Gene Expression in Endocrine Tissues
(W495) LIVER X RECEPTORS (LXRS) IN THE MURINE EPIDIDYMIS: TISSUE DISTRIBUTION AND TARGET GENES.
Saez, Fabrice1, Chabory, Eleonore1, Kocer, Ayhan1, Britan, Aurore1, Lobaccaro, Jean-Marc1, Drevet, Joel1, 1 Blaise Pascal University, Aubiere, France
ABSTRACT- Oxysterol nuclear receptors called Liver X Receptors (LXRs) are involved in cholesterol homeostasis and lipid metabolism. Male mice invalidated for both LXR isoforms, LXR-alpha and beta, present a severe epithelial destructuration specifically located in caput epididymidis segments 1 and 2. This phenotype is associated to a sperm cell fragility thus provoking a sterility appearing in 6 month-old male mice. An immortalized cell line developed in our laboratory and issued from mice epididymal caput epithelium was used in this study (B2 cells). In order to understand the observed phenotype, we investigated the specific LXR target genes in B2 cells stimulated by a synthetic agonist of the LXRs, T0901317 (T09). B2 cells were stimulated for 24h with T09 or DMSO (vehicle), and protein profiles were established using 2D gel electrophoresis. The identity of the spots appearing in the treated cells was characterized by MALDI-TOF. Preliminary results indicate that LXR-alpha is mainly distributed in the perinuclear region of the B2 cells. We analyzed, by immunocytochemistry, the location of both LXR-alpha and LXR-beta in B2 cells stimulated or not with the agonist T09 in the aim to visualize a nuclear translocation, as these nuclear receptors act as transcription factors. The expression profiles of LXR-alpha and beta along the mouse epididymis was investigated, to determine which cell types express the mRNAs and/or the proteins. The mRNAs were detected by non-radioactive in-situ hybridization (ISH) using specific digoxigenin-labelled probes (Roche). The proteins were detected by immunohistochemistry using specific rabbit anti-mouse LXR-alpha and beta raised against synthetic peptides. The overall results suggest that LXRs are important actors in the epididymal tissue, as the lipid metabolism is at the centre of the sperm cell maturation process during epididymal transit. Furthermore, this study emphasizes the usefulness of our model, the B2 cells, to study molecular aspects of the epididymal physiology.
KEY WORDS: epididymis, LXR, gene expression