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T Gridley

Publications and source records attributed to T Gridley.

At least 55 records · Page 3Linked to original sources
PubMed1994

Ectopic Hoxa-1 induces rhombomere transformation in mouse hindbrain.

Homeobox genes are expressed with a specific spatial and temporal order, which is essential for pattern formation during the early development of both invertebrates and vertebrates. Here we show that widespread ectopic expression of the Hoxa-1 (Hox 1.6) gene directed by a human beta-actin promoter in transgenic mice is embryolethal and produces abnormal phenotypes in a subset of domains primarily located in anterior regions. Interestingly, this abnormal development in the Hoxa-1 transgenic mice is associated with ectopic expression of the Hoxb-1 (Hox 2.9) gene in select hindbrain regions. At gestation day 9.5, two domains of strong Hoxb-1 expression are found in the anterior region of the hindbrains of Hoxa-1 transgenic embryos. One region represents the normal pattern of Hoxb-1 expression in rhombomere 4 and its associated migrating neural crest cells, while another major domain of Hoxb-1 expression consistently appears in rhombomere 2. Similar ectopic domains of beta-galactosidase activity are detected in dual transgenic embryos containing both beta-actin/Hoxa-1 transgene and a Hoxb-1/lacZ reporter construct. Expression of another lacZ reporter gene that directs beta-galactosidase activity predominantly in rhombomere 2 is suppressed in the Hoxa-1 transgenic embryos. We have also detected weaker and variable ectopic Hoxb-1 expression in rhombomeres 1, 3 and 6. No ectopic Hoxb-1 expression is detected in rhombomere 5 and the expression of Hoxa-3 and Krox-20 in this region is unchanged in the Hoxa-1 transgenic embryos. While no obvious change in the morphology of the trigeminal or facial-acoustic ganglia is evident, phenotypic changes do occur in neurons that emanate from rhombomeres 2 and 3 in the Hoxa-1 transgenic embryos. Additionally, alterations in the pattern of Hoxa-2 and Hoxb-1 expression in a subpopulation of neural crest cells migrating from the rhombomere 2 region are detected in these transgenics. Taken together, these data suggest that ectopic Hoxa-1 expression can reorganize select regions of the developing hindbrain by inducing partial transformations of several rhombomeres into a rhombomere-4-like identity.

Actins↗
PubMed1993

Hoxa-2 mutant mice exhibit homeotic transformation of skeletal elements derived from cranial neural crest.

Mice homozygous for a targeted mutation of the Hoxa-2 (Hox 1.11) gene are born with cleft palates and die within 24 hr of birth. Analysis of stained skeletons revealed that homozygous mutant animals contained multiple cranial skeletal defects, including a duplication of the ossification centers of the bones of the middle ear. Histological analysis suggested that this duplication resulted from the transformation of skeletal elements derived from the second branchial arch into more anterior structures, resulting in a duplication of Meckel's cartilage adjacent to the otic capsule. Skeletal elements normally derived from the second arch were absent in the mutants. These data provide direct experimental evidence for the existence of a branchial Hox code.

Abnormalities, Multiple↗
PubMed1993

Cloning, sequencing and expression of the mouse mammalian achaete-scute homolog 1 (MASH1).

We describe the cloning of a full length cDNA encoding the mouse mammalian achaete-scute homolog 1 (mouse MASH1). Using a ribonuclease protection assay to examine expression of this gene in cell lines, postimplantation embryos and adult tissues, expression was detected between days 10.5 and 16.5 of gestation and in adult brain. No expression was detected in other adult tissues or in most of the cell lines examined. However, differentiation of P19 embryonal carcinoma cells into neuronal cell types by exposure to retinoic acid resulted in the induction of MASH1 RNA expression.

Amino Acid Sequence↗
PubMed1993

Cloning, analysis, and chromosomal localization of Notch-1, a mouse homolog of Drosophila Notch.

The Notch gene of Drosophila encodes a large transmembrane protein involved in cell-cell interactions and cell fate decisions in the Drosophila embryo. We report here the isolation of cDNA clones encompassing the full-length coding sequence of Notch-1, a mouse homolog of Drosophila Notch. The predicted amino acid sequence of the Notch-1 protein retains all of the conserved amino acid motifs of Notch and the other vertebrate Notch homologs. The cDNA sequence predicts a 2531-amino-acid protein containing a signal peptide, 36 epidermal growth factor-like repeats, 3 Notch/lin-12 repeats, a transmembrane domain, and 6 cdc10/ankyrin repeats. The Notch-1 gene was localized to the proximal portion of mouse chromosome 2 by mapping with an interspecific backcross panel.

Amino Acid Sequence↗
PubMed1993

Cloning and developmental expression of Grg, a mouse gene related to the groucho transcript of the Drosophila Enhancer of split complex.

Genes of the Enhancer of split complex are involved in neural-epidermal cell fate decisions during early embryogenesis in Drosophila. One of these genes, the product of the Enhancer of split m9/10 or groucho transcript, encodes a ubiquitous nuclear protein with homology at the carboxy-terminus to G-protein beta-subunits. Here we describe the cloning and RNA expression analysis of a mouse gene, designated Grg, that is homologous to just the amino-terminal region of the groucho product. Grg encodes a 197 amino acid protein that shares 53% amino acid identity with the corresponding region of the product of the Drosophila groucho gene. However, the mouse Grg protein does not contain the region homologous to G-protein beta-subunits. An analysis by in situ hybridization of the spatial and temporal localization of Grg RNA expression revealed that, while the initial pattern of Grg expression was quite restricted, by midgestation Grg RNA was ubiquitously expressed in the developing embryo. Widespread Grg RNA expression was maintained in adult mice. The implications of these results for the existence of separable functional domains of the Drosophila groucho product, and possible roles of the Grg gene during mouse development, are discussed.

Amino Acid Sequence↗
PubMed1993

Perinatal lethality and defects in hindbrain development in mice homozygous for a targeted mutation of the zinc finger gene Krox20.

Krox20 is a zinc finger gene expressed in rhombomeres 3 and 5 during hindbrain development in vertebrates. Mice homozygous for a targeted mutation that deletes the majority of the Krox20 genes, including the zinc finger DNA-binding domain, died shortly after birth. The primary phenotype of the homozygous mutant animals was the loss of rhombomeres 3 and 5. This resulted in fusions of the trigeminal ganglion with the facial and vestibular ganglia, and of the superior ganglia of the glossopharyngeal and vagus nerves. These fusions resulted in a disorganization of the nerve roots of these ganglia as they entered the brain stem. These data demonstrate that Krox20 plays an essential role during development of the hindbrain and associated cranial sensory ganglia in mice.

Amino Acid Sequence↗
PubMed1992

Expression pattern of Motch, a mouse homolog of Drosophila Notch, suggests an important role in early postimplantation mouse development.

The Notch gene of Drosophila encodes a large transmembrane protein involved in cell-cell interactions and cell fate decisions in the Drosophila embryo. To determine if a gene homologous to Drosophila Notch plays a role in early mouse development, we screened a mouse embryo cDNA library with probes from the Xenopus Notch homolog, Xotch. A partial cDNA clone encoding the mouse Notch homolog, which we have termed Motch, was used to analyze expression of the Motch gene. Motch transcripts were detected in a wide variety of adult tissues, which included derivatives of all three germ layers. Differentiation of P19 embryonal carcinoma cells into neuronal cell types resulted in increased expression of Motch RNA. In the postimplantation mouse embryo Motch transcripts were first detected in mesoderm at 7.5 days post coitum (dpc). By 8.5 dpc, transcript levels were highest in presomitic mesoderm, mesenchyme and endothelial cells, while much lower levels were detected in neuroepithelium. In contrast, at 9.5 dpc, neuroepithelium was a major site of Motch expression. Transcripts were also abundant in cell types derived from neural crest. These data suggest that the Motch gene plays multiple roles in patterning and differentiation of the early postimplantation mouse embryo.

Amino Acid Sequence↗
PubMed1992

Differential screening of a PCR-generated mouse embryo cDNA library: glucose transporters are differentially expressed in early postimplantation mouse embryos.

Differential screening of a cDNA library constructed using PCR amplification techniques from RNA isolated from the distal portion (embryonic ectoderm, mesoderm and visceral endoderm) of 7.5 days post coitum (dpc) mouse embryos led to the isolation of two cDNA clones expressed at higher levels in 7.5 dpc embryos than 12.5 dpc embryos. Nucleotide sequence analysis revealed that each of these clones was a different member of the family of facilitative glucose transporters (Glut genes). The differentially expressed cDNA clones represent mouse Glut-1 and Glut-3. Levels of the Glut-3 mRNA declined 14-fold between days 7.5 and 12.5 of gestation, and were under our limits of detection by 14.5 dpc. The levels of the Glut-1 mRNA declined about 3-fold between days 7.5 and 12.5 of gestation. Analysis of the expression of these genes by in situ hybridization revealed striking differences in transcript localization in early postimplantation mouse embryos. At 7.5 dpc, both transporters were expressed more strongly in extraembryonic tissues than in the embryo proper. While both transporters were expressed in the amnion and chorion, only Glut-1 was expressed in the ectoplacental cone. In the yolk sac, Glut-3 appeared to be expressed only in the endoderm while Glut-1, although expressed in both layers, was expressed more strongly in the mesoderm layer. Thus, the two transporters have relatively reciprocal sites of expression in the developing extraembryonic membranes. Expression of Glut-1 was fairly widespread in the embryo at 8.5 dpc, but by 10.5 dpc expression was down-regulated and was observed in the eye and the spinal cord.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1992

Isolation of Sna, a mouse gene homologous to the Drosophila genes snail and escargot: its expression pattern suggests multiple roles during postimplantation development.

The Drosophila gene snail encodes a zinc-finger protein that is required zygotically for mesoderm formation. Snail acts as a transcriptional repressor during the period of mesoderm formation by preventing expression of mesectodermal and ectodermal genes in the mesoderm anlage. A Xenopus homolog (xsnail) of snail has been cloned and it too is expressed early in the mesodermal germ layer. We have isolated cDNA clones of a mouse gene (termed Sna) closely related to snail and xsnail and another Drosophila gene termed escargot that also encodes a zinc-finger protein. Sna encodes a 264 amino acid protein that contains four zinc fingers. Developmental RNA blot analysis showed that Sna transcripts are expressed throughout postimplantation development. Analysis of the spatial and temporal localization of Sna transcripts by in situ hybridization to both whole-mount and sectioned embryos revealed that, in the gastrulating embryo, Sna is expressed throughout the primitive streak and in the entire mesodermal germ layer. By 9.5 days post coitum (dpc) Sna is expressed at high levels in cephalic neural crest and limb bud mesenchyme. In fact, by 10.5 dpc Sna expression is observed in most mesenchymal cells, whether of neural crest or mesodermal origin. Later in gestation, high levels of Sna expression are observed in condensing cartilage and in the mesenchymal component of several tissues (lung, kidney, teeth and vibrissae) that undergo epithelial-mesenchymal inductive interactions during development. These results suggest multiple roles for the Sna gene in gastrulation and organogenesis during murine development.

Amino Acid Sequence↗
PubMed1991

The murine Mov-34 gene: full-length cDNA and genomic organization.

The Mov-34 mutation is a recessive embryonic lethal mutation caused by experimental introduction of a recombinant Moloney murine leukemia provirus into the mouse germline. We have cloned a full-length cDNA from the Mov-34 gene, the transcription unit disrupted by the proviral integration. This cDNA is predicted to encode a novel 321-amino acid, 36-kDa protein of unknown function. Overlapping phage lambda clones containing the entire Mov-34 gene have been isolated. The Mov-34 gene spans just over 8 kb and contains seven exons. The 5' flanking region of the Mov-34 gene contains neither "TATA" nor "CAAT" box sequences, and 5' end mapping by primer extension and ribonuclease protection reveal multiple transcription initiation sites.

Amino Acid Sequence↗
PubMed1991

Insertional versus targeted mutagenesis in mice.

Recent innovations in mutagenesis techniques for mice have the potential to revolutionize the molecular genetic analysis of mouse development. Insertional mutagenesis by the introduction of exogenous DNA into the mouse germline hs permitted the molecular cloning and analysis of several novel genes important for early embryonic development. Targeted mutagenesis by homologous recombination in embryonic stem cells permits, in theory, the production of mutations in any cloned gene. The complementary information being obtained from these two mutagenesis procedures is shedding new light on the genes important for early mouse development, and the roles these genes play in that process.

Alleles↗
PubMed1990

Molecular analysis of the Mov 34 mutation: transcript disrupted by proviral integration in mice is conserved in Drosophila.

The Mov 34 mutation is a recessive embryonic lethal mutation caused by retroviral integration in the murine germline. This integration disrupts a transcription unit that appears to encode a novel protein. The Mov 34 proviral integration is located on mouse chromosome 8 and the human homolog of this gene has been mapped to chromosome region 16q23-q24. An evolutionarily conserved syntenic relationship exists between this region of human chromosome 16 and a region of mouse chromosome 8 that also contains oligosyndactyly (Os), another recessive lethal mutation. Genetic studies have ruled out Os as residing at the same locus as the Mov 34 integration. The Mov 34 transcript is conserved in evolution, and a Drosophila homolog appears to encode a protein with 62% amino acid identity to the murine protein. In situ hybridization to Drosophila polytene chromosomes localizes the Drosophila homolog to 60B,C on chromosome 2. Several Drosophila lethal mutations also map to this region.

Alleles↗
PubMed1987

Single germline VH and V kappa genes encode predominating antibody variable regions elicited in strain A mice by immunization with p-azophenylarsonate.

We have cloned and sequenced the predominant germline V kappa gene segment expressed by B cells of strain A origin that synthesize antibodies with specificity for Ars. In hybridomas synthesizing anti-Ars antibodies, this V kappa gene segment (V kappa IdCR) has been found exclusively associated with the J kappa 1 gene segment without exhibiting junctional sequence variation. Sequence comparisons of the germline V kappa IdCR gene with expressed derivatives reveals that the latter frequently contain somatically introduced amino acid replacements. Taken together with results of previous structural analyses, these results show that the predominant population of IdCR+ V regions elicited in the secondary immune response is encoded by one or two combinations of V gene segments, has little junctional diversity, and is extensively diversified by somatic mutation in both heavy and light chains.

Animals↗
PubMed1987

Retroviruses and insertional mutagenesis in mice: proviral integration at the Mov 34 locus leads to early embryonic death.

Thirty-four transgenic mouse strains, each carrying a single proviral insert, were generated by infection of preimplantation and postimplantation embryos with retroviruses. Animals homozygous for proviral integrations were derived for all strains with the exception of Mov 24, where the provirus is inserted on the Y chromosome, and Mov 34. Embryos homozygous at the Mov 34 locus develop normally to the blastocyst stage and die shortly after implantation, indicating that virus integration resulted in a recessive lethal mutation. The provirus and flanking sequences were cloned and the virus was mapped to the 5' side of an abundantly and ubiquitously transcribed gene. Similar to the previously derived Mov 13 mutation, proviral integration at the Mov 34 locus interferes with the expression of the adjacent gene. These and our previous results indicate that of a total of 48 proviral integrations in the germ line, two resulted in transgenic mouse strains with recessive lethal mutations.

Animals↗
PubMed1985

The association of various D elements with a single-immunoglobulin VH gene segment: influence on the expression of a major cross-reactive idiotype.

A large fraction of the anti-p-azophenylarsonate antibodies of strain A/J mice share a major cross-reactive idiotype (IdCR). Structural analysis of monoclonal antibodies expressing this idiotype (IdCR+) indicates that a particular combination of variable region gene segments (Vk, Jk, VH, D, and JH) encodes the variable regions of the light and heavy chains of these IdCR+ antibodies. With the use of serologic methods, hybridoma cell lines have been isolated that produce monoclonal antibodies lacking IdCR determinants (IdCR-), but that are derived from most of the same combination of variable region gene segments that encode IdCR+ monoclonal antibodies. Structural analysis of these IdCR- monoclonal antibodies demonstrates that they are very homologous to each other and to IdCR+ monoclonal antibodies with respect to VH and VL sequences, but are markedly different from IdCR+ monoclonal antibodies in their utilization of D region segments. Comparisons of antigen avidity of these IdCR+ and IdCR- antibodies indicates that conservation of D region structure is not crucial for effective antigen binding. These results indicate the importance of the D region in idiotypy in the IdCR system and demonstrate the variation permitted in D region structure while maintaining antigen recognition.

Amino Acid Sequence↗
PubMed1979

Properties and applications of monoclonal antibodies directed against determinants of the Thy-1 locus.

Fusion of cells of the mouse myeloma line, P3/X63-Ag8 with spleen cells from AKR/J mice immunized against C3H thymocytes or from (BALB/c x BALB.K)F1 mice immunized against AKR/J thymocytes gave rise to hybrid cell lines that continuously secrete antibodies specific for the Thy-1.2 and Thy-1.1 antigens, respectively. Monoclonal antibodies from four such cell lines were analyzed in detail. All were 19S IgM, and, in the presence of complement (C), had high lytic titers on T cells of the appropriate antigenicity. Their specificity was shown by lysis of thymocytes from Thy-1 congenic mouse strains, A/J(Thy-1.2) and A. Thy 1.1. Furthermore, they lyse only 60 to 70% of lymph node cells, suggesting cytotoxicity for mature T cells and not B cells. Treatment of peripheral lymphocyte populations with monoclonal antibody plus C eliminated effector cytotoxic T lymphocytes, their precursors, and the mitogenic response to Con A, but did not affect the response to LPS. Purified, fluorescein-labeled monoclonal anti-Thy-1 antibody could be used to distinguish T and B cells. Purified antibody coupled to Sepharose 6MB was used to separate viable T and B cells. Two independently isolated anti-Thy-1.2 hybridomas are indistinguishable and bind the same determinant whereas a third is unique and may bind a separate site.

Animals↗