25(OH) 2D3 signaling pathway, namely the passage of 1, 25(OH) 2D3 through the plasma
membrane, its binding to the vitamin response (VDR), transport to the nucleus, and the binding
of the heterodimer VDR-RXR to its response element cannot be excluded although they did not
result in altered production of the reporter.
These data suggested that other factors in the promoter beside VDRE can affect 1, 25(OH) 2D3-
induced gene expression during microgravity. Recently, it has become evident that chromatin
modifications outside the binding sites for transcription factors contribute to gene transcription
and this has also been observed for vitamin D-regulated gene expression. It therefore remains
possible that 1, 25(OH) 2D3-induced gene transcription was impaired under microgravity due to
chromatin modifications.
PUBLICATION(S)
Coenegrachts L, Stockmans I, Segers I, Bouillon R, Carmeliet G. The effect of microgravity on 1,
25-dihydroxyvitamin d3 signaling in osteoblasts. Microgravity Science and Technology.
September 2007;19(5-6):154-158. doi: 10.1007/BF02919472.
This investigation is complete and all results are published.