Title: Non-IG Aberrations of FOXP1 in B-Cell Malignancies Lead to an Aberrant Expression of N-Truncated Isoforms of FOXP1
Authors: Rouhigharabaei, Leila
Finalet Ferreiro, Julio
Tousseyn, Thomas
van der Krogt, Jo-Anne
Put, Natalie
Haralambieva, Eugenia
Graux, Carlos
Maes, Brigitte
Vicente, Carmen
Vandenberghe, Peter
Cools, Jan
Wlodarska, Iwona # ×
Issue Date: 2014
Publisher: Public Library of Sciene
Series Title: PLoS One vol:9 issue:1 pages:e85851
Article number: 10.1371/journal.pone.0085851
Abstract: The transcription factor FOXP1 is implicated in the pathogenesis of B-cell lymphomas through chromosomal translocations involving either immunoglobulin heavy chain (IGH) locus or non-IG sequences. The former translocation, t(3;14)(p13;q32), results in dysregulated expression of FOXP1 juxtaposed with strong regulatory elements of IGH. Thus far, molecular consequences of rare non-IG aberrations of FOXP1 remain undetermined. Here, using molecular cytogenetics and molecular biology studies, we comprehensively analyzed four lymphoma cases with non-IG rearrangements of FOXP1 and compared these with cases harboring t(3;14)(p13;q32)/IGH-FOXP1 and FOXP1-expressing lymphomas with no apparent structural aberrations of the gene. Our study revealed that non-IG rearrangements of FOXP1 are usually acquired during clinical course of various lymphoma subtypes, including diffuse large B cell lymphoma, marginal zone lymphoma and chronic lymphocytic leukemia, and correlate with a poor prognosis. Importantly, these aberrations constantly target the coding region of FOXP1, promiscuously fusing with coding and non-coding gene sequences at various reciprocal breakpoints (2q36, 10q24 and 3q11). The non-IG rearrangements of FOXP1, however, do not generate functional chimeric genes but commonly disrupt the full-length FOXP1 transcript leading to an aberrant expression of N-truncated FOXP1 isoforms (FOXP1NT), as shown by QRT-PCR and Western blot analysis. In contrast, t(3;14)(p13;q32)/IGH-FOXP1 affects the 5' untranslated region of FOXP1 and results in overexpress the full-length FOXP1 protein (FOXP1FL). RNA-sequencing of a few lymphoma cases expressing FOXP1NT and FOXP1FL detected neither FOXP1-related fusions nor FOXP1 mutations. Further bioinformatic analysis of RNA-sequencing data retrieved a set of genes, which may comprise direct or non-direct targets of FOXP1NT, potentially implicated in disease progression. In summary, our findings point to a dual mechanism through which FOXP1 is implicated in B-cell lymphomagenesis. We hypothesize that the primary t(3;14)(p13;q32)/IGH-FOXP1 activates expression of the FOXP1FL protein with potent oncogenic activity, whereas the secondary non-IG rearrangements of FOXP1 promote expression of the FOXP1NT proteins, likely driving progression of disease.
ISSN: 1932-6203
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Department of Human Genetics - miscellaneous
Clinical Genetics
Laboratory for Genetics of Malignant Disorders
Translational Cell & Tissue Research
Laboratory of Molecular Biology of Leukemia
× corresponding author
# (joint) last author

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