A genetic approach to visualization of multisynaptic neural pathways usingplant lectin transgene

The wiring patterns among various types of neurons via specific synaptic co nnections are the basis of functional logic employed by the brain for infor mation processing. This study introduces a powerful method of analyzing the neuronal connectivity patterns by delivering a tracer selectively to speci fic types of neurons while simultaneously transsynaptically labeling their target neurons. We developed a novel genetic approach introducing cDNA for a plant lectin, wheat germ agglutinin (WGA), as a transgene under the contr ol of specific promoter elements. Using this method, we demonstrate three e xamples of visualization of specific transsynaptic neural pathways: the mou se cerebellar efferent pathways, the mouse olfactory pathways, and the Dros ophila visual pathways. This strategy should greatly facilitate studies on the anatomical and functional organization of the developing and mature ner vous system.