MAD2B acts as a negative regulatory partner of TCF4 on proliferation in human dermal papilla cells

www.nature.com/scientificreports Correction: Author Correction OPEN Received: 1 June 2017 Accepted: 2 August 2017 Published: xx xx xxxx MAD2B acts as a negative regulatory partner of TCF4 on proliferation in human dermal papilla cells Nanlan Yu1, Zhiqiang Song1, Kezhou Zhang2 & Xichuan Yang1 Dermal papilla cells (DPCs) are important components of hair follicles and play a critical role in hair follicle development. However, the mechanisms by which DPCs induce hair follicle development remain unclear. In the present study, we identified the mitotic arrest deficient protein MAD2B as a modifier of DPCs. Overexpression of MAD2B inhibited DPC aggregative growth and proliferation induced by the Wnt signaling activator T cell factor 4 (TCF4), and decreased TCF4-induced expression and the release of hair growth-related cytokines, including hepatocyte growth factor, insulin-like growth factor-1, and vascular endothelial growth factor in DPCs. In contrast, knockdown of MAD2B promoted TCF4-induced DPC proliferation, but did not affect the expression and secretion of cytokines by TCF4-induced DPCs. These results suggest a functional antagonism between MAD2B and TCF4 in DPC-induced hair follicle development. Mechanistically, MAD2B physically interacted with TCF4 to repress TCF4 transcriptional activity via β-catenin mediation, leading to reduced β-catenin/TCF4-dependent transactivation and Wnt signaling activity. These results demonstrate, for the first time, that MAD2B plays a negative role in TCF4-induced DPC growth and proliferation. Human hair serves many functions, including thermal regulation, protection of the skin, sensory perception, as well as an aesthetic purpose1. Alopecia (hair loss) is a common chronic dermatological disorder that, although not life threatening or physically harmful, may result in psychological consequences such as anxiety and depression2. Current medical treatments for hair loss include drug-induced hair growth promotion and hair transplantation, both of which require the formation of new hair follicles, from which hairs emerge1. Thus, a better understanding of the mechanisms underpinning the neogenesis of hair follicles is highly significant for the treatment of alopecia. The hair follicle is structurally composed of epidermal and dermal portions3, and undergoes cyclical phases of growth (anagen), regression (catagen), and quiescence (telogen), throughout postnatal life4,5. Located at the base of the hair follicle, a population of mesenchymal cells, known as dermal papilla cells (DPCs), is characterized by aggregative behavior when cultured in vitro and the ability to induce new hair follicle formation during both embryonic and postnatal life6–8. DPCs promote hair follicle formation and development through the interplay of various signaling pathways such as Wnt, Bmp, Shh, and Notch9,10. Amongst these, Wnt/β-catenin signaling was the first identified and is considered the most important. Wnt/β-catenin signaling functions in hair follicle induction mainly through the binding of β-catenin to members of the lymphoid enhancer factor (LEF)/T cell factor (TCF) family of DNA binding proteins. This is triggered by Wnt-receptor interaction-induced β-catenin stabilization and translocation from the cytoplasm to the nucleus11–14. In our previous study, TCF4, a member of the LEF/TCF family that is encoded by the Tcf7l2 gene, was found to be upregulated in DPCs in anagen hair follicles15. TCF4 and β-catenin form a complex in the nucleus, leading to transcriptional activation of downstream genes in the Wnt/β-catenin signaling pathway16. Furthermore, TCF4 is highly expressed in in vitro cultured low-passage (1‒3) DPCs, displaying an aggregative growth pattern that facilitates hair follicle induction. However, high-passage (>10) DPCs tend to lose their inductive ability during passaging17–19, suggesting that TCF4 is closely related to DPC proliferation and hair follicle neogenesis. 1 Department of Dermatology, The First Affiliated Hospital of the Third Military Medical University, Chongqing, 400038, China. 2Department of Dermatology, The 401st Hospital of Chinese People’s Liberation Army, 22 Minjiang Road, Qingdao, 266000, China. Nanlan Yu and Zhiqiang Song contributed equally to this work. Correspondence and requests for materials should be addressed to X.Y. (email: ) Scientific Reports | 7: 11687 | DOI:10.1038/s41598-017-10350-w 1 www.nature.com/scientificreports/ Figure 1. MAD2B overexpression suppresses the aggregative growth of DPCs. DPCs were transduced with a control vector (upper panels) or an adenoviral vector expressing MAD2B (middle panels) or MAD2 (lower panels) over time, as indicated. Micrographs were captured at 100 × magnification. DPCs, dermal papilla cells. The mitotic arrest deficient protein MAD2B, a homolog of the cell cycle checkpoint protein MAD220,21, has been identified as a TCF4-interacting partner. MAD2B blocks TCF4-mediated transactivation of the Wnt/β-catenin signaling cascade in the epithelial-mesenchymal transdifferentiation of colorectal cancer cells22. These findings prompted us to hypothesize that MAD2B/TCF4 interaction may suppress TCF4-induced DPC growth and proliferation by inactivating the Wnt/β-catenin signaling pathway. To test this hypothesis, we constructed adenoviral and plasmid vectors expressing MAD2B, TCF4, and short hairpin RNA against MAD2B. By transducing or transfecting these vectors, alone or in combination, into DPCs, we examined the role of MAD2B in TCF4-induced DPC growth and proliferation and explored the possible mechanisms involved. Results MAD2B inhibits the aggregative growth of DPCs. DPCs proliferate in a pronounced aggregative pattern in vitro, which has been shown to be important for their hair-inductive ability18,23–26. Furthermore, MAD2B plays a potential role in cell cycle arrest by inhibiting the anaphase-promoting complex (APC)27. To determine if MAD2B affects the aggregative growth of DPCs, an adenoviral vector expressing MAD2B was transfected into DPCs. As shown in Fig. 1, MAD2B-overexpressing DPCs exhibited a gradual loss of aggregative behavior in a time-dependent manner. After 48 h of transfection, the DPCs were loosely arranged and the aggregative behavior was clearly diminished (Fig. 1, middle panel). In contrast, the empty vector-transfected DPCs maintained the aggregative behavior and grew in clusters (Fig. 1, upper panel). Interestingly, MAD2 appeared to have no inhibitory effect on aggressive behavior of DPCs (Fig. 1, lower panel). These data suggest that MAD2B plays a specific role in inhibiting the aggregative growth of DPCs. MAD2B suppresses TCF4-induced DPC proliferation. Since our previous study indicated that TCF4 promoted DPC proliferation in vitro19, we next sought to examine whether MAD2B plays a role in TCF4-induced DPC proliferation. A CCK-8 assay was performed on DPCs transfected with TCF4- and MAD2B-expressing vectors and siMAD2B, individually or in combination. (...truncated)