Figure 5.

Evidence for increased γ-secretase activity during involution in vivo and following TGF-β3 treatment in vitro. (a) Increased γ-secretase activity in rat mammary tissue lysate during postpartum involution. Data are reported as fluorescent units normalized to GAPDH, as described in Methods; *P<0.05, ****P<0.001 Dunnett's multiple comparison test. (b) Increased Psen1 gene expression in the mouse mammary gland during early stages of postpartum involution, using two publically available data sets. Data set 1 error bars=S.D., N=3, P<0.05 versus lactation, Dunnett's multiple comparison's test. (c) TGF-β3 induces a modest increase in Psen1 expression in EpH4 cell monolayers; *P<0.05, one-sample, two-tailed t-test compared with 1 (N=3 experiments). (d) Increased PS-1 dimers and C-terminal fragment (CTF) in EpH4 cell monolayers following TGF-β3 treatment (Immunoblot, left panel; quantification, right panel), *P<0.05, two-tailed t-test (N=3 experiments)