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PubMed1994

In vivo embryogenesis, embryo migration, and embryonic mortality in the domestic cat.

In vivo embryogenesis, embryo migration, and survival were studied in the domestic cat. Queens were naturally mated (three times daily) on the second and third days of behavioral estrus and, if ovulation occurred, ovariohysterectomized at 64 (n = 8), 76 (n = 11), 100 (n = 8), 124 (n = 7), 148 (n = 6), and 480 h (n = 8) after first copulation. Of 52 cats mated, 48 (92.3%) ovulated (as evidenced by the presence of ovarian CL), and of these, 38 (79.2%) either produced good-quality embryos or had implantation sites. From the remaining cats, only unfertilized oocytes (n = 5), degenerating embryos (n = 4), or no oocytes/embryos (n = 1) were recovered. Embryos at 64, 76, 100, and 124 h after the first copulation typically were 1 to 4 cells (17 of 20; 85.0%), 5 to 8 cells (18 of 28; 64.3%), 9 to 16 cells (14 of 24; 58.3%), and morulae (15 of 21; 71.4%), respectively; all were within the oviducts. At 148 h, embryos primarily were compact morulae or early blastocysts (15 of 18; 83.3%), and all were within the uterus. For the preimplantation groups, the overall recovery of embryos plus oocytes per CL was 80.6%, and the mean (+/- SEM) numbers of CL and embryos were 64 h, 4.8 +/- 0.3, 3.1 +/- 0.8; 76 h, 4.7 +/- 0.3, 3.9 +/- 0.6; 100 h, 5.8 +/- 0.5, 3.3 +/- 0.8; 124 h, 4.4 +/- 0.5, 4.0 +/- 0.6; and 148 h, 6.5 +/- 1.1, 3.7 +/- 0.7, respectively. Cats in the 480-h group produced a mean of 5.6 +/- 0.5 CL and 3.9 +/- 0.5 implantation sites. In six of eight cats in this group, there was a disparity between CL number on a given ovary and number of implantation sites in the ipsilateral horn, supporting the concept of transuterine embryo migration. In summary, results indicated that 1) more than 90% of cats ovulated following this multiple mating regimen, but approximately 21% of these failed to produce any fertilized or viable embryos; 2) embryo developmental rate in vivo was biphasic, with a rapid cleavage rate to the 5- to 8-cell stage followed by a slower cleavage rate to the morula stage; 3) cat embryos entered the uterus as compact morulae or early blastocysts approximately 5.5 days after the first copulation; and 4) on the basis of implantation/CL ratio, approximately 30% of all ovulated cat oocytes underwent either fertilization failure or preimplantation embryonic mortality.

Animals↗
PubMed1995

Histological characteristics of the uterine endometrium and corpus luteum during early embryogenesis and the relationship to embryonic mortality in the domestic cat.

Pregnancy rates are low and litter sizes generally small when assisted reproduction techniques are used in gonadotropin-treated felid (cat) species. A prerequisite to determining whether or not abnormal morphological changes in the uterine lumen or corpus luteum (CL) are related to this reproductive failure is the documentation of normal histological kinetics during natural embryogenesis. This study characterized the histological changes of the endometrium and ovarian CL during the early stages of preimplantation embryonic development in the naturally estrous, mated queen. The purpose was to 1) develop a system for dating the cat endometrium and CL of early pregnancy; 2) document the frequency of abnormal uterine and CL history under natural mating conditions; and 3) compare histological traits of queens producing good- vs. poor-quality embryos. Naturally estrous, mated queens were ovariohysterectomized at 64 h (n = 8), 76 h (n = 11), 100 h (n = 8), 124 h (n = 7), 148 h (n = 6), or 480 h (n = 8) after first copulation. Embryos collected from oviductal and uterine flushings were graded for quality, and uteri and ovaries were fixed in formalin. Fixed tissue sections were stained and multiple histological traits described for each uterine (endometrial height, endometrial vacuolation, percentage of glandular cells with subnuclear vacuoles, number of mitoses, nuclear-to-cytoplasmic ratio) and ovarian (presence of tertiary follicles, vacuolation of luteal cell cytoplasm, luteal cell shape) sample. Modest histological changes were observed at each time point, and these were documented in detail. The most prominent modifications occurred at 124 h after first copulation and included thickening of the endometrium, straightening of the glands, increased cytoplasmic vacuolation, and increased epithelial height. Of 15 queens failing to produce good-quality embryos, only 4 expressed unusual histological characteristics; and 3 of 25 queens producing only high-quality embryos exhibited abnormal uterine or CL cellular integrity. Therefore, aberrant histological changes are not primarily responsible for failure of the naturally estrous, mated queen to produce good-quality embryos. Furthermore, a normative database now is available to date the endometrium and CL of early pregnancy and to examine the impact of exogenous gonadotropins and assisted techniques on uterine/CL structure and function.

Animals↗
PubMed1997

Apoptotic cell death during normal embryogenesis of the coronal suture: early detection of apoptosis in mice using annexin V.

Regulation of programmed cell death (apoptosis) is crucial for normal development and growth, both prenatally and postnatally. If its role during normal embryogenesis of a given structure is established, a number of related congenital disorders can be explained by a (local) deregulation of apoptosis. In this study, apoptotic cell death patterns during normal development of the murine coronal suture were investigated. Detection of apoptotic cells was undertaken by labeling with Annexin V. Results showed apoptosis occurring at the same time and place as suture initiation. Apoptotic cells are located along the entire established part of the suture and its developing part. Because apoptosis is shown to be highly associated with sutural genesis, the theory of craniosynostosis being the equivalent of deregulation at this locus seems in line with these findings.

Affinity Labels↗
PubMed1987

Role of transmigration and abnormal embryogenesis in ectopic pregnancy.

Transmigration of ovum and/or sperm may occur, as deduced by the presence of EP in the fallopian tube contralateral to the corpus luteum. The frequency of occurrence of transmigration is relatively low, and, in many cases, other routes of ovum and sperm transport (i.e., intrauterine migration, tubal recanalization, fistula formation) may lead to the ectopic implantation site. In our view, the percentage of abnormal embryos associated with EP is no different from those associated with spontaneous abortions of intrauterine origin. Embryos from spontaneous abortions-of either intrauterine or extrauterine origin-seem to have more abnormalities than embryos from induced abortions. Other etiologic factors such as tubal disease, strictures of the fallopian tube, or endocrinopathies seem to contribute more significantly to the incidence of EP than does abnormal embryogenesis.

Abdomen↗
PubMed1999

Subaortic left innominate vein: radiologic findings and consideration of embryogenesis.

To propose a hypothesis about the embryogenesis of the subaortic left innominate vein, the authors reviewed the radiologic features of 14 patients diagnosed with subaortic left innominate vein made by computed tomography or magnetic resonance imaging scan. The authors retrospectively analyzed the level of the aortic arch, associated aortic arch anomalies, and the presence or absence of obliteration of the prevascular space. A high aortic arch was seen in 10 patients, five with a cervical, two with a right and, one with a double aortic arch. The prevascular space was occupied by the aortic arch, the great arteries, or both in all 10 patients with a high arch. In the remaining four patients with a normal aortic arch, the prevascular space was preserved, but abnormal elongation of the aortic segment between the left common carotid artery and the left subclavian artery was seen in three. The authors postulate that precardinal anastomosis can develop in any pathway where there is the available space. In the presence of abnormal elongation of the aortic arch and resultant widening of the subaortic space, the chance of the development of a subaortic left innominate vein increases.

Adult↗
PubMed1991

Neurenteric cysts of the posterior fossa: recognition, management, and embryogenesis.

Neurenteric cysts are endothelium-lined structures most commonly encountered in the lower cervical or upper thoracic spinal cord. The occurrence of neurenteric cysts within the cranial vault is unusual. We present three patients with neurenteric cysts located within the posterior fossa: one near the jugular foramen deforming the 4th ventricle, a second in the cerebellopontine angle, and a third in the prepontine cistern. Several different theories have been advanced to explain the embryogenesis of neurenteric cysts. We review these theories and conclude that cranial neurenteric cysts may arise from a disturbance of early gastrulation, shortly after the onset of primitive streak regression.

Adult↗
PubMed2006

The murine Pou6f2 gene is temporally and spatially regulated during kidney embryogenesis and its human homolog is overexpressed in a subset of Wilms tumors.

We have previously suggested the transcription factor gene POU6F2 as a novel tumor suppressor involved in Wilms tumor (WT) predisposition. Since WT arises from pluripotent embryonic renal precursors, in this study we analyzed the expression of the murine homolog Pou6f2 during kidney embryogenesis and compared it to that of Wt1, the homolog of WT1, a known WT related gene involved in mesenchyme to epithelium conversion. Quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) performed for Pou6f2 on kidney specimens from embryos, pups, and adult mice, showed that the Pou6f2 mRNA was more abundant in the earliest analyzed phase of kidney organogenesis (E13) than in more advanced fetal stages and in adult animal. In situ RT-PCR demonstrated that Pou6f2 expression parallels the centripetal differentiation of renal morphogenesis. In addition, in E18 kidney, most structures exhibiting Pou6f2 expression stained positively in immunohistochemistry for the Wt1 protein. Finally, quantitative real-time RT-PCR revealed an overexpression (>/=80 times) of POU6F2 compared with normal kidney in 5 of 22 (23%) WTs. The finding of a highly regulated temporal and spatial Pou6f2 expression during renal organogenesis, of its coexpression with Wt1 and of POU6F2 overexpression in a subset of WTs are consistent with a role of POU6F2 in kidney development and provide further support to its involvement in WT.

Adult↗
PubMed1988

Stretch-activated ion channels modulate the resting membrane potential during early embryogenesis.

By using the patch-clamp technique, stretch-activated ionic channels were found in the membrane of cleaving freshwater fish embryos at the early stages of embryogenesis (2-256 cells). The application of negative pressure to the pipette increased the frequency of activation and the duration of bursts. This type of channel has a preferential K+ selectivity. When bathed on both membrane surfaces with 140 mM KCl the channel conductance was 71 pS. The kinetic behaviour did not depend markedly on either membrane potential (in the range from -70 to +70 mV) or calcium concentration on the cytoplasmic side of the membrane. On continuous recording, the probability of the channel being open was found to change periodically over a 5- to 20-fold range for different cells. These variations correlated with changes in resting potential and membrane conductance during the cell cycle. These results suggest that the oscillation of resting potential within the cell cycle is associated with the operation of stretch-activated ion channels.

Animals↗
PubMed1987

En-1 and En-2, two mouse genes with sequence homology to the Drosophila engrailed gene: expression during embryogenesis.

Two mouse genes, En-1 and En-2, have sequence homology to the engrailed (en) and invected (inv) genes of Drosophila (Joyner et al. 1985). Partial nucleotide sequence analyses of genomic and cDNA clones show that the homologous sequences can encode a stretch of 107 amino acids, including a centrally located, 60-amino-acid homeo box. Within the homologous regions of the mouse and Drosophila genes, 78 (73%) of the amino acids are identical. Such extensive conservation of sequence outside the homeo box between vertebrate and Drosophila homeo box-containing genes is thus far unique. En-1 and En-2 are expressed during mouse embryogenesis. Transcripts from both genes were detected in RNA samples from teratocarcinoma cells, which serve as in vitro models for the early embryo, and from embryos at 9.5 through 17.5 days of development. For each gene we observed a unique pattern of changes in the number and relative intensities of transcripts detectable during embryonic development. Transcripts from both genes are represented abundantly in RNA extracted from the posterior portion of the fetal brain, and are much less abundant in RNA from other fetal tissues, including the anterior portion of the brain and the spinal cord. The chromosome map positions of En-1 and En-2 were determined by recombinant inbred strain analyses. Unlike their Drosophila counterparts, they are unlinked: En-1 is in the central portion of the mouse chromosome 1 and En-2 is in the proximal portion of mouse chromosome 5. Both genes map in the vicinity of mutations that are known to cause abnormalities during development.

Amino Acid Sequence↗
PubMed1997

The LKLF transcription factor is required for normal tunica media formation and blood vessel stabilization during murine embryogenesis.

The transcriptional programs that regulate blood vessel formation are largely unknown. In this paper, we examine the role of the zinc finger transcription factor LKLF in murine blood vessel morphogenesis and homeostasis. By in situ hybridization and immunohistochemistry, we show that LKLF is expressed as early as embryonic day 9.5 (E9.5) in vascular endothelial cells throughout the developing mouse embryo. To better understand the function of LKLF, we used homologous recombination in embryonic stem (ES) cells to generate LKLF-deficient (LKLF-/-) mice. Both angiogenesis and vasculogenesis were normal in the LKLF-/- mice. However, LKLF-/- embryos died between E12.5 and E14.5 from severe intra-embryonic and intra-amniotic hemorrhaging. This bleeding disorder was associated with specific defects in blood vessel morphology. Umbilical veins and arteries in the LKLF-/- embryos displayed an abnormally thin tunica media and aneurysmal dilatation before rupturing into the amniotic cavity. Similarly, vascular smooth muscle cells in the aortae from the LKLF-/- animals displayed a cuboidal morphology and failed to organize into a compact tunica media. Consistent with these findings, electron microscopic analyses demonstrated endothelial cell necrosis, significant reductions in the number of vessel-wall pericytes and differentiating smooth muscle cells, and decreased deposition of extracellular matrix in the LKLF-/- vessels. Despite these defects, in situ hybridization demonstrated normal expression of platelet-derived growth factor B, Tie1, Tie2, transforming growth factor beta, and heparin-binding epidermal growth factor in the vasculature of the LKLF-/- embryos. Therefore, LKLF defines a novel transcriptional pathway in which endothelial cells regulate the assembly of the vascular tunica media and concomitant vessel wall stabilization during mammalian embryogenesis.

Animals↗
PubMed2003

Ecsit is required for Bmp signaling and mesoderm formation during mouse embryogenesis.

Bone morphogenetic proteins (Bmps) are members of the transforming growth factor beta (TGFbeta) superfamily that play critical roles during mouse embryogenesis. Signaling by Bmp receptors is mediated mainly by Smad proteins. In this study, we show that a targeted null mutation of Ecsit, encoding a signaling intermediate of the Toll pathway, leads to reduced cell proliferation, altered epiblast patterning, impairment of mesoderm formation, and embryonic lethality at embryonic day 7.5 (E7.5), phenotypes that mimic the Bmp receptor type1a (Bmpr1a) null mutant. In addition, specific Bmp target gene expression is abolished in the absence of Ecsit. Biochemical analysis demonstrates that Ecsit associates constitutively with Smad4 and associates with Smad1 in a Bmp-inducible manner. Together with Smad1 and Smad4, Ecsit binds to the promoter of specific Bmp target genes. Finally, knock-down of Ecsit with Ecsit-specific short hairpin RNA inhibits both Bmp and Toll signaling. Therefore, these results show that Ecsit functions as an essential component in two important signal transduction pathways and establishes a novel role for Ecsit as a cofactor for Smad proteins in the Bmp signaling pathway.

Adaptor Proteins, Signal Transducing↗
PubMed1988

Isolation of the Drosophila segmentation gene runt and analysis of its expression during embryogenesis.

runt is one of the genes required for establishment of the segmented body pattern of the Drosophila embryo. We have isolated DNA sequences containing this gene using P-element transposon tagging. Southern blot analyses of six different DNA rearrangements that are associated with runt mutations revealed a minimal region of 8.5-kb of DNA that was important for function. In germ line transformation experiments, a 14.5-kb segment of DNA that spanned this minimal region provided significant, although not full, levels of runt activity. The runt gene encoded a 2.6-kb poly(A)+ RNA that underwent a series of dynamic changes in its spatial and temporal patterns of accumulation during embryogenesis. The runt RNA was most abundant at the blastoderm stage when it showed the seven stripes of expression characteristic of other Drosophila pair-rule genes.

Animals↗
PubMed2002

The Arabidopsis kinase-associated protein phosphatase controls internalization of the somatic embryogenesis receptor kinase 1.

The AtSERK1 protein is a plasma membrane-located LRR receptor-like serine threonine kinase that is transiently expressed during plant embryogenesis. Our results show that AtSERK1 interacts with the kinase-associated protein phosphatase (KAPP) in vitro. The kinase interaction (KI) domain of KAPP does not interact with a catalytically inactive kinase mutant. Using mutant AtSERK1 proteins in which Thr 462, Thr 463, and Thr 468 in the A-loop of the AtSERK1 kinase domain were replaced by alanines, we show that phosphorylation status of the receptor is involved in interaction with KAPP. KAPP and AtSERK1 cDNAs were fused to two different variants of green fluorescent protein (GFP), the yellow fluorescent protein (YFP) or the cyan fluorescent protein (CFP). Both KAPP and AtSERK1 proteins are found at the plasma membrane. Our results show that AtSERK1-CFP becomes sequestered into intracellular vesicles when transiently coexpressed with KAPP-YFP proteins. AtSERK1(T463A)-CFP and AtSERK1(3T-->A)-CFP proteins were partially sequestered intracellularly in the absence of KAPP-YFP protein, suggesting an active role for KAPP dephosphorylation of threonine residues in the AtSERK1 A-loop in receptor internalization. The interaction between the KAPP-CFP/YFP and AtSERK1-CFP/YFP fusion proteins was investigated with fluorescence spectral imaging microscopy (FSPIM). Our results show that AtSERK1-CFP and KAPP-YFP proteins are colocalized at the plasma membrane but only show fluorescence energy transfer (FRET) indicative of physical interaction in intracellular vesicles. These results suggest that KAPP is an integral part of the AtSERK1 endocytosis mechanism.

Arabidopsis↗
PubMed1991

Transcription factor AP-2 is expressed in neural crest cell lineages during mouse embryogenesis.

We have analyzed the expression pattern of transcription factor AP-2 in mouse embryos to evaluate the potential of AP-2 as a regulator during vertebrate development. A partial cDNA encoding AP-2 was isolated from a mouse embryo cDNA library and used to prepare probes to measure AP-2 mRNA levels by RNase protection and RNA in situ hybridization. Between 10.5 and 15.5 days of embryogenesis, the relative abundance of AP-2 mRNA is greatest at 11.5 days and declines steadily thereafter. RNA in situ hybridization analysis of embryos between 8.5 and 12.5 days of gestation identified a novel expression pattern for AP-2. The principle part of this expression occurs in neural crest cells and their major derivatives, including cranial and spinal sensory ganglia and facial mesenchyme. AP-2 is also expressed in surface ectoderm and in a longitudinal column of the spinal cord and hindbrain that is contacted by neural crest-derived sensory ganglia. Additional expression of AP-2 occurs in limb bud mesenchyme and in meso-metanephric regions. This embryonic expression pattern is spatially and temporally consistent with a role for AP-2 in regulating transcription of genes involved in the morphogenesis of the peripheral nervous system, face, limbs, skin, and nephric tissues.

Amino Acid Sequence↗
PubMed1991

TEF, a transcription factor expressed specifically in the anterior pituitary during embryogenesis, defines a new class of leucine zipper proteins.

We have identified and characterized a new member of the leucine zipper (bZIP) gene family of transcription factors, thyrotroph embryonic factor (TEF). Analysis of the ontogeny of TEF gene expression reveals the presence of TEF transcripts, beginning on embryonic day 14, only in the region of the rat anterior pituitary gland in which thyrotrophs arise. This pattern of gene expression corresponds temporally and spatially to the onset of thyroid-stimulating hormone (TSH beta) gene expression, which defines the thyrotroph phenotype. Coupled with this observation, we find that TEF can bind to and trans-activate the TSH beta promoter. In contrast to this restricted pattern of expression during embryogenesis, TEF transcripts appear in several tissues in the mature organism. We propose that TEF belongs to a new class of bZIP proteins on the basis of the unique homology between TEF and another member of the bZIP gene family, the albumin D box-binding protein (DBP). TEF and DBP transcripts are coexpressed in a pituitary cell line, and these two proteins can readily form heterodimers. The DNA-binding and dimerization domains of TEF correspond to those found in other bZIP proteins. We have however, identified a cluster of basic amino acids, found only in TEF and DBP, that is necessary for the proper DNA-binding site specificity of TEF. A major trans-activation domain of TEF resides outside the region of homology to other bZIP proteins. These data are consistent with a role for a member of a new class of bZIP transcription factors in activating gene expression in the developing thyrotroph.

Amino Acid Sequence↗
PubMed1991

Expression of a retinoic acid response element-hsplacZ transgene defines specific domains of transcriptional activity during mouse embryogenesis.

Treatment with retinoic acid (RA) is known to produce complex teratogenic effects in vertebrates, and its presence in the developing embryo as an endogenous substance has led to the suggestion that RA might be a natural morphogenetic agent. Although our understanding of the molecular mechanism of RA action has improved considerably with the identification of nuclear receptors for RA (RARs) and RA-responsive genes, the exact relationship between the proposed morphogenetic activity of RA and its teratogenic effects remains to be characterized. Here, we show that a RA response element (RARE) present in the RAR beta gene can direct specific spatial and temporal expression of an hsplacZ transgene during mouse embryogenesis. In the early embryo, the transgene is expressed in a specific anterior-posterior domain that is completely obliterated by treatment of pregnant mice with teratogenic doses of RA. The expression of the transgene becomes more restricted as organogenesis progresses and mimics closely the reported expression of the RAR beta gene. These results suggest that, in vivo, some of the morphogenetic effects of RA could be mediated through localized transcriptional activity controlled by the various RARs. The specific pattern of expression of the RAREhsplacZ transgene does not correlate with the proposed sites of action of RA as defined by its teratogenic effects but does support a role for RA in early anterior-posterior patterning along the body axis.

Animals↗
PubMed1994

Distinct molecular mechanism regulate cell cycle timing at successive stages of Drosophila embryogenesis.

The conserved regulators of cell cycle progression--Cyclins, Cdc2 kinase, and String phosphatase (Cdc25)--accommodate multiple modes of regulation during Drosophila embryogenesis. During cell cycles 2-7, Cdc2/Cyclin complexes are continuously present and show little fluctuation in abundance, phosphomodification, or activity. This suggests that cycling of the mitotic apparatus does not require cytoplasmic oscillations of known regulatory activities. During cycles 8-13 a progressive increase in the degradation of Cyclins at mitosis leads to increasing oscillations of Cdc2 kinase activity. Mutants deficient in cyclin mRNAs suffer cell cycle delays during this period, suggesting that Cyclin accumulation times these cycles. During interphase 14, programmed degradation of maternal String protein leads to inhibitory phosphorylation of Cdc2 and cell cycle arrest. Subsequently, mitoses 14-16 are triggered by pulses of zygotic string transcription.

Amino Acid Sequence↗
PubMed2000

Bub3 gene disruption in mice reveals essential mitotic spindle checkpoint function during early embryogenesis.

Bub3 is a conserved component of the mitotic spindle assembly complex. The protein is essential for early development in Bub3 gene-disrupted mice, evident from their failure to survive beyond day 6.5-7.5 postcoitus (pc). Bub3 null embryos appear normal up to day 3.5 pc but accumulate mitotic errors from days 4.5-6.5 pc in the form of micronuclei, chromatin bridging, lagging chromosomes, and irregular nuclear morphology. Null embryos treated with a spindle-depolymerising agent fail to arrest in metaphase and show an increase in mitotic disarray. The results confirm Bub3 as a component of the essential spindle checkpoint pathway that operates during early embryogenesis.

Animals↗