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PubMed2005

MRG15 regulates embryonic development and cell proliferation.

MRG15 is a highly conserved protein, and orthologs exist in organisms from yeast to humans. MRG15 associates with at least two nucleoprotein complexes that include histone acetyltransferases and/or histone deacetylases, suggesting it is involved in chromatin remodeling. To study the role of MRG15 in vivo, we generated knockout mice and determined that the phenotype is embryonic lethal, with embryos and the few stillborn pups exhibiting developmental delay. Immunohistochemical analysis indicates that apoptosis in Mrg15-/- embryos is not increased compared with wild-type littermates. However, the number of proliferating cells is significantly reduced in various tissues of the smaller null embryos compared with control littermates. Cell proliferation defects are also observed in Mrg15-/- mouse embryonic fibroblasts. The hearts of the Mrg15-/- embryos exhibit some features of hypertrophic cardiomyopathy. The increase in size of the cardiomyocytes is most likely a response to decreased growth of the cells. Mrg15-/- embryos appeared pale, and microarray analysis revealed that alpha-globin gene expression was decreased in null versus wild-type embryos. We determined by chromatin immunoprecipitation that MRG15 was recruited to the alpha-globin promoter during dimethyl sulfoxide-induced mouse erythroleukemia cell differentiation. These findings demonstrate that MRG15 has an essential role in embryonic development via chromatin remodeling and transcriptional regulation.

Animals↗
PubMed1989

Characterization of proteins secreted by sheep oviduct epithelial cells and their function in embryonic development.

The role in early development of proteins secreted by oviduct epithelial cells has been investigated. Secreted proteins devoid of serum contamination have been produced by the surgical removal and immediate incubation of oviduct cells in [35S]methionine-containing medium. After electrophoretic separation, secreted polypeptides could be divided into those that were secreted uniformly throughout the oestrous cycle and a second class that showed a cyclical pattern of secretion. The first class of proteins represented a small proportion of total output whilst the predominant second class was composed mainly of polypeptides of Mr 92 and 46 x 10(3), respectively. Both of these polypeptide species, referred to as sheep oviduct proteins 92 and 46 (SOP 92, SOP 46), are detected only during the first 4 to 5 days after oestrus when the embryos are located in the oviduct. Oviduct cells collected at oestrus and maintained thereafter in culture secrete the same pattern of proteins and follow the same time course as their counterparts in vivo. The interaction between the oviduct proteins and the developing embryo was studied firstly by determining whether any of the secreted proteins bound to the zona pellucida. The results of iodination studies showed that two polypeptides of Mr 92 and 46 x 10(3), respectively, were bound to the zona pellucida of eggs removed from the oviduct but were absent from eggs that had not had contact with the oviduct epithelium. That these newly acquired proteins represent SOP 92 and 46 is suggested by their electrophoretic mobility and their ability to bind to the zona of follicular eggs when added in vitro and by the fact that they both disappear from the zonae of embryos after exit from the oviduct. The collection of unlabelled secreted proteins enabled us to produce a monoclonal antibody, which was used in the second series of experiments on oviduct-embryo interactions. The results confirmed that SOP 92 binds to the zona pellucida and moreover showed that this protein crosses the zona and becomes associated with the individual blastomeres of the developing embryo. These findings provide evidence that the mammalian oviduct probably plays a direct role in supporting embryonic development through specific polypeptides produced by its epithelium.

Animals↗
PubMed2006

SLUG (SNAI2) overexpression in embryonic development.

The Snail-related zinc-finger transcription factor, SLUG (SNAI2), is critical for the normal development of neural crest-derived cells and loss-of-function SLUG mutations have been proven to cause piebaldism and Waardenburg syndrome type 2 in a dose-dependent fashion. However, little is known about the consequences of SLUG overexpression in embryonic development. We report SLUG duplication in a child with a unique de novo 8q11.2-->q13.3 duplication associated with tetralogy of Fallot, submucous cleft palate, renal anomalies, hypotonia and developmental delay. To investigate the effects of Slug overexpression on development, we analyzed mice carrying a Slug transgene. These mice were morphologically normal at birth, inferring that Slug overexpression is not sufficient to cause overt morphogenetic defects. In the adult mice, there was a 20% incidence of sudden death, cardiomegaly and cardiac failure associated with incipient mesenchymal tumorigenesis. These findings, while not directly implicating Slug in congenital and acquired heart disease, raise the possibility that Slug overexpression may contribute to specific cardiac phenotypes and cancer development.

Abnormalities, Multiple↗
PubMed2004

Aortic carboxypeptidase-like protein is expressed in collagen-rich tissues during mouse embryonic development.

Aortic carboxypeptidase-like protein (ACLP) was originally identified in vascular smooth muscle cells and contains discoidin and catalytically inactive metallocarboxypeptidase domains. ACLP is a secreted protein that associates with the extracellular matrix and is essential for abdominal wall development and contributes to dermal wound healing. Because of these developmental and adult phenotypes, we examined the expression of ACLP by immunohistochemistry throughout mouse embryonic development. ACLP was not detected in 7.5 days post-coitum (dpc) embryos, however at 9.5 dpc low levels of expression were detected in the somites and dorsal aorta. Expression was detected in both the yolk sac and embryonic vasculature at 10.5d pc. ACLP expression increased in both large and small blood vessels at 11.5 and 13.5 dpc and intense expression was detected within the vascular smooth muscle layer in 16.5 dpc embryos. At later developmental time points, discrete areas of ACLP expression were detected in the mesenchymal cells in the dermal layer, developing skeletal structures, connective tissue, and in the umbilical ring and vessels. The predominance of ACLP immunoreactivity localized with collagen-rich regions including tendons and basement membranes. Overall, the developmental expression pattern is consistent with a regulatory or structural role in the abdominal wall, vasculature, and dermis.

Animals↗
PubMed2000

The role of retinoic acid in embryonic and post-embryonic development.

Retinoic acid (RA) is the bioactive metabolite of vitamin A (retinol) which acts on cells to establish or change the pattern of gene activity. Retinol is converted to RA by the action of two types of enzyme, retinol dehydrogenases and retinal dehydrogenases. In the nucleus RA acts as a ligand to activate two families of transcription factors, the RA receptors (RAR) and the retinoid X receptors (RXR) which heterodimerize and bind to the upstream sequences of RA-responsive genes. Thus, in addition to the well-established experimental paradigm of depriving animals of vitamin A to determine the role of RA in embryonic and post-embryonic development, molecular biology has provided us with two additional methodologies: knockout the enzymes or the RAR and RXR in the mouse embryo. The distribution of the enzymes and receptors, and recent experiments to determine the endogenous distribution of RA in the embryo are described here, as well as the effects on the embryo of knocking out the enzymes and receptors. In addition, recent studies using the classical vitamin A-deprivation technique are described, as they have provided novel insights into the regions of the embryo which crucially require RA, and the gene pathways involved in their development. Finally, the post-embryonic or regenerating systems in which RA plays a part are described, i.e. the regenerating limb, lung regeneration, hair cell regeneration in the ear and spinal cord regeneration in the adult.

Animals↗
PubMed2003

Metaphase II nuclei generated by germinal vesicle transfer in mouse oocytes support embryonic development to term.

BACKGROUND: Cytoplasmic defects are thought to cause aneuploidies in oocytes and embryos and oocyte 'reconstruction' by germinal vesicle (GV) transfer may circumvent such defects. In mice 'reconstructed' oocytes undergo meiosis and fertilize normally, but early embryonic development is compromised if their ooplasm matured in vitro. This study employs sequential MII spindle and/or pronucleus (PN) transfer to assess the embryonic potential of MII nuclei that form following GV transfer. METHODS AND RESULTS: Mouse embryos generated by these procedures were transferred to the oviducts of pseudopregnant mice to monitor pregnancy outcome. Following GV transfer, the resultant metaphase II (MII) nuclei were activated either in situ or transferred and activated in ooplasts from in-vivo matured oocytes. When exchanged with the female PN of a fertilized zygote, only the PNs that developed in in-vivo matured ooplasts generated live offspring. Viable offspring also resulted when MII nuclei were transferred to in-vivo matured ooplasts and fertilized by insemination with sperm or by artificial activation and male PN transfer. Significantly, the offspring displayed normal fertility as adults. CONCLUSION: This report of live births following GV transfer in mice illustrates the importance of the maturational history of the ooplasm at PN formation for normal embryonic and fetal development.

Animals↗
PubMed1998

Disruption of the pial basal lamina during early avian embryonic development inhibits histogenesis and axonal pathfinding in the optic tectum.

Bacterial collagenase was injected into the ventricular cavity of the optic tectum of chick and quail embryos. Histological examination up to 6 days after enzyme injection revealed that the collagenase disrupted the pial basal lamina, which was evident by the fragmented distribution of basal lamina proteins at the pial surface of the midbrain and the brainstem. Although the disrupted basal lamina was not reestablished at later stages of development, the pial basal lamina of the newly developing neuroepithelium in the caudal part of the tectum was continuous and intact. Western blot analysis showed that the collagenase digested collagens but spared noncollagenous proteins. The disruption of the pial basal lamina caused the neuroepithelial cells to retract their pial end feet and caused tectal axons to exit the brain tissue into the adjacent mesenchyme. The vertical migration of neuroblasts to the pial layers of the tectum was inhibited, leading to a disruption of the tectal histogenesis. In the developing optic pathways, retinal axons were misguided at the optic chiasma and terminated in the head mesenchyme instead of the tectum. None of the abnormalities in histogenesis and axonal pathways were observed when the basal lamina was disrupted at a later stage of embryonic development. The present experiments demonstrate that the pial basal lamina has an important function during brain morphogenesis in restricting axons to the brain, providing an anchoring of the neuroepithelial cells to the pial surface, and allowing the formation of a defined cytoarchitecture of the brain.

Animals↗
PubMed1992

Embryonic development of the house shrew (Suncus murinus). I. Embryos at stages 9 and 10 with 1 to 12 pairs of somites.

The embryonic development during the period from 1 to 12 pairs of somites was observed in an insectivore species, the house shrew (Suncus murinus), which has been bred within a closed colony. Embryos were staged by the number of somite pairs. Each stage was punctuated at every addition of three pairs of somites and numbered after the Carnegie system. The first somite became apparent between 8 and 9.0 days after fertilization, and the 12th somite appeared between 9.5 and 10.0 days. The rate of somite formation was one pair in every 3-4 h on average. The embryonic events during this period were as follows: 1. From the beginning of stage 9, the embryonic body consistently displayed a kyphosis, and as development progressed, the caudal portion of the embryo spiralled clockwise. 2. The first and second pharyngeal arches formed; their development was precocious among mammalian embryos in relation to somitic count. 3. The segmental pattern of the neural fold was similar to that of laboratory rodents and primates. The first fusion of the cranial neural folds took place in the occipital somite region, the second fusion in the diencephalic region, and the third at the end of the neural plate, thus leaving two neuropores in the cephalic region. 4. The timing of appearance of the optic sulcus was similar to that of human embryos but was delayed in comparison with that of laboratory rodents. 5. The heart always showed a more advanced state than that of other mammalian embryos. From the beginning of stage 9, an unpaired endocardial tube was seen in the bulbo-ventricular region, and deflection from a symmetrical appearance soon took place. 6. The differentiation of foregut was also precocious, and the thyroid and respiratory primordia appeared earlier than in other mammals. The present study emphasizes that there are considerable variations in timing and manner of morphogenesis among early mammalian embryos.

Animals↗
PubMed2006

Functions of BarH transcription factors during embryonic development.

This paper reviews the developmental role of a group of homeobox-containing genes firstly described in the early nineties as critical factors regulating eye development in Drosophila. These genes received the name of BarH due to the Drosophila "Bar" mutant phenotype and, since then, vertebrate homologues (named BarH-like or Barhl) have been described in a number of species of fish, amphibians and mammals. During embryonic development, BarH/Barhl are expressed primarily in the central nervous system where they play essential roles in decisions of cell fate, migration and survival. Transcriptional regulation mediated by these proteins involves either repression or activation mechanisms. In Drosophila, BarH is involved in morphogenesis and fate determination of the eye and external sensory organs, in regional prepatterning of the notum, and in formation and specification of distal leg segments. Vertebrate Barhl shares some functional properties with the fly counterparts, such as the ability to interact with basic helix-loop-helix (bHLH) proneural proteins, and plays crucial roles during cell type specification within the retina, acquisition of commissural neuron identity in the spinal cord, migration of cerebellar cells, and in cell survival within the neural plate, cochlea and cerebellum.

Amino Acid Sequence↗
PubMed1981

Biochemical studies on the embryonic development of the mammalian inner ear in organ culture.

Adenylate cyclase activity and phospholipid labeling were compared during embryonic development of the mouse inner ear in vivo and in vitro. Inner ears were explanted on the 16th gestational day and cultured in vitro for 3-12 days. The gestation time in vivo is 21 days. During the 1st week in vitro there is very little growth of the inner ear with regard to total protein content. In contrast, the labyrinth increases its protein content threefold during the corresponding period of time in vivo. The activity of adenylate cyclase develops parallel in vivo and in vitro until the 19th gestational day whereafter the specific activity of the enzyme in vitro surpasses that of the enzyme in vivo three- to fivefold suggesting a lack of control mechanisms in organ culture. Phospholipids are labeled by 32P in an essentially similar quantitative relationship in vivo and vitro, while some quantitative differences exist. According to the present study the usefulness of the organ culture for the investigation of inner ear development appears limited to a culture period corresponding to an age prior to birth.

Adenylyl Cyclases↗
PubMed1980

The anatomy and histology of the ecdysial glands of Philosamia ricini (Hutt.) (Lepidoptera: Saturniidae) during the post embryonic development.

A comprehensive account of the anatomy and histophysiology of the ecdysial glands of Philosamia ricini during post embryonic development has been given. The study clearly indicates an increase in number of cells in each larval instar by endomitosis. The maximum number of cells are present in the 5th instar larvae. The cell size decreases before moulting in each instar. The size and shape of the cells of the glands vary considerably from individual to individual or even in the same individual. They are oval, elongate, polygonal in outline. Gland is collectively innervated by transverse nerves arising from the suboesophageal, prothoracic, mesothoracic and metathoracic ganglia as well as medial-1 and medial-2 nerves. The secretory activity of the glands is indicated by a large amount of cytoplasm with a developed brush border, having vacuoles at the periphery. The inactive glands have small amount of cytoplasm, without vacuoles and poorly developed brush border. The glands are absent in the newly moulted adults indicating that they degenerate before imaginal ecdysis.

Animals↗
PubMed1991

Inductive interactions in early embryonic development.

This is an update of a previous review (Current Opinion in Cell Biology 2:969-974) in which we discussed recent work attempting to understand the sequence of inductive interactions responsible for establishing the body plan of the early embryo. As before, we concentrate on inductive interactions in amphibian embryos, where significant progress has been made in the past two years. In this update, however, we also consider recent embryological data obtained with amniote embryos such as the chick, together with complementary data provided by genetic analyses of mouse and Drosophila development.

Animals↗
PubMed2006

Sall4 modulates embryonic stem cell pluripotency and early embryonic development by the transcriptional regulation of Pou5f1.

Embryonic stem (ES) cells are pluripotent cells that can self-renew or differentiate into many cell types. A unique network of transcription factors and signalling molecules are essential for maintaining this capability. Here, we report that a spalt family member, Sall4, is required for the pluripotency of ES cells. Similarly to Oct4, a reduction in Sall4 levels in mouse ES cells results in respecification, under the appropriate culture conditions, of ES cells to the trophoblast lineage. Sall4 regulates transcription of Pou5f1 which encodes Oct4. Sall4 binds to the highly conserved regulatory region of the Pou5f1 distal enhancer and activates Pou5f1 expression in vivo and in vitro. Microinjection of Sall4 small interfering (si) RNA into mouse zygotes resulted in reduction of Sall4 and Oct4 mRNAs in preimplantation embryos and significant expansion of Cdx2 expression into the inner cell mass. These results demonstrate that Sall4 is a transcriptional activator of Pou5f1 and has a critical role in the maintenance of ES cell pluripotency by modulating Oct4 expression. The data also indicates that Sall4 is important for early embryonic cell-fate decisions.

Animals↗
PubMed1987

Effect of heat stress on early embryonic development in the beef cow.

Hereford and Hereford X Angus cows (n = 31) were utilized to determine the effects of heat stress on early embryonic development and survival. After acclimation to handling, cows were cannulated via the jugular vein on d 7 and assigned to either a control (C) chamber environment of 22 C, 35% relative humidity (RH) or one of two heat stress treatments. Ambient temperature was maintained at 37 C for 12 h followed by a decrease to 33 C for the remainder of the day in both treatment groups. Relative humidity was maintained at 27% in treatment 1 (TRT 1) and 38% in treatment 2 (TRT 2). On d 8 to 16, daily measurements of respiration rate (RES), rectal temperature (REC) and water intake were taken along with samples of blood, which were analyzed for hematocrit (HEM) and plasma concentration of protein (PP), progesterone (P4), estradiol-17 beta (E2), thyroxine (T4) and glucose (GLU). The uterus was recovered and flushed with saline on d 17 to recover the conceptus and uterine contents. Conceptus (if present) and corpus luteum (CL) wet weight were determined. Cows subjected to TRT 2 had increased RES and REC (P less than .01), while HEM was decreased (P less than .05) compared with C cows. Plasma T4 concentration was decreased (P less than .10) in TRT 2 compared with TRT 1 and cows, while P4 concentration were not significantly different. Corpora lutea wet weights were reduced (P less than .10) in heat-stressed cows vs C cows.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

[The embryonic development of the intestinal mucosa with special reference to its epithelium].

Electron microscopic examinations were made of different parts of the bovine intestine (n = 13) up to the 10th week of embryonic development. During the 'phase of undifferentiated epithelium' the embryonic intestinal epithelium can be classified as stratified and is perhaps a pool of cells. Microvilli of the apical plasmalemma appear at first in neighboring and opposing cells in the centre of the epithelium. They already show microfilaments as well as a glycocalix. The supranuclear cytoplasm shows many granules, vesicles and arciform structures which may be used in the process of microvilli formation. The importance of infranuclear basal granules in the peripheral epithelial cells is still unknown; perhaps they are merely phylogenetic remnants of a principle of development common to all vertebrate intestines. Single cilia which are formed in the periluminal cytoplasm presumably suppress mitotic activities of the epithelial cells and induce their ensuing differentiation. Epithelial proliferation is the initial event of villigenesis, giving rise to epithelial primary villi. Immediately following is the formation of secondary villi during proliferation of the mesenchyme.

Animals↗
PubMed2002

Fertilization and early embryonic development in heifers and lactating cows in summer and lactating and dry cows in winter.

Two experiments in two seasons evaluated fertilization rate and embryonic development in dairy cattle. Experiment 1 (summer) compared lactating Holstein cows (n = 27; 97.3 +/- 4.1 d postpartum [dppl; 40.0 +/- 1.5 kg milk/d) to nulliparous heifers (n = 28; 11 to 17 mo old). Experiment 2 (winter) compared lactating cows (n = 27; 46.4 +/- 1.6 dpp; 45.9 +/- 1.4 kg milk/d) to dry cows (n = 26). Inseminations based on estrus included combined semen from four high-fertility bulls. Embryos and oocytes recovered 5 d after ovulation were evaluated for fertilization, embryo quality (1 = excellent to 5 = degenerate), nuclei/embryo, and accessory sperm. In experiment 1, 21 embryos and 17 unfertilized oocytes (UFO) were recovered from lactating cows versus 32 embryos and no UFO from heifers (55% vs. 100% fertilization). Embryos from lactating cows had inferior quality scores (3.8 +/- 0.4 vs. 2.2 +/- 0.3), fewer nuclei/embryo (19.3 +/- 3.7 vs. 36.8 +/- 3.0) but more accessory sperm (37.3 +/- 5.8 vs. 22.4 +/- 5.5/embryo) than embryos from heifers. Sperm were attached to 80% of UFO (17.8 +/- 12.1 sperm/UFO). In experiment 2, lactating cows yielded 36 embryos and 5 UFO versus 34 embryos and 4 UFO from dry cows (87.8 vs. 89.5% fertilization). Embryo quality from lactating cows was inferior to dry cows (3.1 +/- 0.3 vs. 2.2 +/- 0.3), but embryos had similar numbers of nuclei (27.2 +/- 2.7 vs. 30.6 +/- 2.1) and accessory sperm (42.0 +/- 9.4 vs. 36.5 +/- 6.3). From 53% of the flushings from lactating cows and 28% from dry cows, only nonviable embryos were collected. Thus, embryos of lactating dairy cows were detectably inferior to embryos from nonlactating females as early as 5 d after ovulation, with a surprisingly high percentage of nonviable embryos. In addition, fertilization rate was reduced only in summer, apparently due to an effect of heat stress on the oocyte.

Animals↗
PubMed2004

The murine Cyp1a1 gene is expressed in a restricted spatial and temporal pattern during embryonic development.

In adult mice the cytochrome P450 Cyp1a1 gene is not constitutively expressed but is highly inducible by foreign compounds acting through the aryl hydrocarbon (Ah) receptor. However, the expression profile of the Cyp1a1 gene in the developing embryo is not well under-stood. Using established transgenic mouse lines where 8.5 kb of the rat CYP1A1 promoter is cloned upstream of the lacZ reporter gene (1), we describe the expression of the CYP1A1-driven reporter gene in all tissues through-out stages E7-E14 of embryonic development. In contrast to the absence of constitutive Cyp1a1 and lacZ transgene expression in tissues of the adult mouse, a constitutive cell-specific and time-dependent pattern of CYP1A1 promoter activity was observed in the embryo. This expression pattern was confirmed as reflecting the endogenous gene by measuring Cyp1a1 mRNA levels and protein expression by immunohistochemistry. The number of cells displaying endogenous CYP1A1 activity could be increased in the embryo upon xenobiotic challenge, but only within areas where the CYP1A1 promotor was already active. When reporter mice were bred onto a genetic background expressing a lower affinity form of the Ah receptor (DBA allele), transgene and murine Cyp1a1 protein expression were both attenuated in the adult mouse liver upon xenobiotic challenge. By comparison, constitutive CYP1A1 promoter activity in the embryo was identical in the presence of either the high or low affinity Ah receptor. These novel data suggest that the Cyp1a1 protein may play a role in murine development and that regulation of the Cyp1a1 gene during this period is either through the action of a high affinity Ah receptor ligand or by an alternative regulatory pathway.

Animals↗