Molecular analysis of t(X;11)(q24;q23) in an infant with AML-M4

Area of Science:

• Genetics
• Molecular Biology
• Oncology

Background:

• Pediatric acute myeloid leukemia (AML) is often associated with recurring chromosomal translocations.
• The MLL (mixed lineage leukemia) gene at 11q23 is frequently involved in these rearrangements, leading to gene fusions that drive leukemogenesis.

Observation:

• This study reports the identification of a novel MLL-SEPT6 fusion transcript in an infant diagnosed with AML-M4.
• The fusion involves MLL (at 11q23) and SEPT6 (at Xq24), confirmed by reverse transcription-polymerase chain reaction.
• Analysis revealed the fusion transcript comprised MLL exon 8 and SEPT6 exon 2, with no reciprocal SEPT6-MLL fusion detected.

Findings:

• Genomic breakpoint analysis suggests a unique rearrangement mechanism involving the insertion of an inverted Xq24 segment into MLL intron 8.
• This segment contained the 3' region of SEPT6 intron 1 and adjacent DNA.
• The presence of deletions, duplications, and non-template DNA at break junctions indicates a role for DNA damage-repair pathways.

Implications:

• This discovery elucidates a novel mechanism for generating MLL gene fusions in pediatric AML.
• Understanding these complex rearrangements is crucial for accurate diagnosis and potential therapeutic strategies targeting MLL-rearranged leukemias.
• The findings highlight the intricate genetic alterations contributing to infant AML and underscore the importance of investigating DNA repair in translocation formation.