Susan J Hayflick, M.D. - US grants

The aim of this project is to clone and characterize the gene for a form of syndromic retinitis pigmentosa (RP), called. Hallervorden-Spatz syndrome (HSS) and characterized by abnormal electroretinogram, lipofuscin accumulation in the retinal pigment epithelium, and pigmentary retinopathy. Other features include dystonia, due to massive iron accumulation in the basal ganglia, and progressive deterioration leading to early death. Though lipid peroxidation is an hypothesized mechanism leading to the HSS phenotype, no knowledge exists of the molecular or biochemical defect in HSS. We have a unique opportunity to map the HSS gene using linkage analysis (homozygosity mapping) in a consanguineous Amish family with multiple affected members. Once the HSS gene has been mapped, we will search for mutations in candidate genes, as well as identify novel transcribed sequences that may contain the HSS gene. We will then characterize the gene and its protein product through homology studies to known sequences. Knowledge of the molecular basis of this disease will lead to a better understanding of the pathophysiologic process causing its pleiotropic effects. Understanding the etiology of a rare disease will often illuminate the mechanism at work in common, related diseases. Furthermore, by studying syndromic RP, we can use information about all of the syndrome manifestations (e.g. patterns of tissue expression, common metabolic or developmental pathways) to theorize a disease mechanism. Inference of a pathophysiologic process from a defective gene has proved frustrating for the forms of RP that are due to mutation in retina-specific genes. The HSS gene is not retina-specific, and a defect in it must account for rod photoreceptor degeneration as well as regional brain iron accumulation. Once the HSS gene is cloned and characterized, the other pathologic changes may provide a context for understanding the mechanism of pigmentary retinopathy. Since defects in this non-retina-specific process may cause other forms of syndromic and isolated RP and may be integral in disorders of lipofuscin accumulation, including aging macular degeneration, identification of the HSS gene may lead to greater understanding of RP as well as the macular dystrophies associated with sene ence. The HSS project forms the research core of Dr. Hayflick's training to become an independent biomedical investigator. Dr. Michael Litt, internationally recognized in the field of genetics, will he her primary sponsor with Dr. Richard Weleber, accomplished in the study of hereditary retinal diseases, as secondary sponsor. Unique strengths of her training program include a period of intense study in the Visiting Investigator Program through the National Center for Human Genome Research, which will provide her with expertise that will complement but not duplicate existing University research strengths, and the Oregon Health Sciences University and Department of Molecular and Medical Genetics research environments, which effectively foster collaboration with a diverse group of outstanding investigators.

Hallervorden-Spatz syndrome (HSS) is a rare autosomal recessive neurodegenerative disorder of childhood. The phenotype includes dystonia, dementia and retinitis pigmentosa, with iron accumulation in the basal ganglia and diffuse axonal swellings. To date, research on HSS has been primarily descriptive, with little progress made toward understanding the basic biology of this disease. The recent mapping of the gene for HSS has facilitated clinical diagnosis and enabled prenatal detection, and identification of the HSS gene will open new avenues for research on this fatal disorder. The primary justification for a workshop on HSS at this time is the need to stimulate new research. The workshop will take place on May 19 and 20, 2000 and will be held at the NIH. Participants are from neurology, neuropathology, neuroradiology, neuroscience, retinal physiology, iron metabolism, and genetics and from the Hallervorden-Spatz Syndrome Association (HSSA), an international family support organization. Individual participants were selected with an emphasis on bringing together a diverse group of young and established scientists. The overall objectives of this workshop are to define HSS research priorities, identify resources that are needed to advance research in this area, and foster collaborations among researchers. The workshop agenda is designed to meet these objectives. Topics to be covered include 1) clinical delineation of Hallervorden-Spatz syndrome, 2) pigmentary retinopathy in HSS, 3) pathology of HSS, 4) genetics of HSS, 5) brain iron transport and metabolism, 6) the basal ganglia - circuitry, development, and the role of iron in basal ganglia function, 7) overlap of HSS and neurodegenerative syndromes with pigmentary retinopathy - clues to pathogenesis?, 8) hypotheses of HSS pathogenesis, and 9) therapeutic approaches. The scientific workshop will overlap partially with the first meeting of family members of the HSSA. The proximity of these meetings demonstrates to families affected by HSS that research in this area is a priority and enables participation in both meetings by key personnel.

DESCRIPTION (provided by applicant): The overall goal of this project is to delineate the molecular pathogenesis of a form of syndromic retinitis pigmentosa called pantothenate kinase-associated neurodegeneration (PKAN, formerly Hallervorden-Spatz syndrome) and characterized by abnormal electroretinogram, lipofuscin accumulation in the retinal pigment epithelium, and early, rapidly progressive pigmentary retinopathy. This autosomal recessive disorder includes extrapyramidal dysfunction and iron accumulation in the basal ganglia. PKAN is caused by mutations in PANK2, one of four human genes to encode a key regulatory enzyme in coenzyme A (CoA) biosynthesis, called pantothenate kinase. Since PANK2 is uniquely associated with mitochondria, we hypothesize that defects lead to CoA deficiency, energy and lipid metabolic abnormalities, oxidative damage and apoptosis in susceptible tissues. We propose to investigate how PANK2 defects cause retinal and neuronal degeneration. Our specific aims are: 1) to create Pank2 defective mouse mutants representing a spectrum of disease severity and delineate their associated phenotypes; 2) to identify metabolic and molecular perturbations in pantothenate kinase 2 deficiency in vivo and in vitro; and 3) to determine whether mutations in PANK2 are associated with age-related macular degeneration or idiopathic pigmentary retinopathy. Knowledge about the genetic basis of PKAN has enabled delineation of a clinically recognizable disease, as well as the development of a molecular diagnostic test and new ideas for rational therapies. This discovery has linked a previously unsuspected metabolic pathway with retinopathy and neurodegeneration and has illuminated a possible role for defects in this pathway in related, more common disorders that share pathologic features with PKAN, including age-related macular degeneration, retinitis pigmentosa and Parkinson disease.

[unreadable] DESCRIPTION (provided by applicant): The goal of this project is to identify the genetic basis of infantile neuroaxonal dystrophy (INAD), an autosomal recessive disorder characterized by progressive motor and sensory impairment. The key pathologic feature of this form of neuroaxonal dystrophy is the widespread distribution of distended axons throughout the central and peripheral nervous systems. Defective retrograde axonal transport is a hypothesized mechanism leading to the INAD phenotype; however, the molecular defect in INAD remains unknown. By identifying a gene or genes for this fatal childhood disorder, we can offer diagnostic molecular testing and begin to investigate disease pathogenesis as a step towards developing rational therapeutics. We have established two unique resources that will accelerate disease gene discovery in humans and mice with INAD. First, we maintain the largest worldwide collection of phenotype data and DNA samples from INAD families, with which we have mapped a major gene (INAD1) for this disorder using linkage analysis. Second, we have established a colony of mutant mice with early-onset neurodegenerative disease and pathologic changes identical to those seen in humans with INAD. This sporadic mutant has been crossed to a genetically distinct strain in order to map and isolate the defective murine gene. Studies in these mice will complement those in humans and extend our knowledge of the molecular basis of the neuroaxonal dystrophies. We will use these resources to achieve our specific aims to: 1) identify the human INAD1 gene and analyze INAD pedigrees for disease-causing mutations; 2) identify the disease gene in a mouse model of INAD; and 3) initiate structural and functional characterization of the INAD genes and their protein products. [unreadable] [unreadable] [unreadable]

? DESCRIPTION (provided by applicant): Neurodegeneration with Brain Iron Accumulation (NBIA) is a group of rare genetic neurological disorders that are attracting new scientific interes due to recent advances in knowledge of the disease processes. Relevant to the NBIA disorders are the biochemistry and cell biology of mitochondrial bioenergetics, membrane homeostasis, autophagy and brain iron trafficking and regulation. Shared clinical and pathological features and intersecting pathogeneses support the continued study of the 10+ NBIA disorders as a group, with knowledge from one informing our understanding of others. Now with most of the causative genes known, this field is moving swiftly towards therapeutics. There is substantial work still needed to advance understanding of the biology of each NBIA disorder and to yield insights that will accelerate the development of rational therapeutics. A scientific conference that brings together experts in NBIA and related fields is needed in order to stimulate new research and collaborations, prioritize questions needing further investigation, and attract early career scientists to this growing field. A meeting is proposed to occur in October 2016 in the Pacific Northwest. Invited participants will include international members of the scientific community, NIH personnel, members of the family advocacy community, and industry partners. A planning committee composed of representatives will ensure that attention is paid to meeting the needs of various stakeholders and achieving the goals of this important gathering.

PROJECT SUMMARY Better ways to treat genetic metabolic disorders are needed. More than 30 inborn errors of metabolism are predicted to lead to a functional deficiency of coenzyme A (CoA), including most conditions detected by expanded neonatal screening. Defects of fatty acid and amino acid metabolism generate high levels of organic acids, which form intracellular acyl CoA esters and lead to the sequestration or redistribution of CoA. Two primary inborn errors of CoA biosynthesis are now recognized, as well. Coenzyme A is critical to a diverse range of cellular processes, including intermediary metabolism, transcriptional regulation, signal transduction, and autophagy. Therefore deficient bioavailable CoA would disrupt myriad cellular processes and contribute to chronic morbidity in people affected by these diseases. Current state of treatment: The mainstay for managing this diverse group of disorders is early diagnosis, prevention of catabolic stress, and treatment with dietary modifications that decrease precursor availability and deliver small molecules (carnitine and glycine) to facilitate urinary excretion of toxic metabolites. While this general approach has improved survival of the acute toxic states, few of these patients are in good health. They suffer from a persistent abnormal metabolic state often with failure to thrive, neurodevelopmental disabilities, dysrhythmias, chronic liver disease and other complications, problems that are predicted to arise in part from depletion of CoA. The primary inborn errors of CoA synthesis cause lethal pediatric neurodegenerative disorders for which there are currently no treatments. Why is this R21 proposal innovative? Here, we propose a novel approach that will not only elucidate the pathophysiology of selected inborn errors metabolism but will also provide a ?go-no go? decision for use of a precursor in CoA synthesis as a rational therapeutic to replenish CoA levels. Phosphopantetheine, a key intermediate in the synthesis of CoA, was recently discovered to serve as the stable precursor for rapid CoA synthesis. Using animal models representing four distinct CoA depletion disorders (propionic acidemia; glutaric acidemia type 1; very long-chain acyl-CoA dehydrogenase deficiency; and pantothenate kinase-associated neurodegeneration), we propose to 1) demonstrate that these mutant animals are more sensitive than controls to selective CoA depletion; and 2) demonstrate the efficacy of phosphopantetheine in ameliorating disease- associated biochemical and clinical defects. These R21 exploratory investigations have the potential to contribute important knowledge to the understanding of these diseases and to advance development of phosphopantetheine and its derivatives for further human studies. If successful, the work could fundamentally change management of 30+ human diseases and significantly improve the lives of tens of thousands of people with poor therapeutic options.

PROJECT SUMMARY/ABSTRACT Single gene disorders provide valuable insights into mechanisms of common diseases and represent highly tractable systems for developing rational therapeutics. PKAN (pantothenate kinase-associated neurodegeneration) is a profoundly disabling and painful genetic disorder causing dystonia, parkinsonism, blindness and early death in children and adults. Currently there are no disease-modifying treatments. Our long-term goals are to elucidate pathogenesis and develop a treatment for this lethal disease. PKAN is an inborn error of coenzyme A (CoA) synthesis that results in neurodegeneration with brain iron accumulation. Though brain iron accumulation is a hallmark of PKAN, the link between defective CoA metabolism, iron dyshomeostasis, and neurodegeneration has remained unclear. The lack of a robust mammalian disease model of PKAN has limited research progress and still represents a critical research resource for the field. Using a mouse knock-out of Pank2 and a new approach to separating disease-vulnerable from disease-protected brain regions, we have discovered a set of disease-relevant brain abnormalities. This molecular `signature' includes markers of perturbed CoA, iron, and dopamine metabolism and oxidative phosphorylation only in the disease-vulnerable regions. We propose to investigate this powerful model with the goals to delineate the molecular pathogenesis of PKAN, to demonstrate efficacy of a candidate therapeutic, and to discover biomarkers that can be translated for use in human interventional trials.