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Identification et caractérisation d’ARNs localisés et de protéines maternels chez Clytia hemisphaerica

Abstract : In all metazoans, the first steps of embryonic development until the beginning of transcription from the zygotic genome, are governed by maternal factors. Accumulated and positioned in the egg during its formation, these molecules constitute nutritive resources and information necessary to direct establishement of the embryonic body plan, for example by determining axes of embryonic polarity and specifying development of the germ line. This thesis illustrates by three examples the important roleof maternal factors for development in the cnidarian Clytia hemisphaerica. Oogenesis and embryogenesis are easily accessible in this emerging model species, whose phylogenetic position at the base of the metazoan tree can help to understand ancestral mechanisms of animal biology. The first example concerns the phenomenon of mRNA localisation. Following the discovery of the determinant mRNAs CheFz1, CheFz3 and CheWnt3, I identified a new set of maternal RNAs, localised in different patterns within the Clytia egg. I initiated the study of the localization mechanisms of these mRNAs through a primary analysis of the 3’UTRs sequences and observation of the behaviour of microinjected fluorescent mRNAs. The particular case of BicD mRNA and protein, associated with dynein-dependent mRNA transport, was examined in more detail. The second part of my thesis concerns the centriolar protein Poc1, encoded by one of the characterized maternal mRNAs. Analysis of Poc1 in Clytia revealed a conserved localization of the protein at the centrosome and a requirement in cell division and gastrulation. The third part of my thesis concerns two linked protein families: Green Fluorescent Proteins and the bioluminescent proteins Clytins. Surprisingly, one GFP gene and one Clytin gene were found in Clytia to be maternally expressed, and their corresponding proteins to be co-targeted to mitochondria. In vivo energy transfer was demonstrated in eggs, showing functional coupling of these two maternal proteins. These observations suggest co evolution of the two genes and closely coupled functions. Overall, my thesis has provided new knowledge about the maternal phase in the development of an emergent model species.
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  • HAL Id : tel-03352775, version 1

Citation

Cécile Fourrage. Identification et caractérisation d’ARNs localisés et de protéines maternels chez Clytia hemisphaerica. Biologie animale. UPMC - Sorbonne University, 2010. Français. ⟨tel-03352775⟩

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