neural tube and later in the somites and limb buds. Expression in the limb buds is restricted to the posterior ectoderm surrounding the zone of polarizing activity. The results show that patched is expressed in target tissues of sonic hedgehog, a murine homolog of Drosophila hedgehog suggesting that patched/hedgehog interactions have been conserved during evolution. Human PATCHED maps to human chromosome 9q22.3, the candidate region for the nevoid basal cell carcinoma syndrome. Patched expression is compatible with the congenital defects observed in the nevoid basal cell carcinoma syndrome.

Amino Acid Sequence↗