Identification of the NUP98-PHF23 fusion gene in pediatric cytogenetically normal acute myeloid leukemia by whole-transcriptome sequencing

Abstract

The genomic landscape of children with acute myeloid leukemia (AML) who do not carry any cytogenetic abnormality (CN-AML) is particularly heterogeneous and challenging, being characterized by different clinical outcomes. To provide new genetic insights into this AML subset, we analyzed through RNA-seq 13 pediatric CN-AML cases, corroborating our findings in an independent cohort of 168 AML patients enrolled in the AIEOP AML 2002/01 study. We identified a chimeric transcript involving NUP98 and PHF23, resulting from a cryptic t(11;17)(p15;p13) translocation, demonstrating, for the first time, that NUP98-PHF23 is a novel recurrent (2.6%) abnormality in pediatric CN-AML.

Fig. 1

Identification of NUP98-PHF23 in pediatric CN-AML. a Schematic representation of NUP98-PHF23 fusion identified by RNA-seq in pediatric CN-AML. Fusion occurs between exon 13 of NUP98 and exon 4 of PHF23. b Electropherogram from Sanger sequencing of the region surrounding the breakpoint confirmed the in-frame fusion. A black arrow indicates the fusion breakpoint, predicted sequence of the fusion protein is shown. c FISH analysis was performed on metaphases and interphase cells using three BlueFISH probes (BlueGnome Ltd., Cambridge), according to the manufacturer’s instructions. BAC clones RP11-120E20 and RP11-348A20 (red) were used to probe the NUP98 gene on chromosome 11, while the BAC clone RP11-542C16 (green) was used to target the PHF23 gene on chromosome 17. Normal metaphases (upper left) and interphase nuclei (upper right) showed two red signals representing normal copies of NUP98 and two green signals representing normal copies of PHF23. Abnormal metaphases (lower left) and interphase cells (lower right) containing the NUP98-PHF23 fusion gene showed one red (NUP98), one green (PHF23) and one yellow fusion signal, which represents the juxtaposition of the translocated portions of the two genes