Development-related and cell-type specific nuclear localization of annexin XI: immunolocalization analysis in rat tissues.

Subcellular distribution of a novel annexin, annexin XI, was examined in rat tissues. As we have previously reported, annexin XI mainly localizes in nuclei of 3Y1, the rat embryonic fibroblast cell line; however, immunoperoxidase staining was not particularly nuclear in most of the tissues examined in adult rats. Nuclear localization of annexin XI was uncommon in adult rat tissues. By contrast, in the day-14 rat embryo, the undifferentiated mesenchymal cells were labeled mainly in the nuclei. The connective tissues of 18-day fetus, however, did not show predominantly nuclear staining any longer. In addition, the developing gray matter of the embryonic rat spinal cord exhibited primarily nuclear localization of annexin XI while the annexin XI immunoreactivity diminished and became absent from the nuclei in the adult spinal cord. On the other hand, the endodermal cells never displayed nuclear annexin XI at any developmental stages examined. All these findings suggested that subcellular localization of annexin XI is regulated depending on developmental stages and the cell types.