Scholarlink

Background <p>Missense variants in <i>TTN</i> pose a major challenge in genetic diagnostics due to their high frequency in the general population, the large size of the gene, and the complex multidomain architecture of the titin protein. While the contribution of truncating variants (TTNtv) to titinopathies is well established, the role of rare <i>TTN</i> missense variants remains poorly defined. Advances in computational prediction and functional testing offer new tools to assess their potential pathogenicity, which however are currently not fully utilized for clinical application.</p> Methods <p>We analyzed an international cohort of unsolved myopathy cases selected based on the presence of a rare missense variant in trans with a TTNtv. Clinical data were collected from neuromuscular centers worldwide. In silico predictions were generated using AlphaMissense and complemented by minor allele frequency (MAF) and exon usage information. Additional inclusion criteria were based on a MAF &lt; 0.010 and an AlphaMissense score ≥ 0.792 for the missense variants, in accordance with the latest ClinGen guidelines. Selected missense variants were characterized in vitro through protein expression and cell imaging assays to assess their effects on domain solubility and aggregation.</p> Results <p>Thirty patients with TTNtv/missense combinations were identified, presenting with heterogeneous myopathic phenotypes, ranging from congenital to adult onset. An in-depth analysis on AlphaMissense predictions highlighted those changes most frequently predicted as possibly pathogenic. Functional assays showed that three selected variants with changes to proline, located in β-sheets of Ig domains, led to impaired folding, cytoplasmic aggregation and co-localisation with proteostasis markers. In our cohort, all non-proline mutations occurred at buried sites, while some proline substitutions affected exposed residues. Notably, the variant p.(Gln7023Pro) was identified in 5 unrelated families sharing a conserved haplotype, indicating a common ancestor. This variant and the previously reported p.(Arg25480Pro) now meet ACMG criteria for classification as likely pathogenic.</p> Conclusions <p>By integrating clinical, computational, and functional evidence, we propose a framework for interpreting <i>TTN</i> missense variants. Combining multiple lines of evidence is essential for variants’ classification and interpretation, especially given <i>TTN</i> complexity. Advancing diagnostic accuracy will require tailored interpretation guidelines and a global effort in data sharing and functional validation.</p>

错误：搜索内容不能为空，请输入英文关键词
错误：关键词超出字数限制，请精简
高级检索

A comprehensive framework for the interpretation of TTN missense variants

  • 期刊论文

  • 出版模式：

    开放获取

  • 发表日期：

    2026年2月26日

查看全文
  • Maria Francesca Di Feo,
  • Martin Rees,
  • Victoria Lillback,
  • Ay Lin Kho,
  • Angelina Meybatova,
  • Mark Holt,
  • Heinz Jungbluth,
  • Francesco Muntoni,
  • Giovanni Baranello,
  • Anna Sarkozy,
  • Chiara Fiorillo,
  • Serena Baratto,
  • Claudio Bruno,
  • Monica Traverso,
  • Michele Iacomino,
  • Marina Pedemonte,
  • Noemi Brolatti,
  • Francesca Faravelli,
  • Federico Zara,
  • G. M. Luana Mandarà,
  • Alan H. Beggs,
  • Casie A. Genetti,
  • Pamela Barraza-Flores,
  • Carmelo Rodolico,
  • Sonia Messina,
  • Franziska Schnabel,
  • Istvan Balogh,
  • Katalin Szakszon,
  • Siiri Sarv,
  • Katrin Õunap,
  • Federica Silvia Ricci,
  • Alessandro Mussa,
  • Edoardo Malfatti,
  • Enrico Silvio Bertini,
  • Adele D’Amico,
  • Daria Diodato,
  • Michela Catteruccia,
  • Gianina Ravenscroft,
  • Mridul Johari,
  • Sergei A. Kurbatov,
  • Polina Chausova,
  • Aysylu Murtazina,
  • Anna Kuchina,
  • Olga Shchagina,
  • Minas Drakos,
  • Martha Spilioti,
  • Athanasios E. Evangeliou,
  • Ioannis Zaganas,
  • Huahua Zhong,
  • Sushan Luo,
  • Luciano Merlini,
  • Cam-Tu-Emilie Nguyen,
  • Giorgio Tasca,
  • Tara Reeves,
  • Stellan Mörner,
  • Olof Danielsson,
  • Bjarne Udd,
  • Daniel Natera-de Benito,
  • Berta Estevez Arias,
  • Aishwarya Dhall,
  • Bandana Jassal,
  • Venugopalan Y. Vishnu,
  • Mohammed Faruq,
  • Sheffali Gulati,
  • Mehar Chand Sharma,
  • Johana Kopčilová,
  • Tereza Kramářová,
  • Jana Zídková,
  • Mathias Gautel,
  • Marco Savarese

摘要

Background

Missense variants in TTN pose a major challenge in genetic diagnostics due to their high frequency in the general population, the large size of the gene, and the complex multidomain architecture of the titin protein. While the contribution of truncating variants (TTNtv) to titinopathies is well established, the role of rare TTN missense variants remains poorly defined. Advances in computational prediction and functional testing offer new tools to assess their potential pathogenicity, which however are currently not fully utilized for clinical application.

Methods

We analyzed an international cohort of unsolved myopathy cases selected based on the presence of a rare missense variant in trans with a TTNtv. Clinical data were collected from neuromuscular centers worldwide. In silico predictions were generated using AlphaMissense and complemented by minor allele frequency (MAF) and exon usage information. Additional inclusion criteria were based on a MAF < 0.010 and an AlphaMissense score ≥ 0.792 for the missense variants, in accordance with the latest ClinGen guidelines. Selected missense variants were characterized in vitro through protein expression and cell imaging assays to assess their effects on domain solubility and aggregation.

Results

Thirty patients with TTNtv/missense combinations were identified, presenting with heterogeneous myopathic phenotypes, ranging from congenital to adult onset. An in-depth analysis on AlphaMissense predictions highlighted those changes most frequently predicted as possibly pathogenic. Functional assays showed that three selected variants with changes to proline, located in β-sheets of Ig domains, led to impaired folding, cytoplasmic aggregation and co-localisation with proteostasis markers. In our cohort, all non-proline mutations occurred at buried sites, while some proline substitutions affected exposed residues. Notably, the variant p.(Gln7023Pro) was identified in 5 unrelated families sharing a conserved haplotype, indicating a common ancestor. This variant and the previously reported p.(Arg25480Pro) now meet ACMG criteria for classification as likely pathogenic.

Conclusions

By integrating clinical, computational, and functional evidence, we propose a framework for interpreting TTN missense variants. Combining multiple lines of evidence is essential for variants’ classification and interpretation, especially given TTN complexity. Advancing diagnostic accuracy will require tailored interpretation guidelines and a global effort in data sharing and functional validation.