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Title: Epigenetic modifications in 3D: Nuclear organization of the differentiating mammary epithelial cell

Author
item KRESS, C - Institut National De La Recherche Agronomique (INRA)
item BALLESTER, M - University Of Barcelona
item DEVINOY, E - Institut National De La Recherche Agronomique (INRA)
item RIJNKELS, M - Children'S Nutrition Research Center (CNRC)

Submitted to: Journal of Mammary Gland Biology and Neoplasia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/21/2010
Publication Date: 2/10/2010
Citation: Kress, C., Ballester, M., Devinoy, E., Rijnkels, M. 2010. Epigenetic modifications in 3D: Nuclear organization of the differentiating mammary epithelial cell. Journal of Mammary Gland Biology and Neoplasia. 15:73-83.

Interpretive Summary: Mammary gland maturation occurs after birth. The way DNA is packaged in the cell’s nucleus is important for gene expression regulation and tissue maturation. Current knowledge of nuclear organization in mammary epithelial cells is discussed in this paper. During maturation of the mammary gland, the organization of the nucleus changes overall and the nuclear localization of genes that are specifically expressed in the mature gland changes. How cells are organized within the tissue is important for mammary gland maturation and influences the organization of the nucleus of the cells. Complex pathways integrate signals from outside of the cell and are important for mammary gland maturation. This study provides researchers with a greater understanding of the development of the mammary gland.

Technical Abstract: During the development of tissues, complex programs take place to reach terminally differentiated states with specific gene expression profiles. Epigenetic regulations such as, histone modifications and chromatin condensation have been implicated in the short and long-term control of transcription. It has recently been shown that the 3D spatial organization of chromosomes in the nucleus also plays a role in genome function. Indeed, the eukaryotic interphase nucleus contains sub-domains that are characterized by their enrichment in specific factors such as RNA Polymerase II, splicing machineries or heterochromatin proteins that render portions of the genome differentially permissive to gene expression. The positioning of individual genes relative to these sub-domains is thought to participate in the control of gene expression as epigenetic mechanism acting in the nuclear space. Here, we review what is known about the sub-nuclear organization of mammary epithelial cells in connection with gene expression and epigenetics. Throughout differentiation, global changes in nuclear architecture occur, notably with respect to heterochromatin distribution. The positions of mammary-specific genes relative to nuclear sub-compartments vary in response to hormonal stimulation. The contribution of tissue architecture to cell differentiation in the mammary gland is also seen at the level of nuclear organization, which is sensitive to microenvironmental stimuli such as extracellular matrix signaling. In addition, alterations in nuclear organization are concomitant with immortalization and carcinogenesis. Thus, the fate of cells appears to be controlled by complex pathways connecting external signal integration, gene expression, epigenetic modifications, and chromatin organization in the nucleus.