TY - JOUR
T1 - Truncated titin proteins and titin haploinsufficiency are targets for functional recovery in human cardiomyopathy due to TTN mutations
AU - Fomin, Andrey
AU - Gärtner, Anna
AU - Cyganek, Lukas
AU - Tiburcy, Malte
AU - Tuleta, Izabela
AU - Wellers, Luisa
AU - Folsche, Lina
AU - Hobbach, Anastasia J
AU - von Frieling-Salewsky, Marion
AU - Unger, Andreas
AU - Hucke, Anna
AU - Koser, Franziska
AU - Kassner, Astrid
AU - Sielemann, Katharina
AU - Streckfuß-Bömeke, Katrin
AU - Hasenfuss, Gerd
AU - Goedel, Alexander
AU - Laugwitz, Karl-Ludwig
AU - Moretti, Alessandra
AU - Gummert, Jan F
AU - Dos Remedios, Cristobal G
AU - Reinecke, Holger
AU - Knöll, Ralph
AU - van Heesch, Sebastiaan
AU - Hubner, Norbert
AU - Zimmermann, Wolfram H
AU - Milting, Hendrik
AU - Linke, Wolfgang A
PY - 2021/11/3
Y1 - 2021/11/3
N2 - Heterozygous truncating variants in TTN (TTNtv), the gene coding for titin, cause dilated cardiomyopathy (DCM), but the underlying pathomechanisms are unclear and disease management remains uncertain. Truncated titin proteins have not yet been considered as a contributor to disease development. Here, we studied myocardial tissues from nonfailing donor hearts and 113 patients with end-stage DCM for titin expression and identified a TTNtv in 22 patients with DCM (19.5%). We directly demonstrate titin haploinsufficiency in TTNtv-DCM hearts and the absence of compensatory changes in the alternative titin isoform Cronos. Twenty-one TTNtv-DCM hearts in our cohort showed stable expression of truncated titin proteins. Expression was variable, up to half of the total titin protein pool, and negatively correlated with patient age at heart transplantation. Truncated titin proteins were not detected in sarcomeres but were present in intracellular aggregates, with deregulated ubiquitin-dependent protein quality control. We produced human induced pluripotent stem cell–derived cardiomyocytes (hiPSC-CMs), comparing wild-type controls to cells with a patient-derived, prototypical A-band-TTNtv or a CRISPR-Cas9–generated M-band-TTNtv. TTNtv-hiPSC-CMs showed reduced wild-type titin expression and contained truncated titin proteins whose proportion increased upon inhibition of proteasomal activity. In engineered heart muscle generated from hiPSC-CMs, depressed contractility caused by TTNtv could be reversed by correction of the mutation using CRISPR-Cas9, eliminating truncated titin proteins and raising wild-type titin content. Functional improvement also occurred when wild-type titin protein content was increased by proteasome inhibition. Our findings reveal the major pathomechanisms of TTNtv-DCM and can be exploited for new therapies to treat TTNtv-related cardiomyopathies.
AB - Heterozygous truncating variants in TTN (TTNtv), the gene coding for titin, cause dilated cardiomyopathy (DCM), but the underlying pathomechanisms are unclear and disease management remains uncertain. Truncated titin proteins have not yet been considered as a contributor to disease development. Here, we studied myocardial tissues from nonfailing donor hearts and 113 patients with end-stage DCM for titin expression and identified a TTNtv in 22 patients with DCM (19.5%). We directly demonstrate titin haploinsufficiency in TTNtv-DCM hearts and the absence of compensatory changes in the alternative titin isoform Cronos. Twenty-one TTNtv-DCM hearts in our cohort showed stable expression of truncated titin proteins. Expression was variable, up to half of the total titin protein pool, and negatively correlated with patient age at heart transplantation. Truncated titin proteins were not detected in sarcomeres but were present in intracellular aggregates, with deregulated ubiquitin-dependent protein quality control. We produced human induced pluripotent stem cell–derived cardiomyocytes (hiPSC-CMs), comparing wild-type controls to cells with a patient-derived, prototypical A-band-TTNtv or a CRISPR-Cas9–generated M-band-TTNtv. TTNtv-hiPSC-CMs showed reduced wild-type titin expression and contained truncated titin proteins whose proportion increased upon inhibition of proteasomal activity. In engineered heart muscle generated from hiPSC-CMs, depressed contractility caused by TTNtv could be reversed by correction of the mutation using CRISPR-Cas9, eliminating truncated titin proteins and raising wild-type titin content. Functional improvement also occurred when wild-type titin protein content was increased by proteasome inhibition. Our findings reveal the major pathomechanisms of TTNtv-DCM and can be exploited for new therapies to treat TTNtv-related cardiomyopathies.
KW - Cardiomyopathies/genetics
KW - Connectin/genetics
KW - Haploinsufficiency
KW - Heart Transplantation
KW - Humans
KW - Induced Pluripotent Stem Cells/metabolism
KW - Mutation
KW - Myocytes, Cardiac/metabolism
KW - Tissue Donors
U2 - 10.1126/scitranslmed.abd3079
DO - 10.1126/scitranslmed.abd3079
M3 - Article
C2 - 34731013
SN - 1946-6234
VL - 13
SP - eabd3079
JO - Science translational medicine
JF - Science translational medicine
IS - 618
ER -