Délétion

Résumé

La délétion (symbole: Δ) est une mutation génétique caractérisée par la perte de matériel génétique sur un chromosome. La taille des délétions varie (d'une paire de bases à toute une région chromosomique) et les délétions peuvent survenir n'importe où sur le chromosome. Les grandes délétions peuvent résulter d'erreurs d'enjambement lors de la méiose, d'un enjambement inégal (crossing-over inégal), d'une cassure sans réparation ou de pertes associées à un chromosome dérivé d'une translocation. Les petites délétions (de quelques nucléotides) peuvent être la conséquence d'erreur lors de la réplication de l'ADN par l'ADN polymérase réplicative. Les petites délétions intragéniques de quelques bases nucléiques peuvent affecter un gène en décalant le cadre de lecture ou en provoquant la perte d’une partie du gène aboutissant à une perte de fonction du gène. Les délétions importantes peuvent provoquer la perte de plusieurs gènes contigus contenus dans la région impliquée. Selon le nomb

Source officielle

https://fr.wikipedia.org/wiki/D%C3%A9l%C3%A9tion

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Analysis of long-range gene regulation at the HoxD locus

Ana Rita De Carvalho Amândio Lhopitallier

Hoxd genes are essential for the development of the various body axes in vertebrates and hence the underlying regulatory mechanisms are of paramount importance. Among these various mechanisms are long-range acting enhancers, which are located in the two adjacent regulatory landscapes. Analyses of chromatin architecture at this gene cluster has revealed the existence of two topologically associating domains (TADs) flanking the cluster and encompassing these regulatory landscapes. However, the dynamics of such regulatory regions as well as the stability and functional contribution of specific enhancer-promoter interactions during development remains to be established. In this work, we analysed the 3D chromatin organization and transcription profile at the HoxD locus, at different time points during genital tubercle (GT) development, and observe that the 3D conformation of this regulatory region predates the embryonic emergence of the GT. Along with this tissue development, we observe a reduction in transcript levels correlating with a decrease in enhancer-promoter chromatin loops within the adjacent gene desert. This decrease occurs while maintaining a subset of CTCF/Cohesin associated contacts, which are preserved independently from the transcriptional status of the gene cluster. To further explore the functional contribution of this regulatory landscape, we used CRISPR-Cas9 technology to generate mice carrying partial deletions of this region, as well as targeted deletions of both transient (enhancer associated) and constitutive (CTCF/Cohesin associated) contacts. We observe that single deletions of both transient and constitutive contacts displayed little if any effect on Hoxd genes expression in the GT. On the contrary, the single deletion of a previous characterized Hoxd enhancer, the Prox element, or deletions comprising several enhancers, result in the reduction of Hoxd genes expression levels. Overall our results suggest that not all enhancer elements within a complex regulatory landscape have the same functional strength, and highlight the existence of a dynamic yet robust system to tightly regulate Hoxd genes expression.

EPFL2019

Chargement

Deficiency for the Cysteine Protease Cathepsin L Impairs Myc-Induced Tumorigenesis in a Mouse Model of Pancreatic Neuroendocrine Cancer

Nicola Rae Brindle, Douglas Hanahan, Ksenya Shchors

Motivated by the recent implication of cysteine protease cathepsin L as a potential target for anti-cancer drug development, we used a conditional MycER(TAM); Bcl-x(L) model of pancreatic neuroendocrine tumorigenesis (PNET) to assess the role of cathepsin L in Myc-induced tumor progression. By employing a cysteine cathepsin activity probe in vivo and in vitro, we first established that cathepsin activity increases during the initial stages of MycER(TAM); Bcl-x(L) tumor development. Among the cathepsin family members investigated, only cathepsin L was predominately produced by beta-tumor cells in neoplastic pancreata and, consistent with this, cathepsin L mRNA expression was rapidly upregulated following Myc activation in the beta cell compartment. By contrast, cathepsins B, S and C were highly enriched in tumor-infiltrating leukocytes. Genetic deletion of cathepsin L had no discernible effect on the initiation of neoplastic growth or concordant angiogenesis. However, the tumors that developed in the cathepsin L-deficient background were markedly reduced in size relative to their typical wild-type counterparts, indicative of a role for cathepsin L in enabling expansive tumor growth. Thus, genetic blockade of cathepsin L activity is inferred to retard Myc-driven tumor growth, encouraging the potential utility of pharmacological inhibitors of cysteine cathepsins in treating late stage tumors.

Public Library of Science2015

Chargement

Transforming Growth Factor beta (TGFβ) signaling plays an important role in a variety of cellular processes during embryonic development, adult tissue homeostasis and cancer. TGFβI ligand is a potent inhibitor of early hematopoietic progenitor [1] cells in vitro, however the exact role and mechanisms of this pathway during adult hematopoietic homeostasis remains poorly understood. The Transcriptional Intermediary Factor 1 gamma (Tif1γ) gene encodes a recently uncovered nuclear protein in the TGFβ transduction pathway. Tif1γ is defective in the zebrafish moonshine mutant, which exhibits primitive and definitive hematopoiesis defects [2]. In addition, Tif1γ has been shown to influence differentiation of human erythroid cells in vitro [3]. Recent work in our laboratory has provided genetic evidence that Tif1γ is required for the generation and survival of hematopoietic stem/progenitor cells during murine development (C.Adolphe, K.Shakhbazov et al., manuscript under submission). Given that Tif1γ function is required for embryonic development and null mutants are embryonic lethal [4] (R.Losson unpublished data), we took advantage of a conditional Tif1γ flox allele (R.Losson unpublished data) and combined it with the inducible MxCre line [5] to generate mice in which Tif1γ function can be specifically ablated during adult hematopoiesis. MxCre:Tif1γKO/flox mutants exhibit a decrease in erythroblasts and dramatic increase in granulocytes within the bone marrow. This phenotype is attributable to a massive increase in granulocyte-monocyte progenitors (GMPs) at the expense of common myeloid progenitors (CMPs) and megakaryocyte- erythrocyte progenitors (MEPs), which are severely decreased in Tif1γ mutant bone marrow. In addition, pre-B cells were dramatically decreased in numbers, attributable to an increase in cell death, indicating a pro-survival role for Tif1γ in B lymphocytes. In addition, we performed deletion of Tif1γ in non-competitive and competitive bone marrow transplantation settings, which indicated that only the CMP/MEP phenotype is a non-cell autonomous effect. Two distinct models have been reported suggesting how Tif1γ functions within the TGFβ pathway: one indicating that Tif1γ binds and acts through Smad2/3 and the other that Tif1γ functions as a Smad4 mono-ubiquitin ligase [3, 6, 7]. To genetically address this apparent discrepancy, we generated double Tif1γ/Smad4 hematopoietic specific mutant mice, whose phenotype was surprisingly similar to that observed in Tif1γ single mutants. These data suggest that Tif1γ function is independent of Smad4 in hematopoietic cells. To address the mechanism by which Tif1γ functions, we performed microarray profiling of normal and mutant progenitors, which revealed prostaglandin D2 synthase as a hub gene linking Tif1γ and TGFβ signaling. Finally, we were able to mimic the hematopoietic-Tif1γ null phenotype by providing 16,16-dimethyl prostaglandin D2 to wild-type hematopoietic cells in vitro. In summary, our data provide genetic evidence for a key role of Tif1γ during early myeloid development as well as pre-B cell survival. In addition, we have identified that the majority of Tif1γ function is Smad4 independent. Finally, we identified a novel link between Tif1γ function and prostaglandin metabolism/signaling as a likely mechanism by which Tif1γ regulates hematopoiesis.

EPFL2009

Chargement

Analysis of long-range gene regulation at the HoxD locus

Ana Rita De Carvalho Amândio Lhopitallier

EPFL2019

EPFL2009