Specifically associated with T-cell Acute Lymphoblastic Leukemia (T-ALL).

This translocation is related to Notch1 (TAN1) dysregulation. Mutation or chromosomal rearrangements of Notch gene have not yet been identified outside of T-ALL but Notch1 was recently studied by immunohistochemistry in various subsets of human lymphomas. Strong staining was found in Hodgkins lymphoma (HL) and anaplastic large cell lymphoma (ALCL) but much additional works is needed to determine whether Notch signaling is necessary for HL and ALCL growth and survival.

T lineage. CD4+ CD8+ double positive stage.

Rare: < 1% among T-ALL.

9q34 is a partner of 7q34. The other partners are 1p34, 1p32, 9q32, 10q24, 11p13, 15q22, 19p13

In T- lymphoblastic cell lines: polyploidy, inv(2)(p22;q11), inv(14)(q11;q32), del(6)(q23q27), del(4)(q13q35)

The t(7;9) disrupts the Notch1 gene, fusing the 3¹end portion encoding its intracellular domain (ICN) to enhancer and promoter elements of the T cell receptor (TCRB). This results in overexpression of a constitutively active form of Notch activating genes that inhibit cell differenciation.The t(7;9)(q34;q34) results in a serie of tumor specific 5¹deleted Notch1 mRNA transcripts. All known beakpoints fall within a single intron in the coding sequence for the EGF repeat 34 of Notch1.
The t(7 ;9) truncated transcripts encode ICN1-like polypetides (ICN = intracellular portion of Notch receptor). These polypeptides localize to the nucleus and structurally resemble ICN1. The intracellular portion of Notch1 contains six ankyrin repeats that are similar to those found in cytoplasmic I kappa B proteins or I kappa B are specific inhibitors of nuclear factor NFKappa B transcription factors.

On primary effect of constitutive Notch 1 activation is the maturation arest of T lymphoblastes at the CD4+ CD8+ double positive stage but recent works suggest that Notch contributes to T cell transformation by influencing proliferation and survival, rather than merely blocking differenciation.