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Biomedical subjects

A Dierich

Publications and source records attributed to A Dierich.

At least 73 records · Page 4Linked to original sources
PubMed1993

Function of retinoic acid receptor gamma in the mouse.

Null mutant mice for retinoic acid receptor gamma 2 (RAR gamma 2) or all RAR gamma isoforms were generated. RAR gamma 2 mutants appeared normal, whereas RAR gamma mutants exhibited growth deficiency, early lethality, and male sterility due to squamous metaplasia of the seminal vesicles and prostate. These defects were previously observed in vitamin A-deficient animals and could be prevented by RA administration, demonstrating that RAR gamma mediates some of the retinoid signal in vivo. Congenital defects included Harderian gland agenesis, tracheal cartilage malformations, and homeotic transformations along the rostral axial skeleton, establishing a direct link between RA and patterning of the axial skeleton. We also show that in utero RA-induced lumbosacral truncations are mediated by RAR gamma. The observed RAR gamma null phenotype suggests a high degree of functional redundancy among the RARs. The variable penetrance of some of the observed defects is discussed in light of this redundancy and stochastic variation of gene activity.

Abnormalities, Multiple↗
PubMed1993

Mice lacking the MHC class II-associated invariant chain.

The invariant chain (li) has aroused much interest because of its close association with major histocompatibility complex (MHC) class II molecules. Various functions have been proposed for it; several of these have received experimental support, but most have not been definitively proven, owing largely to uncertainties inherent in the experimental systems employed. We have now generated a line of mice devoid of the invariant chain by introducing a drastic mutation into the li gene. Cells from mutant animals show aberrant transport of MHC class II molecules, resulting in reduced levels of class II complexes at the surface, and these do not have the typical compact conformation indicative of tight peptide binding. Consequently, mutant cells present protein antigens very poorly and mutant mice are deficient in producing and at negatively selecting CD4+ T cells.

Animals↗
PubMed1993

Graft rejection by T cells not restricted by conventional major histocompatibility complex molecules.

The appropriate crosses of mice lacking conventional major histocompatibility complex (MHC) class I or class II molecules generate single- and double-deficient offspring. These were used as donors for skin grafts across major plus minor, or just minor, histocompatibility differences. Surprisingly, in the two circumstances, there was a rapid rejection of grafts lacking both MHC class I and class II molecules. Rejection was mediated by thymically derived CD4+ T cells of the host. We provide evidence that these T cells recognize an unconventional ligand, capable of activating a pre-formed T cell compartment but incapable of positively selecting it. The existence of this unexpected rejection phenomenon should serve to caution those aiming to engineer "universal donor" cells by simply abrogating expression of MHC class I and class II molecules.

Animals↗
PubMed1993

Roles of Hox genes: what we have learnt from gain of function and loss of function mutations in the mouse.

Transgenic mice expressing ectopically a gene from one of the Hox complexes, and mice carrying a null mutation in a Hox gene, provide useful tools for studying the roles of this gene family during development. Here, we discuss the phenotypes of two kinds of Hox mutant mice which show that vertebrate Hox genes are functional homologues of Drosophila genes of the HOM-C complex.

Alleles↗
PubMed1992

Retinoid receptors and binding proteins.

Retinoids, in particular all-trans retinoic acid (T-RA), are essential for normal development and homeostasis of vertebrates. Although many effects of retinoids, particularly with regard to teratogenicity, have been described in the literature, the mechanisms by which these simple signalling molecules work has only recently begun to be elucidated. We now recognize at least two classes of retinoid-binding proteins and two families of retinoid receptors. The ultimate interpretation of the retinoid signal within a given cell is probably the result of a complex series of interactions between these proteins, yet little is understood concerning the role each member of this signalling pathway plays. It is therefore imperative to dissect the molecular mechanisms which transduce the effects of these ligands, both in vivo and in isolated systems. One approach we are employing is gene targeting of retinoic acid receptors (RARs) and cellular retinoid-binding proteins to generate mice in which one or more of these genes has been functionally inactivated.

Animals↗
PubMed1991

Disruption of the Hox-1.6 homeobox gene results in defects in a region corresponding to its rostral domain of expression.

The Hox-1.6 gene disrupted in embryonic stem cells by homologous recombination was introduced into the mouse germline. Heterozygous mice were normal, but homozygous mice died at birth from anoxia and had numerous defects that were centered at the level of rhombomeres 4 to 7 and included delayed hindbrain neural tube closure, absence of certain cranial nerves and ganglia, and malformed inner ears and bones of the skull. Thus, Hox-1.6 is involved in regional specification along the rostrocaudal axis, but only in its most rostral domain of expression. Hox-1.6 appears to specify neurogenic neural crest cells prior to specification of mesenchymal neural crest cells by Hox-1.5. Thus, within the same region of the presumptive hindbrain, two HOX-1 genes are involved in the patterning of two different populations of neural crest cells. The implication of these results for the function of the Hox network during mouse embryogenesis is discussed.

Age Factors↗
PubMed1991

Mice lacking MHC class II molecules.

We have produced mice that lack major histocompatibility complex class II antigens, permitting us to evaluate the role of these molecules in diverse aspects of T and B cell differentiation. The mutant mice show near-complete elimination of CD4+ T lymphocytes from the spleen and lymph nodes; the few remaining CD4-positive cells are preferentially localized to B cell follicles. Surprisingly, substantial numbers of CD4 single-positive cells reside in the thymus; however, these are not mature thymocytes as we currently recognize them. B lymphocytes occur in normal numbers and are capable of terminal differentiation to plasma cells. Nevertheless, several aberrations in the B cell compartment are demonstrable: a lack of germinal centers, fewer IgM+IgD+ cells in certain individuals, reduced production of serum IgG1, and complete inability to respond to T-dependent antigens. In short, the class II-negative mice have confirmed some old ideas about lymphocyte differentiation, but have provided some surprises.

Animals↗
PubMed1991

Multiple isoforms of the mouse retinoic acid receptor alpha are generated by alternative splicing and differential induction by retinoic acid.

Together with the previously described mouse retinoic acid receptor alpha-1 (mRAR-alpha 1, formerly mRAR-alpha 0), we have isolated and characterized here a total of seven mRAR-alpha cDNA isoforms (mRAR-alpha 1 to alpha 7). These isoforms are generated from mRAR-alpha primary transcript(s) of a single gene by alternative splicing of at least eight different exons with the exon which encodes the amino acid sequence of their common B region. All of these isoforms differ in their 5'-untranslated regions (5'-UTRs) and, in the case of mRAR-alpha 1 and alpha 2, also in the sequences encoding the N-terminal A region which is known to be important for differential trans-activation by other members of the nuclear receptor superfamily. In addition, the sequences encoding the open reading frames (ORFs) of mRAR-alpha 3 and alpha 4 cDNA isoforms remain open to their very 5' ends, which suggests that these two isoforms may also encode RAR-alpha s with unique A region amino acid sequences. The two predominant isoforms, mRAR-alpha 1 and alpha 2, were found to be differentially expressed in mouse adult and fetal tissues, as well as in P19 and F9 embryonal carcinoma (EC) cell lines. Interestingly, the expression of mRAR-alpha 2, in contrast to that of the mRAR-alpha 1 isoform, was induced by retinoic acid (RA) in EC cells, thus suggesting the presence of two promoters in the 5' region of the mRAR-alpha gene, which differ in their response to RA. The conservation between mouse and human RAR-alpha 1 and alpha 2 cDNA isoform sequences, as seen by cross-hybridization in Southern blots or by DNA sequence analysis, together with their differential patterns of expression, strongly suggests that they perform specific functions during embryogenesis and in the adult.

Amino Acid Sequence↗
PubMed1988

Cell-specific activity of a GGTCA half-palindromic oestrogen-responsive element in the chicken ovalbumin gene promoter.

Using a transient co-transfection system we have identified a functional oestrogen responsive element (ERE) in the near vicinity of the TATA box of the chicken ovalbumin gene promoter. Oestrogen induced activation of transcription was observed only in chicken embryo fibroblast cells, and not in human HeLa cells, suggesting the existence of a cell-specific transcription factor(s) that is necessary for the hormonal response. By 5'-deletion mapping and site-directed mutagenesis, a sequence encompassing the more proximal of two GGTCA half-palindromic motifs was identified as a functional ovalbumin gene ERE. Both motifs correspond to oestrogen receptor binding sites in vitro as revealed by DNase I footprinting. Optimal response to the hormonal stimulus apparently requires stereoalignment of the ERE and the TATA box.

Animals↗
PubMed1987

Cell-specificity of the chicken ovalbumin and conalbumin promoters.

A series of recombinant plasmids containing increasing lengths of the 5'-flanking promoter sequences of the chicken conalbumin and ovalbumin genes fused to the sequences coding for the SV40 T-antigen have been constructed. These recombinants were introduced into a variety of established cell lines and primary cultured cells by nuclear microinjection. Promoter activity was estimated by monitoring T-antigen synthesis by indirect immunofluorescence. We show that the microinjected ovalbumin and conalbumin promoter regions do not function in chicken fibroblasts, kidney cells and in a variety of non-chicken cells, irrespective of the presence of steroid hormone receptors. In contrast, these promoter regions are active in primary cultured chicken embryonic hepatocytes and oviduct tubular gland cells, suggesting the presence of cell-specific transcription factors in these cells. Unexpectedly, promoter sequences close to the TATA boxes of both the ovalbumin and conalbumin genes are sufficient to confer cell-specific expression. Most of the controls exerted on the ovalbumin and conalbumin promoters in the whole animal appear to be reproduced in vitro by nuclear microinjection of the chimeric genes into the primary cultured cells. However, the microinjected ovalbumin promoter is active in embryonic hepatocytes and thus escapes the regulation imposed on the corresponding inactive endogenous gene.

Animals↗
PubMed1987

The chicken ovalbumin promoter is under negative control which is relieved by steroid hormones.

Steroid hormone regulation of activity of the chicken ovalbumin promoter was studied by microinjection of chimeric genes into the nuclei of primary cultured oviduct tubular gland cells. The chimeric genes contained increasing lengths of ovalbumin gene 5'-flanking sequences fused to the sequence coding for the SV40 T-antigen. Promoter activity was estimated by monitoring synthesis of T-antigen. The activity of the ovalbumin promoter is cell-specifically repressed in these oviduct cells and the repression is relieved upon addition of steroid hormones. The -132 to -425 region of the ovalbumin promoter which is responsible for this negative regulation behaves as an independent functional unit containing the regulatory elements necessary for both repression (in the presence of steroid hormone antagonists) and induced derepression (in the presence of steroid hormones) of linked heterologous promoters.

Animals↗
PubMed1980

[Free nucleotides of nerve cells, in culture].

In primary cultures the free nucleotide (FN) distribution pattern showed a slight increase of adenylic nucleotides in neuroblasts as compared to glioblasts. Significant differences in the FN distribution were found between primary cultures and clonal nerve cell lines.

Animals↗
PubMed1980

In vitro protein synthesis activity of poly(A) RNA from neuroblastoma cells.

Protein synthesis activity of poly(A) RNA from M1 neuroblastoma cells was studied in a reticulocyte cell-free system. The activity of poly(A) RNA from M1 cells "differentiated" morphologically by bromodeoxyuridine was compared with that of proliferating cells. Poly(A) RNA from differentiated cells was about 10% more active than the corresponding RNA from proliferating cells. The products synthesized in vitro were fractionated by polyacrylamide gradient gel electrophoresis. A 420,000-dalton band was present in the translation products programmed by differentiated cell poly(A) RNA; it was absent in the translation products programmed by proliferating cell poly(A) RNA.

Animals↗
PubMed1980

Brain nucleic acids and protein in various neurological mutant mice.

A study was made to compare alterations in the cerebral contents of nucleic acids and protein of several mouse strains affected by different neurological mutations: jimpy, msd, quaking, reeler, weaver, and dwarf. In normal and affected jimpy and msd mice the brain components analyzed were very similar. On the other hand, the cerebral hemispheres of quaking mice showed significant decreases in total RNA and DNA, when compared with those of normal littermates. In the affected reeler and weaver mice, total protein, RNA, and DNA in the cerebellum differed markedly from controls. Protein decreased slightly, whereas nucleic acids showed no significant variation in the cerebral hemispheres of the same mutants. The cerebella and cerebral hemispheres of affected dwarf mice had wet weights and total protein contents that were about 20% lower than those of their controls; DNA did not vary significantly in the various brain regions analyzed. The decrease of DNA we report in reeler and weaver mutant cerebellum in toto quantifies the lack of cell number, in contrast to histological studies which give only semiquantitative information.

Animals↗
PubMed1980

Purification and characterization of a nicotinamide deamidase released into the growth medium of neuroblastoma in vitro.

Nicotinamide deamidase (nicotinamide amidohydrolase, EC 3.5.1.19) has been demonstrated in the conditioned growth medium of the M1 clonal cell line of mouse C1300 neuroblastoma. The enzyme has been purified 1200-1500-fold by Sephadex G25, hydroxyapatite, DEAE-cellulose, Sephadex G200 and NAD-Sepharose column chromatographies. The purified protein was characterized by polyacrylamide gel electrophoresis under non-denaturing and denaturing conditions. The apparent molecular weight has been estimated to be 230,000, and the subunits had respective molecular weights of 65,000 and 50,000. Histidine was the only NH2-terminal amino acid found. The enzyme is a glycoprotein; mannose and N-acetyl-glucosamine have been identified. The effects of various ions on its activity have been investigated. The enzyme has a Km for nicotinamide in the order of 10(-6) M, a pH optimum of 7.2 and a pHi of 5.4. It is inhibited by heating and by sulfhydryl reagents. The existence of a nicotinamide deamidase with a high affinity for nicotinamide favors the operation of the Preiss-Handler pathway in M1 cells cultured in vitro. We found an induction of nicotinamide deamidase and a cellular increase of NAD with a higher nicotinamide supply and a repression of the released enzyme with supplying NAD in the nutrition medium of M1 cell cultures.

Amidohydrolases↗