A Remote GATA2 Hematopoietic Enhancer Drives Leukemogenesis in inv(3)(q21;q26) by Activating EVI1 Expression

Abstract

SUMMARY Chromosomal inversion between 3q21 and 3q26 results in high-risk acute myeloid leukemia (AML). Here, we identified a mechanism whereby a GATA2 distal hematopoietic enhancer (G2DHE or −77-kb enhancer) is brought into close proximity to the EVI1 gene in inv(3)(q21;q26) inversions, leading to leukemogenesis. We examined the contribution of G2DHE to leukemogenesis by creating a bacterial artificial chromosome (BAC) transgenic model that recapitulates the inv(3)(q21;q26) allele. Transgenic mice harboring a linked BAC developed leukemia accompanied by EVI1 overexpression, neoplasia that was not detected in mice bearing the same transgene but missing the GATA2 enhancer. These results establish the mechanistic basis underlying the pathogenesis of a severe form of leukemia through aberrant expression of the EVI1 proto-oncogene.

The New Clinicopathologic and Molecular Findings in Myeloid Neoplasms With inv(3)(q21q26)/t(3;3)(q21;q26.2)

“…51 As clearly demonstrated by Gröschel et al, 59 there is no new fusion transcript generated, as had been previously thought. 51 By using a completely different approach, namely, bacterial artificial chromosome transgenic mouse model recapitulating the inv(3), Yamazaki et al 60 have shown that the transgenic mice only developed leukemias when EVI1 was ectopically activated by G2DHE, but this did not happen in mice missing GATA2 enhancer, further corroborating the findings by Gröschel and associates. 59 POTENTIAL THERAPEUTIC APPLICATIONS Because MDS and AML patients with inv(3)/t(3;3) exhibit poor prognosis and currently available treatment regimens do not achieve desirable outcomes, a search for better treatment options is needed.…”

“…In summary, based on the aforementioned well-designed functional genomic studies, 59 as well as the use of transgenic mice model recapitulating the inv(3) allele, 60 it is clear that the inv(3)/t(3;3) results in reallocation of G2DHE to the proximity of EVI1, thus leading to the ectopic activation of EVI1 rather than the previously thought RPN1-EVI1 fusion transcript. 51 Therefore, no fusion transcript is produced from the inv(3)/t(3;3).…”

“…51 As has been well commented on by Koche and Armstrong, 58 the exciting breakthrough regarding the molecular event in inv(3)/t(3;3) came from 2 independent groups of investigators who both convincingly demonstrated that the reallocation of GATA2 distal hematopoietic enhancer (G2DHE) to the proximity of the promoter of EVI, and the subsequent activation of the EVI expression are the fundamental molecular events underlying the inv(3)/t(3;3). 59,60 By employing next-generation sequencing and high-resolution chromosome conformation capture sequencing, Gröschel et al 59 have mapped a 9-kb EVI1-promoter-contact fragment within the 18-kb commonly translocated segment in AML and MDS patients with inv(3)/t(3;3). By using functional genomics, including genomic editing and genome engineering, they elegantly identified this 9-kb EVI1-promoter-contact fragment at the enhancer originally located 110 kb upstream of GATA2 rather than RPN1, although RPN1 lies within immediate proximity of this enhancer.…”

GATA Transcription Factors: Basic Principles and Related Human Disorders

“…A recent large-scale genetic analysis demonstrated that GATA-2 mutations, which were critical for clonal evolution in MDS, had a relatively weaker impact on the progression of AML (Makishima et al 2017). Chromosomal translocations involving GATA-2 upstream enhancer region (−77 kb), such as inv(3)(q21q26) and t(3;3) (q21;q26), contribute to the onset of AML (Gröschel et al 2014;Yamazaki et al 2014). Both inv(3)(q21q26) and t(3;3)(q21;q26) were proposed to translocate oncogenic EVI1 gene to an area close to the GATA-2 −77kb enhancer region, leading to the aberrant overexpression of EVI1 (Gröschel et al 2014;Yamazaki et al 2014).…”

“…Chromosomal translocations involving GATA-2 upstream enhancer region (−77 kb), such as inv(3)(q21q26) and t(3;3) (q21;q26), contribute to the onset of AML (Gröschel et al 2014;Yamazaki et al 2014). Both inv(3)(q21q26) and t(3;3)(q21;q26) were proposed to translocate oncogenic EVI1 gene to an area close to the GATA-2 −77kb enhancer region, leading to the aberrant overexpression of EVI1 (Gröschel et al 2014;Yamazaki et al 2014). Additional GATA-2 mutations were identified in acute myeloid transformation of chronic myeloid leukemia, which are caused by activating GATA-2 mutation (L359V) (Zhang et al 2008), leading to the enhanced inhibitory effect on the myeloid transcription factor PU.1.…”