• Authors: Froidevaux, M. S., Berg, P., Seugnet, I., Decherf, S., Becker, N., Sachs, L. M., Bilesimo, P., Nygard, M., Pongratz, I., Demeneix, B. A.
  • Year: 2006
  • Journal: EMBO Rep 7 1182
  • Applications: in vivo / DNA, siRNA / jetSI 10 mM


20 to 200 nM of siRNA were contransfected with two DNA plasmids into the hypothalamus of 1-day-old mice using jetSI 10 mM. The injection volume per mouse was 2 µl.


Transcriptional control of hypothalamic thyrotropin-releasing hormone (TRH) integrates central regulation of the hypothalamo-hypophyseal-thyroid axis and hence thyroid hormone (triiodothyronine (T(3))) homeostasis. The two beta thyroid hormone receptors, TRbeta1 and TRbeta2, contribute to T(3) feedback on TRH, with TRbeta1 having a more important role in the activation of TRH transcription. How TRbeta1 fulfils its role in activating TRH gene transcription is unknown. By using a yeast two-hybrid screening of a mouse hypothalamic complementary DNA library, we identified a novel partner for TRbeta1, hepatitis virus B X-associated protein 2 (XAP2), a protein first identified as a co-chaperone protein. TR-XAP2 interactions were TR isoform specific, being observed only with TRbeta1, and were enhanced by T(3) both in yeast and mammalian cells. Furthermore, small inhibitory RNA-mediated knockdown of XAP2 in vitro affected the stability of TRbeta1. In vivo, siXAP2 abrogated specifically TRbeta1-mediated (but not TRbeta2) activation of hypothalamic TRH transcription. This study provides the first in vivo demonstration of a regulatory, physiological role for XAP2.