Browsing by Author "Lorson, Christian L."

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    Discovery of a Small Molecule Probe That Post-Translationally Stabilizes the Survival Motor Neuron Protein for the Treatment of Spinal Muscular Atrophy
    (ACS Publications, 2017-06-08) Rietz, Anne; Li, Hongxia; Quist, Kevin M.; Cherry, Jonathan J.; Lorson, Christian L.; Burnett, Barrington; Kern, Nicholas L.; Calder, Alyssa N.; Fritsche, Melanie; Lusic, Hrvoje; Boaler, Patrick J.; Choi, Sungwoon; Xing, Xuechao; Glicksman, Marcie A.; Cuny, Gregory D.; Androphy, Elliot J.; Hodgetts, Kevin J.; Dermatology, School of Medicine
    Spinal muscular atrophy (SMA) is the leading genetic cause of infant death. We previously developed a high-throughput assay that employs an SMN2-luciferase reporter allowing identification of compounds that act transcriptionally, enhance exon recognition, or stabilize the SMN protein. We describe optimization and characterization of an analog suitable for in vivo testing. Initially, we identified analog 4m that had good in vitro properties but low plasma and brain exposure in a mouse PK experiment due to short plasma stability; this was overcome by reversing the amide bond and changing the heterocycle. Thiazole 27 showed excellent in vitro properties and a promising mouse PK profile, making it suitable for in vivo testing. This series post-translationally stabilizes the SMN protein, unrelated to global proteasome or autophagy inhibition, revealing a novel therapeutic mechanism that should complement other modalities for treatment of SMA.
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    Optimization of a series of heterocycles as survival motor neuron gene transcription enhancers
    (Elsevier, 2017-12) Choi, Sungwoon; Calder, Alyssa N.; Miller, Eliza H.; Anderson, Kierstyn P.; Fiejtek, Dawid K.; Rietz, Anne; Li, Hongxia; Cherry, Jonathan J.; Quist, Kevin M.; Xing, Xuechao; Glicksman, Marcie A.; Cuny, Gregory D.; Lorson, Christian L.; Androphy, Elliot A.; Hodgetts, Kevin J.; Dermatology, School of Medicine
    Spinal muscular atrophy (SMA) is a neurodegenerative disorder that results from mutations in the SMN1 gene, leading to survival motor neuron (SMN) protein deficiency. One therapeutic strategy for SMA is to identify compounds that enhance the expression of the SMN2 gene, which normally only is a minor contributor to functional SMN protein production, but which is unaffected in SMA. A recent high-throughput screening campaign identified a 3,4-dihydro-4-phenyl-2(1H)-quinolinone derivative (2) that increases the expression of SMN2 by 2-fold with an EC50 = 8.3 µM. A structure-activity relationship (SAR) study revealed that the array of tolerated substituents, on either the benzo portion of the quinolinone or the 4-phenyl, was very narrow. However, the lactam ring of the quinolinone was more amenable to modifications. For example, the quinazolinone (9a) and the benzoxazepin-2(3H)-one (19) demonstrated improved potency and efficacy for increase in SMN2 expression as compared to 2.
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    Short-duration splice promoting compound enables a tunable mouse model of spinal muscular atrophy
    (EMBO Press, 2021-01) Rietz, Anne; Hodgetts, Kevin J.; Lusic, Hrvoje; Quist, Kevin M.; Osman, Erkan Y.; Lorson, Christian L.; Androphy, Elliot J.; Dermatology, School of Medicine
    Spinal muscular atrophy (SMA) is a motor neuron disease and the leading genetic cause of infant mortality. SMA results from insufficient survival motor neuron (SMN) protein due to alternative splicing. Antisense oligonucleotides, gene therapy and splicing modifiers recently received FDA approval. Although severe SMA transgenic mouse models have been beneficial for testing therapeutic efficacy, models mimicking milder cases that manifest post-infancy have proven challenging to develop. We established a titratable model of mild and moderate SMA using the splicing compound NVS-SM2. Administration for 30 d prevented development of the SMA phenotype in severe SMA mice, which typically show rapid weakness and succumb by postnatal day 11. Furthermore, administration at day eight resulted in phenotypic recovery. Remarkably, acute dosing limited to the first 3 d of life significantly enhanced survival in two severe SMA mice models, easing the burden on neonates and demonstrating the compound as suitable for evaluation of follow-on therapies without potential drug-drug interactions. This pharmacologically tunable SMA model represents a useful tool to investigate cellular and molecular pathogenesis at different stages of disease.
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    SMN deficiency negatively impacts red pulp macrophages and spleen development in mouse models of spinal muscular atrophy
    (Oxford University Press, 2017-03-01) Khairallah, Marie-Therese; Astroski, Jacob; Custer, Sarah K.; Androphy, Elliot J.; Franklin, Craig L.; Lorson, Christian L.; Dermatology, School of Medicine
    Spinal muscular atrophy (SMA) is a progressive neurodegenerative disease that is the leading genetic cause of infantile death. It is caused by a severe deficiency of the ubiquitously expressed Survival Motor Neuron (SMN) protein. SMA is characterized by α-lower motor neuron loss and muscle atrophy, however, there is a growing list of tissues impacted by a SMN deficiency beyond motor neurons. The non-neuronal defects are observed in the most severe Type I SMA patients and most of the widely used SMA mouse models, however, as effective therapeutics are developed, it is unclear whether additional symptoms will be uncovered in longer lived patients. Recently, the immune system and inflammation has been identified as a contributor to neurodegenerative diseases such as ALS. To determine whether the immune system is comprised in SMA, we analyzed the spleen and immunological components in SMA mice. In this report, we identify: a significant reduction in spleen size in multiple SMA mouse models and a pathological reduction in red pulp and extramedullary hematopoiesis. Additionally, red pulp macrophages, a discrete subset of yolk sac-derived macrophages, were found to be altered in SMA spleens even in pre-symptomatic post-natal day 2 animals. These cells, which are involved in iron metabolism and the phagocytosis of erythrocytes and blood-borne pathogens are significantly reduced prior to the development of the neurodegenerative hallmarks of SMA, implying a differential role of SMN in myeloid cell ontogeny. Collectively, these results demonstrate that SMN deficiency impacts spleen development and suggests a potential role for immunological development in SMA.
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    The adeno-associated virus 2 genome and Rep 68/78 proteins interact with cellular sites of DNA damage
    (Oxford University Press, 2022) Boftsi, Maria; Whittle, Fawn B.; Wang, Juexin; Shepherd, Phoenix; Burger, Lisa R.; Kaifer, Kevin A.; Lorson, Christian L.; Joshi, Trupti; Pintel, David J.; Majumder, Kinjal; Biomedical Engineering and Informatics, Luddy School of Informatics, Computing, and Engineering
    Nuclear DNA viruses simultaneously access cellular factors that aid their life cycle while evading inhibitory factors by localizing to distinct nuclear sites. Adeno-associated viruses (AAVs), which are Dependoviruses in the family Parvovirinae, are non-enveloped icosahedral viruses, which have been developed as recombinant AAV vectors to express transgenes. AAV2 expression and replication occur in nuclear viral replication centers (VRCs), which relies on cellular replication machinery as well as coinfection by helper viruses such as adenoviruses or herpesviruses, or exogenous DNA damage to host cells. AAV2 infection induces a complex cellular DNA damage response (DDR), in response to either viral DNA or viral proteins expressed in the host nucleus during infection, where VRCs co-localized with DDR proteins. We have previously developed a modified iteration of a viral chromosome conformation capture (V3C-seq) assay to show that the autonomous parvovirus minute virus of mice localizes to cellular sites of DNA damage to establish and amplify its replication. Similar V3C-seq assays to map AAV2 show that the AAV2 genome co-localized with cellular sites of DNA damage under both non-replicating and replicating conditions. The AAV2 non-structural protein Rep 68/78, also localized to cellular DDR sites during both non-replicating and replicating infections, and also when ectopically expressed. Ectopically expressed Rep could be efficiently re-localized to DDR sites induced by micro-irradiation. Recombinant AAV2 gene therapy vector genomes derived from AAV2 localized to sites of cellular DNA damage to a lesser degree, suggesting that the inverted terminal repeat origins of replication were insufficient for targeting.