200 nM siRNA.

Among heterogeneous S100beta-protein-positive (S100beta-positive) cells, star-like cells with extended cytoplasmic processes, the so-called folliculo-stellate cells, envelop hormone-producing cells or interconnect homophilically in the anterior pituitary. S100beta-positive cells are known, from immunohistochemistry, to emerge from postnatal day (P) 10 and to proliferate and migrate in the parenchyma of the anterior pituitary with growth. Recent establishment of S100beta-GFP transgenic rats expressing specifically green fluorescent protein (GFP) under the control of the S100beta-promoter has allowed us to observe living S100beta-positive cells. In the present study, we first confirmed that living S100beta-positive cells in tissue cultures of S100beta-GFP rat pituitary at P5 were present prior to P10 by means of confocal laser microscopy and that they proliferated and extended their cytoplasmic processes. Second, we examined the expression of the Snail-family zinc-finger transcription factors, Snail and Slug, to investigate the mechanism behind the morphological changes and the proliferation of S100beta-positive cells. Interestingly, we detected Slug expression in S100beta-positive cells and its increase together with development in the anterior pituitary. To analyze downstream of SLUG in S100beta-positive cells, we utilized specific small interfering RNA for Slug mRNAs and observed that the expression of matrix metalloprotease (Mmp) 9, Mmp14 and chemokine Cxcl12 was down-regulated and that morphological changes and proliferation were decreased. Thus, our findings suggest that S100beta-positive cells express Slug and that its expression is important for subsequent migration and proliferation.