Fig. 4. In vitro analysis of neuronal clones derived from single CNS precursors taken from sal null (A,C,E) or wild type (B,D) embryos. After 18 hours of culture, mutant clones (A) had thinner and poorly branched fibres compared with wild-type clones (B). After 4 days in culture, the branches in mutant clones (C) were still less elaborated than in wild-type clones (D). Mutant clones were often surrounded by cell debris (C) and their branches formed `anastomosing' structures (arrows in E) not observed in wild-type clones. Staining for the glial marker Repo (arrowhead in E) indicated that mutant clones comprised neuronal and glial cells.