Distinct Expression Patterns of Osteopontin and Dentin Matrix Protein 1 Genes in Pituitary Gonadotrophs

Abstract

Cell-matrix interactions play important roles in pituitary development, physiology, and pathogenesis. In other tissues, a family of non-collagenous proteins, termed SIBLINGs, are known to contribute to cell-matrix interactions. Anterior pituitary gland expresses two SIBLING genes, Dmp1 (dentin matrix protein-1) and Spp1 (secreted phosphoprotein-1) encoding DMP1 and osteopontin proteins, respectively, but their expression pattern and roles in pituitary functions have not been clarified. Here we provide novel evidence supporting the conclusion that Spp1/ osteopontin, like Dmp1 /DMP1, are expressed in gonadotrophs in a sex- and age-specific manner. Other anterior pituitary cell types do not express these genes. In contrast to Dmp1, Spp1 expression is higher in males; in females, the expression reaches the peak during the diestrus phase of estrous cycle. In further contrast to Dmp1 and marker genes for gonadotrophs, the expression of Spp1 is not regulated by gonadotropin-releasing hormone in vivo and in vitro . However, Spp1 expression increases progressively after pituitary cell dispersion in both female and male cultures. We may speculate that gonadotrophs signal to other pituitary cell types about changes in the structure of pituitary cell-matrix network by osteopontin, a function consistent with the role of this secretory protein in postnatal tissue remodeling, extracellular matrix reorganization after injury, and tumorigenesis.

Divergent expression patterns of pituitary gonadotropin subunit and GnRH receptor genes to continuous GnRH in vitro and in vivo

“…In contrast to gonadotropin subunit genes, previous experiments have well clarified that expression of Gnrhr decays during prolonged culturing in the absence and presence of GnRH 26,40,41 . GnRH treatment also elevates Dmp1 expression in vitro with similar kinetics and concentration dependence 27,42 . The same conclusion was reached in this study, which gave us confidence about the reproducibility of in vitro experiments and the validity of the novel conclusions for expression of gonadotropin subunit gene expression during continuous in vitro application.…”

Common and female-specific roles of protein tyrosine phosphatase receptors N and N2 in mice reproduction

“…These results indicate that there is no sex-specific difference in gonadotroph-specific gene expression in DKO animals compared to age-matched controls. Transcription of Lhb, Fshb , and Gnrhr is stimulated by GnRH 26 and Spp1 expression is unaffected by GnRH 27 , suggesting that endogenous GnRH secretion is reduced in DKO animals.

Figure 3 Selective effects of DKO on gonadotroph-specific gene expression.

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A Missense p.Q>R234 Mutation in the Osteopontin Gene Is Associated With the Prolificacy of Iraqi Awassi Ewes

“… 10 This gene-encoded OPN protein, also known as secreted phosphoprotein 1 (SPP1), is a member of the small integrin-binding ligand N-linked glycoprotein (SIBLING) family of extracellular matrix proteins/cytokines and has ~300 amino acids and ~30 carbohydrate residues attached. 11 Osteopontin is expressed initially in osteoblasts, as well as in ovarian follicles and ovaries, and in the myometrium and endometrium in the reproductive tissues. 12 Uterine epitheliums (glands and luminal) express this protein, which interacts with the embryo using integrins to promote adhesion and communication between the uterus and the developing embryos.…”