Fig. 4. Changes in apoptosis associated with brain patterning defects. All embryos are at late ES13, and are view dorsally at the level of the preoral brain commissure. Acridine Orange staining for apoptotic cells (green) is superimposed onto a DIC image taken simultaneously on a confocal microscope. The outline of the brain is indicated by white broken lines for reference. (A) The wild-type brain shows groups of apoptotic cells at the dorsomedial edges of the brain hemispheres (arrows). (B) In fkh loss-of-function embryos, there is a reduction in the number of apoptotic cells at the dorsal midline (arrow). (C) A similar reduction in the number of apoptotic cells is seen in tin loss-of-function embryos.