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PubMed1993

Immunolocalization of basal lamina components during development of chick otic and optic primordia.

Immunolocalization of laminin, fibronectin, and type IV collagen was examined during early morphogenetic shape changes of the avian inner ear and eye. The ear was studied from formation of the otic placode to invagination of the otic pit and the eye from the optic vesicle stage to formation of an optic cup. Distribution and intensity of immunoreactivity were compared in the two organ primordia and in adjacent epithelial layers. Laminin formed a continuous layer at the basal surface of the otic ectoderm and adjacent neural tube at all stages. The basal surfaces of the optic and lens epithelia also were continuously covered with laminin throughout development. The otic placode became attached to the neural ectoderm through a single layer of fibronectin and collagen IV between the layers of laminin. The ring-like attachment between the edges of the optic cup and lens primordium had the same structure. In addition, the central regions of the optic and lens primordia were attached by fibrils containing type IV collagen, whereas finer strands containing fibronectin and laminin also connected the otic epithelium and neural tube. The results are discussed in terms of models of invagination for the two primordia.

Animals↗

PubMed1991

The temporal bone in the Johanson-Blizzard syndrome. A CT study.

The findings of thin-section high-resolution CT of the temporal bone in two children with Johanson-Blizzard syndrome are reported. In both cases an anomaly of the inner ear was found, consisting of bilateral cystic dilatation of the cochlea and the vestibulum. The possible etiologic basis for the hearing loss in this syndrome is discussed and the literature is reviewed.

Child↗

PubMed1979

The effect of prolonged decompaction on the development of the preimplantation mouse embryo.

A rabbit antiserum to a mouse embryonal carcinoma cell line blocks compaction of cleaving mouse embryos. Cell division is not affected up to the 32-cell stage but intracellular junctions fail to develop. Removal of the antibody at this stage permits compaction to occur and a normal blastocyst develops. Prolonged decompaction beyond the 32-cell embryo results in an increasing proportion of malformed blastocysts in which trophectodermal cells predominate and functional inner cell mass (ICM) cells are reduced or absent. The relationship of compaction to the generation of ICM and trophectoderm lineages in the intact embryo is discussed.

Animals↗

PubMed2002

Expression of the transcription factors GATA3 and Pax2 during development of the mammalian inner ear.

The transcription factors GATA3 and Pax2 are expressed throughout development of the mouse inner ear. We have used antibodies to study their temporal and spatial expression patterns from embryonic days E8-E16.5. The two factors show reciprocal relationships in the regional patterning of the early otocyst and cellular patterning within the sensory epithelia. GATA3 is expressed in the whole otic placode at E8. In the otocyst at E9.5-10.5, the distribution is lateral and complementary to the medial expression pattern of Pax2. Only Pax2 is expressed in the endolymphatic duct, but both factors are expressed in the cochlea. At E11.5-13.5, GATA3 is expressed strongly in the cochlea, but in the dorsal, vestibular region it is downregulated. In all sensory epithelia, downregulation coincides with sensory innervation. Pax2 is expressed in all sensory and some nonsensory epithelia, but within sensory epithelia at E16.5 it is restricted to hair cells. GATA3 is expressed throughout key periods of cell proliferation, fate determination, and differentiation and is not specifically associated with any of these processes. Expression persists most strongly in the main components of the developing auditory system. These include the auditory sensory epithelium, the afferent and efferent nerves, and the mesenchymal and ectodermal cells in regions that form key parts of the middle and outer ear. GATA3 is thus expressed in functionally distinct groups of cells that integrate to form a complete sensory system. The results suggest that both factors may be involved in tissue compartmentalisation, morphogenesis, and cell signalling.

Aging↗

PubMed2004

Regulated gene expression of hyaluronan synthases during Xenopus laevis development.

Here reported is the developmental gene expression pattern of the three known vertebrate hyaluronan synthases (XHas1, XHas2 and XHas3) and a comparative analysis of their mRNAs spatio-temporal distribution during Xenopus laevis development. We found that while XHas2 shows a steady-state expression from gastrula to late tailbud stage, XHas1 is mainly present in the early phases of development while XHas3 is predominantly transcribed in tailbud embryos. XHas1, XHas2 and XHas3 show distinct tissue expression patterns. In particular, XHas1 is localized in ectodermal derivatives and in cranial neural crest cells, whereas XHas2 is mainly found in mesoderm-derived structures and in trunk neural crest cells. Moreover, the expression pattern of XHas2 overlaps that of MyoD in cells committed to a muscle fate. Unlike the other hyaluronan synthases, XHas3 mRNA distribution is very restricted. In particular, XHas3 is expressed in the otic vesicles and closely follows the inner ear development. In conclusion, XHas1, XHas2 and XHas3 mRNAs have distinct and never overlapping spatial expression domains, which would suggest that these three enzymes may play different roles during embryogenesis.

Animals↗

PubMed1988

The development potential of parthenogenetically derived cells in chimeric mouse embryos: implications for action of imprinted genes.

Parthenogenetic embryos of mice die shortly after implantation and characteristically contain poorly developed extraembryonic tissue. To investigate the basis of the abnormal development of parthenotes, we combined them with normal embryos to produce chimeras and examined the distribution of the parthenogenetically derived cells during preimplantation and early postimplantation development. The parthenogenetic embryos were derived from a transgenic mouse line bearing a large insert, which allowed these cells to be identified in histological sections using in situ hybridization. At the blastocyst stage, the parthenogenetic embryos contributed cells to the trophectoderm (TE) and inner cell mass (ICM) of chimeras. By 6.5 days, however, in almost every embryo, parthenogenetically derived cells were not detected in the extraembryonic trophoblast tissue descended from the TE. In contrast, parthenogenetically derived cells could contribute to all descendants of the ICM of 6.5-and 7.5-day chimeras, including the extraembryonic visceral and parietal endoderm. Quantitative analysis of the degree of chimerism in the embryonic ectoderm at 6.5-7.5 days indicated that parthenogenetically derived cells could contribute as extensively as normal cells. These results indicate that normal trophoblast development requires gene expression from the paternally inherited genome before 6.5 days of embryogenesis. Tissues of the ICM lineage, however, apparently can develop independently of the paternal genome at least to 7.5 days of embryogenesis. Comparison of these results with those of others suggests that the influence of imprinted genes is manifested at different times and in a variety of tissues during development.

Animals↗

PubMed2004

The primitive streak, the caudal eminence and related structures in staged human embryos.

The caudal region of the trunk was reassessed in 52 serially sectioned human embryos of stages 8-23, 42 of which were controlled by precise graphic reconstructions. The following observations, new for the human, are presented. (1) The neurenteric canal is an important landmark because rostral to it the neural plate of stages 8, 9, and the main part of the notochord develop, whereas caudal to it the neural plate of stages 10-12 and the caudal portion of the notochord are formed. All somites at stages 9-11 and probably also at stage 12 arise rostral to the site of the neurenteric canal. (2) A 'chordoneural hinge' can be detected in stages 10 and 11, where the caudal part of the neural plate gives off cells that probably participate in the production of mesenchyme. (3) When apparent disappearance of the epiblast is used as a criterion, then the primitive streak seems to end during stage 9. (4) The caudal eminence, derived from the primitive streak and covered by ectoderm, forms at stage 10 caudal to the site of the former neurenteric canal and persists as a terminal cap to at least stage 14, although formation of mesenchyme continues in stages 15 to 17 or 18. (5) As the region rostral to the site of the neurenteric canal grows because of the development of somites, the caudal eminence is shifted caudally. (6) The caudal eminence is most active developmentally during stage 13, when most of the required (ca 6 out of 9) pairs of somites appear. (7) The eminence produces the caudal part of the notochord and, after closure of the caudal neuropore, all caudal structures, but it does not produce even a temporary 'tail' in the human. (8) A temporal overlap results between primary and secondary development in the caudal part of the notochord. (9) Primary development begins very early with the formation of the inner cell mass at stage 3, and includes the development of the somites rostral to the neurenteric canal, whereas secondary development, with the exception of the notochord caudally, commences at stage 12. (10) Primary neurulation lasts from stage 8 to stage 12, secondary from stage 12 to stages 17 or 18. (11) Secondary development and secondary neurulation are characterized morphologically by direct formation of structures (notochord, postcloacal gut, neural cord/neural tube) from mesenchyme.

Ectoderm↗

PubMed2000

Flow of cells from polar to mural trophectoderm is polarized in the mouse blastocyst.

During growth of the blastocyst there is a net flow of cells from the polar to the mural trophectoderm which is presumed to be radially symmetrical. However, such a pattern of cell movement is inconsistent with findings from a recent clonal analysis. To visualize the overall flow of cells directly, the polar trophectoderm of expanding blastocysts was labelled globally with fluorescent microspheres. Following further growth, the great majority of blastocysts that remained labelled throughout the polar trophectoderm exhibited a polarized rather than radial spread of label into the mural region. This was the case regardless of the labelling technique, whether the blastocysts were grown in utero or in vitro, or had the zona pellucida removed or left on. Intriguingly, where there were two foci of spread of label into the mural trophectoderm rather than one, these were diametrically opposite each other. In further experiments, fluorescent lineage labels were used to distinguish junctional trophectoderm cells with and without an extension onto the blastocoelic surface of the inner cell mass. The location of clones formed following further blastocyst growth provided no evidence that egress of cells from the polar trophectoderm is restricted circumferentially by the presence of junctional cells having an extension.

Animals↗

PubMed1994

A functional test for maternally inherited cadherin in Xenopus shows its importance in cell adhesion at the blastula stage.

We report here on the consequences of reducing the expression of EP-cadherin at the earliest stages of Xenopus development. Injection of oligodeoxynucleotides antisense to maternal EP-cadherin mRNA into full-grown oocytes reduced the mRNA level in oocytes, and the protein level in blastulae. Adhesion between blastomeres was significantly reduced, as seen in whole embryos, and in assays of the ability of blastomeres to reaggregate in culture. This effect was especially conspicuous in the inner cells of the blastula and included the disruption of the blastocoel. The severity of the EP-cadherin mRNA depletion and of the disaggregation phenotype was dose dependent. This phenotype was rescued by the injection into EP-cadherin mRNA-depleted oocytes of the mRNA coding for a related cadherin, E-cadherin, that is normally expressed at the gastrula stage in the embryonic ectoderm.

Animals↗

PubMed1988

Paternal DNA strands segregate to both trophectoderm and inner cell mass of the developing mouse embryo.

The localization of sperm DNA strands was examined in preimplantation mouse embryos. Male mice were treated with bromodeoxyuridine (BrdU) to label germ-cell-line DNA and were then mated with unlabeled females. Sperm DNA strands in early embryos derived from these matings could be detected by means of a fluorescent antibody specific to BrdU. The position and number of fluorescent spots detected in the developing embryos are consistent with a model in which paternal DNA strands segregate at random into both the trophectoderm and the inner cell mass. Although we could not follow the segregation of individual paternal chromosomes, we could detect no overall segregation pattern of the sperm DNA strands that could be obviously related to chromosome imprinting.

Animals↗

PubMed2003

Analysis of cell lineage in two- and four-cell mouse embryos.

Compared with other animals, the embryos of mammals are considered to have a highly regulative mode of development. However, recent studies have provided a strong correlation between the first cleavage plane and the future axis of the blastocyst, but it is still unclear how the early axes of the preimplantation embryo reflect the future body axes that emerge after implantation. We have carried out lineage tracing during mouse embryogenesis using the Cre-loxP system, which allowed us to analyze cell fates over a long period of development. We used a transgenic mouse strain, CAG-CAT-Z as a reporter line. The descendants of the manipulated blastomere heritably express beta-galactosidase. We examined the distribution of descendants of a single blastomere in the 8.5-day embryo after labeling at the two-cell and four-cell stages. The derivatives of one blastomere in the two-cell embryo randomly mix with cells originating from the second blastomere in all cell layers examined. Thus we find cells from different blastomeres intermingled and localized randomly along the body axis. The results of labeling experiments performed in the four-cell stage embryo fall into three categories. In the first, the labeled cells were intermingled with non-labeled cells in a manner similar to that seen after labeling at the two-cell stage. In the second, labeled cells were distributed only in the extra-embryonic ectoderm layers. Finally in the third category, labeled cells were seen only in the embryo proper and the extra-embryonic mesoderm. Manipulated embryos analyzed at the blastocyst stage showed localized distribution of the descendants of a single blastomere. These results suggest that incoherent clonal growth and drastic cell mixing occurs in the early mouse embryo after the blastocyst stage. The first cell specification event, i.e., partitioning cell fate between the inner cell mass and trophectoderm, can occur between the two-cell and four-cell stage, yet the cell fate is not determined.

Animals↗

PubMed2005

Establishment and characterization of new human embryonic stem cell lines.

Human embryonic stem cells (hESC), with their ability to differentiate into all cell types in the human body, are likely to play a very important therapeutic role in a variety of neurodegenerative and life-threatening disorders in the near future. Although more than 120 different human embryonic stem cell lines have been reported worldwide, only a handful are currently available for researchers, which limits the number of studies that can be performed. This study reports the isolation, establishment and characterization of new human embryonic stem cell lines, as well as their differentiation potential into variety of somatic cell types. Blastocyst-stage embryos donated for research after assisted reproductive techniques were used for embryonic stem cell isolation. A total of 31 blastocysts were processed either for immunosurgery or direct culture methods for inner cell mass isolation. A total of nine primary stem cell colonies were isolated and of these, seven cell lines were further expanded and passaged. Established lines were characterized by their cellular and colony morphology, karyotypes and immunocytochemical properties. They were also successfully cryopreserved/thawed and showed similar growth and cellular properties upon thawing. When induced to differentiate in vitro, these cells formed a variety of somatic cell lineages including cells of endoderm, ectoderm and mesoderm origin. There is now an exponentially growing interest in stem cell biology as well as its therapeutic applications for life-threatening human diseases. However, limited availability of stem cell lines as well as financial or ethical limitations restrict the number of research projects. The establishment of new hESC lines may create additional potential sources for further worldwide and nationwide research on stem cells.

Animals↗

PubMed2004

BMPR1A signaling is necessary for hair follicle cycling and hair shaft differentiation in mice.

Interactions between ectodermal and mesenchymal extracellular signaling pathways regulate hair follicle (HF) morphogenesis and hair cycling. Bone morphogenetic proteins (BMPs) are known to be important in hair follicle development by affecting the local cell fate modulation. To study the role of BMP signaling in the HF, we disrupted Bmpr1a, which encodes the BMP receptor type IA (BMPR1A) in an HF cell-specific manner, using the Cre/loxP system. We found that the differentiation of inner root sheath, but not outer root sheath, was severely impaired in mutant mice. The number of HFs was reduced in the dermis and subcutaneous tissue, and cycling epithelial cells were reduced in mutant mice HFs. Our results strongly suggest that BMPR1A signaling is essential for inner root sheath differentiation and is indispensable for HF renewal in adult skin.

Animals↗

PubMed2004

Essential roles of BMPR-IA signaling in differentiation and growth of hair follicles and in skin tumorigenesis.

Hair differentiation and growth are controlled by complex reciprocal signaling between epithelial and mesenchymal cells. To better understand the requirement and molecular mechanism of BMP signaling in hair follicle development, we performed genetic analyses of bone morphogenetic protein receptor 1A (BMPR-IA) function during hair follicle development by using a conditional knockout approach. The conditional mutation of Bmpr1a in ventral limb ectoderm and its derivatives (epidermis and hair follicles) resulted in a lack of hair outgrowth from the affected skin regions. Mutant hair follicles exhibited abnormal morphology and lacked hair formation and pigment deposition during anagen. The timing of the hair cycle and the proliferation of hair matrix cells were also affected in the mutant follicles. We demonstrate that signaling via epithelial BMPR-IA is required for differentiation of both hair shaft and inner root sheath from hair matrix precursor cells in anagen hair follicles but is dispensable for embryonic hair follicle induction. Surprisingly, aberrant de novo hair follicle morphogenesis together with hair matrix cell hyperplasia was observed in the absence of BMPR-IA signaling within the affected skin of adult mutants. They developed hair follicle tumors from 3 months of age, indicating that inactivation of epidermal BMPR-IA signaling can lead to hair tumor formation. Taken together, our data provide genetic evidence that BMPR-IA signaling plays critical and multiple roles in controlling cell fate decisions or maintenance, proliferation, and differentiation during hair morphogenesis and growth, and implicate Bmpr1a as a tumor suppressor in skin tumorigenesis.

Animals↗

PubMed1984

Waardenburg's syndrome: a case report with CT scanning and cochleovestibular evaluation.

The Waardenburg's syndrome, a congenital ectodermal germ layer defect of autosomal dominant inheritance with variable phenotypic expressivity consists of 6 major characteristics: dystopia canthorum, broad nasal root, hypoplasia of the medial eyebrow, heterochromia irides, white forelock, and congenital deafness. Twelve additional characteristics have been reported including meningocele, atresia of the esophagus, and Hirshsprung's disease supporting an early hypothesis that the neural crest is the embryonic site linking defects of the cervical sympathic system with pigmentary abnormalities and inner ear anomalies. Congenital deafness reported in 20% of Waardenburg patients, and the most disabling characteristic, has been associated with ENG abnormalities in 30% of these deaf patients. A congenitally deaf young person with Waardenburg's syndrome is examined for basic cause of episodic vertiginous symptoms. Diagnostic assistance from previous investigations is lacking because they have not involved state-of-the-art functional evaluations or correlations of behavioral and radiographic findings. In this patient, high-resolution computerized tomography failed to demonstrate bony labyrinthine anomalies. Functional cochleovestibular analysis revealed a bilateral profound sensorineural hearing loss and a unilateral weakness in oculomotor responses to caloric stimulations. Repeated measurements of ocular counterroll show variations compatible with intermittent otolithic dysfunctioning. These findings are consistent with a diagnosis of an acquired active unilateral peripheral vestibular disorder. Some of the technical issues underlying the derivation of this conclusion are discussed.

Abnormalities, Multiple↗

PubMed1975

In vitro development of t6/t6 embryos.

Embryos from matings in which approximately a third of the zygotes were expected to be t6/t6, a condition known to be lethal at the egg cylinder stage in vivo, were compared to normal control embryos during post-implantation culture. The percentage success of trophoblast outgrowths was the same in both groups while the experimental group showed a 25% deficiency of embryos with inner cell masses. Those experimental embryos which did have inner cell masses developed comparably to the control group and both groups showed roughly similar numbers of morphologically abnormal egg cylinders. Autoradiography disclosed no deficiency in 3H-thymidine and 3H-uridine labeling in disorganized egg cylinder embryos.

Animals↗

PubMed1984

Histological and ultrastructural studies of secondary neurulation in mouse embryos.

The histological and ultrastructural features of secondary neurulation in C57BL/6 mouse embryos were examined as a first step in the analysis of how this process occurs in mammalian embryos. Secondary neurulation involves two major events in mouse embryos: (1) formation of the medullary rosette (9.5- to 10-day embryos) or plate (11- to 12-day embryos), and (2) cavitation. These two events occur simultaneously. The medullary rosette consists of elongated tail bud cells, radially arranged around a central lumen formed by cavitation. The secondary portion of the neural tube forms in 9.5- to 10-day embryos by progressive enlargement of the central lumen and addition (by cell recruitment or mitosis) of tail bud cells to the rosette. The medullary plate likewise consists of elongated tail bud cells, but these cells do not surround a central cavity. Instead, cells of the medullary plate extend ventrad from the basal aspect of the dorsal surface ectoderm to a slit-like cavity formed by cavitation. Formation of the secondary neural tube occurs in 11- to 12-day embryos, principally by the recruitment of more lateral and ventral tail bud cells into the medullary plate. Free cells and cellular debris are frequently encountered in the forming lumen of the secondary neural tube, but cells exhibiting signs of necrosis were absent in cavitating regions. Numerous small intercellular junctions form at the inner ( juxtaluminal ) ends of tail bud cells as the medullary rosette or plate is forming and cavitation is occurring. These observations suggest that cavitation per se (i.e., formation of a lumen) during secondary neurulation is a relatively passive phenomenon, which results principally from neighboring cells becoming polarized apicobasally and incorporated into a primitive neuroepithelium. The latter constitutes the walls of the forming secondary neural tube.

Animals↗

PubMed1985

Development of mouse embryos in hanging drop culture.

Mouse blastocysts were cultured in hanging drops for up to 6 days in order to study development under conditions that avoid the distortion of embryos typically seen when they are allowed to attach to a glass or plastic surface. The survival rate of embryos in hanging drops was equal to that of embryos attached to culture dishes and superior to that of embryos suspended in gyrating flasks. Development of the embryonic portion was similar to that in vivo and on culture dishes but slower than in vivo; the egg cylinder stage was reached after 8-10 equivalent gestation days (4 to 6 days in culture), while that stage is reached at 5.5 to 6 days in vivo. The trophectoderm, however, developed in a unique manner. The cells migrated away from the inner cell mass (ICM), similar to embryos on a culture dish, but without a surface on which to spread they clustered distal to the ICM. In vivo, trophectoderm remained covering the ICM. By 5 days in hanging drop culture the embryos had developed a segmented appearance with trophoblast giant cells at the abembryonic pole, extraembryonic cells not covered by vacuolated endoderm in the central region, and embryonic endoderm surrounding a developing proamniotic cavity in embryonic ectoderm at the embryonic pole. These observations suggest that the trophectoderm is able to follow a developmental program independent of that in the embryonic portion and that its behavior is dominated by the different adhesive properties of the trophoblastic and embryonic cells.

Animals↗