Determination of Angptl4 mRNA as a Diagnostic Marker of Primary and Metastatic Clear Cell Renal-Cell Carcinoma

International audienceBACKGROUND: We have previously shown that angiopoietin-like 4 (angptl4) mRNA, a hypoxia-inducible gene, is highly expressed in clear cell renal-cell carcinoma (ccRCC), the most common subtype of RCC for which no specific marker is available. We here investigated whether angptl4 mRNA 1) could be a useful diagnostic and/or prognostic marker of ccRCC in a large and comprehensive retrospective series, 2) induction is dependent on the VHL status of tumors. METHODOLOGY/PRINCIPAL FINDINGS: Using in situ hybridization, we report that angptl4 mRNA is expressed in 100% of both sporadic (n = 102) and inherited (n = 6) primary ccRCCs, without any statistical association with nuclear grade (p = 0.39), tumor size (p = 0.09), stage grouping (p = 0.17), progression-free survival (p = 0.94), and overall survival (p = 0.80). Angptl4 mRNA was also expressed in 26 (87%) of 30 secondary ccRCCs but neither in any other secondary RCCs (n = 7). In contrast, angptl4 mRNA was neither expressed in 94% non-ccRCC renal tumors (papillary RCCs (n = 46), chromophobe RCCs (n = 28), and oncocytomas (n = 9)), nor in non-renal clear cell carcinomas (n = 39). Angptl4 expression was also examined in tumors associated (n = 23) or not associated (n = 66) with VHL disease. 40 (98%) hemangioblastomas expressed angptl4 whereas all pheochromocytomas (n = 23) and pancreatic tumors (n = 25) were angptl4-negative, whatever their VHL status. CONCLUSIONS/SIGNIFICANCE: Angptl4 mRNA expression was highly associated with ccRCC (p = 1.5 10(-49), Chi square test) allowing to define its expression as a diagnosis marker for primary ccRCC. Moreover, angptl4 mRNA allows to discriminate the renal origin of metastases of clear-cell carcinomas arising from various organs. Finally, inactivation of VHL gene is neither necessary nor sufficient for angptl4 mRNA induction

eXtraembryonic ENdoderm (XEN) Stem Cells Produce Factors that Activate Heart Formation

Initial specification of cardiomyocytes in the mouse results from interactions between the extraembryonic anterior visceral endoderm (AVE) and the nascent mesoderm. However the mechanism by which AVE activates cardiogenesis is not well understood, and the identity of specific cardiogenic factors in the endoderm remains elusive. Most mammalian studies of the cardiogenic potential of the endoderm have relied on the use of cell lines that are similar to the heart-inducing AVE. These include the embryonal-carcinoma-derived cell lines, END2 and PYS2. The recent development of protocols to isolate eXtraembryonic ENdoderm (XEN) stem cells, representing the extraembryonic endoderm lineage, from blastocyst stage mouse embryos offers new tools for the genetic dissection of cardiogenesis.Here, we demonstrate that XEN cell-conditioned media (CM) enhances cardiogenesis during Embryoid Body (EB) differentiation of mouse embryonic stem (ES) cells in a manner comparable to PYS2-CM and END2-CM. Addition of CM from each of these three cell lines enhanced the percentage of EBs that formed beating areas, but ultimately, only XEN-CM and PYS2-CM increased the total number of cardiomyocytes that formed. Furthermore, our observations revealed that both contact-independent and contact-dependent factors are required to mediate the full cardiogenic potential of the endoderm. Finally, we used gene array comparison to identify factors in these cell lines that could mediate their cardiogenic potential.These studies represent the first step in the use of XEN cells as a molecular genetic tool to study cardiomyocyte differentiation. Not only are XEN cells functionally similar to the heart-inducing AVE, but also can be used for the genetic dissection of the cardiogenic potential of AVE, since they can be isolated from both wild type and mutant blastocysts. These studies further demonstrate the importance of both contact-dependent and contact-independent factors in cardiogenesis and identify potential heart-inducing proteins in the endoderm

A Comparative Analysis of Extra-Embryonic Endoderm Cell Lines

Prior to gastrulation in the mouse, all endodermal cells arise from the primitive endoderm of the blastocyst stage embryo. Primitive endoderm and its derivatives are generally referred to as extra-embryonic endoderm (ExEn) because the majority of these cells contribute to extra-embryonic lineages encompassing the visceral endoderm (VE) and the parietal endoderm (PE). During gastrulation, the definitive endoderm (DE) forms by ingression of cells from the epiblast. The DE comprises most of the cells of the gut and its accessory organs. Despite their different origins and fates, there is a surprising amount of overlap in marker expression between the ExEn and DE, making it difficult to distinguish between these cell types by marker analysis. This is significant for two main reasons. First, because endodermal organs, such as the liver and pancreas, play important physiological roles in adult animals, much experimental effort has been directed in recent years toward the establishment of protocols for the efficient derivation of endodermal cell types in vitro. Conversely, factors secreted by the VE play pivotal roles that cannot be attributed to the DE in early axis formation, heart formation and the patterning of the anterior nervous system. Thus, efforts in both of these areas have been hampered by a lack of markers that clearly distinguish between ExEn and DE. To further understand the ExEn we have undertaken a comparative analysis of three ExEn-like cell lines (END2, PYS2 and XEN). PYS2 cells are derived from embryonal carcinomas (EC) of 129 strain mice and have been characterized as parietal endoderm-like [1], END2 cells are derived from P19 ECs and described as visceral endoderm-like, while XEN cells are derived from blastocyst stage embryos and are described as primitive endoderm-like. Our analysis suggests that none of these cell lines represent a bona fide single in vivo lineage. Both PYS2 and XEN cells represent mixed populations expressing markers for several ExEn lineages. Conversely END2 cells, which were previously characterized as VE-like, fail to express many markers that are widely expressed in the VE, but instead express markers for only a subset of the VE, the anterior visceral endoderm. In addition END2 cells also express markers for the PE. We extended these observations with microarray analysis which was used to probe and refine previously published data sets of genes proposed to distinguish between DE and VE. Finally, genome-wide pathway analysis revealed that SMAD-independent TGFbeta signaling through a TAK1/p38/JNK or TAK1/NLK pathway may represent one mode of intracellular signaling shared by all three of these lines, and suggests that factors downstream of these pathways may mediate some functions of the ExEn. These studies represent the first step in the development of XEN cells as a powerful molecular genetic tool to study the endodermal signals that mediate the important developmental functions of the extra-embryonic endoderm. Our data refine our current knowledge of markers that distinguish various subtypes of endoderm. In addition, pathway analysis suggests that the ExEn may mediate some of its functions through a non-classical MAP Kinase signaling pathway downstream of TAK1

A close look at the mammalian blastocyst: epiblast and primitive endoderm formation

International audienceDuring early development, the mammalian embryo undergoes a series of profound changes that lead to the formation of two extraembryonic tissues--the trophectoderm and the primitive endoderm. These tissues encapsulate the pluripotent epiblast at the time of implantation. The current model proposes that the formation of these lineages results from two consecutive binary cell fate decisions. The first controls the formation of the trophectoderm and the inner cell mass, and the second controls the formation of the primitive endoderm and the epiblast within the inner cell mass. While early mammalian embryos develop with extensive plasticity, the embryonic pattern prior to implantation is remarkably reproducible. Here, we review the molecular mechanisms driving the cell fate decision between primitive endoderm and epiblast in the mouse embryo and integrate data from recent studies into the current model of the molecular network regulating the segregation between these lineages and their subsequent differentiation

Cell cycle regulation during early mouse embryogenesis.

International audienceElaboration of a multicellular organism requires highly efficient coordination between proliferation and developmental processes. Accordingly, the embryonic cell cycle exhibits a high degree of plasticity; however, the mechanisms underlying its regulation in vivo remain largely unknown. The purpose of this review is to summarize the data on cell cycle regulation during the early mouse embryonic development, a period characterized by major variations in cell cycle parameters which correlate with important developmental transitions. In particular, we analyse the contribution of mutant mice to the study of in vivo cell cycle regulation during early development and discuss possible contributions of cell cycle regulators to developmental programs

Preimplantation development in ungulates: a 'ménage à quatre' scenario

International audienceIn ungulates, early embryonic development differs dramatically from that of mice and humans and is characterized by an extended period of pre-and peri-implantation development in utero. After hatching from the zona pellucida, the ungulate blastocyst will stay free in the uterus for many days before implanting within the uterine wall. During this protracted peri-implantation period, an intimate dialog between the embryo and the uterus is established through a complex series of paracrine signals. The blastocyst elongates, leading to extreme growth of extra-embryonic tissues, and at the same time, the inner cell mass moves up into the trophoblast and evolves into the embryonic disc, which is directly exposed to molecules present in the uterine fluids. In the peri-implantation period, uterine glands secrete a wide range of molecules, including enzymes, growth factors, adhesion proteins, cytokines, hormones, and nutrients like amino and fatty acids, which are collectively referred to as histotroph. The identification, role, and effects of these secretions on the biology of the conceptus are still being described; however, the studies that have been conducted to date have demonstrated that histotroph is essential for embryonic development and serves a critical function during the pre-and peri implantation periods. Here, we present an overview of current knowledge on the molecular dialogue among embryonic, extraembryonic, and maternal tissues prior to implantation. Taken together, the body of work described here demonstrates the extent to which this dialog enables the coordination of the development of the conceptus with respect to the establishment of embryonic and extra-embryonic tissues as well as in preparation for implantation. Reproduction (2020) 159 R151-R17

Analyse fonctionnelle du gène Ovum mutant candidate gene 1 chez la souris (du développement précoce à la régulation du cycle cellulaire)

Bien que très conservé au cours de l'évolution, le cycle cellulaire a été modifié pour répondre à de nouveaux programmes de développement. Récemment, les analyse de souris mutantes ont démontré que la plupart des régulateurs importants du cycle cellulaire ne sont pas nécessaires durant le développement ou bien ont fonction restreinte à un tissu, soulignant le fait qu'/n vivo de nombreux aspects du cycle restent encore à élucider. Durant la recherche de gènes candidats pour une mutation létale conditionnelle portée par la lignée murine DDK, un nouveau gène a été identifié : il s'agit du gène Ovum mutant candidate gène 1. L'inactivation d'Omcgl entraîne la mort des embryons aux alentours de l'implantation. De manière intéressante, cette létalité est précédée par défauts de cycle cellulaire notamment un allongement de la phase M accompagné de désorganisation du fuseau mitotique et de la plaque métaphasique. Le gène Omcgl apparaît donc comme un régulateur important dans le contrôle des premières divisions embryonnaires. Cette létalité très précoce ainsi que l'impossibilité de générer des cellules ES déficientes pour Omcgl ne permettent pas de définir plus précisément sa fonction. C'est la raison pour laquelle nous avons généré des lignées de MEFs et de cellules ES dans lesquelles l'expression de ce gène peut être contrôlée finement. Ces approches perte et gain de fonction ont été réalisées à partir du système inductible à la tétracycline et du système CRE/LoxP. Les conséquences de la modulation d'expression d'Omcgl ont été examinées en terme de prolifération/survie, capacité de différenciation et analyse globale du transcriptome.PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

The Cell Cycle of Early Mammalian Embryos: Lessons from Genetic Mouse Models

International audienceGenes coding for cell cycle components predicted to be essential for its regulation have been shown to be dispensable in mice, at the whole organism level. Such studies have highlighted the extraordinary plasticity of the embryonic cell cycle and suggest that many aspects of in vivo cell cycle regulation remain to be discovered. Here, we discuss the particularities of the mouse early embryonic cell cycle and review the mutations that result in cell cycle defects during mouse early embryogenesis, including deficiencies for genes of the cyclin family (cyclin A2 and B1), genes involved in cell cycle checkpoints (Mad2, Bub3, Chk1, Atr), genes involved in ubiquitin and ubiquitin-like pathways (Uba3, Ubc9, Cul1, Cul3, Apc2, Apc10, Csn2) as well as genes the function of which had not been previously ascribed to cell cycle regulation (Cdc2P1, E4F and Omcg1)