Project description:The genomic mechanisms underlying progressive, irreversible cell lineage commitments and differentiation, which include large scale chromatin re-organization, transcription factor binding, and chromatin modifications, have been well defined. However, we know little about the chromatin changes during transitions between transient cell states such as cell migration. Here we demonstrate the formation of unique complements of typical enhancers and super-enhancers as human progenitor keratinocytes either differentiate or migrate. Unique super-enhancers for each cellular state are linked to gene expression that confer functions associated with each cell state, and sequence variants associated with skin diseases are enriched within super-enhancers. GRHL3, a factor that promotes both differentiation and migration, exhibits prominent super-enhancer interactions in differentiating keratinocytes, while during migration, it preferentially binds to promoters along with REST, repressing the expression of migration inhibitors. Key epidermal differentiation transcription factor genes, including GRHL3, are located within super-enhancers, and many of these transcription factors in turn bind to and regulate super-enhancers. Of note, GRHL3 also represses the formation of a number of progenitor and non-keratinocyte super-enhancers in differentiating keratinocytes. Thus, coordinated GRHL3 binding and enhancer rearrangements regulate the functional states of keratinocytes.
Project description:The genomic mechanisms underlying progressive, irreversible cell lineage commitments and differentiation, which include large scale chromatin re-organization, transcription factor binding, and chromatin modifications, have been well defined. However, we know little about the chromatin changes during transitions between transient cell states such as cell migration. Here we demonstrate the formation of unique complements of typical enhancers and super-enhancers as human progenitor keratinocytes either differentiate or migrate. Unique super-enhancers for each cellular state are linked to gene expression that confer functions associated with each cell state, and sequence variants associated with skin diseases are enriched within super-enhancers. GRHL3, a factor that promotes both differentiation and migration, exhibits prominent super-enhancer interactions in differentiating keratinocytes, while during migration, it preferentially binds to promoters along with REST, repressing the expression of migration inhibitors. Key epidermal differentiation transcription factor genes, including GRHL3, are located within super-enhancers, and many of these transcription factors in turn bind to and regulate super-enhancers. Of note, GRHL3 also represses the formation of a number of progenitor and non-keratinocyte super-enhancers in differentiating keratinocytes. Thus, coordinated GRHL3 binding and enhancer rearrangements regulate the functional states of keratinocytes.
Project description:The genomic mechanisms underlying progressive, irreversible cell lineage commitments and differentiation, which include large scale chromatin re-organization, transcription factor binding, and chromatin modifications, have been well defined. However, we know little about the chromatin changes during transitions between transient cell states such as cell migration. Here we demonstrate the formation of unique complements of typical enhancers and super-enhancers as human progenitor keratinocytes either differentiate or migrate. Unique super-enhancers for each cellular state are linked to gene expression that confer functions associated with each cell state, and sequence variants associated with skin diseases are enriched within super-enhancers. GRHL3, a factor that promotes both differentiation and migration, exhibits prominent super-enhancer interactions in differentiating keratinocytes, while during migration, it preferentially binds to promoters along with REST, repressing the expression of migration inhibitors. Key epidermal differentiation transcription factor genes, including GRHL3, are located within super-enhancers, and many of these transcription factors in turn bind to and regulate super-enhancers. Of note, GRHL3 also represses the formation of a number of progenitor and non-keratinocyte super-enhancers in differentiating keratinocytes. Thus, coordinated GRHL3 binding and enhancer rearrangements regulate the functional states of keratinocytes.
Project description:The genomic mechanisms underlying progressive, irreversible cell lineage commitments and differentiation, which include large scale chromatin re-organization, transcription factor binding, and chromatin modifications, have been well defined. However, we know little about the chromatin changes during transitions between transient cell states such as cell migration. Here we demonstrate the formation of unique complements of typical enhancers and super-enhancers as human progenitor keratinocytes either differentiate or migrate. Unique super-enhancers for each cellular state are linked to gene expression that confer functions associated with each cell state, and sequence variants associated with skin diseases are enriched within super-enhancers. GRHL3, a factor that promotes both differentiation and migration, exhibits prominent super-enhancer interactions in differentiating keratinocytes, while during migration, it preferentially binds to promoters along with REST, repressing the expression of migration inhibitors. Key epidermal differentiation transcription factor genes, including GRHL3, are located within super-enhancers, and many of these transcription factors in turn bind to and regulate super-enhancers. Of note, GRHL3 also represses the formation of a number of progenitor and non-keratinocyte super-enhancers in differentiating keratinocytes. Thus, coordinated GRHL3 binding and enhancer rearrangements regulate the functional states of keratinocytes.
Project description:While the genomic mechanisms underlying progressive, irreversible cell lineage commitments are well-studied, we know little about the chromatin changes during transient cell states such as cell migration. Interestingly, a large number of SEs in NHEK-D and NHEK-M overlap genes encoding transcription factors with important roles in promotion of epidermal differentiation, including GRHL3, TP63, RUNX1, NOTCH3 and FOS. To test the role of these SE-associated transcription factors in a systematic manner, and to place GRHL3 in the context of other keratinocyte differentiation regulators, we used siRNAs to individually knock down GRHL3 and 50 other transcriptional regulators in NHEK-D. These transcriptional regulators were selected based on expression changes during human keratinocyte differentiation. Many have been previously implicated in epidermal differentiation in mice and humans; the genes encoding 22 of them are associated with SEs. To assess the effect of the knockdowns on keratinocyte differentiation, we monitored the expression of approximately 14,000 genes with custom-made Agilent microarrays. Among the 14,000 genes whose expression we monitored were all genes expressed in human keratinocytes and all transcriptional regulators. This 51 x 14,000 gene expression matrix provided a rich dataset to explore gene regulatory networks in epidermal differentiation.
Project description:Human primary keratinocytes were depleted of GRHL3 by siRNA and induced to differentiated for 2 days by addition of Calcium Primary normal human keratinocytes were transfected with GRHL3 or scrambled control siRNA using RNAi max (Life Technologies). 24 hours post transfection medium was raised to 1.8mM to induce differentiation. Cells were collected 48 hours later.
Project description:Epidermal barrier repair mechanisms activated in psoriasis lesions are likely involved in limiting the severity of this disease. We show that loss of grainyhead-like 3 (Grhl3), a pro-terminal differentiation factor in the epidermis, is sufficient to trigger greater sensitivity to and delayed resolution of epidermal lesions resulting from either physical or immune mediated barrier injury. After stimulation of Toll like receptors, the loss of Grhl3 resulted in increased epidermal damage with a striking increase in basal cell proliferation, hyperplasia of partially differentiated suprabasal layers, and a transcriptional profile highlighted by the overexpression of epidermal wound response and alarmin genes. This study reveals an important role for the epidermis in the initiation and recovery from immune-mediated lesions, and indicated that the epidermal regulator Grhl3 acts to both suppress disease initiation and resolve existing lesions. This work suggests that treatments focused on improving barrier function could be used preventatively and therapeutically in psoriasis. Whole skin was collected from E16.5 mouse backskins for Grhl3 ChIP. Adult epidermis for depilation and imiquimod experiments was seperated from dermis using dispase prior to Grhl3 ChIP.
Project description:Stem and progenitor cells maintain the tissue they reside in for life by regulating the balance between proliferation and differentiation. How this is done is not well understood. Here, we report that the human exosome maintains progenitor cell function. The expression of several subunits of the exosome were found to be enriched in epidermal progenitor cells, which were required to retain proliferative capacity and to prevent premature differentiation. Loss of PM/Scl-75 also known as EXOSC9, a key subunit of the exosome complex, resulted in loss of cells from the progenitor cell compartment, premature differentiation, and loss of epidermal tissue. EXOSC9 promotes self-renewal and prevents premature differentiation by maintaining transcript levels of a transcription factor necessary for epidermal differentiation, GRHL3, at low levels through mRNA degradation. These data demonstrate that control of differentiation specific transcription factors through mRNA degradation is required for progenitor cell maintenance in mammalian tissue. Refer to publication (Mistry et. Cell Stem Cell 2012) for more detail For gene expression profiling, cultured primary human keratinocytes were knocked down for EXOSC9, EXOSC9 and GRHL3, or control. RNA was harvested from the cells 5 days after knockdown. Microarray analysis using Affymetrix HG-U133 2.0 plus arrays was performed on duplicate samples. Significantly changed genes were identified as previously described(Sen et al., 2010).
Project description:The antagonistic actions of Polycomb and Trithorax are responsible for proper cell fate determination in mammalian tissues. In the epidermis, a self-renewing epithelium, previous work has shown that release from Polycomb repression only partially explains differentiation gene activation. We now show that Trithorax is also a key regulator of epidermal differentiation, not only through activation of genes repressed by Polycomb in progenitor cells, but also through activation of genes independent of regulation by Polycomb. The differentiation associated transcription factor GRHL3/GET1 recruits the ubiquitously expressed Trithorax complex to a subset of differentiation genes. Examination of WDR5 and GRHL3 binding in human differentited primary keratinocytes (NHEK). High calcium medium was added to NHEK cells at 50% confluency to induce differentiation. Cells were collected for ChIP 24 hours after addition of high calcium medium. ChIP with Wdr5 and Grhl3 antibodies, and an input control were sequenced.