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PubMed2002

Expression patterns of focal adhesion associated proteins in the developing retina.

Adhesive interactions between integrin receptors and the extracellular matrix (ECM) are intimately involved in regulating development of a variety of tissues within the organism. In the present study, we have investigated the relationships between beta(1) integrin receptors and focal adhesion associated proteins during eye development. We used specific antibodies to examine the distribution of beta(1) integrin ECM receptors and the cytoplasmic focal adhesion associated proteins, talin, vinculin, and paxillin in the developing Xenopus retina. Immunoblot analysis confirmed antibody specificity and indicated that beta(1) integrins, talin, vinculin, and paxillin were expressed in developing retina and in the retinal-derived Xenopus XR1 glial cell line. Triple-labeling immunocytochemistry revealed that talin, vinculin, paxillin, and phosphotyrosine proteins colocalized with beta(1) integrins at focal adhesions located at the termini of F-actin filaments in XR1 cells. In the retina, these focal adhesion proteins exhibited developmentally regulated expression patterns during eye morphogenesis. In the embryonic retina, immunoreactivities for focal adhesion proteins were expressed in neuroepithelial cells, and immunoreactivity was especially strong at the interface between the optic vesicle and overlying ectoderm. At later stages, these proteins were expressed throughout all retinal layers with higher levels of expression observed in the plexiform layers, optic fiber layer, and in the region of the inner and outer limiting membrane. Strong immunoreactivities for beta(1) integrin, paxillin, and phosphotyrosine were expressed in the radially oriented Müller glial cells at later stages of development. These results suggest that focal adhesion-associated proteins are involved in integrin-mediated adhesion and signaling and are likely to be essential in regulating retinal morphogenesis.

Animals↗
PubMed2004

Ocular surface epithelial and stem cell development.

Phenotypic features and developmental events involved in the genesis of the limbo-corneal and conjunctival epithelia are described. Together, these two epithelia define the ocular surface. They derive from a small cohort of optic vesicle-induced PAX6+ head ectodermal cells that remain on the surface following lens vesicle formation by the main PAX6+ cell cohort. Both epithelia are stratified, and display wet, non-keratinizing phenotypes. The most significant spatial feature of the limbo-corneal epithelium is the segregation of its supporting stem and early precursor cells to the limbus, the outer vascularized rim separating the cornea from the conjunctiva. These stem cells express ABCG2, a xenobiotic transporter present in stem cells from other organs. ABCG2 transport activity excludes the DNA dye Hoechst 33342, allowing the isolation of the ocular stem cells by flow cytometry, as a unique cohort known as a side 'side population'. Limbal stem cells do not form gap junctions and exist as metabolically isolated entities. Tracking of expression changes in Cx43, the main gap junction protein expressed in both the pre-epithelial ectoderm and in the mature central corneal epithelium, indicates that a limbal stem cell phenotype starts developing very soon after lens vesicle invagination, in advance of the appearance of any recognizable anatomical sub-epithelial limbal feature. Differences in Cx43 expression also reveal the very early nature of the divergence in limbo-corneal and conjunctival lineages. The putative involvement of several early genes, including gradients of PAX6 and differences in expression patterns for members of the Id or msh gene expression regulators are reviewed.

ATP Binding Cassette Transporter, Subfamily G, Mem↗
PubMed2002

Expression of nerve growth factor during the development of nervous system in early chick embryo.

In the chick gastrula, nerve growth factor (NGF) is localized to the endoblast mesoblast presumptive head ectoderm but not in the presumptive neuroectoblast. During early morphogenesis the dorsal body ectoderm presumptive neural crest cells exhibit strong NGF positive cell surface reaction. NGF appears to be a marker of cells participating in morphogenetic movements but not early neural differentiation. NGF is localized where neural folds fuse and cells die allowing detachment of the neural tube from head ectoderm as well as in dead cells in the neurocoele. NGF reactivity in cells lining the evaginated extremities of the optic vesicle the floor of the neural tube the splanchnopleure heart primordia the inner outer surfaces of somites is suggestive of the role of NGF in primitive organ shaping.

Animals↗
PubMed1984

FMRFamide immunoreactivity in the nervous system of the medusa Polyorchis penicillatus.

Three different antisera to the molluscan neuropeptide Phe-Met-Arg-Phe-amide (FMRFamide) and two different antisera to the fragment RFamide were used to stain sections or whole mounts of the hydrozoan medusa Polyorchis penicillatus. All antisera stained the same neuronal structures. Strong immunoreactivity was found in neurons of the ectodermal nerve nets of the manubrium and tentacles, in neurons of the sensory epithelium, and in neurons at the periphery of the sphincter muscle. Strong immunoreactivity was also present in processes and perikarya of the whole outer nerve ring, in the ocellar nerves, and in nerve cells lying at the periphery of the ocellus. The inner nerve ring contained a moderate number of immunoreactive processes and perikarya, which were distinct from the swimming motor neurons. In contrast to the situation in the hydrozoan polyp Hydra attenuata, no immunoreactivity was found with several antisera to oxytocin/vasopressin and bombesin/gastrin-releasing peptide. The morphology and location of most FMRFamide-immunoreactive neurons in Polyorchis coincides with two identified neuronal systems, which have been recently discovered from neurophysiological studies.

Animals↗
PubMed2002

Systematic analysis of E-, N- and P-cadherin expression in mouse eye development.

Cadherins are a family of Ca(2+)-dependent cell adhesion molecules. Through their homophilic binding interactions, cadherins play important roles in tissue formation and maintenance during development. Here the authors compare the expression patterns of the three classical cadherins, E-, N- and P-cadherin, during mouse eye development from embryonic day 9.5 (E9.5) to adult. It was found that: (1) The expression patterns of N- and P-cadherin are mutually exclusive in most ocular tissues during development. N-cadherin mRNA is detected specifically in the lens placode during lens induction at E9.5, and is absent in the rest of the surface ectodermal tissues. In contrast, P-cadherin is expressed in the surface ectoderm but not in the lens vesicle. N-cadherin is expressed continuously in the lens pit, lens vesicle, and in the epithelial cells and newly differentiating fiber cells of the mature lens. P-cadherin is expressed in the epithelial cells of the cornea, eyelids and Harderian gland. Reciprocal expression patterns of N-and P-cadherins are also seen during retinal development. N-cadherin is initially expressed in both the inner and outer layers of the optic cup at E9.5. N-cadherin expression persists in the inner layer as it develops into neural retina, but is turned off in the outer layer where the cells differentiate into retinal pigment epithelial (RPE) cells and express P-cadherin. Reciprocal patterns of expression are also seen in the ciliary epithelium. N-cadherin is expressed in the inner layer and P-cadherin in the outer layer of the ciliary epithelium. (2) E- and P-cadherins are epithelial cadherins. Their expression patterns in the eye are not identical. Both cadherins are found in the epithelia of the cornea, eyelid and Harderian gland. In contrast, lens epithelial cells express E- but not P-cadherin, and RPE cells express P- but not E-cadherin. (3) In addition to its high expression in surface ectoderm-derived tissues, E-cadherin mRNA was also detected in some of the retinal ganglion neurons at postnatal day 14 (P14). E-cadherin expression in the neural retina has not been reported before. This study shows that cell fate determination in the eye occurs in conjunction with distinct changes in the patterns of cadherin gene expression.

Animals↗
PubMed1979

In vitro development of core cells of the inner cell mass of the mouse blastocyst: effects of conditioned medium.

Blastocysts submitted to two rounds of immunosurgery give rise to cores of presumptive ectoderm cells, many of which do not survive for more than 48 hours when cultured individually. Precoating of the culture plates with conditioned medium (CM) from PYS-2 cells increases the incidence with which cores regenerate an outer layer. This procedure also improves the survival frequency of the cores, but only for a limited period of time. The small number of cores which survive for two weeks or more, either in uncoated or CM-coated plates, give rise to any array of cell types, including giant cells resembling trophoblast.

Animals↗
PubMed1977

Surface differentiation antigens of human mammary epithelial cells carried on the human milk fat globule.

Rabbit antibodies against components of the human milk fat globule bind specifically to normal human breast epithelial cells and cell lines derived from breast carcinomas, as well as to the outer surface of the human milk fat globule. Variation in indirect immunofluorescence staining in both intensity per cell and percentage of cells stained is observed for the different brest cell lines. Cells derived from other epithelial and other ectodermal tissues, fetal fibroblasts, cells of the blood buffy coat, and even fibroblasts of the breast itself do not bind the antibodies. This suggests that these antibodies are detecting cell-type-specific antigens. These normal breast epithelial cell antigens are on the cell surface and their expression is stable in long-term cultured cell lines, even after much chromosomal variation in a given line. By affinity chromatography, three distinct antigenic components can be isolated from the milk fat globule, one of which contains carbohydrate. These differentiation antigens of the human breast epithelial cell are not only useful as specific cell-type markers, but also can provide a tool to study the role of the cell surface in normal and neoplastic mammary development.

Animals↗
PubMed1980

In vitro development of inner cell masses isolated from t0/t0 and tW5/tW5 mouse embryos.

Inner cell masses (ICMs) isolated immunosurgically from mouse blastocysts segregating the homozygous lethal mutants t0/t0 and tW5/tW5 were cultured in vitro. Presumed t0/t0 ICMs fail to grow after three days in culture (equivalent gestational day 7.5) when they consist of an outer layer of endoderm cells surrounding about 30 epiblast cells. Presumed homozygous tW5/tW5 ICMs develop to a more advanced stage in culture and on the seventh day (equivalent gestational day 11.5) consist of an inner core of disorganized ectoderm cells with a small proamniotic cavity, surrounded by multiple layers of endoderm cells.

Animals↗
PubMed1991

Differential expression of two cadherins in Xenopus laevis.

Using a cadherin fraction from Xenopus tissue culture cells as an immunogen, two monoclonal antibodies were obtained that allowed the characterization of two distinct cadherins in the Xenopus embryo. The two cadherins differ in molecular weight, in their time of appearance during development and in their spatial pattern of expression. One of the antigens was identified as E-cadherin. It appears in the embryonic ectoderm during gastrulation when epidermal differentiation commences and it disappears from the neural plate area upon neural induction. The second antigen could not be allocated to any of the known cadherin subtypes and was termed U-cadherin. It is present in the egg and becomes deposited in newly formed inner cell membranes during cleavage, the outer apical membranes of the embryo remaining devoid of the cadherin throughout development. U-cadherin is found on membranes of all cells up to the late neurula stages. A conspicuous polarized expression of the antigen on the membranes of individual inner cells suggests its participation in the segregation of cell layers and organ anlagen. These findings are discussed in the context of current hypotheses on the role of cadherins in establishing the spatial structure of the embryo.

Animals↗
PubMed1987

[Changes in the expression of prekeratins with molecular weight of 55 and 40 kD in monolayer epithelium during skin morphogenesis in rats].

It has been shown by indirect immunofluorescence using monoclonal antibodies against adult rat simple epithelial prekeratins with the molecular weight of 55 kD (PK55) and 40 kD (PK40) that PK55 was expressed in the covering ectoderm until the 11th day of the antenatal period. PK55 expression markedly increased in ectodermal cells lining the heart region, with PK40 appearing in the same cells on day 11. Beginning from the 16th day gradual loss of both prekeratins started with the parallel formation of squamous differentiated epidermis. These proteins were retained in the outer layers of peridermal cells and in some cells of the basal layer (probably Merkel cells). PK55 was re-expressed on the 18th day in cells migrating into dermal layer during hair folliculi formation. PK55 disappeared again in mature folliculi. Thus, a correlation between distinct morphogenetic events and PK55 and PK40 expression has been found.

Animals↗
PubMed2005

Proliferation and cornification during development of the mammalian epidermis.

The skin is the largest organ of the body and consists of the underlying dermis and outer epidermis. Proper embryonic development and continual renewal of the adult epidermis are essential to provide an impenetrable barrier against fluid loss and serve as our most important defense against insults from the external environment. During mammalian embryogenesis the epidermis develops from the surface ectoderm, which initially consists of a multipotent single-layer epithelium. Once these epithelial cells receive the appropriate developmental cues, they become committed to stratify, initiate a massive expansion program, and finally embark on a journey of terminal differentiation to produce the morphologically distinct layers of the epidermis. The culmination of this journey is the formation of an impervious cornified envelope via a highly specialized form of programmed cell death, termed "cornification" (reviewed in Candi et al.), which is distinct in many ways from the classic apoptotic pathways. The epidermal developmental program that is first seen in the fetus is recapitulated for the entire life of the organism. The basal layer of adult skin harbors stem cells, which can divide to produce daughter stem cells and transit amplifying (TA) cells that go on to differentiate and cornify (reviewed in Fuchs and Raghavan). In this review we summarize current knowledge about the molecular regulation of proliferation and cornification in the developing mammalian epidermis. We focus on events in the interfollicular epidermis, with special emphasis on transcriptional regulation by p63, Notch, NF-kappaB/IKK, Hox, AP-1, AP-2, and C/EBP factors. We end with a discussion about perturbations in epidermal proliferation and cornification as they pertain to human skin pathologies.

Animals↗
PubMed1994

Immunolocalization of connexin 43 in the tooth germ of the neonatal rat.

Rabbit polyclonal antibodies to amino acids 346-360 of connexin 43, the 'heart' gap junction protein, were employed to immunolocalize connexin 43 gap junctions in the neonatal rat molar tooth germ. Connexin 43 appears early in the differentiation of both ectodermally derived and ectomesenchymally derived cells of the developing tooth. Connexin 43 immunoreactivity is present in the epithelial components of the enamel organ, including the area of the proximal and distal junctional complexes of the ameloblast layer, and the stratum intermedium, stellate reticulum and outer enamel epithelium. Secretory odontoblasts and developing alveolar bone also display a pattern of connexin 43 immunostaining. Both the epithelial and ectomesenchymally-derived components of the developing tooth acquire connexin 43 channels in a manner that correlates with cell differentiation. In addition, three regions can be defined by connexin 43 immunostaining: the epithelia of the enamel organ that are derived from the oral epithelium, the odontoblast layer derived from the ectomesenchyme, and the alveolar bone. The results suggest that connexin 43 may provide the mechanism for functional compartmentalization of the tissues associated with tooth formation. Compartmentalization suggested by connexin 43 expression could play important roles in the development and functions of these tissues.

Animals↗
PubMed2003

Latent form of multiple dermoid cysts in the jaw bone.

Dermoid cysts of the jaw are exceedingly rare, and only six such cases have been documented. The present paper reports a case with multiple microcysts showing histological characteristics of dermoid cyst in the surgically resected mandibular bone. These cysts were located near the inferior border of the mandibular bone, and histologically composed of an inner thin layer of squamous epithelium with marked hyperorthokeratinization and an outer layer of fibrous tissue containing numerous mature sebaceous glands. In addition, a hair follicle-like epithelial sphere was seen in part. The present microcysts suggest that it arises de novo, and one possible cause of jaw cysts could be sequestration of the stomadeal ectoderm that may have been trapped deep in the surface and embedded in the developing mandibular bone during embryogenesis. It may not be possible that such cysts developed from the odontogenic epithelial remnant undergoing dermoid metaplasia.

Adult↗
PubMed2002

Embryogenesis and development of Epimenia babai (Mollusca Neomeniomorpha).

Neomenioid aplacophorans (= Solenogastres) constitute one of the main lineages of molluscs. Developmental data of early embryogenesis and larval development of neomenioids are available for some species based on histological sections. I used other techniques to study the development of Epimenia babai Salvini-Plawen, 1997, and here I report new data on neomenioid development. The embryos of E. babai are lecithotrophic and cleavage is spiral, unequal, and holoblastic. Two polar lobes are formed, one at the first cleavage stage and one at the second cleavage stage. No evidence of external metameric iteration is visible through scanning electron microscopy or histology at any stage. A ciliated foot, a pedal pit, and aragonitic spicules develop from the definitive ectoderm. A spicule begins as a solid tip, continues to an open-ended hollow spicule, and finally becomes a closed-ended hollow spicule. The free-swimming trochophore larvae of E. babai have been considered unusual in lacking the characteristic neomenioid cellular test, an outer locomotory structure within which the entire definitive adult body develops. However, through the use of scanning electron and light microscopy, semithin sections, Hoechst nuclear staining, and programmed cell death staining to study the ontogeny and fate of the apical cells, I show that the entire pre-oral sphere (the apical cap) of the larvae is similar to the test of the other neomenioids. The results suggest that the test of the neomenioid larvae is an enlarged pre-oral sphere of a trochophore. The test morphologies of neomenioid larvae are compared to those of pericalymma larvae of protobranch bivalves, and the homology and evolution of molluscan larval tests is discussed.

Animals↗
PubMed1989

Ornithine aminotransferase distribution in ocular tissues and retinas of cat and mouse.

Ornithine aminotransferase (OAT), a mitochondrial matrix enzyme, is genetically deficient in patients with gyrate atrophy of the choroid and retina. Histologically defined micro-samples (10 ng-6.8 micrograms dry weight) were dissected out from freeze-dried tissue sections of eyeballs of cat and mouse, and the OAT activities were determined by a newly developed microassay method in the ocular tissues and retinal layers. Very high specific activities of OAT, expressed on a dry weight basis, were found in the feline ocular tissues of ectodermal origin, that is, neuroretina, retinal pigment epithelium, ciliary processes and epithelium of iris. In cat and mouse retinas, high OAT activities were distributed in the inner retina with an activity peak in the inner plexiform and ganglion cell layers. Very low activity was present in the outer nuclear layer. The inner segments of photoreceptor cells, which are very rich in mitochondria, contained the highest OAT activity. In contrast, the outer segments of photoreceptor cells contained the low activity resulting from contamination by small pieces of inner segments.

Animals↗
PubMed1993

Development of the eye in the North American opossum (Didelphis virginiana).

Marsupials are unique models for developmental biology-oriented research because of the immature state of their development at birth. The North American opossum (Didelphis virginiana) has several advantages over other marsupials, including large litter size, short prenatal period (12.5 d), an extended postnatal period while accessible in the pouch, and its ability to reproduce reliably in captivity. Studies of ocular development in this species have not been reported previously. The aim of the present investigation was therefore to document the major landmarks in prenatal and postnatal development of the cornea, lens, iris, ciliary body and retina. Fifteen embryos (10.5, 10.7 and 11 d postconception and 6 h after birth [12 d]) were studied by paraffin histology. Eyes of pouch young at 8 d, 2, 6, 9 and 13 wk were studied by transmission electron microscopy and light microscopy. The study revealed a similar pattern of ocular development in Didelphis to other metatherian and eutherian mammals. Differentiation of the eye is particularly rapid in the 2 d before birth. For example, although the lens vesicle separates from the surface ectoderm on d 10, by birth (2.5 d later) a primitive cornea and fused eyelids have formed, presumably to protect the eye during migration to the pouch. At birth the retinal pigment epithelium (RPE) contains melanin; however, the inner layer of the optic cup does not differentiate into an inner and outer neuroblastic layer until 8 d after birth. Around 6 wk after birth most components of the adult eye are identifiable, albeit in an immature form. These include the corneal layers, the iris (including the sphincter pupillae), ciliary processes, RPE tapetum, and a fully laminated retina with immature photoreceptors. A knowledge of the timing of major events in eye development in Didelphis and their comparison with equivalent events in human eye development should allow the appropriate choice of stages for any future experimental studies utilising this marsupial species.

Animals↗
PubMed2006

Involvement of the Edar signaling in the control of hair follicle involution (catagen).

Ectodysplasin (Eda) and its receptor (Edar) are required for normal development of several ectodermal derivatives including hair follicles (HFs). Here, we show that during the murine hair cycle the expression of Eda A1, Edar, Edaradd, and TRAF6 transcripts are minimal in the resting phase and maximal during HF transition from active growth to regression (catagen). Eda A1 mRNA and Edar proteins were expressed in the hair matrix and outer and inner root sheaths of anagen HFs. During catagen, Eda A1 mRNA and Edar protein were expressed in the outer and inner root sheaths and later in the secondary hair germ. Catagen development accompanied by increased apoptosis in the outer root sheath was significantly accelerated in downless mice or after treatment of wild-type mice by a fusion protein that inhibits Edar signaling, compared with the corresponding controls. Microarray, real-time polymerase chain reaction, and immunohistochemical analyses of skin of downless mice revealed a strong decrease of expression of X-linked inhibitor of apoptosis protein (XIAP), compared with the controls, suggesting XIAP as a target for Edar signaling. Thus, our data demonstrate that in addition to its well-established role in HF morphogenesis, Edar signaling is also involved in hair cycle control and regulates apoptosis in HF keratinocytes during catagen.

Animals↗
PubMed1984

Formation of the test in the swimming larva of Ciona intestinalis: an ultrastructural study.

The test of the Ciona intestinalis larva, before hatching, presents a single outer cuticular layer, C1. Ultrastructural observations of swimming larvae, kept in culture at 18 degrees C, show that the test is enriched by a second inner cuticular layer C2. The C2 layer begins to form in the larva immediately after hatching (about 1 h) and is a process caused by the activity of the cells of the ectodermal layer. During this phase of larval development these cells assume the typical ultrastructure of cells with secretory activity, presenting a well developed r.e.r. and a Golgi in the form of dictyosomes in active synthesis phase in the apical zone of their cytoplasm. The formation of C2 layer is complete in the larva 3 h after hatching and in this period it can be seen parallel to, and a short distance from, the plasmalemma of the ectodermal cells. In the cephalenteron region the C2 layer progressively rises towards the C1 layer and, in the larva 8 h after hatching, these two layers are very close together, about 1000 A apart. In contrast, the C2 layer in the tail remains close to the plasmalemma of the ectodermal cells and can only be detected by ultrastructural observations.

Animals↗