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. 2016 Oct 26;7:13207. doi: 10.1038/ncomms13207

Figure 8. Model of the Wnt/Nrg1 paracrine signalling network between luminal and basal mammary epithelial cells.

Figure 8

Basal cells secrete Nrg1, resulting in Nrg1/ErbB signalling activation in luminal cells, promoting luminal progenitor cell expansion and differentiation. In contrast, progesterone-stimulated Wnt4 secretion by luminal ER+ cells, alongside R-spondin 1 produced by luminal ER cells, activate Wnt signalling in the basal stem/progenitor cell population via the Wnt receptors Fz and Lrp5/6 and the R-spondin 1 receptor Lgr5. Wnt signalling activation in this compartment is likely to promote growth and differentiation of the basal cell layer. Fz, frizzled; Lgr5, leucine-rich repeat-containing G-protein-coupled receptor 5; Lrp5/6, low-density lipoprotein receptor-related protein 5/6.