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Deletion of Mediator (Med1) induces epidermal fate in dental epithelial stem cells

ABSTRACT: Cell fates are defined by specific transcriptional program. We developed a mouse model, in which transcriptional program for ectoderm cell fate is altered in tooth and skin. Previously, we showed that genomic deletion of one subunit of Mediator complex, Mediator 1 (Med1) in vivo regenerate ectopic hair in incisors by disrupting Notch mediated enamel epithelial differentiation. However, precise process and molecular mechanism to induce epidermal fate are not clear. Med1 deficient dental epithelial stem cells exerts transcriptional program for skin epithelia reminiscent of the pattern in the skin. Epidermal transcripts were first induced prior to hair genes during dental epithelial differentiation, resemble to the pattern of embryonic developmental process of the skin. Hair genes was specifically induced at the anagen stage synchronized with hair cycling in the skin. Epidermal program was also induced in cultured adult stem cells called dental epithelial stem cell (DESC) that is derived from micro-dissected Med1 KO cervical loop tissues that are essential for continuous regeneration of mouse incisors. Gene expression profiles for the primary DESC with colony forming capability revealed that Med1 deletion suppressed Tgfb signaling by reducing the expression of ligands (Tgfb1, Inhibin ba), receptors and their extracellular targets such as Ctgf. Med1 deletion also induced Tgfb regulated reprogramming transcription factor, Klf4 that also known to drive transcription for epidermal genes. TGFb signaling was also suppressed in Med1 null epidermis in skin, in which epidermal fate was induced in hair follicle keratinocytes. Med1 silencing blocked expression of TGFb1 and suppressed both basal and recombinant TGFb induced Smad2/3 mediated transcription of TGFb target genes in vitro. These results demonstrate that Med1 deletion enhances epidermal transcriptional program in adult stem cells through regulation of TGFb signaling.

ORGANISM(S): Mus musculus

PROVIDER: GSE112884 | GEO | 2018/12/31

REPOSITORIES: GEO

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Project description:Cell fates are defined by specific transcriptional program. Previously, we developed a unique stem cell regeneration mouse model, in which transcriptional program for ectoderm organs such as tooth and skin is switched. Genomic deletion of one subunit of Mediator complex, Med1, resulted in defective enamel regeneration, in which dental stem cells were inhibited from undergoing transcriptional program for dental fate. In stead, they exerted skin program for both hair and epidermis, and post-natally regenerate ectopic hairs in the incisors. Here, we report that Med1 also modulates epidermal and hair cell fates in the skin. Med1 ablation further enhanced epidermal and sebocyte fates, and accelerated injury induced epidermal regeneration. However, it blunted hair fate resulting in hair loss in the skin. Ablation of Med1 increased the number of isthmus stem cells and epidermal stem cells, which regenerate epidermis during cutaneous wound healing process. Med1 deficiency also constitutively activated these stem cells and increased their proliferation. Microarray profiling indicated that Med1 deletion causes activation of β-catenin and suppression of TGFβ signaling. Med1 deficiency induced the expression of β-catenin target genes to control cell fate and proliferation. It also decreased TGFβ expression in interfollicular epidermis. Med1 deficiency increased the proliferation and migration of epidermal cells, and induced nuclear translocation of β-catenin, and decreased TGFβ1 expression in vitro. Our finding together with previous observations demonstrated that Med1 governs ectoderm cell fate in both tooth and skin. Med1 ablation blunts hair fate but induces epidermal and sebocyte cell fates to accelerated injury induced epidermal regeneration in the skin. Accelerated regeneration is derived from constitutive activation of epidermal stem cells accompanied with increased proliferation and migration of their progeny by balancing of β-catenin induced growth promoting and TGFβ mediated growth inhibitory activities in the skin.

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Deletion of Mediator (Med1) induces epidermal fate in dental epithelial stem cells

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