Aldolase C is a novel molecular marker for folliculo-stellate cells in rodent pituitary

The anterior pituitary gland is composed of five types of hormone-producing cells and folliculo-stellate cells. Folliculo-stellate cells do not produce anterior pituitary hormones but they are thought to play important roles as stem cells, phagocytes, or supporting cells of hormone-producing cells in the anterior pituitary. S100β protein has been used as a folliculo-stellate cell marker in some animals, including rats. However, since no reliable molecular marker for folliculo-stellate cells has been reported in mice, genetic approaches for the investigation of folliculo-stellate cells in mice are not yet available. Aldolase C/Zebrin II is a brain-type isozyme and is a fructose-1,6-bisphosphate aldolase. In the present study, we first used immunohistochemistry to verify that aldolase C was produced in the anterior pituitary of rats. Moreover, using transgenic rats expressing green fluorescent protein under the control of the S100β gene promoter, we identified aldolase C-immunoreactive signals in folliculo-stellate cells and marginal cells located in the parenchyma of the anterior pituitary and around Rathke's cleft, respectively. We also identified aldolase C-expressing cells in the mouse pituitary using immunohistochemistry and in situ hybridization. Aldolase C was not produced in any pituitary hormone-producing cells, while aldolase C-immunopositive signal co-localized with E-cadherin- and SOX2-positive cells. Using post-embedding immunoelectron microscopy, aldolase C-immunoreactive products were observed in the cytoplasm of marginal cells and folliculo-stellate cells of the mouse pituitary. Taken together, aldolase C is a common folliculo-stellate cell marker in the anterior pituitary gland of rodents.