Project description:Mammary gland development and luminal differentiation occur largely postnatally during puberty and pregnancy. To explore the role of DNA methylation in luminal cell differentiation and pregnancy-induced changes, we determined the genome-wide DNA methylation and gene expression profiles of mammary epithelial stem, luminal progenitor, and mature luminal cells at different reproductive stages. We found that pregnancy had the most significant effects on stem cells, inducing a distinct epigenetic state that remained stable through life. Integrated analysis of gene expression, DNA methylation, and histone modification profiles revealed cell type and reproductive stage-specific changes in molecular signatures. We also identified p27 and TGFβ signaling as key regulators of luminal progenitor cell proliferation based on their expression patterns and by the use of explant cultures. Our results suggest relatively minor changes in DNA methylation during luminal cell differentiation as compared to the significant effects of pregnancy on mammary epithelial stem cells. Mammary glands were collected from mice treated with DNA methylation inhibitor 5-azacytidine (AzaC) and histone deacetylase inhibitor valproic acid (VPA) at non-pregnant and pregnant stages for RNA extraction and hybridization on Affymetrix microarrays.
Project description:Mammary gland development and luminal differentiation occur largely postnatally during puberty and pregnancy. To explore the role of DNA methylation in luminal cell differentiation and pregnancy-induced changes, we determined the genome-wide DNA methylation and gene expression profiles of mammary epithelial stem, luminal progenitor, and mature luminal cells at different reproductive stages. We found that pregnancy had the most significant effects on stem cells, inducing a distinct epigenetic state that remained stable through life. Integrated analysis of gene expression, DNA methylation, and histone modification profiles revealed cell type and reproductive stage-specific changes in molecular signatures. We also identified p27 and TGFβ signaling as key regulators of luminal progenitor cell proliferation based on their expression patterns and by the use of explant cultures. Our results suggest relatively minor changes in DNA methylation during luminal cell differentiation as compared to the significant effects of pregnancy on mammary epithelial stem cells.
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 development and luminal differentiation occur largely postnatally during puberty and pregnancy. We found that pregnancy had the most significant effects on stem cells, inducing a distinct epigenetic state that remained stable through life. Mammary glands were collected from mice at non-pregnant and pregnant stages for DNA extraction and DNA methylation analysis via mRRBS (multiplexed reduced representation bisulfite sequencing).
Project description:The Mammary gland undergoes complicated epithelial remodeling to form lobuloalveoli during pregnancy, in which basal epithelial cells remarkably increase to form a basket-like architecture. However, it remains largely unknown how dormant mammary basal stem/progenitor cells involve in lobuloalveolar development. Here, we show that Nfatc1 expression marks a rare population of mammary epithelial cells with the majority being basal epithelial cells. Nfatc1 reporter-marked basal epithelial cells are relatively dormant mammary stem/progenitor cells. Although Nfatc1 reporter-marked basal epithelial cells show limited contribution to the homeostasis of mammary epithelium, they divide rapidly during pregnancy and contribute to lobuloalveolar development. Furthermore, Nfatc1 reporter-marked basal epithelial cells are preferentially used for multiple pregnancies. Using single-cell RNA-seq analysis, we identify multiple functionally distinct clusters within the Nfatc1 reporter-marked cell-derived progeny cells during pregnancy. Taken together, our findings underscore Nfatc1 reporter-marked basal cells as dormant stem/progenitor cells that contribute to mammary lobuloalveolar development during pregnancy.
Project description:Maternal exposures during pregnancy influence the risk of many chronic adult-onset diseases in the offspring. We investigated whether feeding pregnant rats a high fat (HF) or ethinyl-estradiol (EE2)-supplemented diet affects carcinogen-induced mammary cancer risk in daughters, granddaughters and great-granddaughters. Here we show that mammary tumorigenesis is higher in daughters and granddaughters of HF rat dams and in daughters, granddaughters and great-granddaughters of EE2 rat dams. Outcross experiments indicate that increased mammary cancer risk is transmitted to HF granddaughters equally through the female or male germlines, but it is only transmitted to EE2 granddaughters through the female germline. The effects of maternal EE2 exposure on offspring's mammary cancer risk are associated with alternations in the DNA methylation machinery and methylation patterns in mammary tissue of all three EE2 generations. We conclude that dietary and estrogenic exposures in pregnancy increase breast cancer risk in multiple generations of offspring, possibly through non-genetic means We examined the whole genome methylation status of both control and EE2-supplemented diet rats in three consecutive generations
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.