Ki-67 regulates heterochromatin organization in neurons and forms condensates with heterochromatic components

The dysregulation of chromatin organization has been associated with numerous forms of neurological disease. In the ANAPC7 neurodevelopmental syndrome, a disease mechanistically linked to defective proteasomal degradation, the mitotic protein Ki-67 accumulates abnormally in heterochromatin compartments. Here, we investigate Ki-67’s role in heterochromatin through in vivo examination of neurons from two relevant genetic mouse models, in vitro assays and computational studies.

We find that Ki-67 modulates the size and number of heterochromatin compartments in neurons. Furthermore, we demonstrate that an engineered Ki-67 construct enhances the propensity of HP1α and nucleosome arrays to form condensates in vitro, a process that is mediated through a complex network of electrostatic interactions and is robust to relevant histone post-translational modifications. These observations suggest that Ki-67 may regulate heterochromatin through a phase separation mechanism involving additional heterochromatin components, thus providing insights into the roles of Ki-67 during both typical neurodevelopment and in disease.

We thank the UC San Diego core facilities used in this study: Biomolecular and Proteomics Mass Spectrometry Facility, the Microscopy Core, the Nikon Imaging Center, the Molecular Mass Spectrometry Facility and the UCSD NMR Center. We are grateful for the technical assistance of J. Huang from the core facilities, as well as the computational resources provided by the Texas A&M High Performance Research Computing (HPRC).

Elathram for sharing various reagents. This work was supported by NIH grants R35GM138382 to G.T.D., R01NS138924 to C.J.F., R35GM153388 to J.M., K99GM159055 to T.M.P., a T32GM139795 fellowship to L.S.A. and a T32GM145427 fellowship to C.T. This publication includes data generated at the UC San Diego Institute for Genomic Medicine Genomics Center utilizing an Illumina NovaSeq X Plus that was purchased with funding from an NIH SIG grant (S10OD026929).

The UCSD Biomolecular and Proteomics Mass Spectrometry Facility is supported through grant S10OD021724, and the UCSD Microscopy Core is supported through grant P30NS047101. Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA, USA Lannah S. Abasi, Challana Tea, Rushabh Bhakta & Galia T.

Debelouchina Department of Pathology, University of California San Diego, La Jolla, CA, USA Challana Tea, Donald Le & Cole J. Ferguson Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX, USA Department of Chemistry, Texas A&M University, College Station, TX, USA Interdisciplinary Graduate Program in Genetics and Genomics, Texas A&M University, College Station, TX, USA Correspondence to Cole J. The authors declare no competing interests.