Project description:R-spondin1 (Rspo1) is a member of a secreted protein family which has pleiotropic functions in development and stem cell growth. Rspo1 knock-out mice are sex-reversed, but some remain sub-fertile, so, they are unable to nurse their pups. A lack of Rspo1 expression in mammary epithelial cells results in an absence of duct side-branching development and defective alveolar formation. In this study we propose to characterize the molecular functions involved to mammary gland phenotype due to Rspo1 knock out. By transcriptional profiling, we have identified gene misregulated in mammary gland of Rspo1 knock-out mice during pregnancy. A stronger expression of genes characterising mesenchymal tissue was observed in the absence of alterations to the structure of mammary epithelial tissue. Mammary epithelial cell characterization, by immunohistochemistry approach, revealed a persistence of virgin markers which sign a delay in their differentiation. Moreover serial transplantation experiments show that Rspo1 is associated with a regenerative potential of mammary epithelial cell control. Our data have also highlighted that in mammary gland during pregnancy the expression of Rspo1’s partners, Lgr4 and RNF43, are negatively regulated and Tgf-β signaling is modified in the absence of Rspo1. Taken together, our results show an abrupt halt in mammary development at mid-pregnancy due to loss of further differentiated function.
Project description:The mammary gland undergoes extensive remodeling between the begin- ning of pregnancy and lactation; this involves cellular processes including cell proliferation, differentiation, and apoptosis, all of which are under the control of numerous regulators. To unravel the role played by miRNA, we describe here 47 new ovine miRNA cloned from mammary gland in early pregnancy displaying strong similari- ties with those already identified in the cow, human, or mouse. A microarray study of miRNA variations in the adult ovine mammary gland during pregnancy and lactation showed that 100 miRNA are regulated according to three principal patterns of expression: a de- crease in early pregnancy, a peak at midpregnancy, or an increase throughout late pregnancy and lactation. One miRNA displaying each pattern (miR-21, miR-205, and miR-200b) was analyzed by qRT- PCR. Variations in expression were confirmed for all three miRNA. Using in situ hybridization, we detected both miR-21 and miR-200 in luminal mammary epithelial cells when expressed, whereas miR-205 was expressed in basal cells during the first half of pregnancy and then in luminal cells during the second half. We therefore conclude that miR-21 is strongly expressed in the luminal cells of the normal mammary gland during early pregnancy when extensive cell prolif- eration occurs. In addition, we show that miR-205 and miR-200 are coexpressed in luminal cells, but only during the second half of pregnancy. These two miRNA may cooperate to maintain epithelial status by repressing an EMT-like program, to achieve and preserve the secretory phenotype of mammary epithelial cells.
Project description:T cells accumulate in the mammary gland during pregnancy and lactation. In order to understand the diversity, transcriptional states, TCR repertoire, and function of mammary gland T cells, and how these change during pregnancy and lactation compared to homeostasis, we performed single cell RNA sequencing on mammary gland T cells in mice.
Project description:The mammary gland undergoes extensive remodeling between the begin- ning of pregnancy and lactation; this involves cellular processes including cell proliferation, differentiation, and apoptosis, all of which are under the control of numerous regulators. To unravel the role played by miRNA, we describe here 47 new ovine miRNA cloned from mammary gland in early pregnancy displaying strong similari- ties with those already identified in the cow, human, or mouse. A microarray study of miRNA variations in the adult ovine mammary gland during pregnancy and lactation showed that 100 miRNA are regulated according to three principal patterns of expression: a de- crease in early pregnancy, a peak at midpregnancy, or an increase throughout late pregnancy and lactation. One miRNA displaying each pattern (miR-21, miR-205, and miR-200b) was analyzed by qRT- PCR. Variations in expression were confirmed for all three miRNA. Using in situ hybridization, we detected both miR-21 and miR-200 in luminal mammary epithelial cells when expressed, whereas miR-205 was expressed in basal cells during the first half of pregnancy and then in luminal cells during the second half. We therefore conclude that miR-21 is strongly expressed in the luminal cells of the normal mammary gland during early pregnancy when extensive cell prolif- eration occurs. In addition, we show that miR-205 and miR-200 are coexpressed in luminal cells, but only during the second half of pregnancy. These two miRNA may cooperate to maintain epithelial status by repressing an EMT-like program, to achieve and preserve the secretory phenotype of mammary epithelial cells. 5 samples for sheep and 5 samples for mouse
Project description:Pregnancy is the major modulator of mammary gland activity. It induces a tremendous expansion of the mammary epithelium and the generation of alveolar structures for milk production. Anecdotal evidence from multiparous humans indicates that the mammary gland may react less strongly to the first pregnancy than it does to subsequent pregnancies. Here we verify that the mouse mammary gland responds more robustly to a second pregnancy, indicating that the gland retains a long-term memory of pregnancy. A comparison of genome-wide profiles of DNA methylation in isolated mammary cell types revealed substantial and long lasting alterations. The majority of these alterations affect sites occupied by the Stat5a transcription factor and mark specific genes that are upregulated during pregnancy. We postulate that the epigenetic memory of a first pregnancy primes the activation of gene expression networks that promote mammary gland function in subsequent reproductive cycles. More broadly, our data indicate that physiological experience can broadly alter epigenetic states, functionally modifying the capacity of the affected cells to respond to later stimulatory events. Mammary gland cells (six distinct cell types) from nulliparous and parous female mice were FACS-sorted using a combination of cell surface markers. Genomic DNA was bisulfite converted and used to obtain genome-wide DNA methylation profiles. The current work focuses on the analysis of the first 12 samples (GSM1646785-96) and uses the other two samples to confirm some properties of the analysis results based on samples 1-12. Consequently, samples GSM1646797, GSM1646798 were analyzed in a much more limited manner compared to the other 12 samples, generating two plots included in the associated manucript.
Project description:Mammary gland ductal morphogenesis depends on the differentiation of mammary stem cells (MaSCs) into basal and luminal lineages. The AP-2γ transcription factor, encoded by Tfap2c, has a central role in mammary gland development but its effect in mammary lineages and specifically MaSCs is largely unknown. Herein, we utilized an inducible, conditional knockout of Tfap2c to elucidate the role of AP-2γ in maintenance and differentiation of MaSCs. Loss of AP-2γ in the basal epithelium profoundly altered the transcriptomes and decreased the number of cells within several clusters of mammary epithelial cells, including adult MaSCs and luminal progenitors. AP-2γ regulated the expression of genes known to be required for mammary development including Cebpb, Nfkbia, and Rspo1. As a result, AP-2γ-deficient mice exhibited repressed mammary gland ductal outgrowth and inhibition of regenerative capacity. The findings demonstrate that AP-2γ can regulate development of mammary gland structures potentially regulating maintenance and differentiation of multipotent MaSCs.
Project description:Breastfeeding is an obligatory requirement of mammalian survival. This fundamental process is associated with the remodeling of maternal physiology including the transformation of mammary gland into milk-secreting organ. While adaptive immunity has been associated with the broad control of host physiology, how maternal immunity contributes to organismal remodeling during pregnancy including mammary gland remodeling and function remains largely unknown. Here, we show that maternal adaptive immunity plays a critical role in shaping lactogenesis. Specifically, physiological adaptation to pregnancy is associated with thymic involution and paradoxical enrichment in intraepithelial lymphocyte precursors that no longer migrate to the gut but preferentially accumulate within the mammary gland. Within this compartment the precursors develop as T-bet expressing lymphocytes accumulating within the mammary epithelium in an IL-15 dependent manner. Mammary intra-epithelial lymphocytes control milk production by favoring differentiation of both contractile and milk-secreting cells, thereby affecting offspring fitness. Altogether, this work uncovers a previously unappreciated contribution of the maternal adaptive immune system in organismal remodeling during pregnancy associated with mammary gland development and function.