Publications by Colleges and Departments (MSU - Bozeman)
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Item Metabolic Deficits in the Retina of a Familial Dysautonomia Mouse Model(MDPI AG, 2024-07) Costello, Stephanaan M.; Schultz, Anastasia; Smith, Donald; Horan, Danielle; Chaverra, Martha; Tripet, Brian; George, Lynn; Bothner, Brian; Lefcort, Frances; Copié, ValérieNeurodegenerative retinal diseases such as glaucoma, diabetic retinopathy, Leber’s hereditary optic neuropathy (LHON), and dominant optic atrophy (DOA) are marked by progressive death of retinal ganglion cells (RGC). This decline is promoted by structural and functional mitochondrial deficits, including electron transport chain (ETC) impairments, increased oxidative stress, and reduced energy (ATP) production. These cellular mechanisms associated with progressive optic nerve atrophy have been similarly observed in familial dysautonomia (FD) patients, who experience gradual loss of visual acuity due to the degeneration of RGCs, which is thought to be caused by a breakdown of mitochondrial structures, and a disruption in ETC function. Retinal metabolism plays a crucial role in meeting the elevated energetic demands of this tissue, and recent characterizations of FD patients’ serum and stool metabolomes have indicated alterations in central metabolic processes and potential systemic deficits of taurine, a small molecule essential for retina and overall eye health. The present study sought to elucidate metabolic alterations that contribute to the progressive degeneration of RGCs observed in FD. Additionally, a critical subpopulation of retinal interneurons, the dopaminergic amacrine cells, mediate the integration and modulation of visual information in a time-dependent manner to RGCs. As these cells have been associated with RGC loss in the neurodegenerative disease Parkinson’s, which shares hallmarks with FD, a targeted analysis of the dopaminergic amacrine cells and their product, dopamine, was also undertaken. One dimensional (1D) proton (1H) nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry, and retinal histology methods were employed to characterize retinae from the retina-specific Elp1 conditional knockout (CKO) FD mouse model (Pax6-Cre; Elp1LoxP/LoxP). Metabolite alterations correlated temporally with progressive RGC degeneration and were associated with reduced mitochondrial function, alterations in ATP production through the Cahill and mini-Krebs cycles, and phospholipid metabolism. Dopaminergic amacrine cell populations were reduced at timepoints P30–P90, and dopamine levels were 25–35% lower in CKO retinae compared to control retinae at P60. Overall, this study has expanded upon our current understanding of retina pathology in FD. This knowledge may apply to other retinal diseases that share hallmark features with FD and may help guide new avenues for novel non-invasive therapeutics to mitigate the progressive optic neuropathy in FD.Item A Comprehensive NMR Analysis of Serum and Fecal Metabolites in Familial Dysautonomia Patients Reveals Significant Metabolic Perturbations(MDPI AG, 2023-03) Costello, Stephanann M.; Cheney, Alexandra M.; Waldum, Annie; Tripet, Brian; Cotrina-Vidal, Maria; Kaufmann, Horacio; Norcliffe-Kaufmann, Lucy; Lefcort, Frances; Copié, ValérieCentral metabolism has a profound impact on the clinical phenotypes and penetrance of neurological diseases such as Alzheimer’s (AD) and Parkinson’s (PD) diseases, Amyotrophic Lateral Sclerosis (ALS) and Autism Spectrum Disorder (ASD). In contrast to the multifactorial origin of these neurological diseases, neurodevelopmental impairment and neurodegeneration in Familial Dysautonomia (FD) results from a single point mutation in the ELP1 gene. FD patients represent a well-defined population who can help us better understand the cellular networks underlying neurodegeneration, and how disease traits are affected by metabolic dysfunction, which in turn may contribute to dysregulation of the gut–brain axis of FD. Here, 1H NMR spectroscopy was employed to characterize the serum and fecal metabolomes of FD patients, and to assess similarities and differences in the polar metabolite profiles between FD patients and healthy relative controls. Findings from this work revealed noteworthy metabolic alterations reflected in energy (ATP) production, mitochondrial function, amino acid and nucleotide catabolism, neurosignaling molecules, and gut-microbial metabolism. These results provide further evidence for a close interconnection between metabolism, neurodegeneration, and gut microbiome dysbiosis in FD, and create an opportunity to explore whether metabolic interventions targeting the gut–brain–metabolism axis of FD could be used to redress or slow down the progressive neurodegeneration observed in FD patients.Item Norepinephrine transporter defects lead to sympathetic hyperactivity in Familial Dysautonomia models(Springer Science and Business Media LLC, 2022-11) Wu, Hsueh-Fu; Yu, Wenxin; Saito-Diaz, Kenyi; Huang, Chia-Wei; Carey, Joseph; Lefcort, Frances; Hart, Gerald W.; Liu, Hong-Xiang; Zeltner, NadjaFamilial dysautonomia (FD), a rare neurodevelopmental and neurodegenerative disorder affects the sympathetic and sensory nervous system. Although almost all patients harbor a mutation in ELP1, it remains unresolved exactly how function of sympathetic neurons (symNs) is affected; knowledge critical for understanding debilitating disease hallmarks, including cardiovascular instability or dysautonomic crises, that result from dysregulated sympathetic activity. Here, we employ the human pluripotent stem cell (hPSC) system to understand symN disease mechanisms and test candidate drugs. FD symNs are intrinsically hyperactive in vitro, in cardiomyocyte co-cultures, and in animal models. We report reduced norepinephrine transporter expression, decreased intracellular norepinephrine (NE), decreased NE re-uptake, and excessive extracellular NE in FD symNs. SymN hyperactivity is not a direct ELP1 mutation result, but may connect to NET via RAB proteins. We found that candidate drugs lowered hyperactivity independent of ELP1 modulation. Our findings may have implications for other symN disorders and may allow future drug testing and discovery.Item Loss of Elp1 disrupts trigeminal ganglion neurodevelopment in a model of Familial Dysautonomia(eLife Sciences Publications, Ltd, 2022-06) Leonard, Carrie E; Quiros, Jolie; Lefcort, Frances; Taneyhill, Lisa AFamilial dysautonomia (FD) is a sensory and autonomic neuropathy caused by mutations in elongator complex protein 1 (ELP1). FD patients have small trigeminal nerves and impaired facial pain and temperature perception. These signals are relayed by nociceptive neurons in the trigeminal ganglion, a structure that is composed of both neural crest- and placode-derived cells. Mice lacking Elp1 in neural crest derivatives (‘Elp1 CKO’) are born with small trigeminal ganglia, suggesting Elp1 is important for trigeminal ganglion development, yet the function of Elp1 in this context is unknown. We demonstrate that Elp1, expressed in both neural crest- and placode-derived neurons, is not required for initial trigeminal ganglion formation. However, Elp1 CKO trigeminal neurons exhibit abnormal axon outgrowth and deficient target innervation. Developing nociceptors expressing the receptor TrkA undergo early apoptosis in Elp1 CKO, while TrkB- and TrkC-expressing neurons are spared, indicating Elp1 supports the target innervation and survival of trigeminal nociceptors. Furthermore, we demonstrate that specific TrkA deficits in the Elp1 CKO trigeminal ganglion reflect the neural crest lineage of most TrkA neurons versus the placodal lineage of most TrkB and TrkC neurons. Altogether, these findings explain defects in cranial gangliogenesis that may lead to loss of facial pain and temperature sensation in FD.Item Elp1 is required for development of visceral sensory peripheral and central circuitry(The Company of Biologists, 2022-05) Tolman, Zariah; Chaverra, Marta; George, Lynn; Lefcort, FrancesCardiovascular instability and a blunted respiratory drive in hypoxic conditions are hallmark features of the genetic sensory and autonomic neuropathy, familial dysautonomia (FD). FD results from a mutation in the gene ELP1, the encoded protein of which is a scaffolding subunit of the six-subunit Elongator complex. In mice, we and others have shown that Elp1 is essential for the normal development of neural crest-derived dorsal root ganglia sensory neurons. Whether Elp1 is also required for development of ectodermal placode-derived visceral sensory receptors, which are required for normal baroreception and chemosensory responses, has not been investigated. Using mouse models for FD, we here show that the entire circuitry underlying baroreception and chemoreception is impaired due to a requirement for Elp1 in the visceral sensory neuron ganglia, as well as for normal peripheral target innervation, and in their central nervous system synaptic partners in the medulla. Thus, Elp1 is required in both placode- and neural crest-derived sensory neurons, and its reduction aborts the normal development of neuronal circuitry essential for autonomic homeostasis and interoception.Item Elongator and codon bias regulate protein levels in mammalian peripheral neurons(2018-03) Goffena, Joy; Lefcort, Frances; Zhang, Yongqing; Lehrmann, Elin; Chaverra, Marta; Felig, Jehremy; Walters, Joseph; Buksch, Richard; Becker, Kevin G.; George, LynnFamilial dysautonomia (FD) results from mutation in IKBKAP/ELP1, a gene encoding the scaffolding protein for the Elongator complex. This highly conserved complex is required for the translation of codon-biased genes in lower organisms. Here we investigate whether Elongator serves a similar function in mammalian peripheral neurons, the population devastated in FD. Using codon-biased eGFP sensors, and multiplexing of codon usage with transcriptome and proteome analyses of over 6,000 genes, we identify two categories of genes, as well as specific gene identities that depend on Elongator for normal expression. Moreover, we show that multiple genes in the DNA damage repair pathway are codon-biased, and that with Elongator loss, their misregulation is correlated with elevated levels of DNA damage. These findings link Elongator's function in the translation of codon-biased genes with both the developmental and neurodegenerative phenotypes of FD, and also clarify the increased risk of cancer associated with the disease.Item The Familial Dysautonomia disease gene, Ikbkap/Elp1, is required in the developing and adult central nervous system(2017-02) Chaverra, Marta; George, Lynn; Mergy, Marc; Waller, Hannah R.; Kujawa, Katharine J.; Murnion, Connor; Sharples, Ezekiel; Thorne, Julian; Podgajny, Nathaniel; Grindeland, Andrea; Ueki, Yumi; Eiger, Steven; Cusick, Cassie; Babcock, A. Michael; Carlson, George A.; Lefcort, FrancesHereditary sensory and autonomic neuropathies (HSANs) are a genetically and clinically diverse group of disorders defined by peripheral nervous system (PNS) dysfunction. HSAN Type III, Familial Dysautonomia (FD), results from a single base mutation in the gene IKBKAP that encodes a scaffolding unit for a multi-subunit complex Elongator. Since mutations in other Elongator subunits (ELP2-4) are associated with central nervous system (CNS) disorders, the goal of this study was to investigate a potential CNS requirement for Ikbkap/Elp1 The sensory and autonomic pathophysiology of FD is fatal, with the majority of patients dying by age 40. While CNS signs and pathology have been noted in FD, the clinical and research focus has been on the sensory and autonomic dysfunction, and no genetic model studies have investigated the requirement for Ikbkap/Elp1 in the CNS. Here we report using a novel mouse line in which Ikbkap/Elp1 is deleted solely in the nervous system, that not only is Ikbkap/Elp1 widely expressed in the embryonic and adult CNS, but its deletion perturbs both the development of cortical neurons and their survival in adulthood. Primary cilia in embryonic cortical apical progenitors and motile cilia in adult ependymal cells are reduced in number and disorganized. Furthermore, we report that in the adult CNS, both autonomic and non-autonomic neuronal populations require Ikbkap for survival, including spinal motor and cortical neurons. In addition, the mice developed kyphoscoliosis, an FD hallmark, indicating its neuropathic etiology. Ultimately, these perturbations manifest in a developmental and progressive neurodegenerative condition that include impairments in learning and memory. Collectively, these data reveal an essential function for Ikbkap/Elp1 that extends beyond the PNS, to CNS development and function. With the identification of discrete CNS cell types and structures that depend on Ikbkap/Elp1, novel strategies to thwart the progressive demise of CNS neurons in FD can be developed.Item TrkB/BDNF signalling patterns the sympathetic nervous system(2015-09) Kasemeier-Kulesa, Jennifer S.; Morrison, Jason A.; Lefcort, Frances; Kulesa, Paul M.The sympathetic nervous system is essential for maintaining mammalian homeostasis. How this intricately connected network, composed of preganglionic neurons that reside in the spinal cord and post-ganglionic neurons that comprise a chain of vertebral sympathetic ganglia, arises developmentally is incompletely understood. This problem is especially complex given the vertebral chain of sympathetic ganglia derive secondarily from the dorsal migration of ‘primary’ sympathetic ganglia that are initially located several hundred microns ventrally from their future pre-synaptic partners. Here we report that the dorsal migration of discrete ganglia is not a simple migration of individual cells but a much more carefully choreographed process that is mediated by extensive interactions of pre-and post-ganglionic neurons. Dorsal migration does not occur in the absence of contact with preganglionic axons, and this is mediated by BDNF/TrkB signalling. Thus BDNF released by preganglionic axons acts chemotactically on TrkB-positive sympathetic neurons, to pattern the developing peripheral nervous system.