Phase separation at the heart of the cell nucleus

Publication of the LBMC  in the journal PNAS on August 7, 2023. Communication of CNRS-INSB on September 8, 2023. The organization of heterochromatin, the part of the genome containing repressed genes, into three-dimensional compartments is essential for the correct functioning of cells. But the mechanisms governing this organization are still not fully understood. In a study published in PNAS , scientists have combined theoretical approaches with measurements on Drosophila embryos and shown that the structural and dynamic properties of these compartments are consistent with an organization pattern based on liquid-liquid phase separation coupled with the intrinsic mechanics of chromosomes. The spatial segregation of pericentromeric heterochromatin (PCH) into distinct, membrane-less nuclear compartments involves the binding of Heterochromatin Protein 1 (HP1) to H3K9me2/3-rich genomic regions. While HP1 exhibits liquid-liquid phase separation properties in vitro, its mechanistic impact on the structure and dynamics of PCH condensate formation in vivo remains largely unresolved.