Geminin-Deficient Neural Stem Cells Exhibit Normal Cell Division and Normal Neurogenesis

Neural stem cells (NSCs) are the progenitors of neurons and glial cells during both embryonic development and adult life. The unstable regulatory protein Geminin (Gmnn) is thought to maintain neural stem cells in an undifferentiated state while they proliferate. Geminin inhibits neuronal differentiation in cultured cells by antagonizing interactions between the chromatin remodeling protein Brg1 and the neural-specific transcription factors Neurogenin and NeuroD. Geminin is widely expressed in the CNS during throughout embryonic development, and Geminin expression is down-regulated when neuronal precursor cells undergo terminal differentiation. Over-expression of Geminin in gastrula-stage Xenopus embryos can expand the size of the neural plate. The role of Geminin in regulating vertebrate neurogenesis in vivo has not been rigorously examined. To address this question, we created a strain of Nestin-Cre/Gmnnfl/fl mice in which the Geminin gene was specifically deleted from NSCs. Interestingly, we found no major defects in the development or function of the central nervous system. Neural-specific GmnnΔ/Δ mice are viable and fertile and display no obvious neurological or neuroanatomical abnormalities. They have normal numbers of BrdU+ NSCs in the subgranular zone of the dentate gyrus, and GmnnΔ/Δ NSCs give rise to normal numbers of mature neurons in pulse-chase experiments. GmnnΔ/Δ neurosphere cells differentiate normally into both neurons and glial cells when grown in growth factor-deficient medium. Both the growth rate and the cell cycle distribution of cultured GmnnΔ/Δ neurosphere cells are indistinguishable from controls. We conclude that Geminin is largely dispensable for most of embryonic and adult mammalian neurogenesis

Geminin Is Required for Zygotic Gene Expression at the Xenopus Mid-Blastula Transition

In many organisms early development is under control of the maternal genome and zygotic gene expression is delayed until the mid-blastula transition (MBT). As zygotic transcription initiates, cell cycle checkpoints become activated and the tempo of cell division slows. The mechanisms that activate zygotic transcription at the MBT are incompletely understood, but they are of interest because they may resemble mechanisms that cause stem cells to stop dividing and terminally differentiate. The unstable regulatory protein Geminin is thought to coordinate cell division with cell differentiation. Geminin is a bi-functional protein. It prevents a second round of DNA replication during S and G2 phase by binding and inhibiting the essential replication factor Cdt1. Geminin also binds and inhibits a number of transcription factors and chromatin remodeling proteins and is thought to keep dividing cells in an undifferentiated state. We previously found that the cells of Geminin-deficient Xenopus embryos arrest in G2 phase just after the MBT then disintegrate at the onset of gastrulation. Here we report that they also fail to express most zygotic genes. The gene expression defect is cell-autonomous and is reproduced by over-expressing Cdt1 or by incubating the embryos in hydroxyurea. Geminin deficient and hydroxyurea-treated blastomeres accumulate DNA damage in the form of double stranded breaks. Bypassing the Chk1 pathway overcomes the cell cycle arrest caused by Geminin depletion but does not restore zygotic gene expression. In fact, bypassing the Chk1 pathway by itself induces double stranded breaks and abolishes zygotic transcription. We did not find evidence that Geminin has a replication-independent effect on transcription. We conclude that Geminin is required to maintain genome integrity during the rapid cleavage divisions, and that DNA damage disrupts zygotic gene transcription at the MBT, probably through activation of DNA damage checkpoint pathways

Immune resistance in lung adenocarcinoma.

Lung cancer is the leading cancer killer worldwide, imposing grievous challenges for patients and clinicians. The incidence of lung adenocarcinoma (LUAD), the main histologic subtype of lung cancer, is still increasing in current-, ex-, and even non-smokers, whereas its five-year survival rate is approximately 15% as the vast majority of patients usually present with advanced disease at the time of diagnosis. The generation of novel drugs targeting key disease driver mutations has created optimism for the treatment of LUAD, but, as these mutations are not universal, this therapeutic line benefits only a subset of patients. More recently, the advent of targeted immunotherapies and their documented clinical efficacy in many different cancers, including LUAD, have started to change cancer management. Immunotherapies have been developed in order to overcome the cancer’s ability to develop mechanisms of immune resistance, i.e., to adapt to and evade the host inflammatory and immune responses. Identifying a cancer’s immune resistance mechanisms will likely advance the development of personalized immunotherapies. This review examines the key pathways of immune resistance at play in LUAD and explores therapeutic strategies which can unleash potent antitumor immune responses and significantly improve therapeutic efficacy, quality of life, and survival in LUAD

Shared epithelial pathways to lung repair and disease.

Chronic lung diseases present tremendous health burdens and share a common pathobiology of dysfunctional epithelial repair. Lung adenocarcinoma, the leading cancer killer worldwide, is caused mainly by chemical carcinogens of tobacco smoke that induce mutations in pulmonary epithelial cells leading to uncontrolled epithelial proliferation. Lung epithelial cells that possess the capacity for self-renewal and regeneration of other lung cell types are believed to underlie the pathobiology of chronic obstructive, fibrotic and neoplastic lung disorders. However, the understanding of lung epithelial progenitor cell hierarchy and turnover is incomplete and a comprehensive model of the cellular and transcriptional events that underlie lung regeneration and carcinogenesis is missing. The mapping of these processes is extremely important, since their modulation would potentially allow effective cure and/or prevention of chronic lung diseases. In this review we describe current knowledge on cellular and molecular pathways at play during lung repair and carcinogenesis and summarise the critical lung cell populations with regenerative and cancerous potential

A method for the establishment and characterization of mouse lung adenocarcinoma cell lines that mimic traits of human adenocarcinomas.

Lung adenocarcinoma (LADC) is the leading cause of cancer death worldwide and is largely inflicted by carcinogens contained in tobacco smoke. The generation of cell lines mimicking traits of human LADC will profoundly advance our understanding of the pathobiology of the disease, as they offer an easy and valuable tool to study the cellular and molecular aspects of carcinogenesis. Here we describe a detailed protocol for the generation of such cell lines, following the exposure of experimental mouse strains to different tobacco carcinogens and isolation of the resulting lung tumors

A role for club cells in smoking-associated lung adenocarcinoma.

The cellular origin of lung adenocarcinoma remains a focus of intense research efforts. The marked cellular heterogeneity and plasticity of the lungs, as well as the vast variety of molecular subtypes of lung adenocarcinomas perplex the field and account for the extensive variability of experimental results. While most experts would agree on the cellular origins of other types of thoracic tumours, great controversy exists on the tumour-initiating cells of lung adenocarcinoma, since this histologic subtype of lung cancer arises in the distal pulmonary regions where airways and alveoli converge, occurs in smokers as well as nonsmokers, is likely caused by various environmental agents, and is marked by vast molecular and pathologic heterogeneity. Alveolar type II, club, and their variant cells have all been implicated in lung adenocarcinoma progeny and the lineage hierarchies in the distal lung remain disputed. Here we review the relevant literature in this rapidly expanding field, including results from mouse models and human studies. In addition, we present a case for club cells as cells of origin of lung adenocarcinomas that arise in smokers

RAS oncogenes direct metastasis.

RAS genes are cardinal driver oncogenes frequently and differentially mutated across bodily tumors. Their tumorigenic potential has been mainly ascribed to autonomous promotion of tumor cell proliferation and survival. However, recent evidence shows that RAS oncogenes also function to define metastatic tropism. Interestingly, RAS-driven metastasis is mediated by distinct chemokine sets that signal to endothelial and myeloid cells

Contribution à l'étude des modalités d'exploitation des rhyolites en Corse : l'exemple des filons du Monte d'Oro (Vivario, Haute-Corse)

In Corsica, where flint and obsidian are absent, rhyolites were often exploited by prehistoric societies, in particular during the third millennium, when they abound on most archaeological sites. This article aims to discuss exploitation methods of rhyolites in Corsica, using archaeological results from the Monte d'Oro veins (Vivario) and from the analysis of the principal sites known from the third millennium. These results suggest that the supply of rhyolites was replenished occasionally, during travel apparently motivated by needs other than the mere acquisition of raw lithic materials.En Corse, où le silex et l'obsidienne font défaut, les rhyolites ont souvent été exploitées par les populations préhistoriques, notamment au cours du 3e millénaire où elles sont abondantes dans la plupart des sites archéologiques. Le présent article a pour objectif de discuter des modalités d'exploitation des rhyolites, en Corse, à partir des résultats des travaux archéologiques entrepris sur les filons du Monte d'Oro (Vivario) en Haute-Corse et de l'analyse des principaux sites connus du 3e millénaire. Ces résultats suggèrent que l'approvisionnement en rhyolites s'effectuait de manière ponctuelle, au cours de déplacements, vraisemblablement motivés par d'autres besoins que la seule acquisition de matières premières lithiques.Costa Laurent Jacques, Ottaviani-Spella Marie-Madeleine, Nicolle Fabrice, Berlinghi Antoine. Contribution à l'étude des modalités d'exploitation des rhyolites en Corse : l'exemple des filons du Monte d'Oro (Vivario, Haute-Corse). In: Bulletin de la Société préhistorique française, tome 99, n°4, 2002. pp. 785-791