The thyroid hormone receptors: molecular basis of thyroid hormone resistance

Area of Science:

• Endocrinology
• Molecular Biology
• Genetics

Background:

• Thyroid hormones regulate cell function and development.
• The thyroid hormone receptor (TR) is a nuclear receptor crucial for these actions.
• Identification of TR as the c-erbA proto-oncogene product advanced understanding of hormone mechanisms.

Purpose of the Study:

• To elucidate the mechanism of action of thyroid hormones.
• To investigate the role of TRbeta mutations in thyroid hormone resistance.
• To understand how altered TRbeta impacts gene regulation.

Main Methods:

• Identification of T3-binding and non-binding receptor subsets.
• Analysis of TRbeta mutations in unrelated families with thyroid hormone resistance.
• Assessment of mutant TR binding to thyroid hormone response elements (TREs).
• Evaluation of TRbeta gene deletion effects.

Main Results:

• Distinct mutations in the TRbeta T3-binding domain were found in unrelated families.
• Mutant TRs bind to TREs on both positive and negative T3-controlled genes.
• Heterozygous TRbeta gene deletion did not affect subjects, supporting a dominant negative effect.
• Mutant TRbeta interferes with normal TR function via competition for TREs or dimer formation.

Conclusions:

• Mutations in TRbeta are a significant cause of thyroid hormone resistance.
• Mutant TRbeta exerts a dominant negative effect on gene regulation.
• Mechanisms include competition for TREs and formation of inactive dimers, impacting cell regulation.