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Transcriptome analysis of mammary epithelial subpopulations identifies novel determinants of lineage commitment and cell fate.

Kendrick H, Regan JL, Magnay FA, Grigoriadis A, Mitsopoulos C, Zvelebil M, Smalley MJ - BMC Genomics (2008)

Bottom Line: One of these, Sox6, was specifically expressed in luminal estrogen receptor negative cells and functional assays confirmed that it maintained mammary epithelial cells in a differentiated luminal cell lineage.The mouse mammary epithelium is composed of three main cell types with distinct gene expression patterns.These suggest the existence of a novel functional cell type within the gland, that the basal/myoepithelial cells are key regulators of paracrine signalling and that there is a complex network of differentially expressed transcription factors controlling mammary epithelial cell fate.

View Article: PubMed Central - HTML - PubMed

Affiliation: Breakthrough Breast Cancer Research Centre, The Institute of Cancer Research, London, UK. howard.kendrick@icr.ac.uk

ABSTRACT

Background: Understanding the molecular control of cell lineages and fate determination in complex tissues is key to not only understanding the developmental biology and cellular homeostasis of such tissues but also for our understanding and interpretation of the molecular pathology of diseases such as cancer. The prerequisite for such an understanding is detailed knowledge of the cell types that make up such tissues, including their comprehensive molecular characterisation. In the mammary epithelium, the bulk of the tissue is composed of three cell lineages, namely the basal/myoepithelial, luminal epithelial estrogen receptor positive and luminal epithelial estrogen receptor negative cells. However, a detailed molecular characterisation of the transcriptomic differences between these three populations has not been carried out.

Results: A whole transcriptome analysis of basal/myoepithelial cells, luminal estrogen receptor negative cells and luminal estrogen receptor positive cells isolated from the virgin mouse mammary epithelium identified 861, 326 and 488 genes as highly differentially expressed in the three cell types, respectively. Network analysis of the transcriptomic data identified a subpopulation of luminal estrogen receptor negative cells with a novel potential role as non-professional immune cells. Analysis of the data for potential paracrine interacting factors showed that the basal/myoepithelial cells, remarkably, expressed over twice as many ligands and cell surface receptors as the other two populations combined. A number of transcriptional regulators were also identified that were differentially expressed between the cell lineages. One of these, Sox6, was specifically expressed in luminal estrogen receptor negative cells and functional assays confirmed that it maintained mammary epithelial cells in a differentiated luminal cell lineage.

Conclusion: The mouse mammary epithelium is composed of three main cell types with distinct gene expression patterns. These suggest the existence of a novel functional cell type within the gland, that the basal/myoepithelial cells are key regulators of paracrine signalling and that there is a complex network of differentially expressed transcription factors controlling mammary epithelial cell fate. These data will form the basis for understanding not only cell fate determination and cellular homeostasis in the normal mammary epithelium but also the contribution of different mammary epithelial cell types to the etiology and molecular pathology of breast disease.

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Network interaction map for luminal ER- specific genes. Interaction data based on physical interactions (solid lines) and transcriptional interactions (dashed lines). The nodes are colour coded to indicate relative strengths of expression of the gene within the cell population. Brighter reds indicate highest levels of expression. Darker reds indicate genes less strongly expressed (although still with enriched expression within the population compared to the other cell types). White nodes indicate interpolated genes used by the network mapping software to extend and link the network [see Additional file 12]. A) Whole interaction map. Box indicates Toll-like receptor module. B) Enlargement of Toll-like receptor interaction module.
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Figure 4: Network interaction map for luminal ER- specific genes. Interaction data based on physical interactions (solid lines) and transcriptional interactions (dashed lines). The nodes are colour coded to indicate relative strengths of expression of the gene within the cell population. Brighter reds indicate highest levels of expression. Darker reds indicate genes less strongly expressed (although still with enriched expression within the population compared to the other cell types). White nodes indicate interpolated genes used by the network mapping software to extend and link the network [see Additional file 12]. A) Whole interaction map. Box indicates Toll-like receptor module. B) Enlargement of Toll-like receptor interaction module.

Mentions: The TLR module within the luminal ER- network was of particular interest (Figure 4) [38], as it indicated a novel role of these cells as non-professional immune cells which can respond to bacterial lipopolysaccharide. To confirm that the luminal ER- population was indeed enriched for cells expressing components of the CD14-TLR4 signalling complex, qPCR analysis of relative expression levels of the three components of the LPS receptor, CD14, Ly96 and Tlr4, its downstream effecter Irak2 and the LPS receptor responsive gene Tnf were carried out [38]. The results (Figure 5) confirmed that all five genes were specifically enriched in the luminal ER- cells compared to both the basal/myoepithelial and luminal ER+ cells. In particular, CD14, Tlr4 and Tnf were expressed at 10-fold, 3-fold and 2-fold, respectively, higher levels in the luminal ER- cells compared to the luminal ER+ cells. CD14 and Tnf were expressed at 30-fold and 5-fold higher levels in the luminal ER- cells compared to the basal/myoepithelial cells. Tlr4 expression was undetectable in the basal/myoepithelial cells.


Transcriptome analysis of mammary epithelial subpopulations identifies novel determinants of lineage commitment and cell fate.

Kendrick H, Regan JL, Magnay FA, Grigoriadis A, Mitsopoulos C, Zvelebil M, Smalley MJ - BMC Genomics (2008)

Network interaction map for luminal ER- specific genes. Interaction data based on physical interactions (solid lines) and transcriptional interactions (dashed lines). The nodes are colour coded to indicate relative strengths of expression of the gene within the cell population. Brighter reds indicate highest levels of expression. Darker reds indicate genes less strongly expressed (although still with enriched expression within the population compared to the other cell types). White nodes indicate interpolated genes used by the network mapping software to extend and link the network [see Additional file 12]. A) Whole interaction map. Box indicates Toll-like receptor module. B) Enlargement of Toll-like receptor interaction module.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2629782&req=5

Figure 4: Network interaction map for luminal ER- specific genes. Interaction data based on physical interactions (solid lines) and transcriptional interactions (dashed lines). The nodes are colour coded to indicate relative strengths of expression of the gene within the cell population. Brighter reds indicate highest levels of expression. Darker reds indicate genes less strongly expressed (although still with enriched expression within the population compared to the other cell types). White nodes indicate interpolated genes used by the network mapping software to extend and link the network [see Additional file 12]. A) Whole interaction map. Box indicates Toll-like receptor module. B) Enlargement of Toll-like receptor interaction module.
Mentions: The TLR module within the luminal ER- network was of particular interest (Figure 4) [38], as it indicated a novel role of these cells as non-professional immune cells which can respond to bacterial lipopolysaccharide. To confirm that the luminal ER- population was indeed enriched for cells expressing components of the CD14-TLR4 signalling complex, qPCR analysis of relative expression levels of the three components of the LPS receptor, CD14, Ly96 and Tlr4, its downstream effecter Irak2 and the LPS receptor responsive gene Tnf were carried out [38]. The results (Figure 5) confirmed that all five genes were specifically enriched in the luminal ER- cells compared to both the basal/myoepithelial and luminal ER+ cells. In particular, CD14, Tlr4 and Tnf were expressed at 10-fold, 3-fold and 2-fold, respectively, higher levels in the luminal ER- cells compared to the luminal ER+ cells. CD14 and Tnf were expressed at 30-fold and 5-fold higher levels in the luminal ER- cells compared to the basal/myoepithelial cells. Tlr4 expression was undetectable in the basal/myoepithelial cells.

Bottom Line: One of these, Sox6, was specifically expressed in luminal estrogen receptor negative cells and functional assays confirmed that it maintained mammary epithelial cells in a differentiated luminal cell lineage.The mouse mammary epithelium is composed of three main cell types with distinct gene expression patterns.These suggest the existence of a novel functional cell type within the gland, that the basal/myoepithelial cells are key regulators of paracrine signalling and that there is a complex network of differentially expressed transcription factors controlling mammary epithelial cell fate.

View Article: PubMed Central - HTML - PubMed

Affiliation: Breakthrough Breast Cancer Research Centre, The Institute of Cancer Research, London, UK. howard.kendrick@icr.ac.uk

ABSTRACT

Background: Understanding the molecular control of cell lineages and fate determination in complex tissues is key to not only understanding the developmental biology and cellular homeostasis of such tissues but also for our understanding and interpretation of the molecular pathology of diseases such as cancer. The prerequisite for such an understanding is detailed knowledge of the cell types that make up such tissues, including their comprehensive molecular characterisation. In the mammary epithelium, the bulk of the tissue is composed of three cell lineages, namely the basal/myoepithelial, luminal epithelial estrogen receptor positive and luminal epithelial estrogen receptor negative cells. However, a detailed molecular characterisation of the transcriptomic differences between these three populations has not been carried out.

Results: A whole transcriptome analysis of basal/myoepithelial cells, luminal estrogen receptor negative cells and luminal estrogen receptor positive cells isolated from the virgin mouse mammary epithelium identified 861, 326 and 488 genes as highly differentially expressed in the three cell types, respectively. Network analysis of the transcriptomic data identified a subpopulation of luminal estrogen receptor negative cells with a novel potential role as non-professional immune cells. Analysis of the data for potential paracrine interacting factors showed that the basal/myoepithelial cells, remarkably, expressed over twice as many ligands and cell surface receptors as the other two populations combined. A number of transcriptional regulators were also identified that were differentially expressed between the cell lineages. One of these, Sox6, was specifically expressed in luminal estrogen receptor negative cells and functional assays confirmed that it maintained mammary epithelial cells in a differentiated luminal cell lineage.

Conclusion: The mouse mammary epithelium is composed of three main cell types with distinct gene expression patterns. These suggest the existence of a novel functional cell type within the gland, that the basal/myoepithelial cells are key regulators of paracrine signalling and that there is a complex network of differentially expressed transcription factors controlling mammary epithelial cell fate. These data will form the basis for understanding not only cell fate determination and cellular homeostasis in the normal mammary epithelium but also the contribution of different mammary epithelial cell types to the etiology and molecular pathology of breast disease.

Show MeSH
Related in: MedlinePlus