Exploration of pathomechanisms triggered by a single-nucleotide polymorphism in titin's I-band: the cardiomyopathy-linked mutation T2580I

Abstract

Missense single-nucleotide polymorphisms (mSNPs) in titin are emerging as a main causative factor of heart failure. However, distinguishing between benign and disease-causing mSNPs is a substantial challenge. Here, we research the question of whether a single mSNP in a generic domain of titin can affect heart function as a whole and, if so, how. For this, we studied the mSNP T2850I, seemingly linked to arrhythmogenic right ventricular cardiomyopathy (ARVC). We used structural biology, computational simulations and transgenic muscle in vivo methods to track the effect of the mutation from the molecular to the organismal level. The data show that the T2850I exchange is compatible with the domain three-dimensional fold, but that it strongly destabilizes it. Further, it induces a change in the conformational dynamics of the titin chain that alters its reactivity, causing the formation of aberrant interactions in the sarcomere. Echocardiography of knock-in mice indicated a mild diastolic dysfunction arising from increased myocardial stiffness. In conclusion, our data provide evidence that single mSNPs in titin's I-band can alter overall muscle behaviour. Our suggested mechanisms of disease are the development of non-native sarcomeric interactions and titin instability leading to a reduced I-band compliance. However, understanding the T2850I-induced ARVC pathology mechanistically remains a complex problem and will require a deeper understanding of the sarcomeric context of the titin region affected.

Twitchin kinase inhibits muscle activity

“…Furthermore, structural studies on mutated protein variants showing decreased thermal stabilities of up to ∼10°C found that fold alterations are rarely detectable in such cases. As an example, a nuclear magnetic resonance study of a variant of domain I10 from titin carrying the exchange T2850I (Δ T m ≈ −11°C) did not reveal any significant structural alteration—globally or locally ( Bogomolovas et al. , 2016 ).…”

High proportion of genetic cases in patients with advanced cardiomyopathy including a novel homozygous Plakophilin 2-gene mutation

“…Because of the background noise in the general population TTN missense variants were classified as VUS although recent large-scale sequencing and functional analysis indicated strong impact on cardiomyopathies [ 40 – 42 ]. Protein unfolding and domain destabilization was shown and/or predicted for TTN missense mutations located in the Z-disk [ 42 ], A/I junction region [ 43 ], and in the I-band [ 41 ] of the protein, respectively. Decreased contractile force generation of a missense mutation located in the Z/I-band junction was reported by Hinson et al [ 35 ].…”

Protein nanomechanics in biological context

“…Prompted by the sophisticated nanomechanical design of these proteins and the fact that mutations can change protein nanomechanics, there has been an interest in examining if disease-causing variants can alter the nanomechanics of titin and MyBP-C. Specifically, arrhythmogenic-cardiomyopathy-causing mutation T16I was found to decrease the mechanical stability of the Ig10 domain of titin (Anderson et al 2013), although this effect is concomitant with a marked decrease in thermodynamic stability (Bogomolovas et al 2016). More recently, nanomechanical alterations in mutant cardiac MyBP-C that cause hypertrophic cardiomyopathy have been detected.…”