Computerized analysis of pericentromere structures and organization in preimplantation mouse embryos. Panel A-A”: Segmentation and classification of the pericentromeric signals in a late 2-cell nucleus. (A) Original confocal section of the 3D-FISH analysis with the pericentromeric probe; (A’) Same confocal section after segmentation and classification into “compact” (red), “elongated” (green), or “non analyzed” (blue) signals; (A”) 3D reconstruction of the pericentromeric signals after segmentation and classification. Panel B: Proximity between elongated pericentromeres and NPBs/nucleoli was analyzed, and five different categories were distinguished: Null, Close, Low, Medium, and Strong. The graph represents the percentage of each group at 2-cell, 4-cell, and 8-cell stages. Panel C: Example of a pericentromeric signal classified as “elongated” through computerized analysis, although it would be classified as “compact” by visual analysis. Note the less intense “core” of this pericentromeric signal. Panel D-D’: Percentage of “compact” (blue) and “elongated” pericentromeres in several nuclei from early versus late 2-cell stage embryos. Panel E: Box plots representing the ratio of “compact” pericentromeres relative to the total observed pericentromeric signals from 2-cell to 32-cell stages (early (E) and late (L) embryos have been analyzed separately at the 2-cell, 4-cell, and 8-cell stages). The number of nuclei analyzed at each stage is indicated in brackets above the box plots. Differences in mean values between stages with different subscripts are highly significant (p < 0.0001) to significant (p = 0.0079).