The tree-like architecture of the mammary gland is generated by branching morphogenesis, a reiterative process of branch site initiation and tubule invasion from a pre-existing epithelial structure. Branching is controlled by the interplay between positive and negative regulators, defects in either of which can give rise to aberrancies ranging from hyperplasia to malignant growth. Our long term goal is to delineate how these positive and negative signals are integrated spatially within the tissue to determine which cells branch, and thereby define the branching pattern. We have developed a lithography-based three-dimensional organotypic culture model that recapitulates the architecture of mammary epithelial ducts, enables micrometer-resolution control of tissue geometry and microenvironment, and provides quantitative data in a physiologically relevant context. The engineered ducts execute a complete series of morphogenetic events that can be predicted computationally. Using this culture model, we have shown that the position of branching is determined in part by the concentration profile of transforming growth factor (TGF)-21, an autocrine inhibitory morphogen. Furthermore, we have found that cells located in positions that branch up- regulate the expression of mesenchymal markers during morphogenesis. Based on these preliminary and published data, we propose: 1- To investigate the features of the TGF21 concentration profile perceived and transduced by mammary epithelial ducts. 2- To determine the mesenchymal markers differentially expressed during morphogenesis, and whether these are necessary and/or sufficient to define position of branching. We will further test whether the pattern of mesenchymal gene expression is regulated by the TGF21 inhibitory profile. 3- To begin to dissect how branching is regulated by the physical properties of the microenvironment, by determining whether the extracellular matrix alters branching pattern, TGF21 inhibitory concentration profile, or neo-expression of mesenchymal markers. These studies will provide insight into the local cues and gene expression changes that govern position of branching. PROJECT

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Cells integrate information from stimulatory and inhibitory signals during branching morphogenesis to develop into the tree-like structure of the mammary gland;disruption or misregulation of these signals can lead to neoplastic growths and eventual development of frank tumors. Here we present studies aimed at understanding how mammary epithelial cells perceive inhibitory signals and translate them into patterned differences in gene expression during branching morphogenesis.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Special Emphasis Panel (ZRG1-ICI-D (01))
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Hoodbhoy, Tanya
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Princeton University
Engineering (All Types)
Schools of Engineering
United States
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Varner, Victor D; Nelson, Celeste M (2014) Toward the directed self-assembly of engineered tissues. Annu Rev Chem Biomol Eng 5:507-26
Lee, KangAe; Nelson, Celeste M (2014) Determining the role of matrix compliance in the differentiation of mammary stem cells. Methods Mol Biol 1202:79-94
Chen, Qike K; Lee, KangAe; Radisky, Derek C et al. (2013) Extracellular matrix proteins regulate epithelial-mesenchymal transition in mammary epithelial cells. Differentiation 86:126-32
Gleghorn, Jason P; Manivannan, Sriram; Nelson, Celeste M (2013) Quantitative approaches to uncover physical mechanisms of tissue morphogenesis. Curr Opin Biotechnol 24:954-61
Varner, Victor D; Nelson, Celeste M (2013) Let's push things forward: disruptive technologies and the mechanics of tissue assembly. Integr Biol (Camb) 5:1162-73
Zhu, Wenting; Nelson, Celeste M (2013) PI3K regulates branch initiation and extension of cultured mammary epithelia via Akt and Rac1 respectively. Dev Biol 379:235-45
Kim, Hye Young; Varner, Victor D; Nelson, Celeste M (2013) Apical constriction initiates new bud formation during monopodial branching of the embryonic chicken lung. Development 140:3146-55
Zhu, Wenting; Nelson, Celeste M (2012) PI3K signaling in the regulation of branching morphogenesis. Biosystems 109:403-11
Gleghorn, Jason P; Kwak, Jiyong; Pavlovich, Amira L et al. (2012) Inhibitory morphogens and monopodial branching of the embryonic chicken lung. Dev Dyn 241:852-62
Chung, Jae Woo; Lee, KangAe; Neikirk, Colin et al. (2012) Photoresponsive coumarin-stabilized polymeric nanoparticles as a detectable drug carrier. Small 8:1693-700

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