caa a22 4500 475768434 CHVBK 20180406123613.0 cr unu---uuuuu 170329e20001001xx s 000 0 eng 10.1007/s004270000097 doi (NATIONALLICENCE)springer-10.1007/s004270000097 Page Damon T. MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK e-mail: paged@mrc-lmb.cam.ac.uk Tel.: +44-1223-402282, Fax: +44-1223-412142, GB aut labial acts to initiate neuronal fate specification, but not axon pathfinding, in the embryonic brain of Drosophila [Elektronische Daten] [Damon T. Page] Abstract : Drosophila embryos lacking the homeotic gene labial (lab) show two types of defects in brain development: (1) cells in the brain lab domain do not express neuronal markers or extend axons, and (2) axons originating from outside the lab domain stop at this region or project ectopically. A severe disruption of neuronal patterning and axon scaffolding is the net result. It is not clear how the absence of Lab can result in both neuronal fate defects and axon pathfinding defects. I have expressed Lab in short pulses in lab loss-of- function embryos, and this gave almost complete rescue; for example, the tritocerebral commissure was restored. Rescue only occurred when Lab was provided at the time when cells in the brain are adopting a neuronal fate. Lab expression later, when the first axons are seen in the lab domain, did not give rescue. I conclude that Lab expression helps to establish neuronal identity in the lab domain, and these neurons act as a permissive substrate for axon extension. However, Lab itself is not required at the time of axon pathfinding through this region. Springer-Verlag Berlin Heidelberg, 2000 Key words Drosophila nationallicence Brain nationallicence labial nationallicence Homeodomain protein nationallicence Tritocerebrum nationallicence https://doi.org/10.1007/s004270000097 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s004270000097 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Page Damon T. MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK e-mail: paged@mrc-lmb.cam.ac.uk Tel.: +44-1223-402282, Fax: +44-1223-412142, GB aut Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer