Functional analysis of a gene-edited mouse model to gain insights into the disease mechanisms of a titin missense variant

He Jiang, Charlotte Hooper, Matthew Kelly, Violetta Steeples, Jillian N. Simon, Julia Beglov, Amar J. Azad, Lisa Leinhos, Pauline Bennett, Elisabeth Ehler, Jacinta I. Kalisch-Smith, Duncan B. Sparrow, Roman Fischer, Raphael Heilig, Henrik Isackson, Mehroz Ehsan, Giannino Patone, Norbert Huebner, Benjamin Davies, Hugh WatkinsKatja Gehmlich*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)

Abstract

Titin truncating variants are a well-established cause of cardiomyopathy; however, the role of titin missense variants is less well understood. Here we describe the generation of a mouse model to investigate the underlying disease mechanism of a previously reported titin A178D missense variant identified in a family with non-compaction and dilated cardiomyopathy. Heterozygous and homozygous mice carrying the titin A178D missense variant were characterised in vivo by echocardiography. Heterozygous mice had no detectable phenotype at any time point investigated (up to 1 year). By contrast, homozygous mice developed dilated cardiomyopathy from 3 months. Chronic adrenergic stimulation aggravated the phenotype. Targeted transcript profiling revealed induction of the foetal gene programme and hypertrophic signalling pathways in homozygous mice, and these were confirmed at the protein level. Unsupervised proteomics identified downregulation of telethonin and four-and-a-half LIM domain 2, as well as the upregulation of heat shock proteins and myeloid leukaemia factor 1. Loss of telethonin from the cardiac Z-disc was accompanied by proteasomal degradation; however, unfolded telethonin accumulated in the cytoplasm, leading to a proteo-toxic response in the mice.We show that the titin A178D missense variant is pathogenic in homozygous mice, resulting in cardiomyopathy. We also provide evidence of the disease mechanism: because the titin A178D variant abolishes binding of telethonin, this leads to its abnormal cytoplasmic accumulation. Subsequent degradation of telethonin by the proteasome results in proteasomal overload, and activation of a proteo-toxic response. The latter appears to be a driving factor for the cardiomyopathy observed in the mouse model.

Original languageEnglish
Article number14
JournalBasic Research in Cardiology
Volume116
Issue number1
DOIs
Publication statusPublished - Dec 2021

Keywords

  • Cardiomyopathy
  • Mouse model
  • Proteasome
  • Proteo-toxic response
  • Telethonin
  • Titin missense variant

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