WP2814 - Mammary gland development: puberty - stage 2 of 4 - Homo sapiens

The primary mammary gland persists until puberty, when it grows and becomes branched. This results in the formation of secondary mammary gland.
ESR1 and NRIP1 co-regulate PGR, STAT5A and AREG, which control proliferation and differentiation during mammary gland development. NRIP1 is also required for ductal elongation, in both epithelial and in stromal compartments [1](http://www.ncbi.nlm.nih.gov/pubmed/23404106). Estrogen may also execute its growth effect through EGF. Especially, ERBB2, an EGF receptor, may activate or inhibit the growth according to the stage of development. In puberty, ERBB2 impairs mammary epithelial cell proliferation [2](http://www.ncbi.nlm.nih.gov/pubmed/11146549).
AP1 regulates postnatal mammary gland development, mainly in puberty. Some AP1-dependent genes are shown in the figure [3](http://www.ncbi.nlm.nih.gov/pubmed/16678816). FOSL1 is a FOS family member. FOS family members dimerize with JUN family members to form AP1 complex. MYC and CCND1 are associated with cell proliferation. VIM is a component of intermediate filaments and FN1 is related to cell adhesion and migration. TIMP1 is a protease inhibitor.