Sink H, Whitington P M
Department of Zoology, University of New England, Armidale, NSW, Australia.
Development. 1991 Oct;113(2):701-7. doi: 10.1242/dev.113.2.701.
The Drosophila RP3 motor axon establishes a stereotypic arborisation along the adjoining edges of muscles 6 and 7 by the end of embryogenesis. The present study has examined the role of the target muscles in determining this axonal arborisation pattern. Target muscles were surgically ablated prior to the arrival of the RP3 axon. Following further development of the embryo in culture medium, the morphology of target-deprived RP3 motor axons was assayed by intracellular injection with the dye Lucifer Yellow. Axonal arborisations were formed on a variety of non-target muscles when muscles 6 and 7 were removed and these contacts were maintained into stage 16. The pattern of axonal arborisations over non-target muscles varied between preparations in terms of the number of muscles contacted, and the distribution of arborisations on individual muscles. Following removal of muscle 6, the RP3 motor axon frequently contacted muscle 7, and axonal arborisations were present along the distal edge of the muscle. In the absence of muscle 7, the RP3 axon often did not contact muscle 6 and when muscle 6 was contacted, the arborisation of RP3 was poorly developed. Axonal processes were retained on non-target muscles when only one target muscle was present. Therefore, the establishment of a stereotypic arborisation by the RP3 motor axon is apparently dependent on growth cone contact with both target muscles.
果蝇RP3运动轴突在胚胎发育结束时，沿着肌肉6和7的相邻边缘形成一种定型的分支。本研究探讨了靶肌肉在确定这种轴突分支模式中的作用。在RP3轴突到达之前，通过手术切除靶肌肉。在培养基中进一步培养胚胎后，通过向细胞内注射荧光黄染料来检测缺失靶标的RP3运动轴突的形态。当肌肉6和7被切除时，轴突分支在各种非靶肌肉上形成，并且这些接触一直维持到第16阶段。不同标本中，非靶肌肉上轴突分支的模式在接触的肌肉数量以及单个肌肉上分支的分布方面存在差异。在切除肌肉6后，RP3运动轴突经常接触肌肉7，并且在肌肉的远端边缘存在轴突分支。在没有肌肉7的情况下，RP3轴突通常不接触肌肉6，而当接触肌肉6时，RP3的分支发育不良。当仅存在一个靶肌肉时，轴突过程保留在非靶肌肉上。因此，RP3运动轴突形成定型分支显然依赖于生长锥与两个靶肌肉的接触。
