Fig. 7
hox5 Acts Independently of Time of Axon Formation
(A–D) hox5 expression does not delay the time of axon formation in anterior mX neurons. Stills from representative time lapses of control (A) or ectopic hox5-expressing (B–D) mX neurons (magenta or black in A′–D′) in a Tg(isl1:mRFP) background (green) are shown. Arrows indicate the emerging axon. See Movies S6, S7, S8, and S9.
(E) Quantification of (A)–(D). Each point represents a single embryo. Analysis was done by unpaired t test.
(F) Model of dual mechanisms governing mX neuron topographic map development. Anterior mX neurons arrive in the head periphery when only anterior PAs are available for innervation. Delayed axon initiation in posterior mX neurons results in delayed arrival in the periphery when posterior PAs have formed. Additionally, hox5 genes are expressed in posterior mX neurons and bias their axons toward posterior, hox5-expressing PAs.