Expression of a dominant-negative type II transforming growth factor β (TGF-β) receptor in the epidermis of transgenic mice blocks TGF-β-mediated growth inhibition

Abstract

To determine whether a functional type II receptor of transforming growth factor ␤ (TGF-␤) is required to mediate the growth inhibitory effect of TGF-␤ on the skin in vivo, we have generated transgenic mice that overexpress a dominant negative-type II TGF-␤ receptor (⌬␤RII) in the epidermis. The ⌬␤RII mice exhibited a thickened and wrinkled skin, and histologically the epidermis was markedly hyperplastic and hyperkeratotic. In vivo labeling with BrdUrd showed a 2.5-fold increase in the labeling index over controls, with labeled nuclei occurring in both basal and suprabasal cells of transgenic epidermis. In heterozygotes, this skin phenotype gradually diminished, and by 10-14 days after birth the transgenic mice were indistinguishable from their normal siblings. However, when F 1 mice were mated to homozygosity, perinatal lethality occurred due to the severe hyperkeratotic phenotype, which restricted movement. Cultured primary keratinocytes from ⌬␤RII mice also exhibited an increased rate of growth in comparison with nontransgenic controls, and were resistant to TGF-␤-induced growth inhibition. These data document the role of the type II TGF-␤ receptor in mediating TGF-␤-induced growth inhibition of the epidermis in vivo and in maintenance of epidermal homeostasis.

Expression of a dominant negative type II TGF-β receptor in mouse skin results in an increase in carcinoma incidence and an acceleration of carcinoma development

“…The undisturbed normal skin in our transgenic mice suggests that TGF-b signaling is not crucial for maintaining homeostasis in basal and follicular keratinocytes in normal skin. Previously described transgenic mice expressing a dominant negative type II TGF-b receptor mutant in basal and suprabasal interfollicular keratinocytes develop hyperproliferative skin conditions in the absence of external stimuli (Wang et al, 1997). Therefore, TGF-b signaling in suprabasal keratinocytes and not in basal cells may be more important for maintaining homeostasis in normal skin.…”

Aberrant cell cycle progression contributes to the early-stage accelerated carcinogenesis in transgenic epidermis expressing the dominant negative TGFβRII

“…To test this hypothesis in the skin, we have generated transgenic mice expressing DbRII in the epidermis, utilizing a truncated mouse loricrin vector (ML.DbRII). ML.DbRII mice exhibit a marked hyperplasia/hyperkeratosis at birth, suggesting that the DbRII can block TGFb mediated growth inhibition in the epidermis (Wang et al, 1997b). This is further supported by the fact that primary keratinocytes isolated from the epidermis of ML.DbRII transgenic mice were resistant to exogenous TGFb1 induced growth inhibition (Wang et al, 1997b).…”

“…This activated receptor complex transduces TGFb signals (Feng et al, 1995). Deletion of the serine/threonine kinase domain of TGFbRII produces a dominant negative form (DbRII), which is able to block the growth inhibitory function of TGFb in vitro (Chen et al, 1993;Wieser et al, 1993) and in transgenic animals (Wang et al, 1997b;Bottinger et al, 1997;Gorska et al, 1998), suggesting that TGFbRII is required to mediate the growth inhibitory e ect of TGFb. Mutations in TGFbRII were initially detected in TGFb-resistant cancer cell lines (Markowitz et al, 1995;Myero et al, 1995;Carcamo et al, 1995).…”

“…ML.DbRII mice exhibit a marked hyperplasia/hyperkeratosis at birth, suggesting that the DbRII can block TGFb mediated growth inhibition in the epidermis (Wang et al, 1997b). This is further supported by the fact that primary keratinocytes isolated from the epidermis of ML.DbRII transgenic mice were resistant to exogenous TGFb1 induced growth inhibition (Wang et al, 1997b). When ML.DbRII mice were subjected to a two-stage chemical carcinogenesis protocol, they exhibited an increased susceptibility compared to non-transgenic mice, with greatly accelerated benign papilloma formation, malignant conversion and metastasis (Go et al, 1999).…”

Temporal Smad7 Transgene Induction in Mouse Epidermis Accelerates Skin Wound Healing

“…19,20 The cells were cultured in Progenitor Cell Targeted Epidermal Keratinocyte medium (CELLnTEC USA, La Vista, NE) to maintain keratinocyte proliferation. For keratinocyte migration assays, cultured keratinocytes at nearly full confluency were treated with 10 Ϫ7 mol/L RU486 for 12 hours to induce Smad7 expression 12 and treated with mitomycin C (Sigma) to block cell proliferation.…”