FIG. 3.

Quantitative image analysis methods. For quantitative analysis of the chromatin structure, 3D images of the chromosomal array of control (A, C, E, and G) or HP1-targeted (B, D, F, and H) cells were analyzed. A number of attributes were tested by two independent methods (see Materials and Methods). (A and B) Illustration of the quantitative selection methods for an optical section of the chromosomal array of a control sample (A) and an HP1β-targeted sample (B). (C and D) Illustration of the selection of a 3D region of interest, i.e., the EGFP-labeled chromosome region of an optical section of a control sample (C) and an HP1β-targeted sample (D). (E and F) Illustration of the filtering used to obtain the intensity gradient of the selected region of an optical section of a control sample (E) and an HP1β-targeted sample (F). (G and H) Illustration of the determined distinct spots within the EGFP-labeled chromosomal domain of an optical section of a control sample (G) and an HP1-targeted sample (H). Nuclei in panels A to H are on the same scale. Bar, 0.9 μm.