Graded expression of semaphorin-1a cell-autonomously directs dendritic targeting of olfactory projection neurons

Cell. 2007 Jan 26;128(2):399-410. doi: 10.1016/j.cell.2006.12.028.


Gradients of axon guidance molecules instruct the formation of continuous neural maps, such as the retinotopic map in the vertebrate visual system. Here we show that molecular gradients can also instruct the formation of a discrete neural map. In the fly olfactory system, axons of 50 classes of olfactory receptor neurons (ORNs) and dendrites of 50 classes of projection neurons (PNs) form one-to-one connections at discrete units called glomeruli. We provide expression, loss- and gain-of-function data to demonstrate that the levels of transmembrane Semaphorin-1a (Sema-1a), acting cell-autonomously as a receptor or part of a receptor complex, direct the dendritic targeting of PNs along the dorsolateral to ventromedial axis of the antennal lobe. Sema-1a also regulates PN axon targeting in higher olfactory centers. Thus, graded expression of Sema-1a contributes to connection specificity from ORNs to PNs and then to higher brain centers, ensuring proper representation of olfactory information in the brain.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Body Patterning / genetics
  • Cell Differentiation / genetics
  • Cues
  • Dendrites / metabolism*
  • Dendrites / ultrastructure
  • Drosophila melanogaster / cytology
  • Drosophila melanogaster / embryology*
  • Drosophila melanogaster / genetics*
  • Gene Expression Regulation, Developmental / genetics
  • Growth Cones / metabolism
  • Growth Cones / ultrastructure
  • Nerve Growth Factors / genetics
  • Nerve Growth Factors / metabolism
  • Neural Pathways / embryology
  • Neural Pathways / metabolism
  • Neural Pathways / ultrastructure
  • Olfactory Pathways / cytology
  • Olfactory Pathways / embryology*
  • Olfactory Pathways / metabolism
  • Olfactory Receptor Neurons / cytology
  • Olfactory Receptor Neurons / embryology*
  • Olfactory Receptor Neurons / metabolism
  • Semaphorins / genetics
  • Semaphorins / metabolism*
  • Signal Transduction / genetics
  • Smell / genetics
  • Synapses / genetics
  • Synapses / metabolism
  • Synapses / ultrastructure


  • Nerve Growth Factors
  • Semaphorins
  • semaphorin 1a, Drosophila