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PHF1 fusions cause distinct gene expression and chromatin accessibility profiles in ossifying fibromyxoid tumors and mesenchymal cells

Hofvander, Jakob LU ; Jo, Vickie Y. ; Fletcher, Christopher D.M. ; Puls, Florian ; Flucke, Uta ; Nilsson, Jenny LU ; Magnusson, Linda LU and Mertens, Fredrik LU (2020) In Modern Pathology
Abstract

Ossifying fibromyxoid tumor (OFMT) is a soft tissue tumor frequently displaying gene fusions, most of which affect the PHF1 gene. PHF1 encodes plant homeodomain finger protein 1, which is involved in various processes regulating gene transcription, including those orchestrated by the polycomb repressor complex 2. Here, a series of 37 OFMTs, including 18 typical, 9 atypical, and 10 malignant variants, was analyzed with regard to transcriptomic features, gene fusion and copy number status, and/or single-nucleotide variants. The effects on gene expression and chromatin accessibility of three detected fusions (EP400–PHF1, MEAF6–PHF1, and PHF1–TFE3) were further evaluated in fibroblasts. Genomic imbalances showed a progression-related... (More)

Ossifying fibromyxoid tumor (OFMT) is a soft tissue tumor frequently displaying gene fusions, most of which affect the PHF1 gene. PHF1 encodes plant homeodomain finger protein 1, which is involved in various processes regulating gene transcription, including those orchestrated by the polycomb repressor complex 2. Here, a series of 37 OFMTs, including 18 typical, 9 atypical, and 10 malignant variants, was analyzed with regard to transcriptomic features, gene fusion and copy number status, and/or single-nucleotide variants. The effects on gene expression and chromatin accessibility of three detected fusions (EP400–PHF1, MEAF6–PHF1, and PHF1–TFE3) were further evaluated in fibroblasts. Genomic imbalances showed a progression-related pattern, with more extensive copy number changes among atypical/malignant lesions than among typical OFMTs; loss of the RB1 gene was restricted to atypical/malignant OFMTs, occurring in one-third of the cases. RNA sequencing identified fusion transcripts in >80% of the cases analyzed, including a novel CSMD1–MEAF6. The gene-expression profile of OFMT was distinct from that of other soft tissue tumors, with extensive transcriptional upregulation of genes in OFMT. These findings were largely recapitulated in gene fusion-expressing fibroblast lines, suggesting that genes involved in, e.g., Wnt signaling and/or being regulated through trimethylation of lysine 27 in histone 3 (H3K27me3) are pivotal for OFMT development. The genes showing differentially higher expression in fusion-expressing cells paralleled increased chromatin accessibility, as revealed by ATAC sequencing. Thus, the present study suggests that OFMT develops through gene fusions that have extensive epigenetic consequences.

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Modern Pathology
publisher
Nature Publishing Group
external identifiers
  • pmid:31932680
  • scopus:85078626234
ISSN
0893-3952
DOI
10.1038/s41379-020-0457-8
language
English
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yes
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35cdb268-c09c-485b-9f41-c274e060ddc7
date added to LUP
2020-02-14 15:58:15
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2020-02-15 01:57:02
@article{35cdb268-c09c-485b-9f41-c274e060ddc7,
  abstract     = {<p>Ossifying fibromyxoid tumor (OFMT) is a soft tissue tumor frequently displaying gene fusions, most of which affect the PHF1 gene. PHF1 encodes plant homeodomain finger protein 1, which is involved in various processes regulating gene transcription, including those orchestrated by the polycomb repressor complex 2. Here, a series of 37 OFMTs, including 18 typical, 9 atypical, and 10 malignant variants, was analyzed with regard to transcriptomic features, gene fusion and copy number status, and/or single-nucleotide variants. The effects on gene expression and chromatin accessibility of three detected fusions (EP400–PHF1, MEAF6–PHF1, and PHF1–TFE3) were further evaluated in fibroblasts. Genomic imbalances showed a progression-related pattern, with more extensive copy number changes among atypical/malignant lesions than among typical OFMTs; loss of the RB1 gene was restricted to atypical/malignant OFMTs, occurring in one-third of the cases. RNA sequencing identified fusion transcripts in &gt;80% of the cases analyzed, including a novel CSMD1–MEAF6. The gene-expression profile of OFMT was distinct from that of other soft tissue tumors, with extensive transcriptional upregulation of genes in OFMT. These findings were largely recapitulated in gene fusion-expressing fibroblast lines, suggesting that genes involved in, e.g., Wnt signaling and/or being regulated through trimethylation of lysine 27 in histone 3 (H3K27me3) are pivotal for OFMT development. The genes showing differentially higher expression in fusion-expressing cells paralleled increased chromatin accessibility, as revealed by ATAC sequencing. Thus, the present study suggests that OFMT develops through gene fusions that have extensive epigenetic consequences.</p>},
  author       = {Hofvander, Jakob and Jo, Vickie Y. and Fletcher, Christopher D.M. and Puls, Florian and Flucke, Uta and Nilsson, Jenny and Magnusson, Linda and Mertens, Fredrik},
  issn         = {0893-3952},
  language     = {eng},
  publisher    = {Nature Publishing Group},
  series       = {Modern Pathology},
  title        = {PHF1 fusions cause distinct gene expression and chromatin accessibility profiles in ossifying fibromyxoid tumors and mesenchymal cells},
  url          = {http://dx.doi.org/10.1038/s41379-020-0457-8},
  doi          = {10.1038/s41379-020-0457-8},
  year         = {2020},
}