Claudin-9 constitutes tight junctions of folliculo-stellate cells in the anterior pituitary gland

Abstract

The anterior pituitary gland regulates growth, metabolism, and reproduction by secreting hormones. Folliculo-stellate (FS) cells are non-endocrine cells located among hormone-producing cells in the anterior pituitary glands. They form follicular lumens, which are sealed by tight junctions (TJs). Although FS cells are hypothesized to contribute to fine-tuning of endocrine cells, little is known about the exact roles of FS cells. Here, we investigated the molecular composition of TJs in FS cells. We demonstrated that occludin is a good marker for TJs in the pituitary gland and examined the structure of the lumens surrounded by FS cells. We also found that claudin-9 is a major component of TJs in the FS cells. In immunoelectron microscopy, claudin-9 was specifically localized at TJs of the FS cells. The expression of claudin-9 was gradually increased in the pituitary gland after birth, suggesting that claudin-9 is developmentally regulated and performs some specific functions on the paracellular barrier of follicles in the pituitary gland. Furthermore, we found that angulin-1, angulin-2, and tricellulin are localized at the tricellular contacts of the FS cells. Our findings provide a first comprehensive molecular profile of TJs in the FS cells, and may lead us towards unveiling the FS cell functions.

Claudin‑9 is a novel prognostic biomarker for endometrial cancer

“…First, the reactivity and specificity of the anti-CLDN9 mAb were tested against the C-terminal cytoplasmic region of human CLDN9 (Fig. 1A), which was recently established by our group (21). To this end, 293T cells were transiently transfected with individual CLDN expression vectors, followed by western blot and immunohistochemistry using whole-cell extracts and cell blocks, respectively.…”

“…In the present study, it was demonstrated that high CLDN9 expression predicts poor prognosis in patients with endometrial cancer using a newly established specific monoclonal antibody (mAb) (21). In addition, it was indicated that the combination of CLDN9 and CLDN6 is beneficial for predicting poor outcome in endometrial cancer.…”

“…Antibodies. Rat monoclonal antibodies (mAbs) against the cytoplasmic tail of human CLDN6 and CLDN9 were generated using an iliac lymph node method, as previously described (16,21). Clone #15 for CLDN6 and clone 1D1 for CLDN9 were used in the present study.…”

Histopathological Characteristics of Folliculo-stellate Cells in Pituitary Glands of Wild Type, Obese and High-fat Diet Induced Mice

“…For this exclusion, in future studies, perhaps another specific marker for FSC should be used, or a panel of markers that would make the marking more specific. These could include, among others, Claudin-9, a marker of tight junctions of FSC [37] , Aldolase C [38] or IL-6 itself, which is stimulated by Adenosine, produced by FSC [39,40] .…”

Expression and localization of tight junction-related proteins in adult rat pituitary stem/progenitor cell niches

“…More recently, Higashi et al . reported that claudin-9 is specifically expressed in S100β-positive cells [ 21 ]. However, whether tight junction-related proteins exist in the pituitary stem/progenitor cell niches remains unclear.…”