{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,18]],"date-time":"2026-08-18T01:54:34Z","timestamp":1787018074519,"version":"build-2736575974"},"reference-count":40,"publisher":"Ovid Technologies (Wolters Kluwer Health)","issue":"3","content-domain":{"domain":["www.ahajournals.org"],"crossmark-restriction":true},"short-container-title":["Circulation"],"published-print":{"date-parts":[[2022,1,18]]},"abstract":"<jats:sec>\n                    <jats:title>Background:<\/jats:title>\n                    <jats:p>Titin truncation variants (TTNtvs) are the most common inheritable risk factor for dilated cardiomyopathy (DCM), a disease with high morbidity and mortality. The pathogenicity of TTNtvs has been associated with structural localization as A-band variants overlapping myosin heavy chain\u2013binding domains are more pathogenic than I-band variants by incompletely understood mechanisms. Demonstrating why A-band variants are highly pathogenic for DCM could reveal new insights into DCM pathogenesis, titin (TTN) functions, and therapeutic targets.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods:<\/jats:title>\n                    <jats:p>We constructed human cardiomyocyte models harboring DCM-associated TTNtvs within A-band and I-band structural domains using induced pluripotent stem cell and CRISPR technologies. We characterized normal TTN isoforms and variant-specific truncation peptides by their expression levels and cardiomyocyte localization using TTN protein gel electrophoresis and immunofluorescence, respectively. Using CRISPR to ablate A-band variant\u2013specific truncation peptides through introduction of a proximal I-band TTNtv, we studied genetic mechanisms in single cardiomyocyte and 3-dimensional, biomimetic cardiac microtissue functional assays. Last, we engineered a full-length TTN protein reporter assay and used next-generation sequencing assays to develop a CRISPR therapeutic for somatic cell genome editing TTNtvs.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results:<\/jats:title>\n                    <jats:p>An A-band TTNtv dose-dependently impaired cardiac microtissue twitch force, reduced full-length TTN levels, and produced abundant TTN truncation peptides. TTN truncation peptides integrated into nascent myofibril-like structures and impaired myofibrillogenesis. CRISPR ablation of TTN truncation peptides using a proximal I-band TTNtv partially restored cardiac microtissue twitch force deficits. Cardiomyocyte genome editing using SpCas9 and a TTNtv-specific guide RNA restored the TTN protein reading frame, which increased full-length TTN protein levels, reduced TTN truncation peptides, and increased sarcomere function in cardiac microtissue assays.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions:<\/jats:title>\n                    <jats:p>An A-band TTNtv diminished sarcomere function greater than an I-band TTNtv in proportion to estimated DCM pathogenicity. Although both TTNtvs resulted in full-length TTN haploinsufficiency, only the A-band TTNtv produced TTN truncation peptides that impaired myofibrillogenesis and sarcomere function. CRISPR-mediated reading frame repair of the A-band TTNtv restored functional deficits, and could be adapted as a one-and-done genome editing strategy to target \u224830% of DCM-associated TTNtvs.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1161\/circulationaha.120.049997","type":"journal-article","created":{"date-parts":[[2021,12,14]],"date-time":"2021-12-14T17:54:17Z","timestamp":1639504457000},"page":"194-205","update-policy":"https:\/\/doi.org\/10.1161\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":40,"title":["Reading Frame Repair of\n                    <i>TTN<\/i>\n                    Truncation Variants Restores Titin Quantity and Functions"],"prefix":"10.1161","volume":"145","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-1947-3233","authenticated-orcid":true,"given":"Robert","family":"Romano","sequence":"first","affiliation":[{"name":"University of Connecticut Health Center, Farmington (R.R., F.A.L., A.M.P., J.T.H.)."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Shahnaz","family":"Ghahremani","sequence":"additional","affiliation":[{"name":"The Jackson Laboratory for Genomic Medicine, Farmington, CT (S.G., T.Z., N.L., K.T., J.T.H.)."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Talia","family":"Zimmerman","sequence":"additional","affiliation":[{"name":"The Jackson Laboratory for Genomic Medicine, Farmington, CT (S.G., T.Z., N.L., K.T., J.T.H.)."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nicholas","family":"Legere","sequence":"additional","affiliation":[{"name":"The Jackson Laboratory for Genomic Medicine, Farmington, CT (S.G., T.Z., N.L., K.T., J.T.H.)."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ketan","family":"Thakar","sequence":"additional","affiliation":[{"name":"The Jackson Laboratory for Genomic Medicine, Farmington, CT (S.G., T.Z., N.L., K.T., J.T.H.)."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Feria A.","family":"Ladha","sequence":"additional","affiliation":[{"name":"University of Connecticut Health Center, Farmington (R.R., F.A.L., A.M.P., J.T.H.)."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5623-8315","authenticated-orcid":true,"given":"Anthony M.","family":"Pettinato","sequence":"additional","affiliation":[{"name":"University of Connecticut Health Center, Farmington (R.R., F.A.L., A.M.P., J.T.H.)."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1455-113X","authenticated-orcid":true,"given":"J. Travis","family":"Hinson","sequence":"additional","affiliation":[{"name":"University of Connecticut Health Center, Farmington (R.R., F.A.L., A.M.P., J.T.H.)."},{"name":"The Jackson Laboratory for Genomic Medicine, Farmington, CT (S.G., T.Z., N.L., K.T., 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