Fig. 3. Patterns of neurogenesis in the zebrafish hindbrain. Expression of asha (A,F), ashb (B,G), ngn1 (C,H), deltaA (D,I) and p27^xic1-a (E,J) at 18 hours (A-E) and 26 hours (F-J). At both these stages expression is excluded from boundaries (arrowheads). At 18 hours, transcripts for these genes are detected in all segments; ashb is detected at high levels in r4 (B). At 26 hours, stripes of proneural, deltaA and p27^xic1-a gene expression occur adjacent to hindbrain boundaries (asha is expressed in stripes adjacent to boundaries by 30 hours). deltaD transcripts (not shown) have a similar distribution to those of deltaA (D,I). Scale bar: 100 µm.