Careful study of genes responsible for rare mendelian forms of human neurological disorders is a powerful approach for gaining insight into the causes, treatment, and potential cure for common, related diseases. The neuronal KCNQ genes were recently discovered as the result of the search for mutant genes causing Benign Familial Neonatal Convulsions, an autosomal dominant epileptic syndrome associated with seizures in infancy and throughout life. Mutations in neuronal KCNQ genes also result in myokymia (a peripheral nerve disorder) and deafness. The KCNQ genes encode subunits of voltage-dependent potassium channels. The long term goals of the proposed work is to understand the in vivo functions of these neuronal KCNQ channels, in order to better understand basic brain signaling mechanisms and to exploit these mechanisms for neurological therapeutics. KCNQ channels regulate neuronal excitability through their intrinsic, voltage-gated activity at particular locations in brain, and through their ability to serve as effectors for neurotransmitter receptors and intracellular signaling pathways. Determining specifically where KCNQ channels are localized in brain circuits, and how receptors, pathways and interacting proteins modulate their activity in the brain, will enhance our ability to exploit these channels as therapeutic targets in conditions involving excessive excitability or alterations and imbalances in modulatory neurotransmission, such as epilepsy and pain syndromes. The current proposal focuses on KCNQ channels on axons in hippocampus, where previous work by the investigator and others indicates KCNQ channels play important roles. It exploits newly available mutant mice with KCNQ2 mutations and phenotypes of increased seizure susceptibility and spontaneous seizures.
The specific aims are to: (1) map the localization of KCNQ subunits in mammalian septohippocampal networks in developing and mature brain of normal and mutant rodents; (2) define the mechanisms targeting KCNQ subunits to axon initial segments and nodes of Ranvier; and (3) analyze the function of axonal KCNQ channels at the subcellular and cellular level.
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