{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,26]],"date-time":"2026-10-26T18:52:15Z","timestamp":1793040735900,"version":"4.5.0"},"reference-count":50,"publisher":"Ovid Technologies (Wolters Kluwer Health)","issue":"16","content-domain":{"domain":["www.ahajournals.org"],"crossmark-restriction":true},"short-container-title":["Circulation"],"published-print":{"date-parts":[[2024,4,16]]},"abstract":"<jats:sec>\n            <jats:title>BACKGROUND:<\/jats:title>\n            <jats:p>\n              <jats:italic toggle=\"yes\">TTN<\/jats:italic>\n              truncation variants (TTNtvs) are the most common genetic lesion identified in individuals with dilated cardiomyopathy, a disease with high morbidity and mortality rates. TTNtvs reduce normal TTN (titin) protein levels, produce truncated proteins, and impair sarcomere content and function. Therapeutics targeting TTNtvs have been elusive because of the immense size of TTN, the rarity of specific TTNtvs, and incomplete knowledge of TTNtv pathogenicity.\n            <\/jats:p>\n          <\/jats:sec>\n          <jats:sec>\n            <jats:title>METHODS:<\/jats:title>\n            <jats:p>We adapted CRISPR activation using dCas9-VPR to functionally interrogate TTNtv pathogenicity and develop a therapeutic in human cardiomyocytes and 3-dimensional cardiac microtissues engineered from induced pluripotent stem cell models harboring a dilated cardiomyopathy\u2013associated TTNtv. We performed guide RNA screening with custom TTN reporter assays, agarose gel electrophoresis to quantify TTN protein levels and isoforms, and RNA sequencing to identify molecular consequences of TTN activation. Cardiomyocyte epigenetic assays were also used to nominate DNA regulatory elements to enable cardiomyocyte-specific TTN activation.<\/jats:p>\n          <\/jats:sec>\n          <jats:sec>\n            <jats:title>RESULTS:<\/jats:title>\n            <jats:p>\n              CRISPR activation of TTN using single guide RNAs targeting either the\n              <jats:italic toggle=\"yes\">TTN<\/jats:italic>\n              promoter or regulatory elements in spatial proximity to the\n              <jats:italic toggle=\"yes\">TTN<\/jats:italic>\n              promoter through 3-dimensional chromatin interactions rescued TTN protein deficits disturbed by TTNtvs. Increasing TTN protein levels normalized sarcomere content and contractile function despite increasing truncated TTN protein. In addition to\n              <jats:italic toggle=\"yes\">TTN<\/jats:italic>\n              transcripts, CRISPR activation also increased levels of myofibril assembly-related and sarcomere-related transcripts.\n            <\/jats:p>\n          <\/jats:sec>\n          <jats:sec>\n            <jats:title>CONCLUSIONS:<\/jats:title>\n            <jats:p>TTN CRISPR activation rescued TTNtv-related functional deficits despite increasing truncated TTN levels, which provides evidence to support haploinsufficiency as a relevant genetic mechanism underlying heterozygous TTNtvs. CRISPR activation could be developed as a therapeutic to treat a large proportion of TTNtvs.<\/jats:p>\n          <\/jats:sec>","DOI":"10.1161\/circulationaha.123.063972","type":"journal-article","created":{"date-parts":[[2024,1,18]],"date-time":"2024-01-18T10:00:34Z","timestamp":1705572034000},"page":"1285-1297","update-policy":"https:\/\/doi.org\/10.1161\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":37,"title":["CRISPR Activation Reverses Haploinsufficiency and Functional Deficits Caused by\n            <i>TTN<\/i>\n            Truncation Variants"],"prefix":"10.1161","volume":"149","author":[{"given":"Shahnaz","family":"Ghahremani","sequence":"first","affiliation":[{"name":"The Jackson Laboratory for Genomic Medicine, Farmington, CT (S.G., A.K., N.L., K.T., Y.Z., H.T., C.-L.W., J.T.H.)."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8066-6798","authenticated-orcid":true,"given":"Aditya","family":"Kanwal","sequence":"additional","affiliation":[{"name":"The Jackson Laboratory for Genomic Medicine, Farmington, CT (S.G., A.K., N.L., K.T., Y.Z., H.T., C.-L.W., J.T.H.)."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5623-8315","authenticated-orcid":true,"given":"Anthony","family":"Pettinato","sequence":"additional","affiliation":[{"name":"Cardiology Center, University of Connecticut Health Center, Farmington (A.P., F.L., A.W., J.C., J.T.H.)."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8576-3976","authenticated-orcid":true,"given":"Feria","family":"Ladha","sequence":"additional","affiliation":[{"name":"Cardiology Center, University of Connecticut Health Center, Farmington (A.P., F.L., A.W., J.C., 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., A.K., N.L., K.T., Y.Z., H.T., C.-L.W., 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., A.K., N.L., K.T., Y.Z., H.T., C.-L.W., J.T.H.)."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yanfen","family":"Zhu","sequence":"additional","affiliation":[{"name":"The Jackson Laboratory for Genomic Medicine, Farmington, CT (S.G., A.K., N.L., K.T., Y.Z., H.T., C.-L.W., J.T.H.)."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1451-3918","authenticated-orcid":true,"given":"Harianto","family":"Tjong","sequence":"additional","affiliation":[{"name":"The Jackson Laboratory for Genomic Medicine, Farmington, CT (S.G., A.K., N.L., K.T., Y.Z., H.T., C.-L.W., J.T.H.)."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4832-9476","authenticated-orcid":true,"given":"Andrea","family":"Wilderman","sequence":"additional","affiliation":[{"name":"Cardiology Center, University of Connecticut Health Center, Farmington (A.P., F.L., A.W., J.C., J.T.H.)."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"W. Tom","family":"Stump","sequence":"additional","affiliation":[{"name":"Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St Louis, MO (W.T.S., L.G., M.J.G.)."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6066-3135","authenticated-orcid":true,"given":"Lina","family":"Greenberg","sequence":"additional","affiliation":[{"name":"Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St Louis, MO (W.T.S., L.G., M.J.G.)."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1320-3547","authenticated-orcid":true,"given":"Michael J.","family":"Greenberg","sequence":"additional","affiliation":[{"name":"Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St Louis, MO (W.T.S., L.G., M.J.G.)."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8230-2157","authenticated-orcid":true,"given":"Justin","family":"Cotney","sequence":"additional","affiliation":[{"name":"Cardiology Center, University of Connecticut Health Center, Farmington (A.P., F.L., A.W., J.C., J.T.H.)."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Chia-Lin","family":"Wei","sequence":"additional","affiliation":[{"name":"The Jackson Laboratory for Genomic Medicine, Farmington, CT (S.G., A.K., N.L., K.T., Y.Z., H.T., C.-L.W., J.T.H.)."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1455-113X","authenticated-orcid":true,"given":"J. 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