Amino Acid-Level Signal-to-Noise Analysis Aids in Pathogenicity Prediction of Incidentally Identified <i>TTN</i>-Encoded Titin Truncating Variants.



TTN, the largest gene in the human body, encodes TTN (titin), a protein that plays key structural, developmental, and regulatory roles in skeletal and cardiac muscle. Variants in TTN, particularly truncating variants (TTNtvs), have been implicated in the pathogenicity of cardiomyopathy. Despite this link, there is also a high burden of TTNtvs in the ostensibly healthy general population. This complicates the diagnostic interpretation of incidentally identified TTNtvs, which are of increasing abundance given expanding clinical exome sequencing.


Incidentally identified TTNtvs were obtained from a large referral database of clinical exome sequencing (Baylor Genetics) and compared with rare population variants from genome aggregation database and cardiomyopathy-associated variants from cohort studies in the literature. A subset of TTNtv-positive children evaluated for cardiomyopathy at Texas Children's Hospital was retrospectively reviewed for clinical features of cardiomyopathy. Amino acid-level signal-to-noise analysis was performed.


Pathological hotspots were identified within the A-band and N-terminal I-band that closely correlated with regions of high percent-spliced in of exons. Incidental TTNtvs and population TTNtvs did not localize to these regions. Variants were reclassified based on current American College of Medical Genetics and Genomics criteria with incorporation of signal-to-noise analysis among Texas Children's Hospital cases. Those reclassified as likely pathogenic or pathogenic were more likely to have evidence of cardiomyopathy on echocardiography than those reclassified as variants of unknown significance.


Incidentally found TTNtvs are common among clinical exome sequencing referrals. Pathological hotspots within the A-band of TTN may be informative in determining variant pathogenicity when incorporated into current American College of Medical Genetics and Genomics guidelines.





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Publication Info

Connell, Patrick S, Amy M Berkman, BriAnna M Souder, Elisa J Pirozzi, Julia J Lovin, Jill A Rosenfeld, Pengfei Liu, Hari Tunuguntla, et al. (2021). Amino Acid-Level Signal-to-Noise Analysis Aids in Pathogenicity Prediction of Incidentally Identified TTN-Encoded Titin Truncating Variants. Circulation. Genomic and precision medicine, 14(1). p. e003131. 10.1161/circgen.120.003131 Retrieved from

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Andrew Paul Landstrom

Associate Professor of Pediatrics

Dr. Landstrom is a physician scientist who specializes in the care of children and young adults with arrhythmias, heritable cardiovascular diseases, and sudden unexplained death syndromes. As a clinician, he is trained in pediatric cardiology with a focus on arrhythmias and genetic diseases of the heart.  He specializes in caring for patients with heritable arrhythmia (channelopathies) such as long QT syndrome, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia, and short QT syndrome.  He also specializes in the evaluation of children following a cardiac arrest or after the sudden and unexplained death of a family member.  He has expertise in cardiovascular genetics and uses it to identify individuals in a family who may be at risk of a disease, even if all clinical testing is negative.  As a scientist, he is trained in genetics and cell biology.  He runs a research lab exploring the genetic and molecular causes of arrhythmias, sudden unexplained death syndromes, and heart muscle disease (cardiomyopathies).  He utilizes patient-derived induced pluripotent stem cells and genetic mouse models to identify the mechanisms of cardiovascular genetic disease with the goal of developing novel therapies.

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