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Title: Investigation of the role of MLL-ENL in leukaemogenesis
Author: Chowdhury, Tanzina
ISNI:       0000 0004 2671 6453
Awarding Body: University of London
Current Institution: University College London (University of London)
Date of Award: 2007
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Acute leukaemia is the most common form of childhood cancer and is the primary cause of cancer-related mortality in children. The major initiating event in infant leukaemia is rearrangement of the Mil gene at 1 lq23, and such leukaemias have a poor survival rate. Chromosomal translocations occur commonly in leukaemia and an in-frame fusion gene is created with altered properties to the original genes involved. Translocations of chromosome 1lq23 result in the fusion of Mil to a variety of partners genes. Mll-Afl results from t(911), Mll-A/4 from t(411) and Mll-Enl from t(1119) and are thought to cause aberrant transcriptional regulation. To identify candidate target genes of t(1119), MLL-ENL has been over-expressed in 32D cells, an immortalised myeloid progenitor cell line. The actions of MLL-ENL on cell survival following growth factor withdrawal, and on G-CSF mediated differentiation have been studied. Potential transcriptional targets of MLL-AF9 and MLL-ENL have been identified using microarray technology. Ten genes were identified as possible candidate target genes of the MLL-ENL protein that might be involved in leukaemogenesis. Of particular interest were Gatal and HTm4 which have a role in haematopoiesis and cell cycle regulation. shRNA constructs were generated to knock down MLL-ENL and allow validation of the potential target genes. The mechanism of leukaemic transformation by MLL-ENL has also been investigated. In leukaemia, fusion proteins may contribute to haematological malignancy in various ways, though the main routes are thought to be either a gain-of-function or dominant negative action. In order to determine the mechanism by which a MLL fusion protein immortalizes murine haematopoietic progenitor cells (HPC), a system was developed where MLL-ENL was expressed in murine HPCs in the absence of both alleles of Mil. The experiments were carried out using murine HPCs from conditional Mil knockout mice generated in our laboratory where the wild- type Mil allele is flanked by LoxP sites at exons 9 and 10, and can be inactivated following Cre-mediated recombination. The ability of cells to undergo sequential re-plating in methylcellulose was used as an indication of immortalization. These experiments now definitively show that the MLL-ENL fusion protein acts in a gain-of-function manner.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available