Fig. 4

Matrix stiffness and MRTF/SRF activity cooperate on protrusion formation in mature murine acini. Acinar organoids were extracted from the mammary gland of 8–12 week old female NMRI mice. Organoids were seeded on matrices with increasing stiffness, and morphologies were analysed 5 days after seeding by microscopy. A Representative images of primary murine acini stained for nuclei (DAPI, blue) and actin (phalloidin, green) on matrigel or collagen I matrices 5 days after seeding. Arrowheads indicate protrusions. Scale bars, 50 μm. Individual acini diameter B, percentage of protrusion-positive acini C and percentage of filled acini D were quantified (≥ 42 individual acini per condition, one-way ANOVA). (E) Representative images of acini after 4 days of treatment with DMSO or 20 μM CCG203971. Scale bars, 25 μm. Individual acini diameter F, percentage of protrusion-positive acini G and percentage of filled acini H (≥ 24 individual acini per condition, two-way ANOVA). *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001. Error bars or whiskers, SEM