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Transcription co-regulator Clim2 plays a role in the maintenance of limbal stem cells

ABSTRACT: Clim1 and Clim2 are transcriptional cofactors that mediate protein-protein interactions within DNA-binding complexes in many cell types. Epithelial specific expression of a dominant negative Clim construct causes epithelial hyperplasia, neovascularization, inflammation, and blistering, followed by epithelial thinning and subsequent epidermal-like differentiation of the cornea epithelium. This phenotype resembles some aspects of limbal stem cell deficiency, suggesting that Clim proteins may be involved in regulating stem cell mainenance for the cornea. K14 DN-Clim cornea epithelium has a decrease in progenitor cells and altered proliferation during epithelial development. Gene expression profiling on DN-Clim corneas identified disrupted genes and pathways, including pathways crucial for stem cell mainenance, as well as regulation of proliferation. In vivo ChIP-Seq experiments confirm that many genes that are highly expressed in the limbus, as well as genes with known roles in stem cell maintenance are directly regulated by Clim factors. Additionally, factors that regulate corneal epithelial differentiation are direct targets of Clim. Together our results identify a role for Clim proteins in regulating stem cell maintenance and the proliferation dynamics of cornea epithelial proliferation.

ORGANISM(S): Mus musculus

PROVIDER: GSE49409 | GEO | 2016/04/28

SECONDARY ACCESSION(S): PRJNA213862

REPOSITORIES: GEO

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Project description:The nuclear LIM-only protein LMO4 is upregulated in breast cancer, especially estrogen receptor negative tumors, and its overexpression in mice leads to hyperplasia and tumor formation. Here, we show that deletion of LMO4 in the mammary glands of mice leads to impaired lobuloalveolar development due to decreased epithelial cell proliferation. With the goal of discovering potential LMO4-target genes, we also developed a conditional expression system in MCF-7 cells for both LMO4 and a dominant negative (DN) form of its co-regulator, Co-factor of LIM domains (Clim/Ldb/Nli). We then used DNA microarrays to identify genes responsive to LMO4 and DN-Clim upregulation. One of the genes common to both datasets was BMP7, whose expression is also significantly correlated with LMO4 transcript levels in a large dataset of human breast cancers, suggesting that BMP7 is a bona fide target gene of LMO4 in breast cancer. Inhibition of BMP7 partially blocks the effects of LMO4 on apoptosis, indicating that BMP7 mediates at least some functions of LMO4. Gene transfer studies show that LMO4 regulates the BMP7 promoter, and chromatin immunoprecipitation studies show that LMO4 and its co-factor Clim2 are recruited to the BMP7 promoter. Furthermore, we demonstrate that HDAC2 recruitment to the BMP7 promoter is inhibited by upregulation of LMO4 and that HDAC2 knockdown upregulates the promoter. These studies suggest a novel mechanism of action for LMO4: LMO4, Clim2 and HDAC2 are part of a transcriptional complex, and increased LMO4 levels can disrupt the complex, leading to decreased HDAC2 recruitment and increased promoter activity. Experiment Overall Design: We used the Tet-off system to establish several distinct MCF-7 cell clones, referred to as MCF7-LMO4-TetOff and MCF7-DN-Clim-TetOff cells, in which the expression of Myc-tagged LMO4 or DN-Clim was repressed by the presence of doxycycline in the medium. Total RNA was isolated from three distinct MCF7-LMO4-TetOff cell lines and three distinct MCF7-DN-Clim-TetOff cell lines in presence and absence of doxycycline after 6 days. Treatment with doxycycline To decrease variability, we pooled RNAs from three experiments for each of the three cell lines.

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Transcription co-regulator Clim2 plays a role in the maintenance of limbal stem cells

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