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The lacrimal gland expresses nuclear retinoid X receptors
J L Ubels1, T H Sulahian, M D Viel
1Biology Department, Calvin College, Grand Rapids, MI 49546, USA.
Purpose:
The lacrimal gland expresses nuclear retinoic acid receptors. This suggests that retinoids are involved in control of gene expression in the lacrimal gland. Retinoid X receptors (RXRs) form heterodimers with and are required for activation of retinoic acid receptors. The purpose of this study was to identify retinoid X receptors in the lacrimal gland.
Methods:
Total RNA was purified from rat, rabbit and human lacrimal glands and from cultured rat lacrimal cells. RNA was analyzed by northern blotting using cDNA probes for RXR alpha, RXR beta and RXR gamma. Nuclear protein extracts from rat and rabbit lacrimal glands were probed for RXR beta by immunoblotting, using a mouse monoclonal antibody.
Results:
RXR alpha mRNA transcripts (5 kb) and RXR beta mRNA transcripts (3.3 kb) are present in the lacrimal glands of all species studied and in cultured rat lacrimal cells. RXR gamma mRNA (1.9 kb) was detected only in the rabbit lacrimal gland. RXR beta is expressed as a 50 kDa protein in rat and rabbit lacrimal glands.
Conclusions:
This study confirms the presence of RXRs in the lacrimal gland, thereby supporting a role for retinoids and their nuclear receptors in the control of gene transcription in the lacrimal gland.