Spatial Actin Structure Does Not Correlate With Nuclear Organization

Cells in situ exhibit a great variety of morphologies that intimately relates to phenotypic controls. Cell morphology regulates cytoskeletal organization, which in turn influences nuclear shape and organization [1–4]. The actomyosin cytoskeleton is connected to a structure known as the linker of nucleoskeleton and cytoskeleton (LINC) complex located on the nuclear membrane. LINC is believed to transmit deformation of the actin cytoskeleton into the nucleus and nucleoskeleton, change nuclear shape as well as chromatin conformation, and modulate gene expression [5, 6]. Khatau and coworkers reported a structure of apical actin dome, called the actin cap, that controls nuclear deformation through LINC [7]. In addition, actin stress fibers hves been shown to compress the nucleus laterally and increase chromatin condensation [4]. Based on these findings, we hypothesize that there is a spatial correlation between the actin cytoskeleton and chromatin density. In the current study, we investigated the role of actin cytoskeleton in nuclear deformation with respect to the z-axis. We found no spatial relationships between actin structure and nuclear deformation or chromatin condensation, suggesting that the actomyosin cytoskeleton acts globally to influence nuclear structure and additional structural components may contribute to the actin-nucleus mechanical coupling.