Alternative expression of TCRζ related genes in patients with chronic myeloid leukemia

Xianfeng Zha,Bo Li,Yangqiu Li,Suxia Geng,Lijian Yang,Jianyu Weng,Yuping Zhang,Xiuli Wu,Shaohua Chen,Xin Du,Xiaojuan Yan,Qi Shen

doi:10.1186/1756-8722-5-74

Abstract

A previous study has demonstrated a significant decrease in the TCRζ gene expression level in chronic myeloid leukemia (CML); thus, we further investigated the expression of TCRζ-regulating factors, the distribution of the TCRζ 3' untranslated region (3'-UTR) splice variants, and the expression level and correlation of the alternative splicing factor/splicing factor 2 (ASF/SF-2), FcεRIγ and ZAP-70 genes. TCRζ 3'-UTR splice variants were identified in peripheral blood mononuclear cells (PBMCs) from 14 healthy individuals, 40 patients with CML and 22 patients with CML in complete remission (CML-CR) by RT-PCR. The expression level of the TCRζ, FcεRIγ, ASF/SF-2 and ZAP-70 genes was analyzed by real-time quantitative PCR. While the expression of TCRζ gene in the CML group was significantly lower than that in the healthy individual and CML-CR groups, a significantly higher expression of the FceRIγ and ASF/SF-2 genes was found in the CML group. Two types of splicing forms were detected in all of the healthy individual CML-CR cases: wild type (WT) TCRζ 3'-UTR and alternatively splieced (AS) TCRζ 3'-UTR which have been alternatively splieced in the WT TCRζ 3'-UTR . However, 35% of the CML cases contained only the wild type TCRζ 3'-UTR isoform. Based on the TCRζ 3'-UTR isoform expression characteristic, we divided the patients with CML into two subgroups: the WT+AS- CML group, containing patients that express only the wild type TCRζ 3'-UTR, and the WT+AS+ CML group, which contained patients that expressed two TCRζ 3'-UTR isoforms. A significantly different ASF/SF-2 and FcεRIγ gene expression pattern was found between the WT+AS- and WT+AS+CML groups. We concluded that defective TCRζ expression may be characterized in the WT+AS-and WT+AS+CML subgroups by the different gene expression pattern. The overexpression of ASF/SF2, which alternatively splices the TCRζ 3’-UTR, is thought to participate in feedback regulation. The characteristics of TCRζ 3'-UTR alternative splicing may be a novel immunological marker for the evaluation of the CML immune status.

Highlights

Chronic myeloid leukemia (CML) is a clonal hematopoietic stem cell disease that is characterized by the Philadelphia chromosome (Ph), which is generated by the reciprocal translocation t(9;22)(q34;q11) that results in the fusion of the c-abl oncogene 1 (ABL1) with the breakpoint cluster region (BCR) gene [1]
TCRζ3′-untranslated region (UTR) isoforms in CML It has been reported that two types of spliceosomes could be found on the TCRζ 3' untranslated region (3'-UTR) [19,23]
Defects inTCR/CD3 signaling in CML The T cell receptor (TCR)/CD3 complex plays a central role in T cell activation, and the alteration of any subunits in the complex may change the T cell activation level [7,8,9,10]

Summary

Introduction

Chronic myeloid leukemia (CML) is a clonal hematopoietic stem cell disease that is characterized by the Philadelphia chromosome (Ph), which is generated by the reciprocal translocation t(9;22)(q34;q11) that results in the fusion of the c-abl oncogene 1 (ABL1) with the breakpoint cluster region (BCR) gene [1]. The TCR/CD3 complex plays a central role in T cell activation This complex comprises of two chains, αβ or γδ, these chains are noncovalently associated with CD3 subunits, which include four transmembrane proteins: CD3γ, CD3δ, CD3ε and CD3ζ ( referred to as TCRζ). These subunits are known to form three distinct dimers, CD3γε, CD3δε, and CD3ζζ, to mediate TCR signal transduction [7,8,9,10]. ZAP-70 is a cytosolic protein that is recruited to the T cell plasma membrane following TCR stimulation and binds to phosphorylated TCRζ immunoreceptor tyrosine-based activation motifs (ITAMs); it plays a critical role in activating downstream T cell signal transduction pathways following TCR engagement [11]. There is evidence that the Fce receptor type Iγ (FcεRIγ) chain, which is a member of the TCRζ chain protein family and a component of the high-affinity IgE receptor, can replace a functionally deficient TCRζ chain and facilitate TCR/CD3 complex-mediated signaling [12,13]

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Results

Conclusion