Distinct Material States of Interphase Chromatin in Normal and Cancer Cells Revealed by CRISPR Live-cell Imaging

Characterizing structural and functional differences of the genome in normal and cancer cells helps to understand the mechanism driving cell transformation during cancer progression. The human genome is hierarchically organized in the cell nucleus. However, how genetic and epigenetic errors affect chromatin organization and dynamics essential in gene regulation and cellular functions is still not fully understood. Using CRISPR-based live-cell DNA imaging techniques, our recent studies demonstrated distinct large-scale chromatin conformations (~17 Mb) in normal (hFOB1.19) and cancerous (U2OS) osteoblasts, controlled by differential regulatory mechanisms. We hypothesize that distinct chromatin conformations possess different material states of chromatin in normal and cancer cells. In this work, we measured the viscoelasticity of chromatin by tracking genomic locus dynamics and calculating dynamic (complex) modulus. We found that the chromatin in normal osteoblasts is more solid-like than that in osteosarcoma cells. This work establishes the correspondence between interphase chromatin conformations and material states using CRISPR-based live-cell DNA imaging techniques that allow non-invasively studying the local rheological properties of chromatin in the live cell nucleus.