Molecular dissection of t(11;17) in acute myeloid leukemia reveals a variety of gene fusions with heterogeneous fusion transcripts and multiple splice variants

Abstract

The majority of translocations that involve the long arms of chromosomes 11 and 17 in acute myeloid leukemia appear identical on the cytogenetic level. Nevertheless, they are diverse on the molecular level. At present, two genes are known in 11q23 and four in 17q12-25 that generate five distinct fusion genes: MLL-MLLT6/AF17, MLL-LASP1, MLL-ACACA or MLL-SEPT9/MSF, and ZBTB16/PLZF-RARA. We analyzed 14 cases with a t(11;17) by fluorescence in situ hybridization and molecular genetic techniques and determined the molecular characteristics of their fusion genes. We identified six different gene fusions that comprised seven cases with a MLL-MLLT6/AF17, three with a MLL-SEPT9/MSF, and one each with MLL-LASP1, MLL-ACACA, and ZBTB16/PLZF-RARA fusions. In the remaining case, a MLL-SEPT6/Xq24 fusion suggested a complex rearrangement. The MLL-MLLT6/AF17 transcripts were extremely heterogeneous and the detection of seven different in-frame transcript and splice variants enabled us to predict the protein domains relevant for leukemogenesis. The putative MLL-MLLT6 consensus chimeric protein consists of the AT-hook DNA-binding, the methyltransferase, and the CXXC zinc-finger domains of MLL and the highly conserved octapeptide and the leucine-zipper dimerization motifs of MLLT6. The MLL-SEPT9 transcripts showed a similar high degree of variability. These analyses prove that the diverse types of t(11;17)-associated fusion genes can be reliably identified and delineated with a proper combination of cytogenetic and molecular genetic techniques. The heterogeneity of transcripts encountered in cases with MLL-MLLT6/AF17 and MLL-SEPT9/MSF fusions clearly demonstrates that thorough attention has to be paid to the appropriate selection of primers to cover all these hitherto unrecognized fusion variants.

Diagnostic Value of Next-Generation Sequencing in an Unusual Sphenoid Tumor

“…Of the 5 rearrangements detected at both DNA and RNA levels, 1 involved already-known fusion-associated genes. The myeloid/ lymphoid or mixed-lineage leukemia translocated to 6 (MLLT6) is a previously described cancer-associated fusion partner [16,17] that was fused to SEZ6L in this case. The fusion breakpoints are in the first intron of SEZ6L and the 59UTR of MLLT6, and this is not a previously described pattern of MLLT6 fusions.…”

“…The fusion breakpoints are in the first intron of SEZ6L and the 59UTR of MLLT6, and this is not a previously described pattern of MLLT6 fusions. MLLT6 is fused to MLL in a subset of acute myeloid leukemias, where it is the 39 partner in a variety of transcripts [17]. SEZ6L has been reported to be interrupted in a subset of lung cancers [18].…”

Septin roles in tumorigenesis

“…Gene fusion AML (Ono et al, 2002;Kadkol et al, 2006;Cerveira et al, 2008) Melanoma (Jaeger et al, 2007) SEPT7 Downregulation Glioma (Nagata et al, 2000;Jiang, 2002;Jiang, 2004;Jia et al, 2010;Tanaka et al, 2010) SEPT8 None None None SEPT9 Amplification/ Breast (Montagna et al, 2003;Scott et al, 2005;overexpression Gonzalez et al, 2007overexpression Gonzalez et al, , 2009) Upregulation Ovary Gene fusion AML, ALL (Strehl et al, 2006;Gulten et al, 2009;Saito et al, 2010) (Santos et al, 2010a,b) (Osaka et al, 1999;Yamamoto et al, 2002;Strehl et al, 2006;Kreuziger et al, 2007) Hypermethylation Colon and head and neck (He et al, 2010;Tierling et al, 2010;Quyun et al, 2010) (Grutzmann et al, 2008;deVos et al, 2009) (Bennett et al, 2008;Lofton-Day et al, 2008;Stanbery et al, 2010) Deletion Ovary, breast Russell et al, 2000) Hodgkin lymphoma (Giefing et al, 2008) SEPT10 None None SEPT11 Gene fusion Deletion AML (Santos et al, 2010b;Stevens et al, 2010) Deletion Liver SEPT12 None None SEPT13 None None SEPT14 None None (Montagna et al, 2003) and the Russell group established that SEPT9 overexpression occurs in various human tumors (Scott et al, 2005). The discovery of DNA hypermethylation at the promoter region of SEPT9 in colorectal (deVos et al, 2009) and head and neck cancer patients (Bennett et al, 2008) complicated the conflicti...…”

An MLL-SEPT9 fusion and t(11;17)(q23;q25) associated with de novo myelodysplastic syndrome

“…SEPT9 is a member of the septin family of GTPases that have diverse cellular activity, including roles in cytokinesis, apoptosis, and vesicle trafficking. (5,8) Inactivating germline mutations in SEPT9 have recently been associated with hereditary neuralgic amyotrophy, whereas abnormal expression or deletion of SEPT9 has been linked to ovarian and breast neoplasia. SEPT9 has many alternative spliceoforms, the functional significance of which is not clearly understood.…”

“…(5) These AML-associated fusion partners include MLLT6 (formerly known as AF17; 17q21), LASP1 (17q12), ACACA (17q21), and SEPT9 (formerly known as MSF; 17q25). (3,5) We recently evaluated a woman who presented with de novo MDS and a t(11;17)(q23;q25) translocation. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis demonstrated a MLL-SEPT9 fusion, a rare translocation in general that has, to our knowledge, not previously been associated with de novo MDS.…”