Tif1γ is essential for the terminal differentiation of mammary alveolar epithelial cells and for lactation through SMAD4 inhibition

Abstract

SUMMARYTransforming growth factor  (TGF) is widely recognised as an important factor that regulates many steps of normal mammary gland (MG) development, including branching morphogenesis, functional differentiation and involution. Tif1 has previously been reported to temporally and spatially control TGF signalling during early vertebrate development by exerting negative effects over SMAD4 availability. To evaluate the contribution of Tif1 to MG development, we developed a Cre/LoxP system to specifically invalidate the Tif1g gene in mammary epithelial cells in vivo. Tif1g-null mammary gland development appeared to be normal and no defects were observed during the lifespan of virgin mice. However, a lactation defect was observed in mammary glands of Tif1g-null mice. We demonstrate that Tif1 is essential for the terminal differentiation of alveolar epithelial cells at the end of pregnancy and to ensure lactation. Tif1 appears to play a crucial role in the crosstalk between TGF and prolactin pathways by negatively regulating both PRL receptor expression and STAT5 phosphorylation, thereby impairing the subsequent transactivation of PRL target genes. Using HC11 cells as a model, we demonstrate that the effects of Tif1g knockdown on lactation depend on both SMAD4 and TGF. Interestingly, we found that the Tif1 expression pattern in mammary epithelial cells is almost symmetrically opposite to that described for TGF. We propose that Tif1 contributes to the repression of TGF activity during late pregnancy and prevents lactation by inhibiting SMAD4.

Trim33 is essential for macrophage and neutrophil mobilization to developmental or inflammatory cues

“…Trim33, previously known as transcriptional intermediary factor 1γ (Tif1-γ), is a nuclear protein endowed with ubiquitin ligase activity, that does not directly bind to DNA but regulates gene transcription by associating with various DNA-binding transcription factors, such as SMADs, PU.1 (also known as Spi1) and Scl (also known as Tal1) (Xi et al, 2011;Hesling et al, 2011;Bai et al, 2010;Kusy et al, 2011;Ferri et al, 2015). Trim33 has notably been implicated in TGF-β-mediated regulation of gene expression (Xi et al, 2011;Hesling et al, 2011), erythropoiesis (Ransom et al, 2004;He et al, 2006;Bai et al, 2010), the long-term fate of hematopoietic stem cells (Kusy et al, 2011;Quere et al, 2014) and epithelial mesenchymal transitions (Hesling et al, 2011(Hesling et al, , 2013, and is considered a tumour suppressor (Aucagne et al, 2011). Here, we have found that, in Trim33-deficient zebrafish embryos, primitive macrophages are unable to colonize the brain and retina to become primitive microglia.…”

TIF1γ requires sumoylation to exert its repressive activity on TGFβ signaling

“…Ubiquitylationmediated degradation of Smad4 can be antagonized by the FAM/ USP9x de-ubiquitylase, thus restoring Smad4 function (Dupont et al, 2009). Results from others as well as our own have shown that TIF1c is a potent inhibitor of Smad4 functions during TGFbinduced EMT (Hesling et al, 2011), terminal differentiation of mammary alveolar epithelial cells and lactation (Hesling et al, 2013) and during specification of the ectoderm in Xenopus embryos (Dupont et al, 2005). Moreover the negative regulation of Smad4 by TIF1c is essential to achieve proper dosage of Nodal responsiveness in mouse embryos (Morsut et al, 2010).…”

“…Several reports indicate that TIF1c is an important regulator of transcription during hematopoiesis (Bai et al, 2010;He et al, 2006;Kusy et al, 2011;Ransom et al, 2004) and may also be a key actor of tumorigenesis (Aucagne et al, 2011;Herquel et al, 2011;Vincent et al, 2009). In addition, we have recently demonstrated that TIF1c regulates the TGFb-induced epithelial-tomesenchymal transition (EMT) in mammary epithelial cells (Hesling et al, 2011) and during terminal differentiation of mammary alveolar epithelial cells and lactation (Hesling et al, 2013) through repression of Smad4 activity.…”

TGF-β Family Signaling in Ductal Differentiation and Branching Morphogenesis

“…Another transcriptional cofactor of the nuclear Smad complex is the chromatin-associated protein tripartite motif containing 33 (TRIM33, also known as TIF1g), which regulates subsets of TGF-b-responsive genes (Massagué 2012). Mammary epithelial cell-specific ablation of the Trim33 gene results in normal mammary gland development with a clear lactation defect owing to perturbation in the terminal differentiation of the alveolar epithelium (Hesling et al 2013). In this model, TRIM33 inhibits the Smad and STAT5 transactivation potential and represses the expression of the prolactin receptor in mammary alveolar cells (Hesling et al 2013).…”

“…Mammary epithelial cell-specific ablation of the Trim33 gene results in normal mammary gland development with a clear lactation defect owing to perturbation in the terminal differentiation of the alveolar epithelium (Hesling et al 2013). In this model, TRIM33 inhibits the Smad and STAT5 transactivation potential and represses the expression of the prolactin receptor in mammary alveolar cells (Hesling et al 2013). Thus, the negative effects of TGF-bs during the late phase of alveolar differentiation and the onset of lactation involve intimate cross talk with the prolactin-STAT5 pathway, whereas several nuclear coregulators take part in the antagonistic cross talk between these two pathways.…”