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Browsing by Author "Spoonamore, Katherine G."
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Item Dysfunction in the βII Spectrin-Dependent Cytoskeleton Underlies Human Arrhythmia.(AHA, 2015-02-24) Smith, Sakima A.; Sturm, Amy C.; Curran, Jerry; Kline, Crystal F.; Little, Sean C.; Bonilla, Ingrid M.; Long, Victor P.; Makara, Michael; Polina, Iuliia; Hughes, Langston D.; Webb, Tyler R.; Wei, Zhiyi; Wright, Patrick; Voigt, Niels; Bhakta, Deepak; Spoonamore, Katherine G.; Zhang, Chuansheng; Weiss, Raul; Binkley, Philip F.; Janssen, Paul M.; Kilic, Ahmet; Higgins, Robert S.; Sun, Mingzhai; Ma, Jianjie; Dobrev, Dobromir; Zhang, Mingjie; Carnes, Cynthia A.; Vatta, Matteo; Rasband, Matthew N.; Hund, Thomas J.; Mohler, Peter J.; Department of Medical & Molecular Genetics, IU School of MedicineBackground: The cardiac cytoskeleton plays key roles in maintaining myocyte structural integrity in health and disease. In fact, human mutations in cardiac cytoskeletal elements are tightly linked with cardiac pathologies including myopathies, aortopathies, and dystrophies. Conversely, the link between cytoskeletal protein dysfunction in cardiac electrical activity is not well understood, and often overlooked in the cardiac arrhythmia field. Methods and Results: Here, we uncover a new mechanism for the regulation of cardiac membrane excitability. We report that βII spectrin, an actin-associated molecule, is essential for the post-translational targeting and localization of critical membrane proteins in heart. βII spectrin recruits ankyrin-B to the cardiac dyad, and a novel human mutation in the ankyrin-B gene disrupts the ankyrin-B/βII spectrin interaction leading to severe human arrhythmia phenotypes. Mice lacking cardiac βII spectrin display lethal arrhythmias, aberrant electrical and calcium handling phenotypes, and abnormal expression/localization of cardiac membrane proteins. Mechanistically, βII spectrin regulates the localization of cytoskeletal and plasma membrane/sarcoplasmic reticulum protein complexes that include the Na/Ca exchanger, RyR2, ankyrin-B, actin, and αII spectrin. Finally, we observe accelerated heart failure phenotypes in βII spectrin-deficient mice. Conclusions: Our findings identify βII spectrin as critical for normal myocyte electrical activity, link this molecule to human disease, and provide new insight into the mechanisms underlying cardiac myocyte biology.Item Evidence for replicative mechanism in a CHD7 rearrangement in a patient with CHARGE syndrome(Wiley, 2013-12) Vatta, Matteo; Niu, Zhiyv; Lupski, James R.; Putnam, Philip; Spoonamore, Katherine G.; Fang, Ping; Eng, Christine M.; Willis, Alecia S.; Medical & Molecular Genetics, School of MedicineHaploinsufficiency of CHD7 (OMIM# 608892) is known to cause CHARGE syndrome (OMIM# 214800). Molecular testing supports a definitive diagnosis in approximately 65-70% of cases. Most CHD7 mutations arise de novo, and no mutations affecting exon-7 have been reported to date. We report on an 8-year-old girl diagnosed with CHARGE syndrome that was referred to our laboratory for comprehensive CHD7 gene screening. Genomic DNA from the subject with a suspected diagnosis of CHARGE was isolated from peripheral blood lymphocytes and comprehensive Sanger sequencing, along with deletion/duplication analysis of the CHD7 gene using multiplex ligation-dependent probe amplification (MLPA), was performed. MLPA analysis identified a reduced single probe signal for exon-7 of the CHD7 gene consistent with potential heterozygous deletion. Long-range PCR breakpoint analysis identified a complex genomic rearrangement (CGR) leading to the deletion of exon-7 and breakpoints consistent with a replicative mechanism such as fork stalling and template switching (FoSTeS) or microhomology-mediated break-induced replication (MMBIR). Taken together this represents the first evidence for a CHD7 intragenic CGR in a patient with CHARGE syndrome leading to what appears to be also the first report of a mutation specifically disrupting exon-7. Although likely rare, CGR may represent an overlooked mechanism in subjects with CHARGE syndrome that can be missed by current sequencing and dosage assays.Item MIB2 variants altering NOTCH signalling result in left ventricle hypertrabeculation/non-compaction and are associated with Ménétrier-like gastropathy(Oxford, 2017) Piccolo, Pasquale; Attanasio, Sergio; Secco, Ilaria; Sangermano, Riccardo; Strisciuglio, Caterina; Limongelli, Giuseppe; Miele, Erasmo; Mutarelli, Margherita; Banfi, Sandro; Nigro, Vincenzo; Pons, Tirso; Valencia, Alfonso; Zentilin, Lorena; Campione, Severo; Nardone, Gerardo; Lynnes, Ty C.; Celestino-Soper, Patricia B. S.; Spoonamore, Katherine G.; D'Armiento, Franco; Giacca, Mauro; Staiano, Annamaria; Vatta, Matteo; Collesi, Chiari; Brunetti-Pierri, Nicola; Medicine, School of MedicineWe performed whole exome sequencing in individuals from a family with autosomal dominant gastropathy resembling Ménétrier disease, a premalignant gastric disorder with epithelial hyperplasia and enhanced EGFR signalling. Ménétrier disease is believed to be an acquired disorder, but its aetiology is unknown. In affected members, we found a missense p.V742G variant in MIB2, a gene regulating NOTCH signalling that has not been previously linked to human diseases. The variant segregated with the disease in the pedigree, affected a highly conserved amino acid residue, and was predicted to be deleterious although it was found with a low frequency in control individuals. The purified protein carrying the p.V742G variant showed reduced ubiquitination activity in vitro and white blood cells from affected individuals exhibited significant reductions of HES1 and NOTCH3 expression reflecting alteration of NOTCH signalling. Because mutations of MIB1, the homolog of MIB2, have been found in patients with left ventricle non-compaction (LVNC), we investigated members of our family with Ménétrier-like disease for this cardiac abnormality. Asymptomatic left ventricular hypertrabeculation, the mildest end of the LVNC spectrum, was detected in two members carrying the MIB2 variant. Finally, we identified an additional MIB2 variant (p.V984L) affecting protein stability in an unrelated isolated case with LVNC. Expression of both MIB2 variants affected NOTCH signalling, proliferation and apoptosis in primary rat cardiomyocytes. In conclusion, we report the first example of left ventricular hypertrabeculation/LVNC with germline MIB2 variants resulting in altered NOTCH signalling that might be associated with a gastropathy clinically overlapping with Ménétrier disease.Item Phosphorylation of the RSRSP stretch is critical for splicing regulation by RNA-Binding Motif Protein 20 (RBM20) through nuclear localization(Nature Publishing Group, 2018-06-12) Murayama, Rie; Kimura-Asami, Mariko; Togo-Ohno, Marina; Yamasaki-Kato, Yumiko; Naruse, Taeko K.; Yamamoto, Takeshi; Hayashi, Takeharu; Ai, Tomohiko; Spoonamore, Katherine G.; Kovacs, Richard J.; Vatta, Matteo; Iizuka, Mai; Saito, Masumi; Wani, Shotaro; Hiraoka, Yuichi; Kimura, Akinori; Kuroyanagi, Hidehito; Medicine, School of MedicineRBM20 is a major regulator of heart-specific alternative pre-mRNA splicing of TTN encoding a giant sarcomeric protein titin. Mutation in RBM20 is linked to autosomal-dominant familial dilated cardiomyopathy (DCM), yet most of the RBM20 missense mutations in familial and sporadic cases were mapped to an RSRSP stretch in an arginine/serine-rich region of which function remains unknown. In the present study, we identified an R634W missense mutation within the stretch and a G1031X nonsense mutation in cohorts of DCM patients. We demonstrate that the two serine residues in the RSRSP stretch are constitutively phosphorylated and mutations in the stretch disturb nuclear localization of RBM20. Rbm20 S637A knock-in mouse mimicking an S635A mutation reported in a familial case showed a remarkable effect on titin isoform expression like in a patient carrying the mutation. These results revealed the function of the RSRSP stretch as a critical part of a nuclear localization signal and offer the Rbm20 S637A mouse as a good model for in vivo study.Item A post mortem assessment of a 25-year-old man with ascending aortic dissection and a novel MYLK variant(PAGEpress, 2015) Hodge, Katelyn; Spoonamore, Katherine G.; Griffith, Christopher B.; Weaver, David D.; Celestino-Soper, Patricia B. S.; Lynnes, Ty C.; Gao, Hongyu; Liu, Yunlong; Vatta, Matteo; Medical and Molecular Genetics, School of MedicineWe report on the process of post mortem evaluation and genetic testing following the death of a 25-year-old man due to ascending aortic dissection leading to aortic rupture. Following the negative clinical testing of a 12- gene thoracic aortic aneurysm and dissection panel, research testing revealed a novel c.5732A>T (p.E1911V) variant in exon 34 of the MYLK gene (NM_053025). Two likely pathogenic variants in this gene have been reported previously in individuals with familial thoracic aortic aneurysm and dissection. Given the unclear clinical consequence of the variant found in our proband, we have classified this change as a variant of uncertain significance. In addition to discussing the complexity involved in variant interpretation, we recognize the need for additional research for more accurate MYLK interpretation. Finally, we comment on the unique challenges of post mortem genetic testing.Item Validation and Utilization of a Clinical Next-Generation Sequencing Panel for Selected Cardiovascular Disorders(Frontiers, 2017-03-15) Celestino-Soper, Patrícia B. S.; Gao, Hongyu; Lynnes, Ty C.; Lin, Hai; Liu, Yunlong; Spoonamore, Katherine G.; Chen, Peng-Sheng; Vatta, Matteo; Department of Medical & Molecular Genetics, IU School of MedicineThe development of high-throughput technologies such as next-generation sequencing (NGS) has allowed for thousands of DNA loci to be interrogated simultaneously in a fast and economical method for the detection of clinically deleterious variants. Whenever a clinical diagnosis is known, a targeted NGS approach involving the use of disease-specific gene panels can be employed. This approach is often valuable as it allows for a more specific and clinically relevant interpretation of results. Here, we describe the customization, validation, and utilization of a commercially available targeted enrichment platform for the scalability of clinical diagnostic cardiovascular genetic tests, including the design of the gene panels, the technical parameters for the quality assurance and quality control, the customization of the bioinformatics pipeline, and the post-bioinformatics analysis procedures. Regions of poor base coverage were detected and targeted by Sanger sequencing as needed. All panels were successfully validated using genotype-known DNA samples either commercially available or from research subjects previously tested in outside clinical laboratories. In our experience, utilizing several of the sub-panels in a clinical setting with 33 real-life cardiovascular patients, we found that 20% of tests requested were reported to have at least one pathogenic or likely pathogenic variant that could explain the patient phenotype. For each of these patients, the positive results may aid the clinical team and the patients in best developing a disease management plan and in identifying relatives at risk.Item Who Pays? Coverage Challenges for Cardiovascular Genetic Testing in U.S. Patients(Frontiers Media SA, 2016) Spoonamore, Katherine G.; Johnson, Nicole M.; Department of Medicine, IU School of MedicineInherited cardiovascular (CV) conditions are common, and comprehensive care of affected families often involves genetic testing. When the clinical presentations of these conditions overlap, genetic testing may clarify diagnoses, etiologies, and treatments in symptomatic individuals and facilitate the identification of asymptomatic, at-risk relatives, allowing for often life-saving preventative care. Although some professional society guidelines on inherited cardiac conditions include genetic testing recommendations, they quickly become outdated owing to the rapid expansion and use of such testing. Currently, these guidelines primarily discuss the benefits of targeted genetic testing for identifying at-risk relatives. Although most insurance policies acknowledge the benefit and the necessity of this testing, many exclude coverage for testing altogether or are vague about coverage for testing in probands, which is imperative if clinicians are to have the best chance of accurately identifying pathogenic variant(s) in a family. In response to uncertainties about coverage, many commercial CV genetic testing laboratories have shouldered the burden of working directly with commercial payers and protecting patients/institutions from out-of-pocket costs. As a result, many clinicians are unaware that payer coverage policies may not match professional recommendations for CV genetic testing. This conundrum has left patients, clinicians, payers, and laboratories at an impasse when determining the best path forward for meaningful and sustainable testing. Herein, we discuss the need for all involved parties to recognize their common goals in this process, which should motivate collaboration in changing existing frameworks and creating more sustainable access to genetic information for families with inherited CV conditions.