TAG-1 knockdown causes defects in MLF axon-axon interactions.(a, b) Images from time-lapse sequence of MLF axon outgrowth in TAG1MO injected (a) and bal;Tg(pitx2c:gfp) (b) embryos. Ventral views, anterior to the left, midline is up. Asterisks denote the caudal-most nucMLF cell. Arrowheads label a growth cone that repeatedly samples neighboring axons, but fails to maintain these interactions. Arrows label a growth cone that contacts another MLF axon, subsequently retracts, and then emerges from the opposite side of the neuron. The time stamp shows hours: minutes. (c-e) Quantification of the average percentage of time each growth cone contacted another MLF axon after contact was initiated (c), the average duration of these contacts (d), and the average number of axons each growth cone contacted (e). *P < 0.001, two sample binomial comparison versus uninjected. #P < 0.001, two-tailed t-test versus uninjected. Error bars represent the standard error of the mean. N equals the number of axons (c, e) and growth cone-axon contacts (d). Scale bar = 25 μm.
|
