Carlos Cepeda - US grants

The Core will be administered by Dr. Michael Levine. His role will be to oversee all Core services. Dr. Cepeda will provide training and instruction in electrophysiological assessment and in some cases will help perform the physiological experiments. Core services will be accessed first by consultation with Drs. Levine and Cepeda. The purpose of the consultation will be to determine which services are needed and when and how they might best be provided. Drs. Levine and Cepeda will meet with the investigator to determine the services needed and set up a time-line for provicling the service. Thus, these services are available on a firstcome, first-served basis. IDDRC investigators that need aid in performing electrophysiological analyses will have access to these Core services which are not to our knowledge presently available at UCLA except when collaborations are set up between investigators. Training and/or use of the Core set-ups will be performed according to an individualized schedule that depends on the sophistication and previous experience of the Core user. Electrophysiological experiments are labor intensive and time-consuming. It is our experience that only one investigator (or perhaps two at most depending on the services they need) will be able to use the Core at one time. We expect that most projects will require one to two months to complete (depending on availability of cultured cells and animals when slices are made), although training in electrophysiology may take longer depending on the ability of the person being trained. Once an individual is trained, they will be able to use the facility to perform experiments. The experiments and the data collected will be monitored both by Drs. Levine and Cepeda. Our experience is that weekly meetings with the investigator collecting the data are sufficient for quality control and assessment. The Physiological Assessment Core will interact directly with Core D, Cell Biology and Cellular Imaging to coordinate electrophysiological and imaging experiments on the same animals or on fixed tissue after electrophysiology is performed and Core E, Animal Models Core to determine availability of animals for experiments.

DESCRIPTION (provided by applicant): Epilepsy is a frequent neurological condition, and approximately 25% of children have medically refractory seizures. In children with pharmacoresistant epilepsy undergoing neurosurgery, cortical dysplasia (CD) is the most frequent etiology. This proposal focuses on identifying mechanisms of epileptogenesis in pediatric epilepsy surgery patients with CD. The use of human surgical tissue is important because animal models of CD do not fully replicate the histopathology seen in humans, especially abnormal cytomegalic neurons and balloon cells. Furthermore, this proposal has a translational aim that will develop new treatments for children with CD. Our previous studies identified the characteristics of normal and abnormal cells in the cerebral cortex of patients with CD. These studies found changes in MRI volumes, neuronal densities, and electrophysiological properties that resembled immature developing cortex. Based on these findings we introduced the Dysmature Cerebral Developmental Hypothesis, that proposes that the histopathology of CD represents tissue in which normal developmental processes, such as apoptosis of cells in the molecular layer and subplate and synaptic maturation are slowed or stopped in association with increased numbers of late born pyramidal neurons in the intermediate layers of the gray matter. We propose that with delayed development, CD cells in ectopic locations, such as the molecular layer and the subcortical transition zone (STZ), participate in seizure generation. In addition, some of the normal and abnormal cells in CD tissue have immature synaptic features that are pro-epileptic. These hypotheses will be tested by: 1) Examining the morphological and electrophysiological properties of neurons in the molecular layer and STZ;2) Examining synaptic interactions between pairs of normal and abnormal neurons using dual patch recordings and;3) Examining the acute effects of drug combinations that affect GABAA receptors and chloride transporters, GABAB receptors, and the mTOR pathway (rapamycin) on synaptic activity and induced epileptiform discharges in CD cases. These studies are significant because they elucidate operational mechanisms of pathogenesis and epileptogenesis in patients with CD to better define causes of the seizures and to develop treatments. PUBLIC HEALTH RELEVANCE: The most common cause of epilepsy in children undergoing neurosurgery is cortical malformations of the brain. We propose that malformed brains do not fully develop and retain immature features. We will test this hypothesis by using clinical, anatomical and electrophysiological approaches to examine brain tissue removed at surgery to understand the causes of epilepsy and alleviate seizures in children.

DESCRIPTION (provided by applicant): Abstract Huntington's disease (HD) is a fatal, inherited neurodegenerative disorder characterized by chorea, cognitive deficits and psychiatric disturbances. The main neuropathology is the loss of medium-sized spiny neurons (MSNs) in the striatum, but cell loss also occurs in cerebral cortex, hypothalamus, as well as other brain regions. Neuronal loss is preceded by reductions in white matter volume, suggesting myelin breakdown and altered synaptic connectivity. Using electrophysiological methods, we previously demonstrated significant alterations in synaptic activity, in particular a progressive disconnectio between cortex and striatum, and an increase in striatal inhibitory activity, both of which markedly alter signaling to output regions of the basal ganglia and contribute to motor symptoms. HD treatments have primarily focused on preventing neurodegenerative changes in the striatum. However, an effective therapy has to consider global changes as the mutation is widely expressed in multiple brain areas and peripheral organs. It is becoming increasingly recognized that one of the main features of HD is a metabolic disturbance that accompanies neurological symptoms. Impaired glucose metabolism and inadequate energy supply can lead to cell stress and eventual degeneration. In addition, a disruption in the brain cholesterol biosynthetic pathway occurs early, which could partially explain synaptic dysfunction and myelin breakdown. The experiments in this application are designed to examine the role of alterations in lipid metabolism, in particular brain cholesterol, as a primary etiologic factor in motor and synaptic disturbances in genetic mouse models of HD and to rescue these alterations by manipulating cholesterol levels. In Aim 1, we will examine the effects of a Ketogenic Diet (a diet rich in fat, low in carbohydrates and normal in protein levels) on behavior and electrophysiology of MSNs. This diet is effective in other neurological disorders and in HD it could provide essential alternative sources of energy to alleviate symptoms. In Aim 2 we will examine potential mechanisms by modulating cholesterol levels in slices. Using this global strategy, we hope to provide a novel method to rescue the synaptic and behavioral phenotype. PUBLIC HEALTH RELEVANCE: Huntington's disease (HD) is a fatal, inherited neurodegenerative disorder characterized by uncontrollable movements and cognitive deficits. One of the main features of HD is a metabolic disturbance leading to cell stress and eventual degeneration. The experiments in this application examine the role of lipid metabolism as a causative agent of motor and synaptic alterations in mouse models and to rescue these changes by manipulating lipid metabolism, in particular brain cholesterol levels.

Abstract: Huntington?s disease (HD) is a hereditary, neurodegenerative disorder caused by a triplet repeat (CAG) expansion in exon 1 of the Huntington (HTT) gene. Although HD typically starts in adulthood, higher CAG repeat numbers produce a shift in disease onset which can start in juveniles and even infants. Juvenile HD is more severe than adult-onset HD and the symptoms, including rigidity, mental retardation, and seizures differ from those typical of adult-onset HD, namely chorea (uncoordinated dance-like movements), cognitive deficits, and mood swings. These symptoms are caused by cell dysfunction and loss primarily in striatum and cerebral cortex. Recent studies have demonstrated that wildtype huntingtin (Htt) is essential for proper cortical development and the presence of the mutant form (mHtt) leads to abnormal cytoarchitecture of the cerebral cortex. However, at present nothing is known about the early development of cortical and striatal morphological and functional abnormalities in HD. The present study will determine how early during brain development aberrant cell membrane properties and synaptic communication can be detected in cortical and striatal projection neurons. Particular emphasis will be placed on trying to understand the origin and mechanism of cortical hyperexcitability in HD, as well as finding methods to restore normal function. Specifically, we hypothesize that in HD calcium signaling in cortical pyramidal neurons is disturbed during cortical development leading to aberrant cytoarchitecture and hyperexcitability. The proposal has two specific aims; aim 1 will test the hypothesis that the presence of mHtt leads to abnormal morphological and electrophysiological development of the cerebral cortex in two mouse models of HD, the R6/2 (a model of juvenile HD) and the Q175 (a model of adult-onset HD), and aim 2 will test the hypothesis that abnormal cortical development leads to aberrant corticostriatal synaptic transmission in HD mice. To accomplish these goals we will use an array of morphological, electrophysiological and imaging techniques. These studies will provide mechanistic insights into disease progression and will help identify early and specific therapeutic targets.