Morphogenèse, structures physiques et évolution biologique

International audienc

Darwin's theory revisited by today's biology

International audienc

Multiple Sox genes are expressed in stem cells or in differentiating neuro-sensory cells in the hydrozoan Clytia hemisphaerica

<p>Abstract</p> <p>Background</p> <p>The <it>Sox </it>genes are important regulators of animal development belonging to the HMG domain-containing class of transcription factors. Studies in bilaterian models have notably highlighted their pivotal role in controlling progression along cell lineages, various <it>Sox </it>family members being involved at one side or the other of the critical balance between self-renewing stem cells/proliferating progenitors, and cells undergoing differentiation.</p> <p>Results</p> <p>We have investigated the expression of 10 <it>Sox </it>genes in the cnidarian <it>Clytia hemisphaerica</it>. Our phylogenetic analyses allocated most of these <it>Clytia </it>genes to previously-identified Sox groups: SoxB (<it>CheSox2, CheSox3, CheSox10, CheSox13, CheSox14</it>), SoxC (<it>CheSox12</it>), SoxE (<it>CheSox1, CheSox5</it>) and SoxF (<it>CheSox11</it>), one gene (<it>CheSox15</it>) remaining unclassified. In the planula larva and in the medusa, the <it>SoxF </it>orthologue was expressed throughout the endoderm. The other genes were expressed either in stem cells/undifferentiated progenitors, or in differentiating (-ed) cells with a neuro-sensory identity (nematocytes or neurons). In addition, most of them were expressed in the female germline, with their maternal transcripts either localised to the animal region of the egg, or homogeneously distributed.</p> <p>Conclusions</p> <p>Comparison with other cnidarians, ctenophores and bilaterians suggest ancient evolutionary conservation of some aspects of gene expression/function at the <it>Sox </it>family level: (i) many <it>Sox </it>genes are expressed in stem cells and/or undifferentiated progenitors; (ii) other genes, or the same under different contexts, are associated with neuro-sensory cell differentiation; (iii) <it>Sox </it>genes are commonly expressed in the germline; (iv) <it>SoxF </it>group genes are associated with endodermal derivatives. Strikingly, total lack of correlation between a given <it>Sox </it>orthology group and expression/function in stem cells/progenitors <it>vs</it>. in differentiating cells implies that <it>Sox </it>genes can easily switch from one side to the other of the balance between these fundamental cellular states in the course of evolution.</p

Des voyages de Cook à l’expédition Santo 2006 : un renouveau des explorations naturalistes des îles du Pacifique

Les îles du Pacifique sont célèbres pour le très haut niveau d'endémisme et la grande vulnérabilité de leurs faunes et de leurs flores. Bien que la valeur scientifique et patrimoniale des écosystèmes du Vanuatu ait conduit à classer ce pays comme « point chaud » de la biodiversité, l'archipel souffre d'un déficit de connaissances en comparaison avec d'autres archipels du Pacifique Sud. L'expédition Santo 2006 sur l'île d'Espiritu Santo a eu pour but d'inventorier les faunes et les flores marines, terrestres et dulçaquicoles de cette île, en portant un accent particulier sur les compartiments négligés de la biodiversité. Tous les milieux, depuis les grands fonds marins au large de l'île jusqu'aux récifs, grottes, rivières, forêts et montagnes ont été inventoriés. Des échantillons de tissus biologiques, des enregistrements de sons et des photos numériques des organismes vivants ont complété les prélèvements d'organismes complets. Une attention particulière a été portée aux espèces introduites et invasives, afin d'établir un état de référence de la biodiversité de Santo en ce début du xxie siècle. L'expédition a impliqué sur le terrain plus de cent cinquante scientifiques, bénévoles et étudiants de vingt-cinq pays.The islands of the Pacific are famous for the high levels of endemism of their flora and fauna, and also the high levels of threats on their faunas and floras. Although Vanuatu is ranked as a biodiversity 'hotspot' under many global analyses, the country suffers from a deficit in scientific knowledge on its biota compared to other South Pacific island groups. The goal of the Santo 2006 expedition on the island of Espiritu Santo was to document the marine, freshwater, and terrestrial species of plants and animals living on or around the island, with a focus on the neglected components of biodiversity. All major environments have been sampled, from deep offshore sea bottoms to coral reefs, caves, rivers, forests and mountains; tissue clips, sound records and digital images supplement samples of dried or preserved specimens. In order to establish a baseline inventory of the biodiversity of Santo, special attention was given to introduced and invasive species. Field work involved over 150 scientists, volunteers and students from 25 countries

Introducing Trait Networks to Elucidate the Fluidity of Organismal Evolution Using Palaeontological Data

International audienceExplaining the evolution of animals requires ecological, developmental, paleontological, and phylogenetic considerations because organismal traits are affected by complex evolutionary processes. Modeling a plurality of processes, operating at distinct timescales on potentially interdependent traits, can benefit from approaches that are complementary treatments to phylogenetics. Here, we developed an inclusive network approach, implemented in the command line software ComponentGrapher, and analyzed trait co-occurrence of rhinocerotoid mammals. We identified stable, unstable, and pivotal traits, as well as traits contributing to complexes, that may follow to a common developmental regulation, that point to an early implementation of the postcranial Bauplan among rhinocerotoids. Strikingly, most identified traits are highly dissociable, used repeatedly in distinct combinations and in different taxa, which usually do not form clades. Therefore, the genes encoding these traits are likely recruited into novel gene regulation networks during the course of evolution. Our evo-systemic framework, generalizable to other evolved organizations, supports a pluralistic modeling of organismal evolution, including trees and networks

A French multicentric prospective prognostic cohort with epidemiological, clinical, biological and treatment information to improve knowledge on lymphoma patients: study protocol of the "REal world dAta in LYmphoma and survival in adults" (REALYSA) cohort.

BACKGROUND: Age-adjusted lymphoma incidence rates continue to rise in France since the early 80's, although rates have slowed since 2010 and vary across subtypes. Recent improvements in patient survival in major lymphoma subtypes at population level raise new questions about patient outcomes (i.e. quality of life, long-term sequelae). Epidemiological studies have investigated factors related to lymphoma risk, but few have addressed the extent to which socioeconomic status, social institutional context (i.e. healthcare system), social relationships, environmental context (exposures), individual behaviours (lifestyle) or genetic determinants influence lymphoma outcomes, especially in the general population. Moreover, the knowledge of the disease behaviour mainly obtained from clinical trials data is partly biased because of patient selection. METHODS: The REALYSA ("REal world dAta in LYmphoma and Survival in Adults") study is a real-life multicentric cohort set up in French areas covered by population-based cancer registries to study the prognostic value of epidemiological, clinical and biological factors with a prospective 9-year follow-up. We aim to include 6000 patients over 4 to 5 years. Adult patients without lymphoma history and newly diagnosed with one of the following 7 lymphoma subtypes (diffuse large B-cell, follicular, marginal zone, mantle cell, Burkitt, Hodgkin, mature T-cell) are invited to participate during a medical consultation with their hematologist. Exclusion criteria are: having already received anti-lymphoma treatment (except pre-phase) and having a documented HIV infection. Patients are treated according to the standard practice in their center. Clinical data, including treatment received, are extracted from patients' medical records. Patients' risk factors exposures and other epidemiological data are obtained at baseline by filling out a questionnaire during an interview led by a clinical research assistant. Biological samples are collected at baseline and during treatment. A virtual tumor biobank is constituted for baseline tumor samples. Follow-up data, both clinical and epidemiological, are collected every 6 months in the first 3 years and every year thereafter. DISCUSSION: This cohort constitutes an innovative platform for clinical, biological, epidemiological and socio-economic research projects and provides an opportunity to improve knowledge on factors associated to outcome of lymphoma patients in real life. TRIAL REGISTRATION: 2018-A01332-53, ClinicalTrials.gov identifier: NCT03869619

Are Hox Genes Ancestrally Involved in Axial Patterning? Evidence from the Hydrozoan Clytia hemisphaerica (Cnidaria)

Background: The early evolution and diversification of Hox-related genes in eumetazoans has been the subject of conflicting hypotheses concerning the evolutionary conservation of their role in axial patterning and the pre-bilaterian origin of the Hox and ParaHox clusters. The diversification of Hox/ParaHox genes clearly predates the origin of bilaterians. However, the existence of a "Hox code' predating the cnidarian-bilaterian ancestor and supporting the deep homology of axes is more controversial. This assumption was mainly based on the interpretation of Hox expression data from the sea anemone, but growing evidence from other cnidarian taxa puts into question this hypothesis. Methodology/Principal Findings: Hox, ParaHox and Hox-related genes have been investigated here by phylogenetic analysis and in situ hybridisation in Clytia hemisphaerica, an hydrozoan species with medusa and polyp stages alternating in the life cycle. Our phylogenetic analyses do not support an origin of ParaHox and Hox genes by duplication of an ancestral ProtoHox cluster, and reveal a diversification of the cnidarian HOX9-14 genes into three groups called A, B, C. Among the 7 examined genes, only those belonging to the HOX9-14 and the CDX groups exhibit a restricted expression along the oralaboral axis during development and in the planula larva, while the others are expressed in very specialised areas at the medusa stage. Conclusions/Significance: Cross species comparison reveals a strong variability of gene expression along the oral-aboral axis and during the life cycle among cnidarian lineages. The most parsimonious interpretation is that the Hox code, collinearity and conservative role along the antero-posterior axis are bilaterian innovations

Le modèle de compensation de l’agence ITER France

Le programme de mesures compensatoires mis en œuvre par l’Agence ITER France (CEA) est inédit tant par l’ampleur des actions engagées que par la démarche sous-tendue. Il est à l’image du programme de recherche ITER : innovant, de grande ampleur et unique en son genre. En vue d’accueillir le projet international ITER, le CEA (Commissariat à l’énergie atomique et aux énergies alternatives) est devenu acquéreur en 2006 d’un espace d’environ 180 ha au sein de la forêt de Cadarache (commune de Sai..

Le concept de plan d'organisation : Quelques aspects de son histoire / The concept of Bauplan : Some aspects of its history

Le Guyader Hervé. Le concept de plan d'organisation : Quelques aspects de son histoire / The concept of Bauplan : Some aspects of its history. In: Revue d'histoire des sciences, tome 53, n°3-4, 2000. pp. 339-380