Contact between the C blastomere and the ABar blastomere directs the spindle orientation of ABar division in a wild-type Caenorhabditis elegans embryo

(Left) Contact between the C blastomere (membrane near contact outlined in blue) and the ABar blastomere (membrane near contact outlined in green). Focal depth (18 μm) of greatest contact is shown. (Right) Shortly after contact between the C and the ABar blastomeres, the mitotic spindle of the ABar blastomere (right line) is shifted toward the contact resulting in a cell division that is perpendicular to orientation of division of the neighboring ABpr blastomere (left line). Focal depth is 7.5 μm. [Supplemental movie from Imaging in Developmental Biology: A Laboratory Manual, Cold Spring Harbor Laboratory Press.]