Laminin alpha 5 regulates mammary gland remodeling through luminal cell differentiation and Wnt4-mediated epithelial crosstalk

Epithelial attachment to the basement membrane (BM) is essential for mammary gland development, yet the exact roles of specific BM components remain unclear. Here, we show that Laminin alpha 5 (Lama5) expression specifically in the luminal epithelial cells is necessary for normal mammary gland growth during puberty, and for alveologenesis during pregnancy. Lama5 loss in the keratin 8-expressing cells results in reduced frequency and differentiation of hormone receptor expressing (HR+) luminal cells. Consequently, Wnt4-mediated crosstalk between HR+ luminal cells and basal epithelial cells is compromised during gland remodeling, and results in defective epithelial growth. The effects of Lama5 deletion on gland growth and branching can be rescued by Wnt4 supplementation in the in vitro model of branching morphogenesis. Our results reveal a surprising role for BM-protein expression in the luminal mammary epithelial cells, and highlight the function of Lama5 in mammary gland remodeling and luminal differentiation.Peer reviewe

Asymmetric apportioning of aged mitochondria between daughter cells is required for stemness

By dividing asymmetrically, stem cells can generate two daughter cells with distinct fates. However, evidence is limited in mammalian systems for the selective apportioning of subcellular contents between daughters. We followed the fates of old and young organelles during the division of human mammary stemlike cells and found that such cells apportion aged mitochondria asymmetrically between daughter cells. Daughter cells that received fewer old mitochondria maintained stem cell traits. Inhibition of mitochondrial fission disrupted both the age-dependent subcellular localization and segregation of mitochondria and caused loss of stem cell properties in the progeny cells. Hence, mechanisms exist for mammalian stemlike cells to asymmetrically sort aged and young mitochondria, and these are important for maintaining stemness properties.National Science Foundation (U.S.). Long-Term Ecological Research Program (DEB-8811884)National Science Foundation (U.S.). Long-Term Ecological Research Program (DEB-9411972)National Science Foundation (U.S.). Long-Term Ecological Research Program (DEB-0080382)National Science Foundation (U.S.). Long-Term Ecological Research Program (DEB-0620652)National Science Foundation (U.S.). Long-Term Ecological Research Program (DEB-1234162)National Science Foundation (U.S.). (Biocomplexity Coupled Biogeocemhical Cycles. DEB-0322057)National Science Foundation (U.S.). Long-Term Research in Environmental Biology (DEB-0716587)National Science Foundation (U.S.). Long-Term Research in Environmental Biology (DEB-1242531)National Science Foundation (U.S.). Long-Term Research in Ecosystem Sciences (DEB-1120064)United States. Dept. of Energy. Program for Ecoysystem Research (DE-FG02-96ER62291)United States. Dept. of Energy. Office of Biological and Environmental Research. National Institute for Climatic Change Research (Grant DE-FC02-06ER64158