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Biomedical subjects

A Dierich

Publications and source records attributed to A Dierich.

At least 19 recordsLinked to original sources
PubMed1997

Requirement of poly(ADP-ribose) polymerase in recovery from DNA damage in mice and in cells.

Poly(ADP-ribose) polymerase [PARP; NAD+ ADP-ribosyltransferase; NAD+: poly(adenosine-diphosphate-D-ribosyl)-acceptor ADP-D-ribosyltransferase, EC 2.4.2.30] is a zinc-finger DNA-binding protein that detects specifically DNA strand breaks generated by genotoxic agents. To determine its biological function, we have inactivated both alleles by gene targeting in mice. Treatment of PARP-/- mice either by the alkylating agent N-methyl-N-nitrosourea (MNU) or by gamma-irradiation revealed an extreme sensitivity and a high genomic instability to both agents. Following whole body gamma-irradiation (8 Gy) mutant mice died rapidly from acute radiation toxicity to the small intestine. Mice-derived PARP-/- cells displayed a high sensitivity to MNU exposure: a G2/M arrest in mouse embryonic fibroblasts and a rapid apoptotic response and a p53 accumulation were observed in splenocytes. Altogether these results demonstrate that PARP is a survival factor playing an essential and positive role during DNA damage recovery.

Alleles↗
PubMed1997

Limited specificity and large overlap of the functions of the mouse RAR gamma 1 and RAR gamma 2 isoforms.

The RAR gamma gene generates two major isoforms, RAR gamma 1 and RAR gamma 2, which originate from two distinct promoters. We report here the engineering of mice lacking RAR gamma 1, but in which RAR gamma 2 is normally expressed. The effect of this null mutation has been compared with those previously described for RAR gamma 2 and all RAR gamma isoforms (total RAR gamma gene inactivation), both in single mutants and in double mutants bearing additional null mutations in their RAR alpha, RAR beta or RXR alpha genes. RAR gamma 1 mutants, but not RAR gamma 2 mutants, displayed a subset of the abnormalities exhibited by total RAR gamma null mutants (growth deficiency, abnormal cricoid cartilage and occasional cervical vertebra defects), suggesting that RAR gamma 1 is the main isoform mediating the corresponding RAR gamma functions. Interestingly, cricoid cartilage defects were also found in a fraction of heterozygote animals for the RAR gamma 1, RAR gamma or RAR alpha mutations, indicating that wild type levels of RARs are required for the normal morphogenesis of this structure. Compound RAR alpha/RAR gamma 1 and RAR alpha/RAR gamma 2 double null mutants exhibited only a small fraction of the defects found in RAR alpha/RAR gamma double null mutants. Moreover, these defects were often partially penetrant, or corresponded to a less severe form. However, they occurred preferentially in certain compound mutants, demonstrating that given isoforms mediate specific functions of RAR gamma in the context of a RAR alpha null background. In a RXR alpha null background, both RAR gamma 1 and gamma 2 isoform mutations resulted in increased severity of the RXR alpha null ocular phenotype. Together, the present observations indicate that the functions of the two RAR gamma isoforms overlap to a large extent, but also that each of these isoforms exhibits a limited functional specificity. Furthermore, the occurrence of morphological defects in heterozygote mutants for a single RAR isoform provides a basis for explaining the strong conservation of these isoforms during vertebrate evolution.

Animals↗
PubMed1997

In vivo functional analysis of the Hoxa-1 3' retinoic acid response element (3'RARE).

Retinoids are essential for normal development and both deficiency and excess of retinoic acid (RA) are teratogenic. Retinoic acid response elements (RAREs) have been identified in Hox gene promoters suggesting that endogenous retinoids may be involved in the direct control of Hox gene patterning functions. In order to test this hypothesis, we have mutated the Hoxa-1 3'RARE using the Cre-loxP targeting strategy, and studied its functional role during mouse development. We find that this enhancer plays an important role in the early establishment of the Hoxa-1 anterior expression boundary in the neural plate. This early disturbance in Hoxa-1 activation results in rhombomere and cranial nerve abnormalities reminiscent of those obtained in the Hoxa-1 total knockout, although their severity and penetrance are lower, thus providing strong evidence for direct control of Hox gene function by retinoids during normal development. Interestingly, we also find that the Hoxa-1 expression response to RA treatment is not entirely controlled by the RARE, suggesting the existence of other retinoid-induced factors mediating the Hoxa-1 response to RA and/or the presence of additional RAREs. Interestingly, although the RARE is not required for the spatiotemporal control of colinear expression of the Hoxa genes, it is absolutely required for correct Hoxa-2 expression in rhombomere 5.

Animals↗
PubMed1997

Role of the retinoic acid receptor beta (RARbeta) during mouse development.

Homozygous RAR beta mutants are growth-deficient, but are fertile and have a normal longevity. They display homeotic transformations and malformations of cervical vertebrae and a retrolenticular membrane. This latter abnormality arises from the persistence and hyperplasia of the primary vitreous body. In contrast, we found that abnormalities of cranial nerves IX and X which were previously proposed to be specific features of the RAR beta mutant phenotype (Luo et al., Mech. Dev. 53: 61-71, 1995) occur with the same low penetrance in wildtype littermates. Although the RAR beta protein is expressed at high levels in the striatum and interdigital mesenchyme, the brain and limbs of RAR beta mutants appear morphologically normal. RAR alpha/RAR beta double mutants display numerous visceral abnormalities, most of which are incompatible with post-natal life. The majority of these abnormalities was previously detected in RAR alpha/RAR beta2 mutants with the notable exceptions of agenesis of the stapedial (2nd aortic arch-derived) artery, thymic and spleen agenesis and abnormal inferior vena cava. RAR beta/RAR gamma double mutants show major ocular defects including a shortening of the ventral retina and pre-natal retinal dysplasia, both of which represent the only abnormalities of the fetal vitamin-A deficiency (VAD) syndrome not previously detected in RAR beta2/RAR gamma compound mutants. In addition, RAR beta is apparently functionally redundant with either RAR alpha or RAR gamma for the formation of a small subset of craniofacial skeletal elements, as well as for eyelid development and digit separation. We also provide evidence that, at least in some instances, this phenomenon of functional redundancy between RARs may be an artifactual consequence of gene knock-out.

Animals↗
PubMed1996

Loss of morphine-induced analgesia, reward effect and withdrawal symptoms in mice lacking the mu-opioid-receptor gene.

Despite tremendous efforts in the search for safe, efficacious and non-addictive opioids for pain treatment, morphine remains the most valuable painkiller in contemporary medicine. Opioids exert their pharmacological actions through three opioid-receptor classes, mu, delta and kappa, whose genes have been cloned. Genetic approaches are now available to delineate the contribution of each receptor in opioid function in vivo. Here we disrupt the mu-opioid-receptor gene in mice by homologous recombination and find that there are no overt behavioural abnormalities or major compensatory changes within the opioid system in these animals. Investigation of the behavioural effects of morphine reveals that a lack of mu receptors abolishes the analgesic effect of morphine, as well as place-preference activity and physical dependence. We observed no behavioural responses related to delta- or kappa-receptor activation with morphine, although these receptors are present and bind opioid ligands. We conclude that the mu-opioid-receptor gene product is the molecular target of morphine in vivo and that it is a mandatory component of the opioid system for morphine action.

Analgesics↗
PubMed1996

Gastric mucosa abnormalities and tumorigenesis in mice lacking the pS2 trefoil protein.

To determine the function of the pS2 trefoil protein, which is normally expressed in the gastric mucosa, the mouse pS2 (mpS2) gene was inactivated. The antral and pyloric gastric mucosa of mpS2-null mice was dysfunctional and exhibited severe hyperplasia and dysplasia. All homozygous mutant mice developed antropyloric adenoma, and 30 percent developed multifocal intraepithelial or intramucosal carcinomas. The small intestine was characterized by enlarged villi and an abnormal infiltrate of lymphoid cells. These results indicate that mpS2 is essential for normal differentiation of the antral and pyloric gastric mucosa and may function as a gastric-specific tumor suppressor gene.

Adenoma↗
PubMed1996

RXR gamma null mice are apparently normal and compound RXR alpha +/-/RXR beta -/-/RXR gamma -/- mutant mice are viable.

The RXR gamma (RXR, retinoid X receptor) gene was disrupted in the mouse. Homozygous mutant mice developed normally and were indistinguishable from their RXR gamma +/- or wild-type littermates with respect to growth, fertility, viability, and apparent behavior in the animal facility. Moreover, RXR alpha -/-/RXR gamma -/- and RXR beta -/-/RXR gamma -/- mutant phenotypes were indistinguishable from those of RXR alpha -/- and RXR beta -/- mutants, respectively. Strikingly, RXR alpha +/-/RXR beta -/-/RXR gamma -/- triple mutants were viable. Thus, it appears that RXR gamma does not exert any essential function that cannot be performed by RXR alpha or RXR beta, and one copy of RXR alpha is sufficient to perform most of the functions of the RXRs.

Animals↗
PubMed1996

Independent modes of natural killing distinguished in mice lacking Lag3.

The LAG3 protein has several features in common with CD4, suggesting that it may be important in controlling T cell reactivity. However, mice with a Lag3 null mutation have now been shown to exhibit a defect in the natural killer cell, rather than the T cell, compartment. Killing of certain tumor targets by natural killer cells from these mice was inhibited or even abolished, whereas lysis of cells displaying major histocompatibility complex class I disparities remained intact. It appears that LAG3 is a receptor or coreceptor that defines different modes of natural killing.

Animals↗
PubMed1996

Spermiogenesis deficiency and germ-cell apoptosis in CREM-mutant mice.

Spermiogenesis is a complex process by which postmeiotic male germ cells differentiate into mature spermatozoa. This process involves remarkable structural and biochemical changes including nuclear DNA compaction and acrosome formation. Transcription activator CREM (cyclic AMP-responsive element modulator) is highly expressed in postmeiotic cells, and CREM may be responsible for the activation of several haploid germ cell-specific genes involved in the structuring of the spermatozoon. The specific role of CREM in spermiogenesis was addressed using CREM-mutant mice generated by homologous recombination. Analysis of the seminiferous epithelium in mutant male mice reveals postmeiotic arrest at the first step of spermiogenesis. Late spermatids are completely absent, and there is a significant increase in apoptotic germ cells. We show that CREM deficiency results in the lack of postmeiotic cell-specific gene expression. The complete lack of spermatozoa in the mutant mice is reminiscent of cases of human infertility.

Animals↗
PubMed1996

Mice lacking H2-M complexes, enigmatic elements of the MHC class II peptide-loading pathway.

We have generated mice lacking H2-M complexes, critical facilitators of peptide loading onto major histo-compatibility complex class II molecules. Ab molecules in these mice matured into stable complexes and were efficiently expressed at the cell surface. Most carried a single peptide derived from the class II-associated invariant chain; the diverse array of peptides normally displayed by class II molecules was absent. Cells from mutant mice presented both whole proteins and short peptides very poorly. Surprisingly, positive selection of CD4+ T cells was quite efficient, yielding a large and broad repertoire. Peripheral T cells reacted strongly to splenocytes from syngeneic wild-type mice, no doubt reflecting the unique peptide complement carried by class II molecules in mutant animals.

Amino Acid Sequence↗
PubMed1996

Abnormal spermatogenesis in RXR beta mutant mice.

We have generated mouse lines in which the RXR beta gene was disrupted by homologous recombination. Approximately 50% of the RXR beta homozygous mutants died before or at birth, but those that survived appeared normal except that the males were sterile, owing to oligo-astheno-teratozoospermia. Failure of spermatid release occurred within the germinal epithelium, and the epididymis contained very few spermatozoa that, in addition, exhibited abnormal acrosomes and tails. There was a progressive accumulation of lipids within the mutant Sertoli cells, which were histochemically characterized as unsaturated triglycerides. In old mutant males, progressive degeneration of the germinal epithelium occurred, ending with the formation of acellular lipid-filled tubules. The selective expression of RXR beta in Sertoli cells, together with the timing of appearance of the histological abnormalities, suggests that the primary defect resulting from the mutation resides in these cells.

Animals↗
PubMed1996

Absence of integrin alpha 6 leads to epidermolysis bullosa and neonatal death in mice.

Cell-extracellular matrix interactions have important roles in many biological processes, including embryonic development, growth control and differentiation. Integrins are the principal receptors for extracellular matrix. They are composed of non-covalently associated alpha and beta chains. Integrin alpha 6 can associate with either beta 1 or beta 4 (refs 2,3). Both integrin complexes are receptors for laminins, major components of basement membranes. The distribution of alpha 6 (refs 4-10) as well as studies using function-blocking antibodies have suggested an essential role for this laminin receptor during embryogenesis, in processes such as endoderm migration or kidney tubule formation9. Here we report that, surprisingly, mice lacking the alpha 6 integrin chain develop to birth. However, they die at birth with severe blistering of the skin and other epithelia, a phenotype reminiscent of the human disorder epidermolysis bullosa. Hemidesmosomes are absent in mutant tissue. This absence is likely to result from the lack of alpha 6/beta 4, the only integrin in hemidesmosomes of stratified squamous and transitional epithelia. Mutations in the genes encoding integrin beta 4 and chains of laminin-5 have been implicated in junctional epidermolysis bullosa. Our study provides evidence that some forms of epidermolysis bullosa may originate from defects of the alpha 6 gene.

Animals↗
PubMed1996

LAG-3 is not responsible for selecting T helper cells in CD4-deficient mice.

The product of the LAG-3 gene is a cell surface protein with significant homology to CD4. It has been suggested that it can serve as a functional equivalent of CD4 and account for the MHC class II-restricted responses which persist in CD4-deficient mice. To test this hypothesis, we have created CD4/LAG-3 double-deficient mice by successive homologous recombinations in embryonic stem cells. These animals turn out to be indistinguishable from CD4 single-deficient mice in their lymphocyte populations and responses that are controlled by MHC class II molecules. LAG-3 thus does not explain class II-restricted lymphocyte selection and function in the absence of CD4, strengthening the idea that these phenomena can occur independently of co-receptor signalling.

Animals↗
PubMed1996

Specific and redundant functions of the paralogous Hoxa-9 and Hoxd-9 genes in forelimb and axial skeleton patterning.

Using gene targeting, we have produced mice with a disruption of Hoxa-9 or Hoxd-9, two paralogous Abdominal B-related genes. During embryogenesis, these genes are expressed in limb buds and along the vertebral axis with anterior expression boundaries at the level of prevertebra #20 for Hoxa-9 and #23 for Hoxd-9. Skeletal analysis revealed homeotic transformations corresponding to anteriorisations of vertebrae #21 to #25 (L1 to L5) in the lumbar region of Hoxa-9-/- mutants; vertebrae #23 to #25 (L3 to L5) in the lumbar region together with vertebrae #28, #30 and #31 (S2, S4 and Ca1) in the sacrum and tail were anteriorized in Hoxd-9-/- mutants. Thus, anteriorisation of vertebrae #23 to #25 were common to both phenotypes. Subtle forelimb (but not hindlimb) defects, corresponding to a reduction of the humerus length and malformation of its deltoid crest, were also observed in Hoxd-9-/-, but not in Hoxa-9-/-, mutant mice. By intercrosses between these two lines of mutant mice, we have produced Hoxa-9/Hoxd-9 double mutants which exhibit synergistic limb and axial malformations consisting of: (i) an increase of penetrance and expressivity of abnormalities present in the single mutants, and (ii) novel limb alterations at the level of the forelimb stylopod and additional axial skeleton transformations. These observations demonstrate that the two paralogous genes Hoxa-9 and Hoxd-9 have both specific and redundant functions in lumbosacral axial skeleton patterning and in limb morphogenesis at the stylopodal level. Taken all together, the present and previously reported results show that disruption of different Hox genes can produce similar vertebral transformations, thus supporting a combinatorial code model for specification of vertebral identity by Hox genes.

Abnormalities, Multiple↗
PubMed1995

Parkinsonian-like locomotor impairment in mice lacking dopamine D2 receptors.

Dopaminergic neuronal pathways arise from mesencephalic nuclei and project axons to the striatum, cortex, limbic system and hypothalamus. Through these pathways dopamine affects many physiological functions, such as the control of coordinated movement and hormone secretion. Here we have studied the physiological involvement of the dopamine D2 receptors in dopaminergic transmission, using homologous recombination to generate D2-receptor-deficient mice. Absence of D2 receptors leads to animals that are akinetic and bradykinetic in behavioural tests, and which show significantly reduced spontaneous movements. This phenotype presents analogies with symptoms characteristic of Parkinson's disease. Our study shows that D2 receptors have a key role in the dopaminergic control of nervous function. These mice have therapeutic potential as a model for investigating and correcting dysfunctions of the dopaminergic system.

Animals↗
PubMed1995

Cryptorchidism and homeotic transformations of spinal nerves and vertebrae in Hoxa-10 mutant mice.

Homozygous mice mutated by homologous recombination for the AbdB-related Hoxa-10 gene are viable but display homeotic transformations of vertebrae and lumbar spinal nerves. Mutant males exhibit unilateral or bilateral criptorchidism due to developmental abnormalities of the gubernaculum, resulting in abnormal spermatogenesis and sterility. These results reveal an important role of Hoxa-10 in patterning posterior body regions and suggest that Hox genes are involved in specifying regional identity of both segmented and nonovertly segmented structures of the developing body.

Animals↗
PubMed1995

Developmental roles of the retinoic acid receptors.

Retinoic acid, one of the principle active metabolites of vitamin A (retinol), is believed to be essential for numerous developmental and physiological processes. Vitamin A deprivation (VAD) during development leads to numerous congenital defects. Previous studies of retinoic acid receptor (RAR) deficient mice failed to reveal any of these VAD-induced defects. This finding suggested that either the RARs are functionally redundant or that they are not critically required during development. In order to address these possibilities, we derived a number of RAR compound mutants. Unlike RAR single mutants, these compound null mutants died either in utero or shortly following birth. Histological analysis revealed essentially all of the defects characteristic of fetal VAD. A number of additional malformations, not described in previous VAD studies, were also observed. These included defects of the ocular and salivary glands and their ducts, the skeletal elements of the fore- and hindlimbs, and the cervical region of the axial skeleton. In addition, with the exception of derivatives forming within the first pharyngeal arch, most of the elements derived from mesectoderm emanating from cranial and hindbrain levels were affected. A number of these mutants also exhibited supernumerary cranial skeletal elements characteristics of the reptilian skull. A summary of the defects found in these RAR double mutants is presented.

Animals↗