Molecular Assemblies and Genome Integrity
Programmed elimination of germline DNA during development provides plasticity to the somatic genome. Using the ciliate Paramecium tetraurelia as a model, we study the contribution of transposable elements and DNA double-strand break repair pathways to programmed DNA elimination, and the epigenetic control of genome rearrangements.
Paramecium is a unicellular eukaryote belonging to the phylum of ciliates. As other ciliates, it harbours two functionally distinct nuclei inside the same cytoplasm. The transcriptionally silent diploid micronucleus (MIC) contains the germline genome that is transmitted to sexual progeny following meiosis. The polyploid somatic macronucleus (MAC), responsible for gene transcription, contains a rearranged version of the germline genome. At each sexual cycle, the parental MAC is destroyed and a new MAC differentiates from a copy of the MIC-derived zygotic nucleus, a process that includes the elimination of a substantial fraction of germline DNA.
We study programmed genome rearrangements in a model species: Paramecium tetraurelia, which carries a ~100 Mb germline genome. During MAC development, the genome undergoes multiple rounds of endoreplication. Concomitantly, massive programmed genome rearrangements eliminate 25 to 30 % of germline DNA: (i) repeated sequences (transposons, minisatellites) are removed, leading to chromosome fragmentation or heterogeneous internal deletions; (ii) ~ 45,000 short, single copy and noncoding sequences scattered throughout the genome (IES, or internal eliminated sequences) are excised precisely to reconstitute functional open reading frames. At least a fraction of Paramecium IESs are degenerated remnants of transposons related to the Tc/mariner family.
Engineer - CNRS
Assistant Engineer CNRS
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ANR LaMarque (2018-2022)
ANR POLYCHROM (2019-2023)
ARC PARNHEJ (2021-2022)