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PubMed2004

The CCCH tandem zinc-finger protein Zfp36l2 is crucial for female fertility and early embryonic development.

The CCCH tandem zinc finger protein, Zfp36l2, like its better-known relative tristetraprolin (TTP), can decrease the stability of AU-rich element-containing transcripts in cell transfection studies; however, its physiological importance is unknown. We disrupted Zfp36l2 in mice, resulting in decreased expression of a truncated protein in which the N-terminal 29 amino acids had been deleted (DeltaN-Zfp36l2). Mice derived from different clones of ES cells exhibited complete female infertility, despite evidence from embryo and ovary transplantation experiments that they could gestate and rear wild-type young. DeltaN-Zfp36l2 females apparently cycled and ovulated normally, and their ova could be fertilized; however, the embryos did not progress beyond the two-cell stage of development. These mice represent a specific model of disruption of the earliest stages of embryogenesis, implicating Zfp36l2, a probable mRNA-binding and destabilizing protein, in the physiological control of female fertility at the level of early embryonic development. This newly identified biological role for Zfp36l2 may have implications for maternal mRNA turnover in normal embryogenesis, and conceivably could be involved in some cases of unexplained human female infertility.

Animals↗

PubMed1975

Embryonic development of tetraploid mice during the second half of gestation.

A small proportion (about 17%) of experimentally produced tetraploid blastocysts are capable of postimplantation development in the randomly bred Q strain of mice. Four newborn mice, three of which were confirmed as tetraploid, were produced but all were eaten by their mother within a few hours of birth. Studies on the embryonic development of tetraploid mice reveal a variety of developmental abnormalities, especially during the later stages of gestation. At 14 1/2 and 16 1/2 days, tetraploid embryos weigh significantly less than corresponding stage diploids, especially so if litter size is taken into account. Histologically, aberrations are found in many different tissues with a clear hierarchy of susceptibility shown among the organs. For instance, yolk-sac-derived blood, and gonads, are invariably affected and the anterior end of the neural tube also seems to be particularly at risk. Possible explanations for the aberrant development are discussed and it is concluded that strictly genetic reasons can be ruled out and that physiological difficulties imposed by the increased size of tetraploid cells and/or problems produced by lack of cell numbers are instrumental in causing abnormal development. Using weight as a guide it is estimated that tetraploid embryos at 14 1/2 and 16 1/2 days gestation contain about one-quarter as many cells as similar stage diploids.

Abnormalities, Multiple↗

PubMed2004

Telomere-associated protein TIN2 is essential for early embryonic development through a telomerase-independent pathway.

TIN2 is a negative regulator of telomere elongation that interacts with telomeric DNA repeat binding factor 1 (TRF1) and affects telomere length by a telomerase-dependent mechanism. Here we show that inactivation of the mouse TRF1-interacting protein 2 (TIN2) gene results in early embryonic lethality. We further observed that the embryonic lethality of TIN2 mutant mice was not affected by inactivation of the telomerase reverse transcriptase gene, indicating that embryonic lethality is not the result of telomerase-dependent changes in telomere length or function. Our findings suggest that TIN2 has a role independent of telomere length regulation that is essential for embryonic development and cell viability.

Animals↗

PubMed1985

Morphological changes in the ovary of newly hatched chickens treated with chorionic gonadotropin during embryonic development.

The present study describes morphological changes produced in the ovary of newly hatched chickens by treatment with human chorionic gonadotropin (hCG). Morphometric measurements of the volume of steroidogenic cells and structures of the ovarian medulla were performed in controls and experimental chickens treated with hCG (1.0 IU/embryo) at 13, 15, and 17 days of embryonic development. After hCG treatment, the volume of interstitial cell cords increased, and modifications in poorly differentiated cells neighbouring the interstitial cells were also observed. Other changes obtained after hCG treatment were an increment in the development of the lacunar system and blood capillaries, as well as a reduction in the number of germ cells in the stroma of the ovarian medulla.

Animals↗

PubMed2005

Drosophila microRNAs exhibit diverse spatial expression patterns during embryonic development.

MicroRNAs (miRNAs) are an extensive class of regulatory RNA whose specific functions in animals are generally unknown. Although computational methods have identified many potential targets of miRNAs, elucidating the spatial expression patterns of miRNAs is necessary to identify the sites of miRNA action. Here, we report the spatial patterns of miRNA transcription during Drosophila embryonic development, as revealed by in situ hybridization to nascent miRNA transcripts. We detect expression of 15 "stand-alone" miRNA loci and 9 intronic miRNA loci, which collectively represent 38 miRNA genes. We observe great variety in the spatial patterns of miRNA transcription, including preblastoderm stripes, in aspects of the central and peripheral nervous systems, and in cellular subsets of the mesoderm and endoderm. We also describe an intronic miRNA (miR-7) whose expression pattern is distinct from that of its host mRNA (bancal), which demonstrates that intronic miRNAs can be subject to independent cis-regulatory control. Intriguingly, the expression patterns of several fly miRNAs are analogous to those of their vertebrate counterparts, suggesting that these miRNAs may have ancient roles in animal patterning.

Animals↗

PubMed1993

Expression of the helix-loop-helix factor Id during mouse embryonic development.

Expression and regulation of the helix-loop-helix (HLH) protein Id in cardiac cells and its negative effect on cardiac gene expression indicate that Id may play a role in cardiac development. To investigate this issue further, we have performed in situ analysis of Id mRNA in developing mouse embryos from Embryonic Days 7 to 15.5 and in neonatal heart. Consistent with its postulated role as an inhibitor of differentiation, Id mRNA was expressed in specific populations of proliferating mesenchymal and epithelial tissues, with its expression declining as differentiation progressed. In addition, patterns of Id mRNA hybridization overlapped considerably with those of two other developmentally important genes, twist and hox 7/7.1, of the HLH and homeobox family, respectively. Id mRNA hybridization was not observed in early epithelial somites or in the myotomal compartment of the somite, suggesting that Id is unlikely to play an inhibitory role in these early myogenic precursors. Id mRNA was expressed in specific regions of the developing nervous system. In the heart, Id mRNA was expressed at high levels in developing cardiac cushions and ridges of the outflow tract and continued to be expressed at high levels in valvular tissue of the neonatal heart.

Animals↗

PubMed1996

Involvement of Ras/Raf/AP-1 in BMP-4 signaling during Xenopus embryonic development.

Previously, we elucidated the role of bone morphogenetic protein 4 (BMP-4) in the dorsal-ventral patterning of the Xenopus embryo by using a dominant negative mutant of the BMP-4 receptor (DN-BR). The present paper describes the involvement of Ras, Raf, and activator protein 1 (AP-1) in BMP-4 signaling during Xenopus embryonic development. The AP-1 activity was determined by injecting an AP-1-dependent luciferase reporter gene into two-cell-stage Xenopus embryos and measuring the luciferase activity at various developmental stages. We found that injection of BMP-4 mRNA increased AP-1 activity, whereas injection of DN-BR mRNA inhibited AP-1 activity. Similar inhibitory effects were seen with injection of mRNAs encoding dominant negative mutants of c-Ha-Ras, c-Raf, or c-Jun. These results suggest that the endogenous AP-1 activity is regulated by BMP-4/Ras/Raf/Jun signals. We next investigated the effects of Ras/Raf/AP-1 signals on the biological functions of BMP-4. DN-BR-induced dorsalization of the embryo, revealed by the formation of a secondary body axis or dorsalization of the ventral mesoderm explant analyzed by histological and molecular criteria, was significantly reversed by coinjection of [Val12]Ha-Ras, c-Raf, or c-Jun mRNA. Furthermore, the BMP-4-stimulated erythroid differentiation in the ventral mesoderm was substantially inhibited by coinjection with the dominant negative c-Ha-Ras, c-Raf, or c-Jun mutant. Our results suggest the involvement of Ras/Raf/AP-1 in the BMP-4 signaling pathway.

Animals↗

PubMed1976

Embryonic development in rabbits after insemination with spermatozoa stored at 37, 5 or-196 degrees C for various periods.

Rabbit spermatozoa stored at 37 degrees C for 5 hr, 5 degrees C for 5 hr or 5 days, and-196 degrees C for 5 hr, 5 days, or 1 year were used to artificially inseminate does induced to ovulate normal or excess numbers of eggs. Fertility and subsequent embryonic development were examined. Frozen spermatozoa stored for 5 hr fertilized fewer oocytes than those stored for 5 days or longer. Fewer embryos were recovered on Day 6 than on Day 2. Blastocysts were smaller when spermatozoa were stored for 5 days, were frozen or were placed in superovulating does, but no statistically significant differences in the % of fetal survival were found in the groups of normally ovulating does. Embryonic wastage associated with storage of spermatozoa resulted from a reduced fertilization rate and/or increased embryonic mortality before implantation.

Animals↗

PubMed1993

Calponin and SM 22 as differentiation markers of smooth muscle: spatiotemporal distribution during avian embryonic development.

Calponin and SM 22 are two proteins related in sequence that are particularly abundant in smooth muscle cells. Here, the distribution patterns of calponin and SM 22 were compared with that of other smooth muscle contractile and cytoskeletal components in the avian embryo using immunofluorescence microscopy and immunoblotting. Like myosin-light-chain kinase and heavy caldesmon, both calponin and SM 22 were more or less exclusively found in smooth muscle cells, during embryonic development and in the adult. Labelling of other cell types including striated muscle was not observed. In contrast, tropomyosin, smooth muscle alpha-actin, filamin and desmin could also be detected in many other cell types in addition to smooth muscles, at least during part of embryonic life. Calponin and SM 22 appeared almost synchronously during the differentiation of all smooth muscle cell populations, though with a slight time difference in the case of the aorta. The appearance of calponin, SM 22 and heavy caldesmon was generally delayed in relation to desmin, tropomyosin, smooth muscle alpha-actin, myosin-light-chain kinase and filamin and a marked increase in abundance of these proteins was observed in the late embryo and in the adult. From these observations we can conclude that both calponin and SM 22 belong to a group of late differentiation determinants in smooth muscle and may constitute convenient and reliable markers to follow the differentiation of most, if not all, smooth muscle cell populations.

Actins↗

PubMed2000

Expression analysis of the chicken homologue of CITED2 during early stages of embryonic development.

Members of the Cited family are nuclear transactivators which bind to the coactivators p300 and CBP. While Cited1 also binds to the TGFbeta signal transducer Smad4, this has not been shown for Cited2. We isolated a chicken homologue of Cited2 from a HH stage 3-6 cDNA library and examined its expression pattern during early stages of embryonic development by whole-mount in situ hybridization. CITED2 expression is detectable in the epiblast as early as stage XI. From HH stage 2 onwards CITED2 is expressed in an anterior domain in the elongating primitive streak in cells which are fated to become heart. During gastrulation the expression pattern is highly dynamic and transiently displays left-right asymmetry with stronger expression on the right side. CITED2 expression appears at multiple sites of forming mesodermal structures. Most prominently, CITED2 is expressed in presomitic and lateral plate mesoderm, in the headfold (future forebrain), the head mesoderm, the pharyngeal floor, the ventral blood islands, somitomeres and the intermediate mesoderm which gives rise to the kidney anlagen.

Amino Acid Sequence↗

PubMed1983

Vitamin carrier proteins during embryonic development in birds and mammals.

Egg maturation in oviparous vertebrates involves the hepatic synthesis, secretion, and deposition in the developing oocyte of several maternal proteins with specific nutrient carrier function. Thus, in the chicken, adequate yolk deposition of riboflavin, thiamin, etc. is obligatorily mediated by carrier proteins specific to each vitamin. Like vitellogenin, these are oestrogen-inducible specific gene products. Despite differences in patterns of embryonic development in mammals vis-à-vis oviparous species, immunologically and biochemically similar maternal vitamin carriers participate in the transplacental transport and fetal accumulation of these vitamins during gestation in the rat. The rodent riboflavin and thiamin carrier proteins are also oestrogen-induced maternal proteins of hepatic origin. Their functional importance in fetal development was established by in vivo passive immunoneutralization of the endogenous proteins, which precipitated fetal wastage leading to pregnancy termination, due to curtailment of the vitamin supply to the fetuses. Similarly, active immunization of female rats with the vitamin carrier proteins led to early fetal resorption without interference with maternal health, cyclicity and fecundity. The discovery of similar gestation-specific carrier proteins in higher mammals and humans suggests that carrier-mediated vitamin delivery mechanisms ensuring embryonic growth have been conserved during evolution.

Animals↗

PubMed2004

Consequences of elevated homocysteine during embryonic development and possible modes of action.

Elevated maternal homocysteine (Hcys) is a well-established risk factor for embryonic toxicity and the development of congenital defects, particularly neural tube closure defects and neurocristopathies. The mechanisms responsible are unclear but early work has focused on the role of folate metabolism because these defects are greatly reduced by folate supplementation. As a consequence, elevated Hcys is often looked upon as being an indirect consequence of faulty folate metabolism, although more recent studies show Hcys may act directly as a teratogen. Because Hcys is at the crossroads of protein and DNA metabolism, has a propensity to chemically modify proteins directly, can generate free radicals, and even perturb ligand binding to certain receptors, the developmental processes Hcys can potentially disturb are enumerable. But in recent years, investigators have begun identifying cellular and molecular targets for the direct action of Hcys. While elevating Hcys can alter a myriad of basic cellular activities needed for normal development, our current understanding as to the specific etiological mechanisms responsible for congenital defects is very speculative. Here we provide an overview of what is currently known regarding the toxicity and teratogenicity of elevated Hcys during embryonic development, paying particular attention to neural tube and neural crest cell morphogenesis.

Embryonic and Fetal Development↗

PubMed2000

Expression of the RNA recognition motif-containing protein SEB-4 during Xenopus embryonic development.

RNA binding proteins play key roles in the post-transcriptional regulation of gene expression. Here we present the molecular cloning and spatio-temporal expression of Xseb-4, which codes for a putative RNA binding protein containing a single RNA recognition motif (RRM). XSEB-4 shares 60-65% identity with the mammalian SEB-4 proteins. Xseb-4 is strongly expressed maternally. Zygotic transcription is initiated in the early gastrula embryo in paraxial mesoderm that is fated to give rise to somites. During the course of gastrulation and neurulation Xseb-4 expression in somitic paraxial mesoderm is centered within the XmyoD expression domain. As development proceeds Xseb-4 expression is in addition initiated in the cardiac primordium and the lens vesicle. In the heart expression is confined to the myocardium. Thus, the RRM-containing putative RNA binding protein XSEB-4 is differentially expressed during embryonic development in Xenopus.

Amino Acid Motifs↗

PubMed2003

The embryonic development of the bodywall and nervous system of the cestode flatworm Hymenolepis diminuta.

Cestodes (tapeworms) are a derived, parasitic clade of the phylum Platyhelminthes (flatworms). The cestode body wall represents an adaptation to its endoparasitic lifestyle. The epidermis forms a non-ciliated syncytium, and both muscular and nervous system are reduced. Morphological differences between cestodes and free-living flatworms become apparent already during early embryogenesis. Cestodes have a complex life cycle that begins with an infectious larva, called the oncosphere. In regard to cell number, cestode oncospheres are among the simplest multicellular organisms, containing in the order of 50-100 cells. As part of our continuing effort to analyze embryonic development in flatworms, we describe here the staining pattern obtained with acTub in embryos and larvae of the cestode Hymenolepis diminuta and, briefly, the monogenean Neoheterocotyle rhinobatidis. In addition, we labeled the embryonic musculature of Hymenolepis with phalloidin. In Hymenolepis embryos, two different cell types that we interpret as neurons and epidermal gland cells express acTub. There exist only two neurons that develop close to the midline at the anterior pole of the embryo. The axons of these two neurons project posteriorly into the center of the oncosphere, where they innervate the complex of muscles that is attached to the hooklets. In addition to neurons, acTub labels a small and invariant set of epidermal gland cells that develop at superficial positions, anteriorly adjacent to the neurons, in the dorsal midline, and around the posteriorly located hooklets. During late stages of embryogenesis they spread and form a complete covering of the embryo. We discuss these data in the broader context of platyhelminth embryology.

Animals↗

PubMed2000

Direct effects of varying doses of oestradiol on early embryonic development in in vitro culture of rat's two-cell embryos.

Hyperstimulation in the rat using pregnant mares' serum gonadotrophin (PMSG) has been known to cause death in pre-implantation embryos, as well as enhancement of oestradiol production. This study examines the effect of oestradiol, in levels that are found in hyperstimulated pregnant rats, on pre-implantation embryonic development. Using a simplified in vitro system, 2-cell embryos retrieved from rats on the 2nd day of pregnancy were cultured in rat two-cell embryo culture medium (R2ECM) containing pharmacological doses of oestradiol for 96 h and scored daily in the morning. Three ngxmL(-1) oestradiol reduced the incidence of >8-cell embryos to morulae on the 5th day and blastocysts on the 6th day of development. Most embryos were retarded at the lower cell stages on the 5th day and degenerated by the 6th day. None of the blastocysts expanded on the last day of culture. Fifteen ngxmL(-1) oestradiol accelerated embryo development on the 3rd day but retarded development on the 4th day, and increased the incidence of degenerated embryos by the 5th and 6th day of development. These results suggest that the elevated oestradiol may constitute a mechanism by which PMSG induces death in pre-implantation rat embryos, possibly via a direct action on the embryos.

Animals↗

PubMed1998

Histochemical localization of hyaluronic acid in vitreous during embryonic development.

PURPOSE: To determine the chronology of the appearance and localization of hyaluronic acid (HA) in mouse vitreous during the embryonic and early postnatal stages of development and in human vitreous during early embryonic development. METHODS: A histochemical method using the specific affinity for HA of a bovine cartilage proteoglycan was used on mouse eyes at embryonic (11 to 18 days) and early postnatal (8 and 18 days) stages. The same technique was applied to human embryonic eyes of 6, 8, 9, and 10 weeks. RESULTS: In the mouse, HA is detected early (12-day embryo stage) in the equatorial vitreous and in the internal portion of the corresponding retinal epithelium, behind the anterior rim of the optic cup. Later in development, HA staining extends temporarily to the posterior vitreous and to the internal layers of the posterior retinal epithelium. In human embryos, HA staining is clearly visible in the posterior vitreous and in the equatorial vitreous, where it is more intense at all the developmental stages. From the 8-week stage onward, the internal layers of the developing retina are also heavily stained. CONCLUSIONS: HA appears very early in developing vitreous of mice and humans, and staining is observed first and predominantly in the equatorial portion of the vitreous. In contrast to human embryos, HA staining in the posterior mouse fetal vitreous is only faint and transient. In both species, staining of the internal layers of the retinal epithelium is detected in the presumptive ciliary body region and in the more posterior retina. The observed temporal and regional simultaneous localization of HA staining in the vitreous and the internal layers of the retinal epithelium is suggestive of a possible role for these cells in the production of the molecule.

Animals↗

PubMed1999

Generation of multiple transcripts from the chicken chondromodulin-I gene and their expression during embryonic development.

Chondromodulin-I (ChM-I) is an angiogenesis inhibitor isolated from fetal bovine cartilage. Here, we report the nucleotide sequence of chicken ChM-I cDNA. Chicken mature ChM-I had a significantly larger N-terminal hydrophilic domain than its mammalian counterparts. Chicken embryos expressed multiple transcripts (3.3, 2.0 and 1.7 kb in size) due to the alternative utilization of polyadenylation signals, whereas only the 1.7 kb transcripts were detected in mammals. Although confined to cartilage and eye at a later stage of development, whole-mount in situ hybridization revealed the expression of ChM-I mRNA in somites, heart, bronchial arches, roof plate, retina and limb buds. The expression pattern of the gene suggests a role for ChM-I in the morphogenesis during embryonic development.

3' Untranslated Regions↗

PubMed2006

Exposure to 3,3',4,4',5-pentachlorobiphenyl during embryonic development has a minimal effect on the cytochrome P4501A response to 2,3,7,8-tetrachlorodibenzo-p-dioxin in cultured chicken embryo hepatocytes.

Concentrations of dioxin-like compounds in avian eggs can vary substantially between individuals, species, and collection sites. Although the inducibility of cytochrome P4501A (CYPIA) in hepatocyte cultures is commonly used to predict species sensitivity to environmental contaminants, it is not known how exposure to dioxin-like compounds during embryonic development might alter this biomarker response. To investigate this question, we injected vehicle or 0.4, 0.8, or 1.6 microg/kg of 3,3',4,4',5-pentachlorobiphenyl (PCB 126) into the air cell of fertilized chicken eggs before incubation, and we measured CYP1A endpoints in cultured hepatocytes of day-19 embryos from each treatment group. The CYP1A response to PCB 126 also was assessed in whole liver tissue. Embryonic exposure to the most environmentally relevant treatment, 0.4 microg/kg of PCB 126, increased CYPIA4 mRNA expression 29-fold compared to control values in whole liver tissue but only twofold compared to control values in cultured hepatocytes. The CYPIA response to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was not altered in hepatocytes cultured from embryos treated with 0.4 microg/kg of PCB 126, but at 0.8 and 1.6 microg/kg of PCB 126, several concentration-dependent effects were observed. For example, embryos exposed to higher concentrations of PCB 126 in ovo were more responsive to CYP1A mRNA induction by TCDD in vitro. These findings suggest that exposure to environmental levels of dioxin-like compounds during incubation is not likely to alter species-sensitivity estimates derived from in vitro CYP1A data.

Animals↗