[Visualization of selective transsynaptic neural pathways using a genetic method].

Functional logic employed by the nervous system for coding and processing information is determined by the wiring patterns among specific types of neurons. Therefore, detailed knowledge about neuronal circuits is essential for understanding the wide range of brain functions. In our opinion, an effective and long-awaited method for analyzing the neuronal connectivity patterns would be to selectively deliver tracers to specific types of neurons and simutaneously performing transsynaptic labeling of the target neurons. A unique property of plant lectins, such as wheat germ agglutinin (WGA) have the unique property of traveling across synapses and this property has been applied in classical neuroanatomical studies in order to label various neural pathways. In 1999, we developed a novel strategy that employs WGA cDNA as a transgene in order to visualize selective and functional neural pathways. Over the last decade, this method has gained popularity; further with substantial technical improvement and refinement, this method has been successfully employed for the analysis of various neural systems such as the olfactory, visual, gustatory, somatosensory, motor, and serotonergic systems. However, a few studies that employed this method failed because of the misinterpretation of the results. In this review, I summarize the principle, application, recent progress, and caveats of the WGA transgene technology.