Restless Legs Syndrome: Pathophysiology using Btbd9 Conditional Knockout Mice Grant uri icon

abstract

  • Restless legs syndrome (RLS) is a chronic sleep motor disorder characterized by unpleasant sensations in the legs and an uncontrollable urge to move them for relief. Past pathophysiological studies have associated RLS to the disorder of the central dopaminergic system and iron metabolism. Family and twin studies strongly support a genetic contribution to the pathogenesis of RLS. Tremendous progress has been made recently of uncovering genes linked to RLS. Three independent studies published in the last two years all pointed to the role of BTBD9 in RLS. The function of BTBD9 protein is not known. Current animal models include 6-hydroxydopamine-lesioned rodents, iron deficiency mice, and dopamine receptor 3 knockout mice. The identification of the RLS genes paves the way for making genotypic model of RLS that will be more relevant in elucidating the pathophysiology of RLS and developing therapeutic treatments. The broad, long-term objective of our research is to use both complete and targeted conditional knockout mice to determine: 1) the function of the BTBD9 protein in vivo, and 2) how mutations in the BTBD9 protein can lead to RLS. The specific goal of this application is to generate conditional Btbd9 knockout mice and to use our previously generated complete Btbd9 knockout mice to answer these questions. We hypothesize that using a conditional knockout of Btbd9 we will be able to determine the relevant contribution of various brain regions in the pathophysiology of RLS. We further hypothesize that mutations in BTBD9 lead to alterations in the central dopaminergic system, in particular the D2 receptor mediated indirect pathway of the striatum. In turn these striatal alterations will affect plasticity in the basal ganglia, in particular the striatum, thereby leading to an urge to move, unpleasant sensations, and other RLS-like phenotypes. We plan to test our hypothesis with the following Specific Aims. 1) To test the hypothesis that functional alterations in the central nervous system underlie the pathophysiology of RLS, we will generate conditional knockout mice of Btbd9 and analyze for RLS-like behavioral and molecular phenotypes. 2) To test the hypothesis that loss of Btbd9 disrupts the dopaminergic system, we will conduct an extensive analysis of the dopaminergic system, including measuring tissue level dopamine and its metabolites by HPLC, striatal dopamine receptors by radioligand bindings assays, western blots analysis of receptors and transporter, dopamine release under basal conditions and after amphetamine challenge, and pharmacological administration of dopaminergic agonist and antagonists in the open field apparatus. 3) To test the hypothesis that loss of Btbd9 alters neural plasticity in basal ganglia circuitry, we will prepare acute slices from mouse brain that includes both the striatum and the cortex and perform electrophysiological recordings to measure short- and long-term plasticity. The successful completion of the above Specific Aims will help us to determine the function of BTBD9 protein in vivo and how the mutation of BTBD9 causes RLS. The results should significantly increase our understanding of the pathophysiology of RLS, which can ultimately aid the development of therapeutic treatments for RLS patients.

date/time interval

  • April 2015 - September 2018

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