Figure 2. Inner-outer polarization of early embryonic somatic cells at the 4-cell stage.

Anterior is to the left and ventral is down. The germline precursor cell, P₂, is marked with an asterisk; the localization of PAC-1 and CDC-42 is not shown in this cell, which does not display the inner-outer asymmetry of PAR-6 seen in somatic cells. Early in the 4-cell stage, PAC-1 (yellow) localizes to the inner cortex, and PAR-6 (red) and CDC-42 (bright blue) localize to both the inner and outer cortex of the somatic cells. By the late 4-cell stage, in response to an unknown cue, CDC-42 is inactivated (light blue) by PAC-1 at the inner cortex, and active CDC-42 (bright blue) recruits PAR-6 (red) to the outer cortex of the somatic cells.