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Results for “embryonic lethality”

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At least 145 records · Page 8Linked to original sources

PubMed2003

Embryonic lethal effect of expressing a dominant negative mutant human thyroid hormone receptor alpha1 in mice.

Resistance to thyroid hormone (RTH) is caused mainly by mutations of the thyroid hormone receptor (TR) beta gene. Although, in vitro, TRalpha1 and TRbeta1 mutants exhibit similar dominant negative effects against wild-type TR, no TRalpha mutants have ever been identified in RTH patients. It has been postulated that mutations in TRalpha gene may be lethal, compensated completely by intact TRbeta or associated with phenotypic manifestations different from RTH. To investigate the consequences of mutant TRalpha1 expression in vivo, we tried to generate two different lines of transgenic mice which express a strong or a weak dominant negative mutant TR alpha1, respectively. First, we expressed betaF451X identified in a patient with severe RTH and alphaF397X, which has an identical C-terminal truncation and a similarly strong dominant negative potency to betaF451X, under the control of human polypeptide chain elongation factor 1alpha promoter. Six betaF451X-transgenic mice were born from 223 transferred embryos, giving a transgenic frequency of 2.7%. By contrast, expression of alphaF397X resulted in quite a low transgenic frequency with 0.39% of the transferred embryos bearing the transgene. Only three transgenic mice were born with no apparently overt abnormalities, of which one male produced F1 offspring. The transgenic progeny expressed alphaF397X in the testis but we did not succeed in generating transgenic mice expressing alphaF397X in multiple organs. To avoid toxic effects mediated by a strong dominant negative activity of mutant TRalpha1, we exchanged alphaF397X for alphaK389E, which has an identical missense mutation and a relatively weak transdominant potency as betaK443E identified in a patient with mild RTH. When expressed by cytomegalovirus immediate early enhancer-chicken beta-actin promoter, we did not succeed in creating alphaK389E-transgenic mice despite three independent transgene-injections. These findings define crucial in vivo functions of mutant TRalpha1s during mouse fetal development and suggest the possibility that the expression of a dominant negative mutant TRalpha1 in extensive tissues from the early embryonal stages might be lethal.

Animals↗

PubMed2003

Neural and mammary gland defects in ErbB4 knockout mice genetically rescued from embryonic lethality.

Mice lacking the epidermal growth factor receptor family member ErbB4 exhibit defects in cranial neural crest cell migration but die by embryonic day 11 because of defective heart development. To examine later phenotypes, we rescued the heart defects in ErbB4 mutant mice by expressing ErbB4 under a cardiac-specific myosin promoter. Rescued ErbB4 mutant mice reach adulthood and are fertile. However, during pregnancy, mammary lobuloalveoli fail to differentiate correctly and lactation is defective. Rescued mice also display aberrant cranial nerve architecture and increased numbers of large interneurons within the cerebellum.

Animals↗

PubMed2004

Deletion of mouse rad9 causes abnormal cellular responses to DNA damage, genomic instability, and embryonic lethality.

The fission yeast Schizosaccharomyces pombe rad9 gene promotes cell survival through activation of cell cycle checkpoints induced by DNA damage. Mouse embryonic stem cells with a targeted deletion of Mrad9, the mouse ortholog of this gene, were created to evaluate its function in mammals. Mrad9(-/-) cells demonstrated a marked increase in spontaneous chromosome aberrations and HPRT mutations, indicating a role in the maintenance of genomic integrity. These cells were also extremely sensitive to UV light, gamma rays, and hydroxyurea, and heterozygotes were somewhat sensitive to the last two agents relative to Mrad9(+/+) controls. Mrad9(-/-) cells could initiate but not maintain gamma-ray-induced G(2) delay and retained the ability to delay DNA synthesis rapidly after UV irradiation, suggesting that checkpoint abnormalities contribute little to the radiosensitivity observed. Ectopic expression of Mrad9 or human HRAD9 complemented Mrad9(-/-) cell defects, indicating that the gene has radioresponse and genomic maintenance functions that are evolutionarily conserved. Mrad9(+/-) mice were generated, but heterozygous intercrosses failed to yield Mrad9(-/-) pups, since embryos died at midgestation. Furthermore, Mrad9(-/-) mouse embryo fibroblasts were not viable. These investigations establish Mrad9 as a key mammalian genetic element of pathways that regulate the cellular response to DNA damage, maintenance of genomic integrity, and proper embryonic development.

Animals↗

PubMed1999

Absence of basement membranes after targeting the LAMC1 gene results in embryonic lethality due to failure of endoderm differentiation.

The LAMC1 gene coding for the laminin gamma1 subunit was targeted by homologous recombination in mouse embryonic stem cells. Mice heterozygous for the mutation had a normal phenotype and were fertile, whereas homozygous mutant embryos did not survive beyond day 5.5 post coitum. These embryos lacked basement membranes and although the blastocysts had expanded, primitive endoderm cells remained in the inner cell mass, and the parietal yolk sac did not develop. Cultured embryonic stem cells appeared normal after targeting both LAMC1 genes, but the embryoid bodies derived from them also lacked basement membranes, having disorganized extracellular deposits of the basement membrane proteins collagen IV and perlecan, and the cells failed to differentiate into stable myotubes. Secretion of the linking protein nidogen and a truncated laminin alpha1 subunit did occur, but these were not deposited in the extracellular matrix. These results show that the laminin gamma1 subunit is necessary for laminin assembly and that laminin is in turn essential for the organization of other basement membrane components in vivo and in vitro. Surprisingly, basement membranes are not necessary for the formation of the first epithelium to develop during embryogenesis, but first become required for extra embryonic endoderm differentiation.

Animals↗

PubMed1999

Embryonic lethality and vascular defects in mice lacking the Notch ligand Jagged1.

The Notch signaling pathway is an evolutionarily conserved intercellular signaling mechanism essential for embryonic development in mammals. Mutations in the human JAGGED1 ( JAG1 ) gene, which encodes a ligand for the Notch family of transmembrane receptors, cause the autosomal dominant disorder Alagille syndrome. We have examined the in vivo role of the mouse Jag1 gene by creating a null allele through gene targeting. Mice homozygous for the Jag1 mutation die from hemorrhage early during embryogenesis, exhibiting defects in remodeling of the embryonic and yolk sac vasculature. We mapped the Jag1 gene to mouse chromosome 2, in the vicinity of the Coloboma ( Cm ) deletion. Molecular and complementation analyses revealed that the Jag1 gene is functionally deleted in the Cm mutant allele. Mice heterozygous for the Jag1 null allele exhibit an eye dysmorphology similar to that of Cm /+ heterozygotes, but do not exhibit other phenotypes characteristic of Cm /+ mice or of humans with Alagille syndrome. These results establish the phenotype of Cm /+ mice as a contiguous gene deletion syndrome and demonstrate that Jag1 is essential for remodeling of the embryonic vasculature.

Animals↗

PubMed1976

Maternally influenced embryonic lethality: allele specific genetic rescue at a female fertility locus in Drosophila melanogaster.

A new locus, mel(1)R1, with a maternal effect on embryonic development, has been mapped at about 0.5 on the X chromosome of Drosophila melanogaster and localized cytologically between bands 2D6 and 3A1. Genotypically mutant embryos die if produced by homozygous mutant females but survive if produced by heterozygous females. Two mutant alleles have been isolated. One of these is genetically rescuable: when homozygous mutant females are mated to mutant males, all the embryos die, but when these females are mated to normal males, female offspring are produced. The other allele is not rescuable. Genetic rescue is dominant at this locus since females heterozygous for the two mutant alleles produce female offspring in crosses to normal males.

Alleles↗

PubMed1998

Loss of function of the tuberous sclerosis 2 tumor suppressor gene results in embryonic lethality characterized by disrupted neuroepithelial growth and development.

Germline defects in the tuberous sclerosis 2 (TSC2) tumor suppressor gene predispose humans and rats to benign and malignant lesions in a variety of tissues. The brain is among the most profoundly affected organs in tuberous sclerosis (TSC) patients and is the site of development of the cortical tubers for which the hereditary syndrome is named. A spontaneous germline inactivation of the Tsc2 locus has been described in an animal model, the Eker rat. We report that the homozygous state of this mutation (Tsc2(Ek/Ek)) was lethal in mid-gestation (the equivalent of mouse E9.5-E13.5), when Tsc2 mRNA was highly expressed in embryonic neuroepithelium. During this period homozygous mutant Eker embryos lacking functional Tsc2 gene product, tuberin, displayed dysraphia and papillary overgrowth of the neuroepithelium, indicating that loss of tuberin disrupted the normal development of this tissue. Interestingly, there was significant intraspecies variability in the penetrance of cranial abnormalities in mutant embryos: the Long-Evans strain Tsc2(Ek/Ek) embryos displayed these defects whereas the Fisher 344 homozygous mutant embryos had normal-appearing neuroepithelium. Taken together, our data indicate that the Tsc2 gene participates in normal brain development and suggest the inactivation of this gene may have similar functional consequences in both mature and embryonic brain.

Animals↗

PubMed1992

Identification and characterization of a novel, evolutionarily conserved gene disrupted by the murine H beta 58 embryonic lethal transgene insertion.

The H beta 58 transgenic mouse line carries a recessive insertional mutation that results in developmental abnormalities beginning at day 7.5 p.c. and embryonic arrest at about day 9.5. In this paper, we describe the characterization of a novel gene encoded at the H beta 58 locus, whose disruption appears to be responsible for the mutant phenotype. The wild-type H beta 58 gene encodes a single 2.7 kb mRNA during embryonic and fetal development, and in many adult somatic tissues. In the mutant locus, this transcription unit is split by the transgene insertion, and one of its coding exons is deleted. Consistent with the physical disruption of the gene, the level of the H beta 58 mRNA in heterozygous mutant mouse tissues was half the normal level, indicating that the mutant allele fails to encode a stable mRNA. In situ hybridization studies revealed that expression of the wild-type H beta 58 gene begins in the oocyte, and continues throughout pre- and post-implantation embryogenesis, despite the fact that homozygous mutant embryos develop successfully through the egg cylinder stage (day 6.5 p.c.). In the early post-implantation embryo, expression of the normal H beta 58 gene is relatively low in the embryonic ectoderm, the tissue displaying the earliest phenotypic effects of the mutation, and highest in the visceral endoderm. We therefore propose that the effects of the mutation on the embryonic ectoderm may be exerted indirectly, via the visceral endoderm. Sequence analysis of H beta 58 cDNA clones revealed no homology between the 38 x 10(3) M(r) H beta 58 protein and other known proteins. However, the H beta 58 gene displayed extremely strong conservation between mammals and birds (greater than 96% amino acid identity), although it appeared less conserved in amphibians and invertebrates.

Amino Acid Sequence↗

PubMed2004

Deletion of the mouse P450c17 gene causes early embryonic lethality.

Dehydroepiandrosterone (DHEA), a 19-carbon precursor of sex steroids, is abundantly produced in the human but not the mouse adrenal. However, mice produce DHEA and DHEA-sulfate (DHEAS) in the fetal brain. DHEA stimulates axonal growth from specific populations of mouse neocortical neurons in vitro, while DHEAS stimulates dendritic growth from those cells. The synthesis of DHEA and sex steroids, but not mouse glucocorticoids and mineralocorticoids, requires P450c17, which catalyzes both 17 alpha-hydroxylase and 17,20-lyase activities. We hypothesized that P450c17-knockout mice would have disordered sex steroid synthesis and disordered brain DHEA production and thus provide phenotypic clues about the functions of DHEA in mouse brain development. We deleted the mouse P450c17 gene in 127/SvJ mice and obtained several lines of mice from two lines of targeted embryonic stem cells. Heterozygotes were phenotypically and reproductively normal, but in all mouse lines, P450c17(-/-) zygotes died by embryonic day 7, prior to gastrulation. The cause of this early lethality is unknown, as there is no known function of fetal steroids at embryonic day 7. Immunocytochemistry identified P450c17 in embryonic endoderm in E7 wild-type and heterozygous embryos, but its function in these cells is unknown. Enzyme assays of wild-type embryos showed a rapid rise in 17-hydroxylase activity between E6 and E7 and the presence of C(17,20)-lyase activity at E7. Treatment of pregnant females with subcutaneous pellets releasing DHEA or 17-OH pregnenolone at a constant rate failed to rescue P450c17(-/-) fetuses. Treatment of normal pregnant females with pellets releasing pregnenolone or progesterone did not cause fetal demise. These data suggest that steroid products of P450c17 have heretofore-unknown essential functions in early embryonic mouse development.

17-alpha-Hydroxypregnenolone↗

PubMed2006

Loss of the mouse ortholog of the shwachman-diamond syndrome gene (Sbds) results in early embryonic lethality.

Mutations in SBDS are responsible for Shwachman-Diamond syndrome (SDS), a disorder with clinical features of exocrine pancreatic insufficiency, bone marrow failure, and skeletal abnormalities. SBDS is a highly conserved protein whose function remains largely unknown. We identified and investigated the expression pattern of the murine ortholog. Variation in levels was observed, but Sbds was found to be expressed in all embryonic stages and most adult tissues. Higher expression levels were associated with rapid proliferation. A targeted disruption of Sbds was generated in order to understand the consequences of its loss in an in vivo model. Consistent with recessive disease inheritance for SDS, Sbds(+/-) mice have normal phenotypes, indistinguishable from those of their wild-type littermates. However, the development of Sbds(-/-) embryos arrests prior to embryonic day 6.5, with muted epiblast formation leading to early lethality. This finding is consistent with the absence of patients who are homozygous for early truncating mutations. Sbds is an essential gene for early mammalian development, with an expression pattern consistent with a critical role in cell proliferation.

Animals↗

PubMed2002

Truncation of c-fes via gene targeting results in embryonic lethality and hyperproliferation of hematopoietic cells.

The c-fes protooncogene encodes a nonreceptor tyrosine kinase (Fes) implicated in cytokine receptor signal transduction, granulocyte survival, and myeloid differentiation. To study the role of c-fes during myelopoiesis, we generated embryonic stem (ES) cells with a targeted disruption of the c-fes locus. Targeted mutagenesis deletes the C-terminal SH2 and tyrosine kinase domains of c-fes (referred to as c-fes(Delta c/Delta c)). We demonstrate that the c-fes(Delta c/Delta c) allele results in a truncated Fes protein that retains the N-terminal oligomerization domain, but lacks both the SH2 and the tyrosine kinase domain. In vitro differentiation of c-fes(Delta c/Delta c) ES cells results in hyperproliferation of an early myeloid cell. Generation of c-fes(Delta c/Delta c) mutant chimeric mice causes lethality by E13.5 with embryos exhibiting pleiotropic defects, the most striking being cardiovascular abnormalities. These results establish that c-fes is an important regulator of myeloid cell proliferation and embryonic development.

Animals↗

PubMed2003

Targeted disruption of the heat shock transcription factor (hsf)-2 gene results in increased embryonic lethality, neuronal defects, and reduced spermatogenesis.

Heat shock transcription factors (Hsfs) are major transactivators of heat shock protein (Hsp) genes in the response to stress stimuli, but are also thought to be involved in embryonic development and spermatogenesis. Among the three known mammalian Hsfs, Hsf1 is recognized as the most effective transactivator of Hsps in response to thermal challenge, but the role of Hsf2 in regulation of genes under normal or increased stress conditions in vivo remains elusive. To study its physiological function in vivo, we generated mice deficient in hsf2 by gene targeting. We report here that hsf2(-/-) mice exhibit multiple phenotypes, including an increased prenatal lethality occurring between mid-gestation to birth, with fetal death probably due to central nervous system defects including collapse of the lateral ventricles and ventricular hemorrhages. Approximately 30% of hsf2(-/-) animals surviving to adulthood exhibited brain abnormalities characterized by marked dilation of the third and lateral ventricles. In addition, disruption of hsf2 resulted in reduced female fertility; however, despite ubiquitous expression in the testes and markedly reduced testis size and sperm count, only a small reduction in fertility was apparent in hsf2(-/-) male mice. Immunoblotting and gene expression microarray analysis of hsf2(-/-) embryos did not reveal reduced Hsp expression levels, indicating that the defects observed in hsf2(-/-) embryos may not result from disruption of Hsp expression. These findings suggest that hsf2 has a major function in controlling expression of genes important for embryonic development and maintenance of sperm production.

Animals↗

PubMed2005

Inactivation of the Sema5a gene results in embryonic lethality and defective remodeling of the cranial vascular system.

The semaphorins are a large family of proteins involved in the patterning of both the vascular and the nervous systems. In order to analyze the function of the membrane-bound semaphorin 5A (Sema5A), we generated mice homozygous for a null mutation in the Sema5a gene. Homozygous null mutants die between embryonic development days 11.5 (E11.5) and E12.5, indicating an essential role of Sema5A during embryonic development. Mutant embryos did not show any morphological defects that could account for the lethality of the mutation. A detailed analysis of the vascular system uncovered a role of Sema5A in the remodeling of the cranial blood vessels. In Sema5A null mutants, the complexity of the hierarchically organized branches of the cranial cardinal veins was decreased. Our results represent the first genetic analysis of the function of a class 5 semaphorin during embryonic development and identify a role of Sema5A in the regional patterning of the vasculature.

Animals↗

PubMed1997

Embryonic lethality and radiation hypersensitivity mediated by Rad51 in mice lacking Brca2.

Inherited mutations in the human BRCA2 gene cause about half of the cases of early-onset breast cancer. The embryonic expression pattern of the mouse Brca2 gene is now defined and an interaction identified of the Brca2 protein with the DNA-repair protein Rad51. Developmental arrest in Brca2-deficient embryos, their radiation sensitivity, and the association of Brca2 with Rad51 indicate that Brca2 may be an essential cofactor in the Rad51-dependent DNA repair of double-strand breaks, thereby explaining the tumour-suppressor function of Brca2.

3T3 Cells↗

PubMed1998

A phenotype-based screen for embryonic lethal mutations in the mouse.

The genetic pathways that control development of the early mammalian embryo have remained poorly understood, in part because the systematic mutant screens that have been so successful in the identification of genes and pathways that direct embryonic development in Drosophila, Caenorhabditis elegans, and zebrafish have not been applied to mammalian embryogenesis. Here we demonstrate that chemical mutagenesis with ethylnitrosourea can be combined with the resources of mouse genomics to identify new genes that are essential for mammalian embryogenesis. A pilot screen for abnormal morphological phenotypes of midgestation embryos identified five mutant lines; the phenotypes of four of the lines are caused by recessive traits that map to single regions of the genome. Three mutant lines display defects in neural tube closure: one is caused by an allele of the open brain (opb) locus, one defines a previously unknown locus, and one has a complex genetic basis. Two mutations produce novel early phenotypes and map to regions of the genome not previously implicated in embryonic patterning.

Animals↗

PubMed1996

Targeted mutation of Ncam to produce a secreted molecule results in a dominant embryonic lethality.

The neural cell adhesion molecule (NCAM) is a membrane-associated member of the immunoglobulin superfamily capable of both homophilic and heterophilic binding. To investigate the significance of this binding, a gene targeting strategy in embryonic stem (ES) cells was used to replace the membrane-associated forms of NCAM with a soluble, secreted form of its extracellular domain. Although the heterozygous mutant ES cells were able to generate low coat color chimeric mice, only the wild-type allele was transmitted, suggesting the possibility of dominant lethality. Analysis of chimeric embryos with high level of ES cell contribution revealed severe growth retardation and morphological defects by E8.5-E9.5. The second allele was also targeted, and embryos derived almost entirely from the homozygous mutant ES cells exhibited the same lethal phenotype as observed with heterozygous chimeras. Together, these results indicate that dominant lethality associated with the secreted NCAM does not require the presence of membrane-associated NCAM. Furthermore, the data indicate that potent bioactive cues or signals can be generated by NCAM.

Animals↗

PubMed2002

Disruption of the endothelial cell protein C receptor gene in mice causes placental thrombosis and early embryonic lethality.

The endothelial cell protein C receptor (EPCR) is a type 1 transmembrane protein found primarily on endothelium that binds both protein C and activated protein C with similar affinity. EPCR augments the activation of protein C by the thrombin-thrombomodulin complex. To determine the physiological importance of EPCR, we generated EPCR-deficient mice by homologous targeting in embryonic stem cells. Genotyping of progeny obtained from EPCR(+/-) interbreeding indicated that EPCR(-/-) embryos died on or before embryonic day 10.5 (E10.5). Reverse transcriptase-PCR confirmed the absence of EPCR mRNA in EPCR(-/-) embryos. EPCR(-/-) embryos removed from extra-embryonic membranes and tissues at day E7.5 and cultured in vitro developed beyond E10.5, suggesting a role for EPCR in the normal function of the placenta and/or at the materno-embryonic interface. Immunohistochemistry revealed the lack of EPCR in trophoblast giant cells of EPCR(-/-) embryos. These cells, which normally express EPCR, are in direct contact with the maternal circulation and its clotting factors. In EPCR(-/-) embryos, greatly increased fibrin deposition was detected around these cells. To prevent this fibrin deposition, EPCR(+/-)-crossed female mice received a daily subcutaneous injection of enoxaparin through pregnancy. Although some EPCR(-/-) embryos were rescued from midgestational lethality, this regimen yielded no EPCR(-/-) pups. We conclude that EPCR is essential for normal embryonic development. Moreover, EPCR plays a key role in preventing thrombosis at the maternal-embryonic interface.

Animals↗

PubMed1999

Disruption of muREC2/RAD51L1 in mice results in early embryonic lethality which can Be partially rescued in a p53(-/-) background.

muREC2/RAD51L1 is a radiation-inducible gene that regulates cell cycle progression. To elucidate the biological function of muREC2/RAD51L1, the gene was disrupted in embryonic stem cells by homologous recombination. Mice heterozygous for muREC2/RAD51L1 appear normal and fertile; however, no homozygous pups were born after interbreeding of heterozygous mice. Timed pregnancy studies showed that homozygous mutant embryos were severely retarded in growth as early as ca. 5 days gestation (E5.5) and were completely resorbed by E8.5. Mutant blastocyst outgrowth was also severely impaired in a double-knockout embryo, but embryonic development did progress further in a p53-null background. These results suggest that muREC2/RAD51L1 plays a role in cell proliferation and early embryonic development, perhaps through interaction with p53.

Animals↗