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Pierre Chambon

Publications and source records attributed to Pierre Chambon.

125 records · Page 7Linked to original sources
PubMed2002

The phosphorylation site located in the A region of retinoic X receptor alpha is required for the antiproliferative effect of retinoic acid (RA) and the activation of RA target genes in F9 cells.

Mouse F9 embryocarcinoma cells constitute a well established cell autonomous model system for investigating retinoic acid (RA) signaling in vitro. RA induces the differentiation of F9 cells grown as monolayers into endodermal-like cells and decreases their rate of proliferation. Knock-out of the retinoic X receptor alpha (RXRalpha) gene abolishes endodermal differentiation and the induction of several endogenous RA-responsive genes. RXRalpha null cells are also drastically impaired in their antiproliferative response to RA. The role of the RXRalpha phosphorylation site located in the N-terminal A region (Ser(22)) has been investigated here by establishing cell lines re-expressing RXRalpha either wild type or mutated at the phosphorylation site (RXRalphaS22A) in a RXRalpha-null background. We show that Ser(22) is dispensable for RA-induced endodermal differentiation but is crucial for the expression of several RA-responsive genes. Ser(22) is also indispensable for the antiproliferative effect of RA and necessary for the RA-induced down-regulation of p21(CIP) and p27(KIP) CKIs proteins that are known to be involved in the control of cell cycle progression.

Animals↗
PubMed2002

Genetic evidence that oxidative derivatives of retinoic acid are not involved in retinoid signaling during mouse development.

Retinoic acid, the active derivative of vitamin A (retinol), is a hormonal signaling molecule that acts in developing and adult tissues. The Cyp26a1 (cytochrome p450, 26) protein metabolizes retinoic acid into more polar hydroxylated and oxidized derivatives. Whether some of these derivatives are biologically active metabolites has been debated. Cyp26a1(-/-) mouse fetuses have lethal morphogenetic phenotypes mimicking those generated by excess retinoic acid administration, indicating that human CYP26A1 may be essential in controlling retinoic acid levels during development. This hypothesis suggests that the Cyp26a1(-/-) phenotype could be rescued under conditions in which embryonic retinoic acid levels are decreased. We show that Cyp26a1(-/-) mice are phenotypically rescued by heterozygous disruption of Aldh1a2 (also known as Raldh2), which encodes a retinaldehyde dehydrogenase responsible for the synthesis of retinoic acid during early embryonic development. Aldh1a2 haploinsufficiency prevents the appearance of spina bifida and rescues the development of posterior structures (sacral/caudal vertebrae, hindgut, urogenital tract), while partly preventing cervical vertebral transformations and hindbrain pattern alterations in Cyp26a1(-/-) mice. Thus, some of these double-mutant mice can reach adulthood. This study is the first report of a mutation acting as a dominant suppressor of a lethal morphogenetic mutation in mammals. We provide genetic evidence that ALDH1A2 and CYP26A1 activities concurrently establish local embryonic retinoic acid levels that must be finely tuned to allow posterior organ development and to prevent spina bifida.

Aldehyde Oxidoreductases↗
PubMed2002

Differential expression of retinoic acid-synthesizing (RALDH) enzymes during fetal development and organ differentiation in the mouse.

Three retinaldehyde dehydrogenases (RALDH1, RALDH2 and RALDH3), which catalyze the oxidation of retinaldehyde into retinoic acid, have been shown to be differentially expressed during early embryogenesis. Here, we report their differential expression patterns throughout later mouse organogenesis. Raldh1 is prominently expressed in developing lung (notably in bronchial and tracheal epithelia), and shows stage-specific expression in stomach and intestine epithelial and mesenchymal layers. Raldh3 expression is specific to the differentiating intestinal lamina propria. Raldh2 is expressed throughout the kidney nephrogenic zone, whereas Raldh1 and Raldh3 are mostly expressed in collecting duct epithelia. Raldh3 expression is more restricted than that of Raldh1 in the urogenital tract and sex gland epithelia, whereas Raldh2 expression is mesenchymal. Raldh1 is coexpressed with Raldh2 in the early heart epicardium, and is later specifically expressed in developing heart valves. All three genes exhibit distinct expression patterns in respiratory and olfactory epithelia and/or mesenchymes, and in developing teeth. Only Raldh1 expression is seen after birth in specific brain structures. These data indicate a requirement for regulated RA synthesis in various differentiating organs.

Abdomen↗
PubMed2002

Differential expression of the retinoic acid-metabolizing enzymes CYP26A1 and CYP26B1 during murine organogenesis.

We recently cloned the murine homologue of Cyp26B1, a novel retinoic acid (RA)-metabolizing enzyme and showed that its gene expression pattern is unique from that of Cyp26A1 during early embryogenesis. Here, we complete this comparative expression analysis from embryonic day (E) 12 to postnatal stages. Cyp26B1 expression was found in developing tendons and precartilaginous elements and in perichondrium by E14.5, while Cyp26A1 expression was restricted to extremities of rib and vertebral cartilage. Cyp26A1 and Cyp26B1 were expressed, in the distal epithelium and mesenchyme of the limbs and genital tubercle, respectively. High Cyp26B1 expression was found in craniofacial areas undergoing morphogenetic growth, whereas Cyp26A1 message was restricted to the mouth and dental epithelium. Cyp26A1 alone was expressed in the developing neural retina, while both genes were co-expressed in the retinal pigment epithelium. Cyp26B1 was specifically expressed in the developing hindbrain (pons, cerebellum) and forebrain (striatum, hippocampus), with forebrain expression persisting postnatally. In addition, Cyp26B1 was expressed at specific levels of the differentiating upper and lower thoracic spinal cord, adjacent to the cervical and lumbar regions that express the RA-synthesizing enzyme RALDH-2. In viscera, Cyp26B1 transcripts were detected in the developing lung, kidney, spleen, thymus and testis, whereas Cyp26A1 transcripts were found in the diaphragm and outer stomach mesenchyme. Cyp26B1 was also specifically expressed in dermis surrounding the developing hair follicles. Regulated RA metabolism may therefore be required in many developing systems.

Animals↗
PubMed2002

Interdigital apoptosis and downregulation of BAG-1 expression in mouse autopods.

Digit formation during vertebrate limb development is a well-known example of programmed cell death. We have used this system to analyze whether the formation of the interdigital necrotic zone in mouse autopods is linked with the expression of BAG-1, a gene with an anti-death activity. Here, we demonstrate that during development of mouse autopods, BAG-1 expression is downregulated upon the initiation of interdigital apoptosis. We further show that retinoic acid induced interdigital apoptosis is also correlated with a downregulation of BAG-1 expression. On the contrary, the expression of BAG-1 remains unaltered in autopods of RARbeta(-/-)/RARgamma(-/-) mice which show severe interdigital webbing due to a marked decrease in interdigital apoptosis.

Amino Acid Sequence↗
PubMed2002

The retinoic acid receptors RARalpha and RARgamma are required for inner ear development.

To define the signal transduction pathway of retinoic acid during inner ear development, we analyzed the expression patterns of transcripts encoding the three retinoic acid receptors (RARalpha, beta, and gamma) and related them to phenotypes resulting from single or compound inactivation of these nuclear receptors. The expression of all three RARs was observed in the developing mouse otocyst as early as embryonic day 10.5 (E10.5)-E12.5 and continued into adulthood. Expression domains of the three RAR receptors, however, were largely non-overlapping: RARalpha was predominantly expressed in the developing sensory epithelium, RARbeta in inner ear mesenchymal tissues and RARgamma in the differentiating otic capsule. In the adult, RARalpha and RARgamma transcripts were found in the organ of Corti and the spiral ganglion, whereas RARbeta transcripts were localized in mesenchyme-derived tissues. RARalpha, beta, and gamma null mutant mice, as well as RARalpha/RARbeta and RARbeta/RARgamma combined null fetuses, did not present any noticeable morphological abnormalities in the inner ear. In contrast, RARalpha/RARgamma null mutants displayed a severe hypoplasia of the otocyst that was already visible at E10.5 without any visible endolymphatic duct. The hypoplastic otocyst in RARalpha/RARgamma null mutants was characterized by impaired chondrocyte differentiation and neural development. After the second week of gestation, these mutant fetuses lacked all of the semi-circular canals and the endolymphatic duct and displayed strong anomalies in the inner ear structures. The morphological deficits were generally more severe in the cochlear portion than in the vestibular portion of the inner ear. Altogether, these results demonstrate that RARalpha and RARgamma play an essential role in the initial differentiation of otic placode derivatives, whereas RARbeta plays a minimal role in this process.

Animals↗
PubMed2002

Association of CBP/p300 acetylase and thymine DNA glycosylase links DNA repair and transcription.

DNA repair in chromatin is subject to topological constraints, suggesting a requirement for chromatin modification and remodeling activities. Thymine DNA glycosylase (TDG) initiates repair of G/T and G/U mismatches, commonly associated with CpG islands, by removing thymine and uracil moieties. We report that TDG associates with transcriptional coactivators CBP and p300 and that the resulting complexes are competent for both the excision step of repair and histone acetylation. Furthermore, TDG stimulates CBP transcriptional activity in transfected cells and reciprocally serves as a substrate for CBP/p300 acetylation. Remarkably, this acetylation triggers release of CBP from DNA ternary complexes and also regulates recruitment of repair endonuclease APE. These observations reveal a potential regulatory role for protein acetylation in base mismatch repair and a role for CBP/p300 in maintaining genomic stability.

Acetylation↗
PubMed2002

The function of TIF2/GRIP1 in mouse reproduction is distinct from those of SRC-1 and p/CIP.

Human TIF2 (hTIF2) is a member of the p160 family of nuclear receptor coactivators, which includes SRC-1 and p/CIP. Although the functions of hTIF2 and of its mouse homolog (GRIP1 or mTIF2) have been clearly established in vitro, their physiological role remains elusive. Here, we have generated mice lacking mTIF2/GRIP1 and examined their phenotype with a particular emphasis on reproductive functions. TIF2(-/-) mice are viable, but the fertility of both sexes is impaired. Male hypofertility is due to defects in both spermiogenesis (teratozoospermia) and age-dependent testicular degeneration, and TIF2 expression appears to be essential for adhesion of Sertoli cells to germ cells. Female hypofertility is due to a placental hypoplasia that most probably reflects a requirement for maternal TIF2 in decidua stromal cells that face the developing placenta. We conclude that TIF2 plays a critical role in mouse reproductive functions, whereas previous reports have not revealed serious fertility impairment in SRC-1(-/-) or p/CIP(-/-) mutants. Thus, even though the three p160 coactivators exhibit strong sequence homology and similar activity in assays in vitro, they play distinct physiological roles in vivo, as their genetic eliminations result in distinct pathologies.

Age Factors↗
PubMed2002

Thyroid function in mice with compound heterozygous and homozygous disruptions of SRC-1 and TIF-2 coactivators: evidence for haploinsufficiency.

Steroid receptor coactivator (SRC)-1 and transcriptional intermediary factor (TIF)-2 are homologous nuclear receptor coactivators. We have investigated their possible redundancy as thyroid hormone (TH) coactivators by measuring thyroid function in compound SRC-1 and TIF-2 knock out (KO) mice. Whereas SRC-1 KO (SRC-1(-/-)) mice are resistant to TH and SRC-1(+/-) are not, we now demonstrate that TIF-2 KO (TIF-2(-/-)) mice have normal thyroid function. Yet double heterozygous, SRC-1(+/-)/TIF-2(+/-) mice manifested resistance to TH of a similar degree as that in mice completely deficient in SRC-1. KO of both SRC-1 and TIF-2 resulted in marked increases of serum TH and thyrotropin concentrations. This work demonstrates gene dosage effect in nuclear coactivators manifesting as haploinsufficiency and functional redundancy of SRC-1 and TIF-2.

Animals↗
PubMed2002

Germ cell expression of the transcriptional co-repressor TIF1beta is required for the maintenance of spermatogenesis in the mouse.

The gene for transcriptional intermediary factor 1beta (TIF1beta) encodes a transcriptional co-repressor known to play essential roles in chromatin remodeling as well as in early embryonic development. During spermatogenesis, TIF1beta is preferentially associated with heterochromatin structures of Sertoli cells and round spermatids, as well as with meiotic chromosomes. Its expression is tightly regulated within spermatocyte and spermatid populations, and it is undetectable in spermatogonia. Spatiotemporally controlled ablation of TIF1beta by using a germ cell lineage-specific CreER(T)/loxP system leads to testicular degeneration. This degeneration is not due to impairment of chromatin remodeling processes during meiosis and spermiogenesis, as TIF1beta-deficient spermatocytes are able to complete their differentiation into spermatozoa. It rather occurs as a consequence of shedding of immature germ cells (spermatocytes and spermatids), and disappearance of stem spermatogonia. These results indicate that TIF1beta has important functions in the homeostasis of the seminiferous epithelium, and probably plays a crucial role in the network of paracrine interactions between germ cell subpopulations and/or Sertoli cells.

Animals↗
PubMed2002

Embryonic retinoic acid synthesis is required for forelimb growth and anteroposterior patterning in the mouse.

Numerous studies, often performed on avian embryos, have implicated retinoic acid (RA) in the control of limb bud growth and patterning. Here we have investigated whether the lack of endogenous RA synthesis affects limb morphogenesis in mutant mouse embryos deficient for the retinaldehyde dehydrogenase 2 (Raldh2/Aldh1a2). These mutants, which have no detectable embryonic RA except in the developing retina, die at E9.5-E10 without any evidence of limb bud formation, but maternal RA supplementation through oral gavage from E7.5 can extend their survival. Such survivors exhibit highly reduced forelimb rudiments, but apparently normal hindlimbs. By providing RA within maternal food, we found both a stage- and dose-dependency for rescue of forelimb growth and patterning. Following RA supplementation from E7.5 to 8.5, mutant forelimbs are markedly hypoplastic and lack anteroposterior (AP) patterning, with a single medial cartilage and 1-2 digit rudiments. RA provided until E9.5 significantly rescues forelimb growth, but cannot restore normal AP patterning. Increasing the RA dose rescues the hypodactyly, but leads to lack of asymmetry of the digit pattern, with abnormally long first digit or symmetrical polydactyly. Mutant forelimb buds are characterized by lack of expression or abnormal distal distribution of Sonic hedgehog (Shh) transcripts, sometimes with highest expression anteriorly. Downregulation or ectopic anterior expression of Fgf4 is also seen. As a result, genes such as Bmp2 or Hoxd genes are expressed symmetrically along the AP axis of the forelimb buds, and/or later, of the autopod. We suggest that RA signaling cooperates with a posteriorly restricted factor such as dHand, to generate a functional zone of polarizing activity (ZPA).

Aldehyde Oxidoreductases↗
PubMed2002

Site-specific somatic mutagenesis in the retinal pigment epithelium.

PURPOSE: Generate site-specific somatic mutations selectively in the retinal pigment epithelium (RPE) in mice. METHODS: A transgenic mouse line expressing the Cre recombinase under the control of the tyrosinase-related protein (TRP)-1 promoter was generated. The presence of Cre was determined by in situ hybridization, and Cre-mediated excision of DNA was analyzed by PCR and alkaline phosphatase (AP) histochemistry in reporter mice carrying a loxP-flanked (floxed) retinoid X receptor alpha (RXRa) gene and in Z/AP mice, respectively. RESULTS: Cre was expressed in the RPE from embryonic day 10.5 to postnatal day 12, resulting in efficient floxed excision of DNA in the RPE from embryonic day 10.5 to adulthood in TRP1-Cre mice. Expressed Cre and excision of DNA were also detected in the ciliary margin of the retina and in some cells in the neural retina, but not in the embryonic periocular mesenchyme or in the choroid. CONCLUSIONS: The TRP1-Cre mouse line, which induces efficient Cre-mediated excision of DNA selectively in the RPE, provides a new, powerful tool to study gene functions in the RPE in vivo.

Animals↗
PubMed2002

Analysis of the visual cycle in cellular retinol-binding protein type I (CRBPI) knockout mice.

PURPOSE: To determine whether the visual cycle is affected in mice without a functional gene for cellular retinol-binding protein type I (CRBPI(-/-) mice). METHODS: Visual-cycle retinoids and rhodopsin levels were analyzed in eyes of dark adapted (DA) CRBPI(-/-) and wild-type (wt) mice before and during recovery from a flash. The rate of dark adaptation was analyzed using electroretinography (ERG). RESULTS: all-trans-retinyl esters were reduced to approximately 33% of wt levels in DA CRBPI(-/-) mice. Recovery from a flash in wt mice produced transient accumulations of all-trans-retinal and all-trans-retinyl ester, as the pulse of retinoid produced by the flash traversed the visual cycle. In CRBPI(-/-) mice, all-trans-retinal accumulated transiently, as in wt mice. However, all-trans-retinol also accumulated transiently in the neural retina, and the transient increase in all-trans-retinyl ester of the wt was reduced. Rates of 11-cis-retinal and rhodopsin formation were comparable in wt and CRBPI(-/-) mice. Dark adaptation was delayed by a factor of approximately two. CONCLUSIONS: The accumulation of all-trans-retinol in neural retina, in the absence of CRBPI and the reduced amount of retinyl esters in the RPE suggest that the binding protein participates in a process that drives diffusion of all-trans-retinol from photoreceptor cells to RPE, perhaps by delivering vitamin A to lecithin-retinol acyltransferase (LRAT) for esterification. Because the perturbation occurred upstream of a slow step of the visual cycle, there was no major impairment of the rate of visual pigment regeneration.

Acyltransferases↗