In numb985 mutant embryos, glial migration is defective. In most hemisegments, the ventral peripheral glial and medial intersegmental peripheral glial cells fail to migrate dorsally to their wild-type destinations, but stay close to the nerve roots. However, in approximately 15% of cases these glial cells migrate too far and form a cluster close to the oenocytes. Furthermore, the dIPG is prevented from its ventral migration and stays close to where it originates.