Fras 1 related extracellular matrix protein 2 (FREM 2) localization in the human fetal adrenal gland

Abstract

OBJECTIVE: To investigate the presence of Fras 1 related extracellular matrix protein 2 (FREM 2) in the human fetal adrenal. DESIGN: The expression profile of genes that are responsible for cortical growth and zonation in the fetal adrenal are poorly characterized. In prior studies, we found that many genes in adrenals of normal fetuses and in adrenals of anencephalic were differentially expressed. One of the most striking differences in expression was that of the FREM 2 gene, which was expressed at 50-fold greater levels in the normal adrenal. FREM 2 may be important for normal adrenal development and we sought to investigate the presence and cellular localization of this protein in the fetal adrenal. MATERIALS AND METHODS: Paraffin embedded tissue sections (5 microns) of human tissues were utilized for immunostaining for FREM 2. The immunostaining was completed using a rabbit polyclonal antibody that has been found to recognize the immunizing peptide fragment of human FREM 2 by western blot as well as an antiserum that was specific for mouse FREM 2. Antisera was kindly provided by Dr. Giorgos Chalepakis. Incubations were conducted at neutral pH and immunodetection reagents were obtained from Covance. RESULTS: FREM 2 immunostaining was noted in the human fetal adrenal by use of the anti-human FREM 2 antiserum but not with the anti-mouse FREM 2 antiserum. Deletion of the primary antiserum resulted in no immunostaining of any tissues. Antigen retrieval at pH 6.0 did not alter results. Fetal zone cells were prominently immunostained whereas the neocortex was stained to a lesser degree; pheochromoblasts and neuroblasts were negative. CONCLUSIONS: FREM 2 is expressed in the normal human fetal adrenal. FREM2 is most prominent in the fetal zone cortical cells which are the most affected cells in the hypoplastic adrenals associated with the neural tube defect anencephaly. The production of FREM 2 in the fetal adrenal may play a role in adrenal development.