Histone variants are key epigenetic players, whose incorporation confers novel structural and functional properties of the nucleosome. The histone variant H2A.Z, a member of the H2A family, exists as two major isoforms (H2A.Z-1 and -2). Studies have implicated both H2A.Z isoforms in several nuclear events, including transcription, repair and mitosis. H2A.Z is likely to be redistributed and recruited to pericentromeric/centromeric chromatin at the onset of mitosis, and the centromeric H2A.Z nucleosome appears to have a unique structure. However, how H2A.Z nucleosomes function remains highly elusive. Elucidating these questions will advance our understanding of fundamental chromatin epigenetics and shed light on the molecular mechanisms underlying the role of histone variants in epigenetic disorders.
Objectives: The aims of this project are to dissect the function of H2A.Z in mitosis and transcription as well as to shed light on the involvement of H2A.Z in both skin development and ageing of skeletal muscle.
Methodology: This is an interdisciplinary project that will use the methods of structural biology [X-ray diffraction and cryo-electron microscopy (cryo-EM), including phase-plate cryo-EM], a cohort of biochemistry techniques (EMSA, OH footprinting and pull-down assays), proteomics and genome-wide approaches (RNA-seq, ChIP-seq, MeDip-seq) to understand the function of H2A.Z in both mitosis and transcription. The unique conditional knock-out (cKO) mouse lines will be used to deplete both H2A.Z isoforms in either skin or skeletal muscle, to analyze the resulting phenotypes and to uncover the role of H2A.Z in skin renewal and muscle ageing.
Consortium: The project is an interdisciplinary collaboration involving four research teams located in Strasbourg, Grenoble and Lyon. The work envisaged is a comprehensive effort that combines expertise in the structural biology, biophysics, biochemistry, proteomics, mouse genetics and cell biology of chromatin.
Expected results and impact: This project is expected to generate new knowledge regarding: (i) the implication of H2A.Z in mitosis and the understanding of its mitotic function, (ii) the involvement of H2A.Z in both basal and activated transcription by using in cellulo and mouse models, and the role(s) of H2A.Z in both (iii) skin formation and (iv) the aging of skeletal muscle. This foundational knowledge will advance our understanding of the organization of the genome by unravelling the genetic and epigenetic mechanisms that underlie the function of histone variants in modulating the chromatin landscape and will elucidate their role in such important processes as organ formation and ageing.
Biomedical relevance: Understanding the organization of histone variant chromatin and the regulatory role played by the histone variant H2A.Z is critical for understanding how several severe diseases arise at the molecular level. Alterations in H2A.Z chromatin are associated with chromosome segregation defects as well as perturbed cytokinesis. These lead to meiotic aneuploidy, a major cause of spontaneous abortions, infertility and birth defects, including Down, Edwards and Patau syndromes that affect a significant proportion of newborns every year. This project is expected to advance our understanding of the detailed molecular mechanisms that give rise to the above disorders.
Monsieur Ali Hamiche (INSTITUT DE GENETIQUE ET DE BIOLOGIE MOLECULAIRE ET CELLULAIRE)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
IGBMC INSTITUT DE GENETIQUE ET DE BIOLOGIE MOLECULAIRE ET CELLULAIRE
IAB Institut for Advanced Biosciences
INMG Institut NeuroMyoGène
IBS INSTITUT DE BIOLOGIE STRUCTURALE
Help of the ANR 670,661 euros
Beginning and duration of the scientific project: September 2018 - 48 Months