Chromosome 12p deletions in TEL-AML1 childhood acute lymphoblastic leukemia are associated with retrotransposon elements and occur postnatally.
TEL-AML1 (ETV6-RUNX1) is the most common translocation in the childhood leukemias, and is a prenatal mutation in most children. This translocation has been detected at a high rate among newborns ( approximately 1%); therefore, the rate-limiting event for leukemia seems to be secondary mutations. One such frequent mutation in this subtype is partial deletion of chromosome 12p, trans from the translocation. Nine del(12p) breakpoints within six leukemia cases were sequenced to explore the etiology of this genetic event, and most involved cryptic sterile translocations. Twelve of 18 del(12p) parent sequences involved in these breakpoints were located in repeat regions (8 of these in long interspersed nuclear elements). This stands in contrast with TEL-AML1, in which only 21 of 110 previously assessed breakpoints (19%) occur in DNA repeats (P=0.0001). An exploratory assessment of archived neonatal blood cards revealed significantly more long interspersed nuclear element CpG methylations in individuals at birth who were later diagnosed with TEL-AML1 leukemia, compared with individuals who did not contract leukemia (P=0.01). Nontemplate nucleotides were also more frequent in del(12p) than in TEL-AML1 junctions (P=0.004), suggesting formation by terminal deoxynucleotidyl transferase. Assessment of six archived neonatal blood cards indicated that no del(12p) rearrangements backtracked to birth, although two of these patients were previously positive for TEL-AML1 using the same assay with comparable sensitivity. These data are compatible with a two-stage natural history: TEL-AML1 occurs prenatally, and del(12p) occurs postnatally in more mature cells with a structure that suggests the involvement of retrotransposon instability.
Wiemels
Joseph L
JL
Laboratory for Molecular Epidemiology, Department of Epidemiology and Biostatistics, University of California San Francisco, San Francisco, California 941143-0441, USA. joe.wiemels@ucsf.edu
Hofmann
Jerry
J
Kang
Michelle
M
Selzer
Rebecca
R
Green
Roland
R
Zhou
Mi
M
Zhong
Sheng
S
Zhang
Luoping
L
Smith
Martyn T
MT
Marsit
Carmen
C
Loh
Mignon
M
Buffler
Patricia
P
Yeh
Ru-Fang
RF
D002648:Child; D002872:Chromosome Deletion; D002881:Chromosomes, Human, Pair 12; D050676:Core Binding Factor Alpha 2 Subunit / Q000235:genetics*; D019175:DNA Methylation; D006801:Humans; D015514:Oncogene Proteins, Fusion / Q000235:genetics*; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000235:genetics*; D018626:Retroelements; D000097764:ETS Translocation Variant 6 Protein
D050676:Core Binding Factor Alpha 2 Subunit; D015514:Oncogene Proteins, Fusion; D018626:Retroelements; C102421:TEL-AML1 fusion protein; D000097764:ETS Translocation Variant 6 Protein