Fig. 5. Prospero is required to upregulate gcm expression in NGB lineages. (A) Prospero is required for Gcm expression in NGB 6-4T glial progeny. Paired confocal images are from the same focal plane. Ventral view; midline is towards the left; anterior is upwards. Expression of Gcm in the Engrailed-negative lateral glial precursor is seen at the bottom right of most images. (i) prospero mutants show normal levels Gcm in the predivisional NGB 6-4T (arrowhead). (ii) By the time the G daughter cell migrates medially, both the G cell (arrow) and post-divisional NGB 6-4T (arrowhead) have down-regulated Gcm. (iii) Later in development all G cell progeny have severely reduced Gcm levels and they fail to migrate to the midline (arrows). Compare with Fig. 1A. The graph shows a quantitation of the percentage of Gcm-positive cells in the NGB 6-4T lineage in wild type (n=61) and prospero mutants (n=90): wild type Gcm levels, black bar; strongly reduced Gcm levels, gray bar; and lack of detectable Gcm, no bar. G, G alone; G1+G2, the first two G-derived cells; G1+G2+G3, all three G-derived cells. (B) Prospero is required for Gcm expression in the NGB 7-4 lineage (oriented as in A). In the wild type, there are 4-5 Gcm-positive progeny (dotted circle) derived from NGB 7-4 (arrowhead). In prospero mutants, Gcm expression is severely reduced (dotted circle). The graph shows a quantitation of the percentage of Gcm-positive cells in the NGB 7-4 lineage in wild type (n=45) and prospero mutant (n=76) hemisegments. Bars indicate Gcm levels as described in A.