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International audience; Sox9 is a member of the gene family of SOX transcription factors, which is highly conserved among vertebrates. It is involved in different developmental processes including gonadogenesis. In all amniote species examined thus far, Sox9 is expressed in the Sertoli cells of the male gonad, suggesting an evolutionarily conserved role in testis development. However, in the anamniotes, fishes and amphibians, it is also expressed in the oocyte but the significance of such an expression remains to be elucidated. Here, we have investigated the nuclear localization of the SOX9 protein in the oocyte of three amphibian species, the urodelan Pleurodeles waltl, and two anurans, Xenopus laevis and Xenopus tropicalis. We demonstrate that SOX9 is associated with ribonucleoprotein (RNP) transcripts of lampbrush chromosomes in an RNA-dependent manner. This association can be visualized by Super-resolution Structured Illumination Microscopy (SIM). Our results suggest that SOX9, known to bind DNA, also carries an additional function in the posttranscriptional processes. We also discuss the significance of the acquisition or loss of Sox9 expression in the oocyte during evolution at the transition between anamniotes and amniotes.

The bilharziasis is a human parasitic disease which is in the second world rank, after the malaria, in terms of morbidity and mortality inferred by the parasite. More than 200 million people are infested in 74 countries and more than 200 000 people die a year (Chitsulo and al. 2004; Gryseels and al. 2006). Schistosoma mansoni, here studied, is responsible for the intestinal bilharziasis. This parasite possesses a complex life cycle, getting through necessarily two hosts: an intermediate host mollusk of fresh water and a human definitive host or murin. During the cycle of development, the various stages are exposed to diverse environments. For example, the embryonic stages can be confronted with several intermediate hosts (origin of mollusk) or definitive (human being or murin). My thesis research concerns the influence of the environment on the épigénome of Schistosoma mansoni. The epigenetic information is an additional source for the creation of variants phenotypic, we propose that some of these variants can be inherited and selected, and so confer an advantage to the parasite. To invest this hypothesis we decided to modify the environment of the parasite of a way biotick and abiotique, when it develops within the definitive host or when it is for the contact of the intermediate host. Indeed, Schistosoma mansoni is an endoparasite thus every host, in whom he is going to remain, represents its direct environment. For it we used a drug anti-helminthe and an intermediate host allopatrique. The answer of the parasite to the various changes of environments was analyzed by the population (milked by life history) in the molecule (genome, épigénome, transcriptome). The new techniques of molecular biology and massive sequencing allowed us to realize global studies. During this thesis research, the various experimental evolutions led to two riddles: (1) " Fast Adaptation of Schistosoma mansoni to a drug anti-helminthes " and (2) " Fast Adaptation of Schistosoma mansoni to South America ". The results obtained for the latter brought the third riddle: (3) " Sexual Differentiation in the absence of gene W-spécifique in a system ZW "!; La bilharziose est une maladie parasitaire humaine qui se trouve au second rang mondial, après la malaria, en termes de morbidité et de mortalité induites par le parasite. Plus de 200 millions de personnes sont infestées dans 74 pays et plus de 200 000 personnes décèdent par an (Chitsulo et al. 2004; Gryseels et al. 2006). Schistosoma mansoni, ici étudié, est responsable de la bilharziose intestinale. Ce parasite possède un cycle de vie complexe, passant obligatoirement à travers deux hôtes : un hôte intermédiaire mollusque d'eau douce et un hôte définitif humain ou murin. Lors du cycle de développement, les différents stades sont exposés à divers environnements. Par exemple, les stades larvaires peuvent être confrontés à plusieurs hôtes intermédiaires (souche de mollusque) ou définitifs (humain ou murin). Mes travaux de thèse concernent l'influence de l'environnement sur l'épigénome de Schistosoma mansoni. L'information épigénétique est une source supplémentaire pour la création de variants phénotypiques, nous proposons que certains de ces variants puissent être hérités et sélectionnés, et ainsi conférer un avantage au parasite.Pour investir cette hypothèse nous avons décidé de modifier l'environnement du parasite de façon biotique et abiotique, lorsqu'il se développe au sein de l'hôte définitif ou lorsqu'il est au contact de l'hôte intermédiaire. En effet, Schistosoma mansoni est un endoparasite donc chaque hôte, dans lequel il va se maintenir, représente son environnement direct. Pour cela nous avons utilisé une drogue anti-helminthe et un hôte intermédiaire allopatrique. La réponse du parasite aux différents changements d'environnements a été analysée de la population (traits d'histoire de vie) à la molécule (génome, épigénome, transcriptome). Les nouvelles techniques de biologie moléculaire et de séquençage massif nous ont permis de réaliser des études globales. Lors de ces travaux de thèse, les différentes évolutions expérimentales ont mené à deux énigmes : (1) " Adaptation rapide de Schistosoma mansoni à une drogue anti-helminthes " et (2) " Adaptation rapide de Schistosoma mansoni à l'Amérique du Sud ". Les résultats obtenus pour cette dernière ont amené une troisième énigme : (3) "Différenciation sexuelle en l'absence de gène W-spécifique dans un système ZW"!

We describe a collection of P-element insertions that have considerable utility for generating custom chromosomal aberrations in Drosophila melanogaster. We have mobilized a pair of engineered P elements, p[RS3] and p[RS5], to collect 3243 lines unambiguously mapped to the Drosophila genome sequence. The collection contains, on average, an element every 35 kb. We demonstrate the utility of the collection for generating custom chromosomal deletions that have their end points mapped, with base-pair resolution, to the genome sequence. The collection was generated in an isogenic strain, thus affording a uniform background for screens where sensitivity to genetic background is high. The entire collection, along with a computational and genetic toolbox for designing and generating custom deletions, is publicly available. Using the collection it is theoretically possible to generate >12,000 deletions between 1 bp and 1 Mb in size by simple eye color selection. In addition, a further 37,000 deletions, selectable by molecular screening, may be generated. We are now using the collection to generate a second-generation deficiency kit that is precisely mapped to the genome sequence.

Background: In the leuphotrochozoan parasitic platyhelminth Schistosoma mansoni, male individuals are homogametic (ZZ) whereas females are heterogametic (ZW). To elucidate the mechanisms that led to the emergence of sex chromosomes, we compared the genomic sequence and the chromatin structure of male and female individuals. As for many eukaryotes, the lower estimate for the repeat content is 40%, with an unknown proportion of domesticated repeats. We used massive sequencing to de novo assemble all repeats, and identify unambiguously Z-specific, W-specific and pseudoautosomal regions of the S. mansoni sex chromosomes. Results: We show that 70 to 90% of S. mansoni W and Z are pseudoautosomal. No female-specific gene could be identified. Instead, the W-specific region is composed almost entirely of 36 satellite repeat families, of which 33 were previously unknown. Transcription and chromatin status of female-specific repeats are stage-specific: for those repeats that are transcribed, transcription is restricted to the larval stages lacking sexual dimorphism. In contrast, in the sexually dimorphic adult stage of the life cycle, no transcription occurs. In addition, the euchromatic character of histone modifications around the W-specific repeats decreases during the life cycle. Recombination repression occurs in this region even if homologous sequences are present on both the Z and W chromosomes. Conclusion: Our study provides for the first time evidence for the hypothesis that, at least in organisms with a ZW type of sex chromosomes, repeat-induced chromatin structure changes could indeed be the initial event in sex chromosome emergence. Made available in DSpace on 2020-04-15T00:58:37Z (GMT). No. of bitstreams: 1 gb2012132r14.pdf: 1862898 bytes, checksum: 698a905e28096b6b6554c71aa717c8c2 (MD5) Previous issue date: 2012