The Aiolos transcription factor is up-regulated in chronic lymphocytic leukemia

Abstract

The Aiolos transcription factor, member of the Ikaros family of zinc finger proteins, plays an important role in the control of mature B lymphocyte differentiation and proliferation, and its function appears to be modulated through alternative splicing. IntroductionMature B-cell neoplasms, including chronic lymphocytic leukemia (CLL), represent frequent malignancies of mature B cells whose cell derivation and pathogenesis are unknown. 1,2 Here we focused on Aiolos, a hematopoietic chromatin remodeler and transcription factor of the Ikaros family that plays critical roles in B-cell differentiation, 3-6 and we examined whether a deregulation of its expression was an integral part of malignant transformation in CLL and other B-cell lymphomas. Methods Subjects and B-cell isolationCryopreserved peripheral blood mononuclear cell (PBMC) samples were collected and informed consent obtained in accordance with the Declaration of Helsinki from CLL or other B-cell lymphoma patients followed at the Hematological Department of Pitié-Salpêtrière Hospital, according to a protocol approved by the institutional ethic committee. Diagnosis was assessed according to the recent World Health Organization classification. In all cases, blood sample collection was performed at the time of diagnosis. Fresh blood from healthy donors was collected by the Etablissement Francais du Sang (France), and PBMCs were frozen after density gradient isolation. Total RNA extraction was done after B cells isolation by anti-CD19 magnetic beads (Dynal Biotech, Oslo, Norway). Reverse-transcribed quantitative polymerase chain reaction analysisRNA (500 ng) was reversed transcribed and amplified, either by Titanium one-step RT-PCR (Clontech, Mountain View, CA) or by Superscript II (Invitrogen, Carlsbad, CA) and quantitative polymerase chain reaction (PCR) done using predeveloped TaqMan gene expression assays (Applied Biosystems, Foster City, CA). Chromatin immunoprecipitationAnti-CD19 Dynal beads were detached by DETACHaBEAD before proceeding to chromatin cross-link. Chromatin immunoprecipitation (ChIP) assays were carried out as previously described 7 with primers spanning a 2-kb region upstream and downstream of the Aiolos translation initiation site. Western blot analysisWestern blot analysis was carried out as previously described. 8 Results and discussion The hAio1 transcript represents more than 80% of the Aiolos isoforms in B cellsWe first investigated the expression pattern of different Aiolos isoforms in PBMCs of patients diagnosed with mature B-cell malignancies (17 CLL, 8 mantle zone, and 2 marginal zone lymphomas; Figure 1A; Table 1). Analysis of healthy donors revealed the presence of 6 Aiolos variants. Five corresponded to hAio1, hAio2, hAio3/4, and hAio5 as previously described. 9 A new shorter variant was observed and identified by direct sequencing of the PCR products as hAio-del(4,5,6), lacking the 4 N-terminal zinc fingers. No major differences in the distribution of Aiolos isoforms were detected between healthy donors and CLL/other B-cell...

Deregulation of Aiolos expression in chronic lymphocytic leukemia is associated with epigenetic modifications

“…7 Aiolos functions and the parameters involved in its transcriptional regulation are largely unknown in humans and need be better defined. Recently, we reported for the first time that Aiolos expression is deregulated in CLL, 9 which was subsequently confirmed by the authors of other studies. 10,11 Chronic lymphocytic leukemia (CLL) 12 is characterized by the accumulation of monoclonal B lymphocytes in blood, bone marrow, and peripheral lymphoid tissues.…”

“…This new data set confirmed our previous observation that Aiolos expression is up-regulated in B cells from CLL patients. 9 To investigate whether Ikaros, an homologue of Aiolos, is deregulated in B-CLL cells, we analyzed by RT-PCR the expression pattern of different Ikaros isoforms in PBMC from 5 CLL patients and 2 HDs. An analysis of HDs revealed the presence of 4 Ikaros variants: Ik-1, Ik-2, Ik-3, and Ik-4 but not Ik-6 ( Figure 1D).…”

Elucidation of tonic and activated B-cell receptor signaling in Burkitt’s lymphoma provides insights into regulation of cell survival

“…The latter has also been described as a negative regulator of BCR signaling (24). We also identified significantly regulated phosphorylation of the Ikaros transcription factor family member Aiolos (IKZF3), which is known to be important for B-cell activation (25) and to be up-regulated in CLL (26). Ikaros proteins are pivotal regulators of hematopoiesis and immunity (27) and have been reported to be essential for B-cell development (28).…”

Why is Chromosome 17q21 linked to Asthma?

“…IKZF3 (Aiolos) belongs to the Ikaros family of zinc-finger proteins which encodes hematopoietic-specific transcription factors involved in the regulation of lymphocyte development [20]. IKZF3 plays a critical role in regulating B and T cell development, and several alternative coding as well as non-coding transcripts variants of IKZF3 have been described [21]. Since various T cell subsets and B cells are well-known to influence the nature and magnitude of the allergic immune response, future studies on IKZF3 could unravel its biological role in asthma pathogenesis.…”