Simultaneous localization of MLL, AF4 and ENL genes in interphase nuclei by 3D-FISH: MLL translocation revisited.
BACKGROUND
Haematological cancer is characterised by chromosomal translocation (e.g. MLL translocation in acute leukaemia) and two models have been proposed to explain the origins of recurrent reciprocal translocation. The first, established from pairs of translocated genes (such as BCR and ABL), considers the spatial proximity of loci in interphase nuclei (static "contact first" model). The second model is based on the dynamics of double strand break ends during repair processes (dynamic "breakage first" model). Since the MLL gene involved in 11q23 translocation has more than 40 partners, the study of the relative positions of the MLL gene with both the most frequent partner gene (AF4) and a less frequent partner gene (ENL), should elucidate the MLL translocation mechanism.


METHODS
Using triple labeling 3D FISH experiments, we have determined the relative positions of MLL, AF4 and ENL genes, in two lymphoblastic and two myeloid human cell lines.


RESULTS
In all cell lines, the ENL gene is significantly closer to the MLL gene than the AF4 gene (with P value < 0.0001). According to the static "contact first" model of the translocation mechanism, a minimal distance between loci would indicate a greater probability of the occurrence of t(11;19)(q23;p13.3) compared to t(4;11)(q21;q23). However this is in contradiction to the epidemiology of 11q23 translocation.


CONCLUSIONS
The simultaneous multi-probe hybridization in 3D-FISH is a new approach in addressing the correlation between spatial proximity and occurrence of translocation. Our observations are not consistent with the static "contact first" model of translocation. The recently proposed dynamic "breakage first" model offers an attractive alternative explanation.
Gué
Michaël
M
USM 0503, Département Régulations, Développement et Diversité Moléculaire, Muséum National d'Histoire Naturelle, UMR 5153 CNRS-MNHN, U 565 INSERM, 43 rue Cuvier, CP26, 75231 Paris Cedex 05, France. michael.gue@curie.u-psud.fr
Sun
Jian-Sheng
JS
Boudier
Thomas
T
D000293:Adolescent; D000328:Adult; D002461:Cell Line, Transformed / Q000737:chemistry / Q000648:ultrastructure; D045744:Cell Line, Tumor / Q000737:chemistry / Q000648:ultrastructure; D002467:Cell Nucleus / Q000737:chemistry* / Q000648:ultrastructure; D002880:Chromosomes, Human, Pair 11 / Q000235:genetics / Q000648:ultrastructure; D002888:Chromosomes, Human, Pair 19 / Q000235:genetics / Q000648:ultrastructure; D002894:Chromosomes, Human, Pair 4 / Q000235:genetics / Q000648:ultrastructure; D004268:DNA-Binding Proteins / Q000235:genetics*; D005796:Genes; D018922:HL-60 Cells / Q000737:chemistry / Q000648:ultrastructure; D004854:Herpesvirus 4, Human; D011495:Histone-Lysine N-Methyltransferase; D006801:Humans; D021621:Imaging, Three-Dimensional; D017404:In Situ Hybridization, Fluorescence / Q000379:methods*; D007399:Interphase; D007948:Leukemia, Monocytic, Acute / Q000235:genetics / Q000473:pathology; D008297:Male; D008957:Models, Genetic; D009101:Multiple Myeloma / Q000473:pathology; D051788:Myeloid-Lymphoid Leukemia Protein / Q000235:genetics*; D009363:Neoplasm Proteins / Q000235:genetics*; D009687:Nuclear Proteins / Q000235:genetics*; D015452:Precursor B-Cell Lymphoblastic Leukemia-Lymphoma / Q000235:genetics / Q000473:pathology; D014157:Transcription Factors / Q000235:genetics*; D035602:Transcriptional Elongation Factors; D014178:Translocation, Genetic
D004268:DNA-Binding Proteins; C497422:KMT2A protein, human; C081448:MLLT1 protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D014157:Transcription Factors; D035602:Transcriptional Elongation Factors; D051788:Myeloid-Lymphoid Leukemia Protein; C081449:AFF1 protein, human; D011495:Histone-Lysine N-Methyltransferase