Abstract
During puberty, mouse mammary epithelial ducts invade the stromal mammary fat pad in a wave of branching morphogenesis to form a complex ductal tree. Using pharmacologic and genetic approaches, we find that mammary gland branching morphogenesis requires transient matrix metalloproteinase (MMP) activity for invasion and branch point selection. MMP-2, but not MMP-9, facilitates terminal end bud invasion by inhibiting epithelial cell apoptosis at the start of puberty. Unexpectedly, MMP-2 also represses precocious lateral branching during mid-puberty. In contrast, MMP-3 induces secondary and tertiary lateral branching of ducts during mid-puberty and early pregnancy. Nevertheless, the mammary gland is able to develop lactational competence in MMP mutant mice. Thus, specific MMPs refine the mammary branching pattern by distinct mechanisms during mammary gland branching morphogenesis.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Apoptosis / drug effects
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Apoptosis / genetics
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Cell Differentiation / drug effects
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Cell Differentiation / genetics*
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Dipeptides / pharmacology
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Embryonic Induction / drug effects
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Embryonic Induction / genetics
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Enzyme Inhibitors / pharmacology
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Epithelial Cells / cytology
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Epithelial Cells / drug effects
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Epithelial Cells / enzymology*
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Female
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Immunohistochemistry
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Lactation / drug effects
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Lactation / genetics
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Mammary Glands, Animal / cytology
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Mammary Glands, Animal / enzymology*
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Mammary Glands, Animal / growth & development*
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Matrix Metalloproteinase 2 / genetics
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Matrix Metalloproteinase 2 / metabolism*
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Matrix Metalloproteinase 3 / genetics
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Matrix Metalloproteinase 3 / metabolism*
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Matrix Metalloproteinase Inhibitors
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Mice
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Mice, Inbred BALB C
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Mice, Transgenic
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Morphogenesis / drug effects
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Morphogenesis / genetics
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Mutation / drug effects
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Mutation / genetics
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Organ Culture Techniques
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Pregnancy
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Protease Inhibitors / pharmacology
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Sexual Maturation / drug effects
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Sexual Maturation / genetics
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Tissue Inhibitor of Metalloproteinase-1 / genetics
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Tissue Inhibitor of Metalloproteinase-1 / metabolism
Substances
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Dipeptides
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Enzyme Inhibitors
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Matrix Metalloproteinase Inhibitors
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N-(2(R)-2-(hydroxamidocarbonylmethyl)-4-methylpentanoyl)-L-tryptophan methylamide
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Protease Inhibitors
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Tissue Inhibitor of Metalloproteinase-1
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Matrix Metalloproteinase 3
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Matrix Metalloproteinase 2