Fig. 3: Nucleated chromatin rigidification results in a spool-like organization.
From: Biophysical ordering transitions underlie genome 3D re-organization during cricket spermiogenesis
A Chromatin re-organization via a nucleated, in cis propagation of fiber rigidification. Fiber segments undergoing gradual stiffening are marked in green, denoting a putative peak in acetylation activity. Fully-rigidified segments are depicted in blue, representing SNBP-based chromatin. Unmodified chromatin regions are rendered in black. B Same as Fig. 3a in full-fiber view. The segregation of rigidified chromatin segments into a toroidal structure at the nuclear periphery is clearly visible, and leads to the formation of a spool-like ordered structure towards the late round spermatid stage. C Simulated radial monomer density profiles at different rigidified fiber fractions. Distance is normalized to nucleus radius. Nucleated rigidification results in a significantly more pronounced peripheral accumulation of chromatin than the simple uniform stiffening process (Fig. 2E), although the mechanical properties of the fully-rigidified fiber are identical in both cases. D Radially-averaged local alignment parameter \(\left\langle \alpha (r)\right\rangle\), as computed from the simulations (black line) and evaluated from TEM images at the spermatocyte (purple box) and elongating stage (gray box). The width of the experimental bars represents the standard error of the mean (see “Methods” section).
