A single nucleotide insertion prevents the in vivo response of the Hairless gene to thyroid hormone

The transcription of the Hairless gene (Hr), which encodes a histone demethylase, is strongly induced by thyroid hormone (T3) in many cell types. This is mediated by heterodimers formed between T3 nuclear receptors and retinoid X receptors. These heterodimers are bound to specific DNA response elements present in regulatory sequences and activate transcription upon T3 binding. To address the significance of this regulation, we identified a single DNA response element upstream of the Hr transcription start site, which plays a key role in this regulation. A single nucleotide mutation in this DNA response element, which prevents the binding of heterodimers, was shown to prevent the activation of Hr by T3 signaling in mice. Analysis of gene expression in the heart and striatum of mice homozygous for this mutation highlights the influence of the Hairless cofactor on thyroid hormone signaling.