Confinement with Myosin-II suppression increases heritable loss of chromosomes, using live-cell ChReporters

Abstract

Matrix around cells exerts many effects, some of which depend on the putative tumor suppressor Myosin-II, but whether such factors affect DNA sequences in a cell remains unclear. Here, live-cell monitoring of changes to chromosome copy numbers is developed and studied under diverse perturbations, including Myosin-II inhibition in confined mitosis. Squeezing of mitotic cells is seen in vivo and kills in vitro, but stem cells and cancer cells that survive show heritable loss of mono-allelic GFP/RFP-tagged constitutive genes that function as novel Chromosome-reporters (ChReporters). Myosin-II suppression increases such loss in 3D & 2D confinement but not in standard 2D, with "lethal" multipolar divisions proving myosin-dependent. Viable chromosome loss after confined mitosis associates more with mis-segregation than with multipolars or division number. Solid human tumors and teratomas in mice also show ChReporter loss and a confinement-signature of Myosin-II suppression, although losses are selected against in 2D culture. Heritable loss in rigid-confinement also appears independent of a spindle assembly checkpoint that functions in 2D. Confinement and myosin-II thus regulate pathways of heritable mechanogenetic change.