Fig. 3.

Mud acts in neurons and its role in axon guidance is independent of Pins. (A) Mud has previously been identified to function in a Partner of inscuteable (Pins)-dependent pathway within neuroblasts. In common with the loss of mud, absence of pins does not lead to significant axon guidance deficits as revealed by the BP102 antibody. Embryos deficient for mud and pins also show no outgrowth defects. Absence of pins does not enhance the axon guidance defects associated with loss of fra, suggesting that Mud acts in a Pins-independent pathway to enhance the axon guidance defects caused by a loss of Netrin signalling. (B) Mud overexpression in Eagle-positive neurons causes a reduction of midline crossing by the EG neurons (arrowheads), which cross through the anterior commissure (AC), revealing that Mud can influence the guidance of neurons. PC, posterior commissure. (C) Venus-YFP-tagged Mud protein driven by the mud promoter is expressed widely within the CNS at stage 13 and becomes restricted to subsets of neurons and glia by stage 16. (D) Mud has been found to act downstream from Frizzled (Fz). Loss of fz has little impact on axon outgrowth at the midline as revealed by BP102, yet the double mutant NetA,B;fz is as severe as Df(1)KA9 or mud;fra. This suggests that Mud and Fz might act in the same pathway, which is supported by the fact that a mud;fz mutant phenotype resembles that of mud or fz single mutants.