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t(6;7)(q23;q34) TRB/MYB and AHI1

Written2007-07Emmanuelle Clappier, Jean Soulier
Group Genome Rearrangements, Cancer, Hematology Laboratory APHP, INSERM U728, Paris 7 University, Institut Universitaire d_Hématologie, Hôpital Saint-Louis, Paris, France

(Note : for Links provided by Atlas : click)

Identity

ICD-Topo C420,C421,C424 BLOOD, BONE MARROW, & HEMATOPOIETIC SYS
ICD-Morpho 9837/3 T lymphoblastic leukaemia/lymphoma
Atlas_Id 1465
 
  R-band analysis. Partial karyotype showing t(6;7)(q23;q34)

Clinics and Pathology

Disease T cell acute lymphoblastic leukemia (T-ALL).
Phenotype / cell stem origin T cell precursor.
Epidemiology Less than 5% among a series of non selected adult and pediatric T-ALLs (n = 3 out of 92). Six cases were described, all of them children, and 5 out of 6 being under 3 years old (1.1, 1.3, 1.8, 2.5, and 2.9 years old, respectively), which is very young for T-cell leukemia. The t(6;7) translocation could therefore be relatively common in this very low range of age.
Cytology Lymphoblasts
Prognosis The prognosis is yet to be evaluated.

Cytogenetics

Cytogenetics Morphological t(6;7)(q23;q34) may be barely detectable by chromosome banding techniques alone.
 
  Left: Whole chromosome painting of chromosomes 6 (green) and 7 (red). Right: Locus-specific break-apart FISH using 6q23 probes RP11-184J4 (red) and RP11-845K5 (green) showing translocation involving the 6q23 locus.
Cytogenetics Molecular Involvement of the TCRB locus and the MYB locus can be demonstrated using flanking FISH probes.

Genes involved and Proteins

Gene Name TRB
Location 7q34
Protein T-cell receptor beta chain
Gene Name MYB
Location 6q23.3
Dna / Rna Spans over 38 kb, 15 exons (and additionnal alternative exons), mRNA 3.3 kb.
Protein v-myb myeloblastosis viral oncogene homolog. Transcription factor. 640 amino acids.
Gene Name AHI1
Location 6q23.3
Dna / Rna Spans over 214 kb, 28 exons (and additional alternative exons), mRNA 5.5 kb.
Protein Jouberin (Abelson helper integration site 1 protein homolog) (AHI-1). 1196 amino acids including one SH3 domain and WD repeats.

Result of the chromosomal anomaly

Hybrid gene
Note No fusion gene
The t(6;7)(q23.3;q34) translocation results in juxtaposition of TRB regulatory sequences to the MYB-AHI1 locus. It results in deregulated expression of C-MYB, as demonstrated by skewed allelic expression.
  
Fusion Protein
Oncogenesis C-MYB is a transcription factor involved in hematopoiesis. In T-cell differenciation, discrete threshold levels of MYB activity regulate transition through distinct stages, suggesting that a deregulated expression could disturb the maturation process and play a role in oncogenesis.
A potential role of AHI1 deregulation as a cofactor has to be evaluated.
Of note, the same locus at 6q23.3 is also involved in short tandem duplications of a about 230 kb genomic region which includes the C-MYB gene (about 10% T-ALL in children and adults). This somatic abnormality can be detected by array-CGH, genomic Q-PCR or fiber-FISH, but not or hardly by standard metaphasic or interphasic FISH.
  

To be noted

Additional cases are needed to delineate the epidemiology of this rare entity:
you are welcome to submit a paper to our new Case Report section.

Bibliography

The C-MYB locus is involved in chromosomal translocation and genomic duplications in human T-cell acute leukemia (T-ALL), the translocation defining a new T-ALL subtype in very young children.
Clappier E, Cuccuini W, Kalota A, Crinquette A, Cayuela JM, Dik WA, Langerak AW, Montpellier B, Nadel B, Walrafen P, Delattre O, Aurias A, Leblanc T, Dombret H, Gewirtz AM, Baruchel A, Sigaux F, Soulier J
Blood. 2007 ; 110 (4) : 1251-1261.
PMID 17452517
 
Duplication of the MYB oncogene in T cell acute lymphoblastic leukemia.
Lahortiga I, De Keersmaecker K, Van Vlierberghe P, Graux C, Cauwelier B, Lambert F, Mentens N, Beverloo HB, Pieters R, Speleman F, Odero MD, Bauters M, Froyen G, Marynen P, Vandenberghe P, Wlodarska I, Meijerink JP, Cools J
Nature genetics. 2007 ; 39 (5) : 593-595.
PMID 17435759
 
Analysis of balanced rearrangements of chromosome 6 in acute leukemia: clustered breakpoints in q22-q23 and possible involvement of c-MYB in a new recurrent translocation, t(6;7)(q23;q32 through 36).
Sinclair P, Harrison CJ, Jarosová M, Foroni L
Haematologica. 2005 ; 90 (5) : 602-611.
PMID 15921375
 

Citation

This paper should be referenced as such :
Clappier, E ; Soulier, J
t(6;7)(q23;q34)
Atlas Genet Cytogenet Oncol Haematol. 2008;12(3):248-249.
Free journal version : [ pdf ]   [ DOI ]
On line version : http://AtlasGeneticsOncology.org/Anomalies/t0607q23q34ID1465.html


Other genes implicated (Data extracted from papers in the Atlas) [ 1 ]

Genes MYB

Translocations implicated (Data extracted from papers in the Atlas)

 t(6;7)(q23;q34) TRB/MYB and AHI1

External links

Mitelman databaset(6;7)(q23;q34) [Case List]    t(6;7)(q23;q34) [Association List] Mitelman database (CGAP - NCBI)
arrayMapTopo ( C42) Morph ( 9837/3) - arrayMap (UZH-SIB Zurich)  [auto + random 100 samples .. if exist ]   [tabulated segments]
 
 
Disease databaset(6;7)(q23;q34) TRB/MYB and AHI1
REVIEW articlesautomatic search in PubMed
Last year articlesautomatic search in PubMed
All articlesautomatic search in PubMed


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