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Functional annotation of the 2q35 breast cancer risk locus implicates a structural variant in influencing activity of a long-range enhancer element

Baxter, J.S. ; Augustinsson, Annelie LU ; Olsson, Håkan LU orcid and Fletcher, O. (2021) In American Journal of Human Genetics 108(7). p.1190-1203
Abstract
A combination of genetic and functional approaches has identified three independent breast cancer risk loci at 2q35. A recent fine-scale mapping analysis to refine these associations resulted in 1 (signal 1), 5 (signal 2), and 42 (signal 3) credible causal variants at these loci. We used publicly available in silico DNase I and ChIP-seq data with in vitro reporter gene and CRISPR assays to annotate signals 2 and 3. We identified putative regulatory elements that enhanced cell-type-specific transcription from the IGFBP5 promoter at both signals (30- to 40-fold increased expression by the putative regulatory element at signal 2, 2- to 3-fold by the putative regulatory element at signal 3). We further identified one of the five credible... (More)
A combination of genetic and functional approaches has identified three independent breast cancer risk loci at 2q35. A recent fine-scale mapping analysis to refine these associations resulted in 1 (signal 1), 5 (signal 2), and 42 (signal 3) credible causal variants at these loci. We used publicly available in silico DNase I and ChIP-seq data with in vitro reporter gene and CRISPR assays to annotate signals 2 and 3. We identified putative regulatory elements that enhanced cell-type-specific transcription from the IGFBP5 promoter at both signals (30- to 40-fold increased expression by the putative regulatory element at signal 2, 2- to 3-fold by the putative regulatory element at signal 3). We further identified one of the five credible causal variants at signal 2, a 1.4 kb deletion (esv3594306), as the likely causal variant; the deletion allele of this variant was associated with an average additional increase in IGFBP5 expression of 1.3-fold (MCF-7) and 2.2-fold (T-47D). We propose a model in which the deletion allele of esv3594306 juxtaposes two transcription factor binding regions (annotated by estrogen receptor alpha ChIP-seq peaks) to generate a single extended regulatory element. This regulatory element increases cell-type-specific expression of the tumor suppressor gene IGFBP5 and, thereby, reduces risk of estrogen receptor-positive breast cancer (odds ratio = 0.77, 95% CI 0.74–0.81, p = 3.1 × 10−31). © 2021 The Authors (Less)
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@article{a678bca8-9c60-4f2d-b241-08fb6933bd00,
  abstract     = {{A combination of genetic and functional approaches has identified three independent breast cancer risk loci at 2q35. A recent fine-scale mapping analysis to refine these associations resulted in 1 (signal 1), 5 (signal 2), and 42 (signal 3) credible causal variants at these loci. We used publicly available in silico DNase I and ChIP-seq data with in vitro reporter gene and CRISPR assays to annotate signals 2 and 3. We identified putative regulatory elements that enhanced cell-type-specific transcription from the IGFBP5 promoter at both signals (30- to 40-fold increased expression by the putative regulatory element at signal 2, 2- to 3-fold by the putative regulatory element at signal 3). We further identified one of the five credible causal variants at signal 2, a 1.4 kb deletion (esv3594306), as the likely causal variant; the deletion allele of this variant was associated with an average additional increase in IGFBP5 expression of 1.3-fold (MCF-7) and 2.2-fold (T-47D). We propose a model in which the deletion allele of esv3594306 juxtaposes two transcription factor binding regions (annotated by estrogen receptor alpha ChIP-seq peaks) to generate a single extended regulatory element. This regulatory element increases cell-type-specific expression of the tumor suppressor gene IGFBP5 and, thereby, reduces risk of estrogen receptor-positive breast cancer (odds ratio = 0.77, 95% CI 0.74–0.81, p = 3.1 × 10−31). © 2021 The Authors}},
  author       = {{Baxter, J.S. and Augustinsson, Annelie and Olsson, Håkan and Fletcher, O.}},
  issn         = {{0002-9297}},
  keywords     = {{breast cancer risk; functional annotation; risk locus; deoxyribonuclease I; transcription factor; Article; binding affinity; breast cancer; cancer risk; chromosome 2q; chromosome chromosome 2q35; computer model; controlled study; CRISPR Cas system; enhancer region; estrogen receptor positive breast cancer; gene deletion; gene expression; gene function; gene locus; gene mapping; genetic analysis; human; human cell; IGFBP5 gene; in vitro study; molecular genetics; odds ratio; regulatory sequence; reporter gene; risk reduction; tumor suppressor gene}},
  language     = {{eng}},
  number       = {{7}},
  pages        = {{1190--1203}},
  publisher    = {{Cell Press}},
  series       = {{American Journal of Human Genetics}},
  title        = {{Functional annotation of the 2q35 breast cancer risk locus implicates a structural variant in influencing activity of a long-range enhancer element}},
  url          = {{http://dx.doi.org/10.1016/j.ajhg.2021.05.013}},
  doi          = {{10.1016/j.ajhg.2021.05.013}},
  volume       = {{108}},
  year         = {{2021}},
}