PMC

From left to right: no involution (a), partial involution (b), complete involution (c).

Histology and accumulation of whey acidic protein (WAP) during early involution. A: Histology from mammary tissues during involution. a,c,e: Control mammary tissues expressing only the WAP-Cre transgene at days 1 (a), 2 (c), and 3 (e) after forced involution. b,d,f: TβRII^(WKO)Rosa26R tissues at days 1 (b), 2 (d), and 3 (f) after forced involution. No differences were noted in histology associated with the first 2 days of involution. However, by the third day of involution control lobular alveolar structures began to collapse while many lobular alveolar structures in TβRII^(WKO)Rosa26R tissues at the same time point remained distended. B: Western blot analysis of WAP protein abundance indicated an accumulation in TβRII^(WKO)Rosa26R tissues when compared with the control tissues at the same timepoint. Ctl, WAP-Cre; KO, TβRII^(WKO)Rosa26R; L3, lactation day 3; D1, involution day 1; D2, involution day 2; D3, involution day 3.

Blockage of STAT3 activity during involution in Nucling-KO mice. A, Western blot analysis of STAT3 and phosphorylated STAT3 expression during involution. Protein samples were prepared from the mammary glands of WT and Nucling-KO mice at 0, 36, and 72 h of involution. B, the quantification of immunoblots for STAT3/β-actin. The bar graph shows the relative density of the bands normalized to WT at 0 h involution. C, quantification of immunoblots for p-STAT3/β-actin. The bar graph shows the relative density of the bands normalized to WT at 0 h of involution. D, quantification of the mRNA expression of C/EBPδ in mammary glands of WT and Nucling-KO mice at 0, 36, and 72 h of involution by quantitative RT-PCR. Data were normalized with those of WT mice at 0 h of involution and represent mean ± S.D. Data were represented as mean ± S.D. (n = 3 per genotype, per age group). **, p < 0.01.

(A) Involution in the wild-type control, E2f1-knockout and E2f3 heterozygous samples. (B) To examine apoptosis in the wild type and E2f3 mutant, a TUNEL analysis was conducted at day 2 and day 3 of involution. TUNEL-positive cells stain brown and the sections are lightly counterstained with Hematoxylin. (C) The results of the TUNEL staining were quantitated, with the day 2 and day 3 differences being significant (P<0.0001 and P=0.0073, respectively). (D) An involution signature from a wild-type mammary involution dataset was generated and the probability of fitting the signature was assessed for the wild type and E2f3 mutant at successive days of involution. Red indicates a high probability of matching the involution day 4 signature; blue indicates a high probability of matching the involution day 1 signature.