RESUMO
The zinc finger homeobox 3 (ZFHX3, also named ATBF1 for AT motif binding factor 1) is a transcription factor that suppresses prostatic carcinogenesis and induces neuronal differentiation. It also interacts with estrogen receptor α to inhibit cell proliferation and regulate pubertal mammary gland development in mice. In the present study, we examined whether and how Zfhx3 regulates lactogenic differentiation in mouse mammary glands. At different stages of mammary gland development, Zfhx3 protein was expressed at varying levels, with the highest level at lactation. In the HC11 mouse mammary epithelial cell line, an in vitro model of lactogenesis, knockdown of Zfhx3 attenuated prolactin-induced ß-casein expression and morphological changes, indicators of lactogenic differentiation. In mouse mammary tissue, knock-out of Zfhx3 interrupted lactogenesis, resulting in underdeveloped glands with much smaller and fewer alveoli, reduced ß-casein expression, accumulation of large cytoplasmic lipid droplets in luminal cells after parturition, and failure in lactation. Mechanistically, Zfhx3 maintained the expression of Prlr (prolactin receptor) and Prlr-Jak2-Stat5 signaling activity, whereas knockdown and knock-out of Zfhx3 in HC11 cells and mammary tissues, respectively, decreased Prlr expression, Stat5 phosphorylation, and the expression of Prlr-Jak2-Stat5 target genes. These findings indicate that Zfhx3 plays an essential role in proper lactogenic development in mammary glands, at least in part by maintaining Prlr expression and Prlr-Jak2-Stat5 signaling activity.
Assuntos
Diferenciação Celular , Proteínas de Homeodomínio/metabolismo , Glândulas Mamárias Animais/metabolismo , Prolactina/metabolismo , Transdução de Sinais , Animais , Western Blotting , Caseínas/metabolismo , Linhagem Celular , Linhagem Celular Tumoral , Células Epiteliais/efeitos dos fármacos , Células Epiteliais/metabolismo , Feminino , Células HEK293 , Proteínas de Homeodomínio/genética , Humanos , Imuno-Histoquímica , Janus Quinase 2/metabolismo , Lactação/genética , Lactação/metabolismo , Células MCF-7 , Glândulas Mamárias Animais/citologia , Glândulas Mamárias Animais/crescimento & desenvolvimento , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Knockout , Prolactina/farmacologia , Receptores da Prolactina/genética , Receptores da Prolactina/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Fator de Transcrição STAT5/metabolismoRESUMO
Progesterone (Pg)/progesterone receptor (PR) signaling drives mammary gland side-branching and alveologenesis, but the mechanisms through which Pg/PR signaling functions remain to be clarified. Using in vitro and in vivo models and histological and molecular analyses, we determined the role of Zfhx3 transcription factor in mammary gland development driven by Pg/PR signaling. Postnatal deletion of Zfhx3 in mouse mammary epithelial cells attenuated side-branching morphogenesis and alveologenesis. These effects were undetectable in the absence of Pg/PR signaling. During the estrus cycle, Zfhx3 expression corresponded to that of Pg, being at the highest level at the diestrus stage; Zfhx3 deletion inhibited mammary gland branching more potently at diestrus than estrus stage. Loss of Zfhx3 not only attenuated the expansion of stem/progenitor cells driven by Pg/PR signaling, but also impaired the function of Pg/PR signaling in the transcriptional activation of multiple genes. In addition, Pg/PR signaling significantly expanded PR- and Zfhx3-positive epithelial cells, and induced the physical association of ZFHX3 with PR. These findings establish Zfhx3 as an integral transcription factor of Pg/PR signaling in driving side-branching and alveologenesis during mammary gland development.