EVI1 is consistently expressed as principal transcript in common and rare recurrent 3q26 rearrangements

Abstract

In contrast to the well-documented involvement of EVI1 in various 3q26 aberrations, the transcriptional status of EVI1 in rare recurrent or sporadic 3q26 chromosomal defects has remained largely unexplored. Moreover, in a recent report, the association between 3q26 alterations in myeloid proliferations and ectopic EVI1 expression was questioned. Therefore, we performed a detailed physical mapping of 3q26 breakpoints using a 1.3-Mb tiling path BAC contig covering the EVI1 locus and a carefully designed quantification of both EVI1 and MDS/EVI1 transcripts in 30 hematological malignancies displaying 3q26 aberrations. Cases included well-known rare, recurring chromosomal aberrations such as t(3;17)(q26;q22), t(2;3)(p21-22;q26), and t(3;6)(q26;q25), as well as 10 new sporadic cases. Extensive 3q26 breakpoint mapping allowed unequivocal and sensitive FISH detection of EVI1 rearrangements on both metaphases and interphase nuclei. Real-time quantitative PCR analyses indicated that typically both MDS1/EVI1 and EVI1, but not MDS1, were expressed in these malignancies, with EVI1 the primary transcript. In conclusion, we have demonstrated EVI1 involvement in numerous novel sporadic and recurrent 3q26 rearrangements. Our results underscore the feasibility of FISH as an adjunct to PCR for the identification of EVI1 deranged leukemias and identified EVI1 as the principal transcript expressed in these malignancies.

Newly diagnosed acute lymphoblastic leukemia in China (I): abnormal genetic patterns in 1346 childhood and adult cases and their comparison with the reports from Western countries

“…Among them, several chromosomal translocations with at least one known gene involved had already been reported in the literatures, such as t(3;9) (q26;p23)/EVI1 --?, 19 t(12;17) (p13;q11)/ ZNF384 --TAF15, 20 t(9;14) (q34;q32)/ABL1 --EML1, 21 t(10;14) (q24;q11)/HOX11 --TRD, 22 t(8;14) (q24;q11) /MYC --TCR 23 in children, and t(1;5) (q23;q33)/? --PDGFRB, 24 der(9)t(7;9) (q11;p13)/PAX5 --ELN, 25 t(8;14) (q11;q32)/CEBPD --IGH@, 26 t(3;11) (q29q13;p15)del(3) (q29)/NUP98 --IQCG 27 in adults.…”

EVI1 overexpression in t(3;17) positive myeloid malignancies results from juxtaposition of EVI1 to the MSI2 locus at 17q22

“…8 To characterize the 17q breakpoints, eight different 17q BAC/PAC probes over a region of 34.3 Mb on 17q were selected from the UCSC (http://genome.ucsc.edu) or Ensembl (http://ensembl.org) databases. The 17q and EVI1 probes were all obtained from the Sanger Wellcome Trust Institute, Hinxton, Cambridge (United Kingdom).…”

“…EVI1 activation in the translocations t(3;12)(q26;p13) and t(3;21)(q26;q22) is due to generation of the fusion genes ETV6/EVI1 and RUNX1/EVI1 respectively. 6,7 In addition to these well-characterized rearrangements, the EVI1 locus is also involved in rare 3q26 aberrations such © F e r r a t a S t o r t i F o u n d a t i o n as the t(3;17)(q26;q22), 8 the t(2;3)(p21~22;q26) 9,10 and the t(3;6)(q26;q25). 11 For these EVI1 rearrangements, the true recurrent nature and the partner chromosomes involved, have not been analyzed in detail.…”

A simple FISH assay for the detection of 3q26 rearrangements in myeloid malignancy

“…Previous molecular and FISH mapping studies of 3q26-rearranged leukaemia are, in keeping with our observations, documenting a preponderance of breakpoints centromeric of EVI1 for the inv(3) and telomeric of EVI1 for all other 3q26 rearrangements. 1,5,7,8 However, close scrutiny of published data reveals a degree of overlap between the breakpoint regions of these two cytogenetic subgroups, suggesting that the precise distribution of breakpoints for different types of 3q26 rearrangement may be more complex than observed in the present cohort. Notwithstanding, our findings further stress the importance of a wide genomic region at 3q26 in unravelling the molecular mechanism responsible for deregulated EVI1 expression in myeloid malignancy.…”

“…However, two recent PCR studies of 3q26-rearranged leukaemias yielded contradictory results, with one report demonstrating a good correlation between 3q26 rearrangements and detectable EVI1 expression, 4 whereas the second reported absence of detectable EVI1 expression in the majority of cases. 5 The large 3q26 breakpoint region also presents a challenge for FISH analysis. Wieser et al 6 described a dualcolour FISH probe spanning some 2.5 Mb at 3q26, however, the large genomic region represented by the probe resulted in a threshold for positivity of over 10% thus limiting its use for the detection of residual disease.…”