2009 — 2013 |
Zhai, Rong Grace |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Mechanisms of Neuronal Maintenance and Protection. @ University of Miami School of Medicine
DESCRIPTION (provided by applicant): Neurodegeneration can be triggered by a variety of genetic, epigenetic, and environmental factors. Healthy neurons are able to maintain their integrity throughout the life of an organism, suggesting the existence of a maintenance mechanism that allows neurons to sustain, mitigate or even repair damage. Recently, we have identified a neuronal maintenance factor NMNAT in a forward genetic screen in Drosophila. Loss of nmnat causes rapid and severe neurodegeneration, whereas over-expression of NMNAT protein offers protection against neurodegeneration. These findings suggest that normal level of NMNAT maintains neuronal homeostasis, and increased level offers protection. NMNAT is a highly conserved housekeeping enzyme, and the neuroprotective function of NMNAT has also been implicated in a mouse model of slow Wallerian Degeneration. Currently, the detailed mechanisms of this maintenance function and the protective capability of NMNAT in mammalian neurons are unclear. Our preliminary experiments suggest that in addition to its NAD synthesis activity, NMNAT has a chaperone function that is involved in regulating protein misfolding and degradation. We hypothesize that like other chaperones, NMNAT is up-regulated under stress, reduces protein aggregation, and thus protects neurons from degenerative conditions. In the proposed research, we will characterize the biochemical and cellular mechanisms underlying the protective process mediated by NMNAT using both Drosophila and mammalian primary neuronal models. In Specific Aim 1, we will use structure- function analysis to define the protein domains that are required for chaperone function, and characterize the transcriptional regulation of NMNAT under stress. In Specific Aim 2, we will first determine the neuroprotective activity of mammalian NMNAT isoforms in primary neurons, and then characterize the role of NMNAT in reducing protein aggregation-induced neurotoxicity. In Specific Aim 3, we will test whether NMNAT proteins can exert protective activity when their expression is induced after the onset of degeneration. For this last study, we will take advantage of the Drosophila genetic system and control the expression of NMNAT using a heat-inducible promoter. In summary, our proposed research in both Drosophila and mammalian model systems will help unmask the function of NMNAT and its regulation as a molecular chaperone, determine the neuroprotective properties of human NMNAT in primary neurons, and reveal the repair potential of NMNAT in neural regeneration after neuronal damage. PUBLIC HEALTH RELEVANCE: Neurodegenerative conditions are among the most intractable of diseases and therefore present an urgent need for developing effective treatments. Our studies on the neuronal maintenance process suggest that neurons have a self-defense system that can be augmented to protect against neurodegeneration. The experiments in this proposal will help us better understand the molecular events of protein folding and aggregation in neurodegenerative conditions, reveal potential neuroprotective mechanisms in mammalian neurons, and aid in the design of therapeutic treatments.
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0.998 |
2015 |
Zhai, Rong Grace |
R56Activity Code Description: To provide limited interim research support based on the merit of a pending R01 application while applicant gathers additional data to revise a new or competing renewal application. This grant will underwrite highly meritorious applications that if given the opportunity to revise their application could meet IC recommended standards and would be missed opportunities if not funded. Interim funded ends when the applicant succeeds in obtaining an R01 or other competing award built on the R56 grant. These awards are not renewable. |
Mechanisms of Neuronal Maintenance and Protection @ University of Miami School of Medicine
? DESCRIPTION (provided by applicant): Neurodegeneration can be triggered by a variety of genetic, epigenetic, and environmental factors. Healthy neurons are able to maintain their integrity throughout the life of an animal, suggesting the existence of a maintenance mechanism that allows neurons to sustain, mitigate or even repair damage. Previous work in our lab and others has found NMNAT proteins in Drosophila and mammals to be robust and versatile neuroprotective factors. However, it remains unclear whether and how neurons regulate the neuroprotective processes mediated by maintenance factors such as NMNAT. How neurons partition NMNAT into two distinct functions - housekeeping (NAD synthesis) and neuroprotection, and how such partitioning is regulated under normal and adverse conditions to achieve neuroprotection are the foci of this proposal. Our preliminary data indicate that Drosophila nmnat gene is alternatively spliced into two mRNA variants (RA and RB) that lead to two sets of functionally distinct proteins: PA/PC, with higher enzyme activity, and PB/PD, with enhanced chaperone function. We hypothesize that post-transcriptional regulation, including alternative splicing, functions as a switch between the neuroprotective and enzymatic roles of NMNAT, and that neurons use this switch mechanism to regulate the neuroprotective response under normal and disease conditions. We propose to characterize the hypothesized switch mechanism in Drosophila and then extend the study to human NMNATs in mammalian neurons. First, we will characterize the biochemical and cellular properties of Drosophila and human NMNAT protein variants, and illustrate the role of alternative splicing in post- transcriptional regulation of nmnat genes. Next, we will identify alternative splicing as a stress response that affords protection to neurons, and further reveal the functional role of microRNAs in regulating the abundance of neuroprotective RNA variants and modulating the neuroprotective efficacy of NMNAT. Finally, we will study human NMNAT protein variants and characterize the neuroprotective function of alternatively spliced NMNAT variants in cultured DRG explants and in vivo in cortical spinal track neurons, and identify key mechanisms underlying the divergent neuroprotective effects of NMNAT variants in degenerative conditions. Studies on Drosophila and human NMNATs - a two-model approach - will reveal the evolutionarily conserved regulatory mechanisms and identify strategies relevant to enhancing neuroprotection in humans.
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0.998 |
2016 — 2019 |
Zhai, Rong Grace |
R21Activity Code Description: To encourage the development of new research activities in categorical program areas. (Support generally is restricted in level of support and in time.) |
Functional Interaction of Gbas and Slc41a2 in Drosophila Models For Udp_755 @ University of Miami School of Medicine
? DESCRIPTION (provided by applicant): UDP_755 patient presents craniosynostosis, microcephaly, congenital extremity contractures, and global developmental delay. Genomic sequencing and bioinformatics analyses by the NIH-UDP program have identified two mutant variants, GBAS (NM_001483.2: c.181C>G; p.His61Asp) and SLC41A2 (NM_032148.3: c.1648G>A; p.Gly550Arg) as candidate causal mutations for UDP_755. GBAS gene encodes glioblastoma amplified sequence, a member of the NIPSNAP (4-nitrophenylphosphatase domain and non-neuronal SNAP25-like) gene family. GBAS is also known as NIPSNAP2. SLC41A2 encodes solute carrier family 41, member 2. SLC41A2 has been reported to mediate voltage-dependent Mg2+ uptake activity when expressed in Xenopus oocytes. The function of GBAS and SLC41A2 are largely unknown and no previous mutations have been identified or characterized. We plan to study the function of GBAS and SLC41A2 in vivo and establish Drosophila models for UDP_755, in collaboration with UDP to investigate the underlying genetics, biochemistry and pathophysiology of the GBAS and SLC41A2 mutant variants. The goal of this proposal is to seek mechanistic understanding of (1) the nature of mutant variant of GBAS and SLC41A2 identified in UDP_755, (2) the normal function of GBAS and SLC41A2, specifically in the nervous system, (3) the genetic interaction of GBAS and SLC41A2 in vivo, and (4) the pathological consequence of the combination of GBAS and SLC41A2 mutant alleles. Our studies proposed here will characterize the neuronal function of GBAS and SLC41A2 and analyze the neurological phenotypes associated with human mutant variants. The result will provide significant and important insights into the function of GBAS and SLC41A2 and the disease pathophysiology associated with UDP_755 neurological disorder. We believe that our multidisciplinary approaches involving several research models are the most appropriate to accelerate discoveries that can be subsequently translated to humans.
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0.998 |
2017 |
Zhai, Rong Grace |
R56Activity Code Description: To provide limited interim research support based on the merit of a pending R01 application while applicant gathers additional data to revise a new or competing renewal application. This grant will underwrite highly meritorious applications that if given the opportunity to revise their application could meet IC recommended standards and would be missed opportunities if not funded. Interim funded ends when the applicant succeeds in obtaining an R01 or other competing award built on the R56 grant. These awards are not renewable. |
Enhance Neuroprotection Through Post-Transcriptional Regulations @ University of Miami School of Medicine
Neurodegeneration can be triggered by a variety of genetic, epigenetic, and environmental factors. Healthy neurons are able to maintain their integrity throughout the life of an animal, suggesting the existence of a maintenance mechanism that allows neurons to sustain, mitigate or even repair damage. Previous work in our lab and others has found NMNAT proteins in Drosophila and mammals to be robust and versatile neuroprotective factors. However, it remains unclear whether and how neurons regulate the neuroprotective processes mediated by maintenance factors such as NMNAT. How neurons partition NMNAT into two distinct functions ? NAD metabolism and neuroprotection, and how such partitioning is regulated under normal and adverse conditions to achieve neuroprotection are the focus of this proposal. Our preliminary studies have found that Drosophila nmnat is alternatively spliced, producing splice isoforms with divergent neuroprotective activities, and that neurons could alter the preference for splice variants production under stress towards the neurprotective variant and therefore achieve self-protection. We hypothesize that alternative splicing and other post-transcriptional regulations are an essential endogenous program for regulating neuronal self-protective response under normal, stress, and disease conditions. Importantly this mechanism is likely conserved between fly and mammals as we have collected preliminary data indicating that human NMNAT genes are also alternatively spliced. In this proposal, we plan to uncover the key mechanisms to enhance neuroprotection in Drosophila and then extend the study to human NMNATs in mammalian neurons. First, we will characterize the biochemical and cellular properties of Drosophila and human NMNAT protein isoforms, and illustrate the role of alternative splicing in post-transcriptional regulation of nmnat genes. Next, we will identify alternative splicing as a stress response that affords protection to neurons, and further reveal the functional role of microRNAs in regulating the abundance of neuroprotective RNA variants and modulating the neuroprotective efficacy of NMNAT. Finally, we will study human NMNAT protein isoforms and characterize the neuroprotective function of alternatively spliced NMNAT isoforms in cultured DRG explants and in vivo in corticospinal track (CST) neurons, and identify key mechanisms underlying the divergent neuroprotective effects of NMNAT variants in degenerative conditions. Studies on Drosophila and human NMNATs using a ?two-model? approach will reveal the evolutionarily conserved posttranscriptional regulatory mechanisms and identify strategies relevant to enhancing neuroprotection in humans.
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0.998 |
2019 — 2020 |
Zhai, Rong Grace |
R61Activity Code Description: As part of a bi-phasic approach to funding exploratory and/or developmental research, the R61 provides support for the first phase of the award. This activity code is used in lieu of the R21 activity code when larger budgets and/or project periods are required to establish feasibility for the project. |
Microrna Regulation of Nmnat-Mediated Neuroprotection Against Peripheral Neuropathy and Chronic Pain @ University of Miami School of Medicine
MicroRNA Regulation of NMNAT-Mediated Neuroprotection Against Peripheral Neuropathy and Chronic Pain PROJECT SUMMARY Peripheral neuropathy and neuropathy pain can be caused by a myriad of genetic and environment factors as well as therapeutic or recreational drug use. In particular, chemotherapy-induced peripheral neuropathy (CIPN) is the major dose-limiting neurotoxic side effect of standard chemotherapy regiments. Over 68% of cancer patients experience neuropathic symptoms after chemotherapy, and that contributes to a significant percent of the population that suffer from chronic pain and have to resort to opioid use. Currently there are no effective treatments available, largely due to a lack of understanding of the in vivo mechanisms of CIPN and related peripheral neuropathy. Recently, we have optimized a model of peripheral neuropathy using Drosophila larvae that recapitulates salient behavior and neuronal morphological aspects of chemotherapy- induced sensory dysfunction. Our preliminary work using this model has uncovered a new mechanism underlying peripheral neuropathy, and identified a neuroprotective protein NMNAT with promising potential for mitigating neuropathic pain. The ultimate goal of our research is to uncover the endogenous mechanisms underlying peripheral neuropathy and to identify neuroprotective mechanisms and potential targets that facilitate the development of new therapeutic agents against CIPN and related neuropathic pain. Our previous work on neuronal maintenance and protection has identified NMNAT (nicotinamide mononucleotide adenylyl transferase), the last enzyme in NAD+ synthesis pathway, as an essential gene that maintains neuronal structural and functional integrity. Extensive mechanistic studies from our lab and others have found NMNAT proteins in Drosophila and mammals to be among the most robust and versatile neuroprotective factors, and a positive correlation between NMNAT expression levels and the neuronal self- protective capacity. Excitingly, from a compound screen, several natural compounds were identified to upregulate NMNAT transcription, and we have collected intriguing preliminary results suggesting that the expression of NMNAT is regulated by microRNAs. We hypothesize that regulation of NMNAT RNA expression by natural compounds and microRNAs at the steps of transcription, pre-mRNA splicing, and mRNA stability allows rapid and dynamic shifting between NMNAT mediated NAD+ metabolism and neuronal resilience, and confers protection in sensory neurons against peripheral neuropathy. In this application we outline experiments to (1) identify microRNAs that regulate nociceptive hypersensitivity, (2) identify and characterize the molecular pharmacology of natural compounds in regulating NMNAT expression, and (3) modulate NMNAT transcriptional regulation to enhance neuroprotection against peripheral neuropathy. Within the network of convergent pathways responding to chemotherapy induced peripheral neuropathy, understanding the regulation of NMNAT in both NAD+-metabolism and enhancing neuronal homeostasis will facilitate discovery of neuroprotective strategies in peripheral neuropathy and neuropathic pain.
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0.998 |
2019 — 2021 |
Zhai, Rong Grace |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Neurotoxicity of Spermine Synthase-Deficiency and Polyamine Imbalance @ University of Miami School of Medicine
Neurotoxicity of Spermine Synthase-Deficiency and Polyamine Imbalance PROJECT SUMMARY Polyamines, namely spermidine, spermine, and their precursor putrescine are tightly regulated polycations essential for life. Dysregulation of polyamine metabolism has been observed to accompany several neurological disease conditions include hypoxic and ischemic brain damage. However, the pathological consequence of polyamine imbalance in the nervous system remains unclear. The pivotal role of polyamine metabolism in the nervous system recently emerged with the mapping of causal mutation of Snyder-Robinson Intellectual Disability Syndrome (SRS, OMIM 309583) to spermine synthase (SMS), an enzyme that catalyzes the conversion of spermidine to spermine. SRS is the first confirmed genetic disorder associated with the polyamine metabolic pathway. Neurological manifestations in SRS indicate the long-term pathological consequence of polyamine imbalance, and provide a unique opportunity to uncover nervous system-specific function of SMS and polyamine metabolism. We have established a Drosophila model for SRS and found that human and Drosophila SMS proteins are functionally conserved, and loss of SMS in Drosophila recapitulated several key features of SRS pathology, including polyamine imbalance, reduced survival rate, and synaptic dysfunction. We discovered that SMS deficiency leads to excessive spermidine catabolism, and consequent lysosomal dysfunction and oxidative stress in vivo. We hypothesize that spermidine/spermine imbalance due to SMS deficiency causes altered polyamine catabolism, and that neutralizing the detrimental metabolites from polyamine catabolism will ameliorate phenotypes and disease progression in SRS. In this application, we will characterize the neuronal function of SMS in vivo, analyze the neurotoxicity resulted from polyamine imbalance, study cellular phenotypes in SRS patient blood lymphoblast, skin fibroblast and bone BMSC cells, and further discover genetic suppressors and potential pharmacological interventions for SRS. The proposed work will provide significant and important insights into the function of polyamines and SMS, and delineate the neuronal mechanisms underlying the neuropathology of spermine synthase-deficiency, and have long-lasting and sustained impact on polyamine-associated neurological disorders.
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0.998 |