Maureen M. Barr - US grants

DESCRIPTION (Applicant's Abstract): Autosomal Dominant Polycystic Kidney Disease (ADPKD) strikes 1 in 1000 individuals, often resulting in end-stage renal failure. Mutations in either PKD1 or PKD2 account for 95 percent of all cases. ADPKD1 and ADPKD2 are phenotypically indistinguishable, leading to the hypothesis that pathology is caused by defects in the same pathway. The cellular roles of the PKD 1 and PKD2 gene products (polycystin 1 and polycystin 2, respectively) still remain unknown. The powerful molecular genetic tools of the nematode Caenorhabditis elegans (C. Elegans)will enable us to address fundamental questions regarding polycystin function and physiological relevance of partner interactions. The C. elegans homologs of PKD1 and PKD2, LOV-1 and PKD-2, are coexpressed and colocalized in three types of male chemosensory neurons: the cephalic CEMs, the HOB hook neuron, and the ray neurons. Furthermore, lov-1 and pkd-2 are required in the male nervous system for the mating behaviors of response to hermaphrodite contact and location of the hermaphrodite vulva (Lov). The C. elegans homolog of Tg737 (a murine gene associated with Autosomal Recessive PKD) exhibits an expression pattern that partially overlaps with lov-1 and pkd-2 and maps closely to osm-5. osm-5 is also necessary for response and Lov behavior, suggesting that the three may operate in the same cell. This proposal is designed to test the hypothesis that LOV-1, PKD-2, and possibly CeTg737 act in a common pathway. Experiments will explore several models of LOV-1, PKD-2, and CeTg737 function. Hypotheses include the following: CeTg737 may localize LOV-1 and PKD-2 to the cilia where LOV-1 and PKD-2 are required for function. Moreover, LOV-1 may be involved in transducing an extracellular signal via PKD-2 in the cilia, culminating in activation of an intracellular signaling pathway. Alternatively, LOV-1 and PKD-2 may be involved in the formation and maintenance of sensory cilia or the establishment and maintenance of neuronal cell polarity. A number of complementary studies are proposed to address the function of the C. elegans polycystins and CeTg737 in male mating behavior. Genetic and molecular interactions between lov-1, pkd-2, and CeTg737 will be explored. Cellular functions of the C. elegans polycystins will be ascertained. The function of CeTg737 in male sensory mating behaviors will be determined. New components in the LOV/PKD pathway will be isolated. These experiments will analyze LOV/PKD at the cellular, genetic, and molecular levels.

DESCRIPTION (provided by applicant): Nephronophthisis (NPHP) is the most common genetic cause of end stage renal disease in infants, children, and young adults. NPHP is caused by a mutation in one of at least nine different genes (NPHP1 - NPHP9), accounting for less than 50% NPHP cases and indicating that many other disease loci remain unidentified. NPHP and other cystic kidney diseases are associated with defects in cilia. While the NPHP gene products (the nephrocystins) are localized to cilia, their functions in this sensory organelle remain largely unknown. The nematode Caenorhabditis elegans is a powerful model organism to study the roles of the nephrocystins in their native cellular environment. In C. elegans, NPHP-1 and NPHP-4 act globally to modulate ciliary development and morphogenesis in a cell-type specific manner. Human and worm nephrocystin-1 and nephrocystin-1 localize to the transition zone of cilia on renal epithelial cells and sensory neurons, respectively, suggesting an evolutionarily conserved role. Proposed studies in Aim 1 will define how NPHP-1 and NPHP-4 function at the ciliary transition zone. Proposed studies in Aim 2 will determine the role of the C. elegans NPHP2, NPHP8, and NPHP9 homologs. Proposed studies in Aim 3 will reveal genetic and functional interactions between the NPHP genes and known ciliopathy disease gene homologs. An understanding of human ciliary diseases such as Nephronophthisis relies on a complete understanding of ciliary components and of complex genetic and developmental interactions with modifier loci. These proposed studies will broaden our understanding of the nephrocystins and cilia biology at the genetic, molecular, cellular, and organismal levels. Such understanding is essential in order to identify the functions of the NPHP genes, their role in disease processes, and their potential as therapeutic targets. PUBLIC HEALTH RELEVANCE: Cilia are motile or sensory organelles found on almost every non-dividing human cell. The mechanism of ciliary development is evolutionarily conserved in organisms ranging from alga, worms, flies, fish, mouse, to human. Recent studies have revealed that defects in cilia are linked to human cystic kidney diseases such as Nephronophthisis (NPHP), autosomal dominant polycystic kidney disease (ADPKD), autosomal recessive PKD, Bardet-Biedl Syndrome (BBS), and Meckel Gruber Syndrome (MKS). The nematode Caenorhabditis elegans is an exceptional animal model system for the study of cilia-related human disease genes. Many of the genes required for the formation, maintenance, and function of C. elegans cilia have human counterparts that, when mutated, cause diseases with renal pathologies. The study is designed to use the powerful molecular genetic tools of C. elegans to model Nephronophthisis, the most common genetic cause of end stage renal disease in infants, children, and young adults.

DESCRIPTION (provided by applicant): The goal of this research is to understand how cilia form and function. The nematode Caenorhabditis elegans is a powerful model system to study cilia biology. Many proteins that are required for formation, maintenance, and function of cilia in C. elegans are linked to human renal diseases, including autosomal dominant polycystic kidney disease (ADPKD). ADPKD affects 1 in 1000 individuals, often resulting in end-stage renal disease. In humans, mutations in the polycystin-1 (PC-1) or polycystin-2 (PC-2) ciliary mechanosensory complex cause ADPKD. In C. elegans, the polycystins LOV-1 and PKD-2 localize on the ciliary membrane and are required for sensory transduction. Hence, the connection between the polycystins and cilia seems to be an ancient one. The polycystins must ultimately be localized to cilia in order to conduct the sensory function of the cell, whether it is a human renal epithelial cell or a worm sensory neuron. How the polycystins and other ciliary proteins localize and gain access to the cilium, a spatially restricted organelle, is not known. In C. elegans it is possible to identify the mechanisms controlling polycystin ciliary localization and function in living animals. This study will use classical and reverse genetics, molecular biology, transgenic nematodes, microscopy, electrophysiology, calcium imaging, and biochemical methods to understand the regulation, function, and localization of the polycystins. One specific aim is to identify and characterize the molecular mechanisms regulating PKD-2/PC-2 ciliary protein localization and function. A second aim is to examine the role of the kinesin KLP-6 in ciliary protein transport and sensation, as well as identify KLP-6 cargoes. A third aim is to identify new genes required for ciliogenesis and polycystin ciliary localization. These studies in a tractable model organism will provide basic insights into the mechanisms governing cilia formation and function.

? DESCRIPTION (provided by applicant): This is a request for funds to support travel/registration expenses for junior investigators involved in research relevant to NIDDK to attend the 2015 FASEB Biology of Cilia and Flagella Summer Conference. The objectives of the conference are to provide a venue for active discussion of recent advances in cilia and flagella biology and to foster collaborations between basic and clinical scientists interested in the cilium. The cilium has undergone a remarkable renaissance from being an arcane, vestigial structure to an organelle of great biomedical importance. Rapid advances in our understanding of the cilium are due to a remarkable convergence of basic research in Chlamydomonas and C. elegans with clinical studies in what were thought to be unrelated human disease syndromes. The finding that mutations in proteins needed for cilia/flagella assembly or signaling activities were responsible for human pathology was a remarkable advance fueling the growth of research activity in this field. Defects in ciliary/activity cause multiple human syndromes called the ciliopathies. These include Bardet-Biedl Syndrome (BBS), Meckel Syndrome, Joubert Syndrome, Alstrom Syndrome (ALS), Senior-Loken Syndrome, Primary Ciliary Dyskinesia, Nephronophthisis, Retinitis Pigmentosa, and Polycystic Kidney Diseases (PKD). PKD itself affects 1 in 1,000 individuals ultimately requiring dialysis and transplantation. Notable hallmarks of ciliopathies are the formation of cysts in the kidney as well as in other duct structures of the pancreas and liver. In addition, JBTS, BBS, and ALS patients have defects in the nervous system. Other phenotypes include abnormalities in formation of the heart, neural tube, skin, and bone, along with respiratory problems, hydrocephalus, and sterility. Remarkably, defects in the functions of cilia/flagella affect nearly every tissue and organ system and the impact of ciliary dysfunction on mortality and morbidity and their overall cost to the health care are immense. The striking association between cilia dysfunction and human disorders makes it vital that we understand the mechanisms of assembly and maintenance of this organelle and to dissect properties that endow the cilium with its unique sensory and signaling functions. The impetus behind the rapid and significant advances made in the ciliopathies has been the intriguing dance between basic science studies in model systems and human disease syndromes. This continues to be the central theme of the remarkably well-attended Biology of Cilia and Flagella meeting. As in previous meetings, junior scientists compose a substantial portion of invited speakers. Additionally, nearly a third of the speaking slots are being selected from submitted abstracts with many being devoted to junior investigators. The oral presentations are complemented by two poster sessions along with ample discretionary time to allow further discussion of research activities and to facilitate collaborative projects. To capitalize on the diversity of attendees, w also have Interest Group Tables for lunch and dinner to foster interactions between established and junior investigators.

? DESCRIPTION (provided by applicant): Cilia and extracellular vesicles (ECVs) are signaling organelles. Cilia act as a cellular antennae and function in sensation and adhesion, with defects resulting in human ciliopathies. ECVs act as intercellular signaling parcels that contain and deliver donor cell cargoes to recipient cells. In Chlamydomonas, C. elegans, and mammals, ECVs are closely associated with cilia, suggesting that cilia may be essential in ECV-mediated communication as both senders and receivers. Alternatively, ECVs may play a role in maintaining ciliary structure. In humans, the polycystin (PC)-encoding genes PKD1 and PKD2 are needed for kidney function; loss of polycystin function leads to Autosomal Dominant Polycystic Kidney Disease (ADPKD, frequency 1/400- 1:1000), one of the most common monogenic diseases. ECVs mediate a broad range of physiological processes. Urinary ECVs released from renal epithelial cells are enriched in PC1, PC2, and the ARPKD protein fibrocystin, and are a source of biomarkers for renal disease. In ARPKD patients and mice, ECVs are associated with renal primary cilia. In vitro, PC-containing ECVs interact with primary cilia of cultured renal cells. Consistent with a possible role for ECVs in PKD and other ciliopathies, ECVs also play sinister roles in the spread of toxic cargoes in cancer, infectious diseases, and neurodegenerative disorders. In C. elegans and mammals, the PCs act in the same genetic pathway, act in a sensory capacity, localize to cilia, and are contained in secreted ECVs, indicating ancient conserved functions. This application uses C. elegans as a springboard to study the fundamental biology of ECVs in vivo and the roles of the PCs in cilia and ECVs, which will advance frontiers of knowledge where very little is known. First, we will define the molecular signature of a PC-containing and ECV-releasing cell. This approach will provide a comprehensive picture of the molecules that influence PC function in ECVs and cilia, and will provide important insight to the fundamental biology of ciliary ECVs. Second, we will determine the mechanisms regulating PC ciliary localization and formation of PC-containing ECVs. By using novel approaches to visualize GFP-labeled ciliary ECVs released from living animals in real time and to measure ECV activity, we developed the first and only animal system to study ECVs in vivo and are uniquely poised to study their biogenesis, dynamics, and functions. Finally, we aim to understand the relationship between cilia and ECVs. This knowledge is essential for determining the biological significance of ECVs, for understanding their relationship to human cystic kidney disease, and for harnessing their potential therapeutic uses. A genetically tractable model can make inroads where other systems have not, and advance frontiers of knowledge where little is known.

Project Summary Cilia are cellular organelles that are essential for human development and health. It has long been known that cilia are organized into structurally and functionally distinct compartments known as the basal body, the transition zone, and the cilia shaft. Nephronophthisis-related ciliopathy (NPHP-RC) proteins localize to subregions within the previously known compartments, revealing a hidden complexity. For example, NPHP2/Inversin localizes to a proximal region of the ciliary shaft called the Inversin Compartment (InvC) that is not identifiable by any ultrastructural features. Despite the profound medical importance of cilia in human health and disease, how the ciliary shaft is spatially and functionally organized remains poorly understood. Identifying mechanisms controlling cilia shaft compartmentalization and understanding the physiological relevance of ciliary territories will be important in identifying therapeutic targets to combat cystic kidney diseases and other ciliopathies. The InvC is conserved in the nematode C. elegans, suggesting that the logic underlying the establishment of the InvC and ciliary compartmentalization is similar in worm and human cilia. In C. elegans, we found that the InvC regulates microtubule patterning and tubulin glutamylation. We also discovered that the Tubulin Code ? via tubulin isotypes and tubulin post-translational modifications ? sculpts ciliary structure, ciliary motor-based transport, and ciliary functions including release of ciliary extracellular vesicles. In this new application, we use C. elegans, an exceptional model for ciliary biology and human ciliopathies, to address the question of how the cilium is spatially and functional organized. First, we will define the origin and function of the InvC and examine the relationship between the InvC and tubulin glutamylation. Second, we determine how the Tubulin Code regulates microtubule ultrastructure, motor-based intraflagellar transport, and specialized ciliary functions. Finally, we will identify new genes and pathways that control ciliary homeostasis and protect against ciliary degeneration. This research will address the medically relevant question of how cilia are structurally and functionally organized in healthy and diseased states, and will provide fundamental insight to the molecules, mechanisms, and functions of ciliary compartmentalization and the Tubulin Code. These studies have direct implications for cystic kidney disease research because many of the genes and pathways explored in our work are associated with ciliopathies.

Project Summary Extracellular vesicles carry A? and tau that may spread pathogenic proteins across the brain, promote A? aggregation and accelerate amyloid plaque formation, and may also serve as biomarkers of Alzheimer's disease. EVs from blood, cerebral spinal fluid, and cell culture contain A? and tau and are proposed to be central mediators in the progression of Alzheimer's disease pathology. Conversely, EVs may have benefits in Alzheimer's disease: neuron-derived EVs promote uptake of A? by microglia and reduce extracellular levels of A? in cultured cells. Up-regulation of EV secretion - induced by neutral sphingomyelinase knockdown - efficiently reduced extracellular levels of A? in a co-culture of neuronal and microglial cells. The role of EVs in Alzheimer's disease is currently a major mystery of the disease mechanism. We will study how neuronal EV shedding is modulated by factors relevant to Alzheimer's disease, including age, oxidative stress, and proteostasis and neuron-glia dysfunction. Virtually all cell types in the brain release EVs including stem cells, neurons, astrocytes, microglia, and oligodendrocytes. EVs may be used by cells as a form of intercellular communication and may thereby mediate a broad range of physiological and pathological processes. Cells package beneficial or toxic EV cargo to promote health or disease. In the mammalian nervous system, EVs have neuroprotective roles against oxidative stress, cellular stress, and ischemia; and may also promote myelination in aging. In the brain, EVs may carry aggregation-prone cargo and contribute to the spread of Alzheimer's diseases. Understanding the fundamental biology of an EV-based signaling in vivo is essential for elaborating their physiological and pathological functions in Alzheimer's disease. A basic molecular dissection is critical for developing novel therapeutic applications. biology has been thwarted by a A big problem, however, is that advancing mechanistic dissection of EV lack of tractable experimental animal systems. We propose to take advantage of the powerful and unparalleled cell biological and molecular approaches that can be applied in the nematode C. elegans as a springboard to study the fundamental biology of neuronal EVs in vivo. We developed the first system to study neuronal EV biogenesis, shedding, targeting and signaling in living animals, and this strategy will overcome limitations of cell-culture based studies. This innovative approach will be used to tackle major challenges in the EV field . Our goals are to: 1) Determine the impact of neuronal activity, age and stress on neuronal EV shedding and signaling; 2) Decipher molecular mechanisms that control neuronal EV shedding; and 3) Determine the functions of neuronal EVs in long- distance intercellular communication and in neuron-glia communication. Our work should inform the fundamental biology of neuronal EVs relevant to both healthy brain aging and Alzheimer's disease and identify therapeutic targets to combat diseases like Alzheimer's associated with abnormal EV signaling.