Progesterone enhances branching morphogenesis in the mouse mammary gland by increased expression of Msx2

Abstract

Branching morphogenesis within the peripubertal mouse mammary gland is directed by progesterone (P). A role for the homeobox-containing transcription factor, Msx2, during branching morphogenesis is suggested from its ontogenic expression profile and hormonal regulation. Herein, we define the spatio-temporal control of Msx2 expression, the regulation of its expression by P and its direct role in ductal branching morphogenesis. P induces Msx2 in the presence of estrogen (E) both in vitro and in vivo while absence of the P receptor (PR) decreased Msx2 expression. Stable transfection of PR into mouse mammary epithelial cells increased the endogenous expression of Msx2 and their ability to undergo branching morphogenesis in vitro. Furthermore, normal mammary cells stably-transfected with Msx2 demonstrated increased branching morphogenesis in vitro while transgenic mice expressing Msx2 in their mammary glands demonstrated enhanced lateral branching during early development. The action of P on branching morphogenesis appears to involve Bmp2/4. Together, these data demonstrate that P, acting through PR-A and the Bmp2/4 pathway, induces Msx2 to enhance ductal branching in the mammary glands.

Progesterone induces expression of the prolactin receptor gene through cooperative action of Sp1 and C/EBP

“…EpH4 cells were originally derived from the mid-pregnant murine mammary gland (Pinkas and Leder, 2002;Reichmann et al, 1992) and lack PR (Satoh et al, 2007). Transfection of the EpH4 cells with cDNA for the mouse PR resulted in expression of PR-A (Satoh et al, 2007), which is known to act in an unliganded manner (Jacobsen et al, 2002).…”

“…In the mouse, mammary ductal elongation occurs through the action of E while lateral branching occurs through the interaction of E plus P. Tertiary ductal branching and alveolar development result from signaling pathways downstream of the PR and PrlR. We found that transfection of PR into EpH4 mouse mammary epithelial cells increased branching morphogenesis in collagen gels through induction of the homeobox gene Msx2 (Satoh et al, 2007). Additionally, the cooperative effects of these three hormones may occur in part due to mutual induction of each other's receptors.…”

“…EpH4 cells, a mouse mammary epithelial cell line, were transfected and clones selected as previously described (Satoh et al, 2007). Seven EpH4-PR clones were isolated from the EpH4 transfected lines; all clones expressed similar levels of PrlR message.…”

“…Following DNase treatment, 1 μg RNA was used for each 25 μl reverse transcriptase reaction as described (Satoh et al, 2007). For all PCR analyses, the number of cycles used was selected at the linear expression level for each gene tested.…”

Extensive expression of craniofacial related homeobox genes in canine mammary sarcomas

“…A growing body of evidence indicates a connection between dysregulated homeobox genes with disease and congenital abnormalities [21]. Expression of several homeobox genes, for example MSX-2, has been identified during the development of the mammary gland [22,23] where they are candidates for the orchestration of the cell signaling that enables the gland to undergo repeated cycles of growth and functional differentiation [24]. Homeobox genes are also known to be upregulated in tumors, where they have been linked to differentiation and prognosis [24][25][26][27].…”