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.
Project description:Epidermal lineages and injury induced regeneration are controlled by transcriptional programs coordinating cellular signaling and epigenetic regulators, but the mechanism remains unclear. Previous studies showed that conditional deletion of the transcriptional coactivator Mediator 1 (Med1) changes epidermal lineages and accelerates wound re-epithelialization. Here, we studied a molecular mechanism by which Med1 facilitates these processes, in particular, by focusing on TGFb signaling through genome wide transcriptome analysis. The expression of the TGF ligands (Tgfb1/b2) and their downstream target genes is decreased in both normal and wounded Med1 null skin. Med1 silencing in cultured keratinocytes likewise reduces the expression of the ligands (TGFb1/b2) and diminishes activity of TGFb signaling as shown by decreased p-Smad2/3. Silencing Med1 increases keratinocyte proliferation and migration in vitro. Epigenetic studies using chromatin immuno-precipitation and next generation DNA sequencing reveals that Med1 regulates transcription of TGFb components by forming large clusters of enhancers called super-enhancers at the regulatory regions of the TGFb ligand and SMAD3 genes. These results demonstrate that Med1 is required for the maintenance of the TGFb signaling pathway. Finally, we show that pharmacological inhibition of TGFb signaling enhances epidermal lineages and accelerates wound re-epithelialization in skin similar to that seen in the Med1 null mice, providing new insights into epidermal regeneration.
Project description:Transcriptional coactivator Mediator complex facilitates transcription of various transcription factors. Previously, we have generated Med1 conditional null mice, where a critical subunit of Mediator, Med1, is removed from keratinocytes. Here we present evidence that ablation of Med1 accelerated epidermal regeneration after injury. As bulge keratinocyte stem cells are important contributors to regenerate epidermis, we first analyzed properties of stem cells in Med1 null mice. BrdU long retaining analysis revealed that deletion of Med1 still maintained quiescence of bulge keratinocyte stem cells, despite of general hyperplasia observed in Med1 deficient keratinocytes. Gene expression analysis demonstrated that a series of niche matrix proteins decreased in Med1 deficient keratinocytes. In contrast, the expression of stem cell marker Sox9 was not altered, suggesting stem cells are present but activated because of abnormal niche surrounding stem cells. In addition, Med1 deletion suppressed injury induced inflammatory reaction, which indirectly regulates epidermal regeneration. We also indicated that TGFβ1 significantly decreased in both bulge and epidermal keratinocytes upon Med1 deletion. Our study demonstrates that coactivator Med1 has a critical role to maintain bulge stem cells and epidermal regeneration presumably through regulation in TGFβ signaling. n=4 WT and KO (each sample contain RNA from one mouse)
Project description:Transcriptional coactivator Mediator complex facilitates transcription of various transcription factors. Previously, we have generated Med1 conditional null mice, where a critical subunit of Mediator, Med1, is removed from keratinocytes. Here we present evidence that ablation of Med1 accelerated epidermal regeneration after injury. As bulge keratinocyte stem cells are important contributors to regenerate epidermis, we first analyzed properties of stem cells in Med1 null mice. BrdU long retaining analysis revealed that deletion of Med1 still maintained quiescence of bulge keratinocyte stem cells, despite of general hyperplasia observed in Med1 deficient keratinocytes. Gene expression analysis demonstrated that a series of niche matrix proteins decreased in Med1 deficient keratinocytes. In contrast, the expression of stem cell marker Sox9 was not altered, suggesting stem cells are present but activated because of abnormal niche surrounding stem cells. In addition, Med1 deletion suppressed injury induced inflammatory reaction, which indirectly regulates epidermal regeneration. We also indicated that TGFβ1 significantly decreased in both bulge and epidermal keratinocytes upon Med1 deletion. Our study demonstrates that coactivator Med1 has a critical role to maintain bulge stem cells and epidermal regeneration presumably through regulation in TGFβ signaling. n=3 WT and KO (each sample contain RNA isolated from wounded or nonwounded skins excised from 3 mice)
Project description:Transcriptional coactivator Mediator complex facilitates transcription of various transcription factors. Previously, we have generated Med1 conditional null mice, where a critical subunit of Mediator, Med1, is removed from keratinocytes. Here we present evidence that ablation of Med1 accelerated epidermal regeneration after injury. As bulge keratinocyte stem cells are important contributors to regenerate epidermis, we first analyzed properties of stem cells in Med1 null mice. BrdU long retaining analysis revealed that deletion of Med1 still maintained quiescence of bulge keratinocyte stem cells, despite of general hyperplasia observed in Med1 deficient keratinocytes. Gene expression analysis demonstrated that a series of niche matrix proteins decreased in Med1 deficient keratinocytes. In contrast, the expression of stem cell marker Sox9 was not altered, suggesting stem cells are present but activated because of abnormal niche surrounding stem cells. In addition, Med1 deletion suppressed injury induced inflammatory reaction, which indirectly regulates epidermal regeneration. We also indicated that TGFβ1 significantly decreased in both bulge and epidermal keratinocytes upon Med1 deletion. Our study demonstrates that coactivator Med1 has a critical role to maintain bulge stem cells and epidermal regeneration presumably through regulation in TGFβ signaling. n=3 WT and KO (each group contains keratinocytes isolated from adult skins excised from 2 mice)
Project description: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.
Project description:Transcriptional coactivator Mediator complex facilitates transcription of various transcription factors. Previously, we have generated Med1 conditional null mice, where a critical subunit of Mediator, Med1, is removed from keratinocytes. Here we present evidence that ablation of Med1 accelerated epidermal regeneration after injury. As bulge keratinocyte stem cells are important contributors to regenerate epidermis, we first analyzed properties of stem cells in Med1 null mice. BrdU long retaining analysis revealed that deletion of Med1 still maintained quiescence of bulge keratinocyte stem cells, despite of general hyperplasia observed in Med1 deficient keratinocytes. Gene expression analysis demonstrated that a series of niche matrix proteins decreased in Med1 deficient keratinocytes. In contrast, the expression of stem cell marker Sox9 was not altered, suggesting stem cells are present but activated because of abnormal niche surrounding stem cells. In addition, Med1 deletion suppressed injury induced inflammatory reaction, which indirectly regulates epidermal regeneration. We also indicated that TGFβ1 significantly decreased in both bulge and epidermal keratinocytes upon Med1 deletion. Our study demonstrates that coactivator Med1 has a critical role to maintain bulge stem cells and epidermal regeneration presumably through regulation in TGFβ signaling.
Project description:Transcriptional coactivator Mediator complex facilitates transcription of various transcription factors. Previously, we have generated Med1 conditional null mice, where a critical subunit of Mediator, Med1, is removed from keratinocytes. Here we present evidence that ablation of Med1 accelerated epidermal regeneration after injury. As bulge keratinocyte stem cells are important contributors to regenerate epidermis, we first analyzed properties of stem cells in Med1 null mice. BrdU long retaining analysis revealed that deletion of Med1 still maintained quiescence of bulge keratinocyte stem cells, despite of general hyperplasia observed in Med1 deficient keratinocytes. Gene expression analysis demonstrated that a series of niche matrix proteins decreased in Med1 deficient keratinocytes. In contrast, the expression of stem cell marker Sox9 was not altered, suggesting stem cells are present but activated because of abnormal niche surrounding stem cells. In addition, Med1 deletion suppressed injury induced inflammatory reaction, which indirectly regulates epidermal regeneration. We also indicated that TGFβ1 significantly decreased in both bulge and epidermal keratinocytes upon Med1 deletion. Our study demonstrates that coactivator Med1 has a critical role to maintain bulge stem cells and epidermal regeneration presumably through regulation in TGFβ signaling.
Project description:Transcriptional coactivator Mediator complex facilitates transcription of various transcription factors. Previously, we have generated Med1 conditional null mice, where a critical subunit of Mediator, Med1, is removed from keratinocytes. Here we present evidence that ablation of Med1 accelerated epidermal regeneration after injury. As bulge keratinocyte stem cells are important contributors to regenerate epidermis, we first analyzed properties of stem cells in Med1 null mice. BrdU long retaining analysis revealed that deletion of Med1 still maintained quiescence of bulge keratinocyte stem cells, despite of general hyperplasia observed in Med1 deficient keratinocytes. Gene expression analysis demonstrated that a series of niche matrix proteins decreased in Med1 deficient keratinocytes. In contrast, the expression of stem cell marker Sox9 was not altered, suggesting stem cells are present but activated because of abnormal niche surrounding stem cells. In addition, Med1 deletion suppressed injury induced inflammatory reaction, which indirectly regulates epidermal regeneration. We also indicated that TGFβ1 significantly decreased in both bulge and epidermal keratinocytes upon Med1 deletion. Our study demonstrates that coactivator Med1 has a critical role to maintain bulge stem cells and epidermal regeneration presumably through regulation in TGFβ signaling.