Transgenic Investigation of the Neural Circuitry of Memory

This protocol supports experiments aimed at elucidating the functional circuitry underlying mammalian learning and memory. As such, it has two basic aims: 1) generating and characterizing molecular genetic tools (transgenic mice and viral vectors) which express transgenes specifically in particular neuronal subtypes comprising the basic circuitry of the mammalian brain; and 2) using such tools to determine the various roles played by distinct cell types in brain regions related to memory by determining the network effects of manipulating their activity. Just as one cannot understand electronic circuits without an accurate circuit diagram or the ability to manipulate specific circuit elements, one cannot understand brain function without the ability to deliver transgenes to the myriad specific neuronal subtypes. We cannot REPLACE the mouse with an organism from lower orders as the mammalian brain is the only brain with a neocortex, nor can one model the role played by particular neuronal cell types without first identifying what they are, and knowing their properties. Trying to do so in cultured neurons would be akin to trying to understand how a car works purely by studying its water pump, and the brain is an infinitely more complex system. Since our goal is understanding normal brain function, our protocols have been REFINED to ensure not only minimal pain or discomfort, but to ensure that there are absolutely zero phenotypes to our transgenic lines that would occlude the interrogation of the specific neural circuit under study. Thus, any transgenic constructs leading to any noticeable effects on the animal in more than one founder line (random integration can occasionally result in a phenotypes) is discontinued. Finally, we are currently exploring the possibility that the same enhancer constructs may work in viral vectors as well. This would significantly REDUCE the number of animals needed because rather than having to make transgenic lines, we need only inject into the brain of a wildtype animal. While knowledge for its own sake is a societal good, this last approach has the most potential for direct benefits to society at large. Most disorders of the brain can be thought of as imbalances in neural circuits. Since the receptors for drugs are present in many brain regions, drugs may be able to do the right thing in the right circuit (i.e. the one out of balance), but they do the wrong thing in other circuits, leading to serious side effects. The generation of vectors capable of targeting therapeutic transgenes specific to particular cell types thus holds the promise of a new generation of circuit-specific therapeutic approaches. The change notification is simply to add the use of MR-guided FUS to augment the regional specifcity of systemically-applied EDGE AAV vectors.