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The functions of members of the large family of transcriptional repressors, the KRAB domain zinc finger proteins, are not well described. We have identified a new member of this family, Zfp157, as a downstream target of the transcription factor Stat6 in mammary gland. Using a gene-trap approach, we have generated mice harboring a Zfp157-LacZ reporter gene. We have characterized the expression of this reporter during mouse embryogenesis and show that it is expressed in the epiblast and subsequently in a number of embryonic tissues including brain, ovary, intestine, kidney, lung, mammary gland, and hair follicle. In the adult, Zfp157 continues to be expressed in a wide range of tissues while specific patterns of reporter gene expression are apparent in the mammary gland, primarily in the basal epithelial cells of ducts and in the sebaceous glands of hair follicles. These data lay the foundation for further work on the function of Zfp157. genesis 51:179–186, 2013. © 2013 Wiley Periodicals, Inc.

Mammary gland development occurs in three distinct stages during the lifetime of the female mammal: in embryonic, pubertal and reproductive life. At each of these developmental stages, different signalling molecules induce changes in both the epithelium and the surrounding stroma. However, it is during pregnancy that the most dramatic changes occur, resulting in a massive increase in the number of epithelial cells and in their function. Pregnancy initiates the development of a new epithelial lineage, the alveolar cells, which form the milk-producing lobuloalveolar structures. These cells become redundant at the end of lactation and are removed in an exquisitely controlled process of tissue remodelling coupled with extensive cell death. All of these events require not only steroid hormones but also sequential signalling by cytokines. A recent surprising discovery was that the signalling pathways and cytokines that regulate lineage determination in T helper cells are also involved in mammary gland development during pregnancy.

The functions of members of the large family of transcriptional repressors, the KRAB domain zinc finger proteins, are not well described. We have identified a new member of this family, Zfp157, as a downstream target of the transcription factor Stat6 in mammary gland. Using a gene-trap approach, we have generated mice harboring a Zfp157-LacZ reporter gene. We have characterized the expression of this reporter during mouse embryogenesis and show that it is expressed in the epiblast and subsequently in a number of embryonic tissues including brain, ovary, intestine, kidney, lung, mammary gland, and hair follicle. In the adult, Zfp157 continues to be expressed in a wide range of tissues while specific patterns of reporter gene expression are apparent in the mammary gland, primarily in the basal epithelial cells of ducts and in the sebaceous glands of hair follicles. These data lay the foundation for further work on the function of Zfp157.

The transcription factor STAT5A is essential for two processes during mammary gland development. First, it controls the development of luminal progenitor cells from stem cells1 and second, it has a role during pregnancy where it is required for alveologenesis2,3 the production of clusters of luminal cells that synthesize and secrete milk during lactation. Thus, deletion of STAT5A in late pregnancy results in lactation failure. Alveologenesis requires the proliferation of a different lineage of luminal epithelial cells in response to the pregnancy hormones progesterone and prolactin, the latter of which activates STAT5. Prolactin is required additionally during lactation to ensure adequate milk production and the transcription of several milk protein genes has been shown to be regulated by STAT5.4,5 On the other hand, the PI3K/Akt pathway is essential for the synthesis of other milk components such as lipids and lactose.6 In recent elegant work from Lewis Chodosh’s laboratory, published in Genes and Development, these two pathways are now shown to be directly linked.7 More specifically, it is shown that the PI3K/Akt pathway induces autocrine prolactin production and that this is required for the initiation of lactation.