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Plakoglobin as a regulator of desmocollin gene expression.

Tokonzaba E, Chen J, Cheng X, Den Z, Ganeshan R, Műller EJ, Koch PJ - J. Invest. Dermatol. (2013)

Bottom Line: Specifically, we found that Lef-1 acts as a switch activating Dsc2 and repressing Dsc3 in the presence of Pg.Interestingly, we also determined that NF-κB pathway components, the downstream effectors of the ectodysplasin-A (EDA)/ ectodysplasin-A receptor (EDAR)/NF-κB signaling cascade, can activate Dsc2 expression.It is tempting to speculate that this shift is required for the invasive growth of placode keratinocytes into the dermis, a crucial step in skin appendage formation.

View Article: PubMed Central - PubMed

Affiliation: Department of Dermatology, University of Colorado School of Medicine, Aurora, Colorado, USA.

ABSTRACT
Desmosomes are cell adhesion junctions required for the normal development and maintenance of mammalian tissues and organs such as the skin, skin appendages, and the heart. The goal of this study was to investigate how desmocollins (DSCs), transmembrane components of desmosomes, are regulated at the transcriptional level. We hypothesized that differential expression of the Dsc2 and Dsc3 genes is a prerequisite for normal development of skin appendages. We demonstrate that plakoglobin (Pg) in conjunction with lymphoid enhancer-binding factor 1 (Lef-1) differentially regulates the proximal promoters of these two genes. Specifically, we found that Lef-1 acts as a switch activating Dsc2 and repressing Dsc3 in the presence of Pg. Interestingly, we also determined that NF-κB pathway components, the downstream effectors of the ectodysplasin-A (EDA)/ ectodysplasin-A receptor (EDAR)/NF-κB signaling cascade, can activate Dsc2 expression. We hypothesize that Lef-1 and EDA/EDAR/NF-κB signaling contribute to a shift in Dsc isoform expression from Dsc3 to Dsc2 in placode keratinocytes. It is tempting to speculate that this shift is required for the invasive growth of placode keratinocytes into the dermis, a crucial step in skin appendage formation.

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Effects of Pg on Dsc reporter activities(a-b). ChIP assays demonstrating direct binding of Pg to the Dsc2 promoter in the presence of Lef-1. Note that Pg does not bind the Dsc3 promoter in the presence of Lef-1 (b) or TCF4 (data not shown). Input, chromatin used for immunoprecipitation; IgG, IP with unspecific IgG. (c-f) Reporter assays in keratinocytes. (c) Co-expression of Pg and Lef-1 dramatically increases Dsc2 reporter activity while all other combinations of Pg and TCF/Lef factors have no effect. (d) The Dsc3 promoter is activated in the presence of Pg. This activation is reversed in cells co-expressing Pg and TCF4 or Lef-1. (e) Dsc2 promoter activation by Pg and Lef-1 is dependent on the presence of a functional TCF/Lef binding site. (f) Pg over-expression and loss of a functional TCF/Lef binding site increase Dsc3 reporter activity to a similar extend. Note that expression is normalized to the baseline expression of the WT promoter (set to 1). (g-h) Endogenous Dsc gene expression in keratinocytes transfected with different combinations of Pg and TCF/Lef factors. Error bars, standard deviation. Stars indicate statistically significant results (p-value < 0.05).
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Figure 2: Effects of Pg on Dsc reporter activities(a-b). ChIP assays demonstrating direct binding of Pg to the Dsc2 promoter in the presence of Lef-1. Note that Pg does not bind the Dsc3 promoter in the presence of Lef-1 (b) or TCF4 (data not shown). Input, chromatin used for immunoprecipitation; IgG, IP with unspecific IgG. (c-f) Reporter assays in keratinocytes. (c) Co-expression of Pg and Lef-1 dramatically increases Dsc2 reporter activity while all other combinations of Pg and TCF/Lef factors have no effect. (d) The Dsc3 promoter is activated in the presence of Pg. This activation is reversed in cells co-expressing Pg and TCF4 or Lef-1. (e) Dsc2 promoter activation by Pg and Lef-1 is dependent on the presence of a functional TCF/Lef binding site. (f) Pg over-expression and loss of a functional TCF/Lef binding site increase Dsc3 reporter activity to a similar extend. Note that expression is normalized to the baseline expression of the WT promoter (set to 1). (g-h) Endogenous Dsc gene expression in keratinocytes transfected with different combinations of Pg and TCF/Lef factors. Error bars, standard deviation. Stars indicate statistically significant results (p-value < 0.05).

Mentions: Pg has been shown to regulate gene expression in keratinocytes and other epithelial cell types (see references in the INTRODUCTION section). To determine whether Pg can affect Dsc promoter activity, we first assessed the ability of this protein to bind the Dsc2 and Dsc3 promoter fragments. As shown in Figure 2a-b, Pg binds to the Dsc2 promoter but not the Dsc3 promoter in the presence of Lef-1. Reporter assays demonstrated that Pg can affect both promoters, although its effects are dependent on Lef-1 (Figure 2c-d); in the presence of Lef-1, Pg activates the Dsc2 promoter, while Dsc3 promoter activation occurs in the absence of ectopic TCF/Lef expression. These results suggest that Lef-1 can act as a switch that shifts activity from the Dsc3 to the Dsc2 promoter in the presence of Pg.


Plakoglobin as a regulator of desmocollin gene expression.

Tokonzaba E, Chen J, Cheng X, Den Z, Ganeshan R, Műller EJ, Koch PJ - J. Invest. Dermatol. (2013)

Effects of Pg on Dsc reporter activities(a-b). ChIP assays demonstrating direct binding of Pg to the Dsc2 promoter in the presence of Lef-1. Note that Pg does not bind the Dsc3 promoter in the presence of Lef-1 (b) or TCF4 (data not shown). Input, chromatin used for immunoprecipitation; IgG, IP with unspecific IgG. (c-f) Reporter assays in keratinocytes. (c) Co-expression of Pg and Lef-1 dramatically increases Dsc2 reporter activity while all other combinations of Pg and TCF/Lef factors have no effect. (d) The Dsc3 promoter is activated in the presence of Pg. This activation is reversed in cells co-expressing Pg and TCF4 or Lef-1. (e) Dsc2 promoter activation by Pg and Lef-1 is dependent on the presence of a functional TCF/Lef binding site. (f) Pg over-expression and loss of a functional TCF/Lef binding site increase Dsc3 reporter activity to a similar extend. Note that expression is normalized to the baseline expression of the WT promoter (set to 1). (g-h) Endogenous Dsc gene expression in keratinocytes transfected with different combinations of Pg and TCF/Lef factors. Error bars, standard deviation. Stars indicate statistically significant results (p-value < 0.05).
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Related In: Results  -  Collection

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Figure 2: Effects of Pg on Dsc reporter activities(a-b). ChIP assays demonstrating direct binding of Pg to the Dsc2 promoter in the presence of Lef-1. Note that Pg does not bind the Dsc3 promoter in the presence of Lef-1 (b) or TCF4 (data not shown). Input, chromatin used for immunoprecipitation; IgG, IP with unspecific IgG. (c-f) Reporter assays in keratinocytes. (c) Co-expression of Pg and Lef-1 dramatically increases Dsc2 reporter activity while all other combinations of Pg and TCF/Lef factors have no effect. (d) The Dsc3 promoter is activated in the presence of Pg. This activation is reversed in cells co-expressing Pg and TCF4 or Lef-1. (e) Dsc2 promoter activation by Pg and Lef-1 is dependent on the presence of a functional TCF/Lef binding site. (f) Pg over-expression and loss of a functional TCF/Lef binding site increase Dsc3 reporter activity to a similar extend. Note that expression is normalized to the baseline expression of the WT promoter (set to 1). (g-h) Endogenous Dsc gene expression in keratinocytes transfected with different combinations of Pg and TCF/Lef factors. Error bars, standard deviation. Stars indicate statistically significant results (p-value < 0.05).
Mentions: Pg has been shown to regulate gene expression in keratinocytes and other epithelial cell types (see references in the INTRODUCTION section). To determine whether Pg can affect Dsc promoter activity, we first assessed the ability of this protein to bind the Dsc2 and Dsc3 promoter fragments. As shown in Figure 2a-b, Pg binds to the Dsc2 promoter but not the Dsc3 promoter in the presence of Lef-1. Reporter assays demonstrated that Pg can affect both promoters, although its effects are dependent on Lef-1 (Figure 2c-d); in the presence of Lef-1, Pg activates the Dsc2 promoter, while Dsc3 promoter activation occurs in the absence of ectopic TCF/Lef expression. These results suggest that Lef-1 can act as a switch that shifts activity from the Dsc3 to the Dsc2 promoter in the presence of Pg.

Bottom Line: Specifically, we found that Lef-1 acts as a switch activating Dsc2 and repressing Dsc3 in the presence of Pg.Interestingly, we also determined that NF-κB pathway components, the downstream effectors of the ectodysplasin-A (EDA)/ ectodysplasin-A receptor (EDAR)/NF-κB signaling cascade, can activate Dsc2 expression.It is tempting to speculate that this shift is required for the invasive growth of placode keratinocytes into the dermis, a crucial step in skin appendage formation.

View Article: PubMed Central - PubMed

Affiliation: Department of Dermatology, University of Colorado School of Medicine, Aurora, Colorado, USA.

ABSTRACT
Desmosomes are cell adhesion junctions required for the normal development and maintenance of mammalian tissues and organs such as the skin, skin appendages, and the heart. The goal of this study was to investigate how desmocollins (DSCs), transmembrane components of desmosomes, are regulated at the transcriptional level. We hypothesized that differential expression of the Dsc2 and Dsc3 genes is a prerequisite for normal development of skin appendages. We demonstrate that plakoglobin (Pg) in conjunction with lymphoid enhancer-binding factor 1 (Lef-1) differentially regulates the proximal promoters of these two genes. Specifically, we found that Lef-1 acts as a switch activating Dsc2 and repressing Dsc3 in the presence of Pg. Interestingly, we also determined that NF-κB pathway components, the downstream effectors of the ectodysplasin-A (EDA)/ ectodysplasin-A receptor (EDAR)/NF-κB signaling cascade, can activate Dsc2 expression. We hypothesize that Lef-1 and EDA/EDAR/NF-κB signaling contribute to a shift in Dsc isoform expression from Dsc3 to Dsc2 in placode keratinocytes. It is tempting to speculate that this shift is required for the invasive growth of placode keratinocytes into the dermis, a crucial step in skin appendage formation.

Show MeSH
Related in: MedlinePlus