A new mechanism in thra resistance: the first disease-associated variant leading to an increased inhibitory function of thra2

Sarah Paisdzior, Ellen Knierim, Gunnar Kleinau, Heike Biebermann, Heiko Krude, Rachel Straussberg*, Markus Schuelke*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

The nuclear thyroid hormone receptors (THRs) are key mediators of thyroid hormone function on the cellular level via modulation of gene expression. Two different genes encode THRs (THRA and THRB), and are pleiotropically involved in development, metabolism, and growth. The THRA1 and THRA2 isoforms, which result from alternative splicing of THRA, differ in their C-terminal ligand-binding domain (LBD). Most published disease-associated THRA variants are located in the LBD of THRA1 and impede triiodothyronine (T3) binding. This keeps the nuclear receptor in an inactive state and inhibits target gene expression. Here, we investigated a new dominant THRA variant (chr17:g.38,241,010A > G, GRCh37.13 | c.518A > G, NM_199334 | p.(E173G), NP_955366), which is located between the DNA-and ligand-binding domains and affects both splicing isoforms. Patients presented partially with hypothyroid (intellectual disability, motor developmental delay, brain atrophy, and constipation) and partially with hyperthyroid symptoms (tachycardia and behav-ioral abnormalities) to varying degrees. Functional characterization of THRA1p.(E173G) by reporter gene assays revealed increased transcriptional activity in contrast to THRA1(WT), unexpectedly revealing the first gain-of-function mutation found in THRA1. The THRA2 isoform does not bind T3 and antagonizes THRA1 action. Introduction of p.(E173G) into THRA2 increased its inhibitory effect on THRA1, which helps to explain the hypothyroid symptoms seen in our patients. We used protein structure models to investigate possible underlying pathomechanisms of this variant with a gain-of-antagonistic function and suggest that the p.(E173G) variant may have an influence on the dimerization domain of the nuclear receptor.

Original languageEnglish
Article number5338
JournalInternational Journal of Molecular Sciences
Volume22
Issue number10
DOIs
StatePublished - 2 May 2021

Funding

FundersFunder number
Deutsche ForschungsgemeinschaftEXC-2049—390688087, TRR 296 TP06

    Keywords

    • Gain-of-antagonistic function
    • Gain-of-function
    • Resistance to thyroid hormones
    • Thyroid hormone receptor alpha

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