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Title: Investigation of 13q14.3 abnormalities in B-cell chronic lymphocytic leukaemia
Author: Corcoran, Martin M.
ISNI:       0000 0004 2732 294X
Awarding Body: University of Portsmouth
Current Institution: University of Portsmouth
Date of Award: 1999
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A region of chromosome 13q14.3, telomeric to the retinoblastoma gene (REI) is frequently deleted in patients with B cell chronic lymphocytic leukaemia (B-CLL). A cosmid and P AC contig spanning over 600 kb has been constructed which encompasses this locus. The contig clones have been used to order a number of markers along the minimally deleted region and to localise a series of CpG islands corresponding to possible candidate genes. A novel polymorphic dinucleotide repeat, 6E3.2 present in . one of the ordered cosmid clones has been isolated for use in deletion mapping studies of patient DNA. Leukaemic samples from 229 CLL patients have been screened for loss of heterozygosity using microsatellite markers and analysed for hemi- and homozygous deletions by Southern blot techniques, using genomic probes selected from cosmids across the region. Hemizygous deletions were found in 31 % of cases with an additional 10% showing homozygous loss. The use of these probes has defined the commonly deleted area to less than 10 kb, centromeric to the locus D 13s272. A transcriptional map as well as a detailed restriction map of the region of interest has been constructed. Using these tools a panel of 229 primary CLL clones and 3 cell lines has been screened. In 6 CLL cases limited deletions were found defining the region of interest to an area of no more than 10 kb. Seven separate expressed transcripts were found within the overall contig region, and a transcriptional map was prepared for the region. Two adjacent genes, termed LEUI and LEU2 (leukaemia-associated gene 1 and 2), were mapped to the minimally deleted region, with patients showing deletion borders within these genes. The LEUI and LEU2 genes show little homology to previously published genes at the nucleotide and expected translated amino acid sequence level. Mutational analysis of the LEUI and LEU2 genes in 170 CLL samples revealed no small intragenic mutations or point-mutations. However, in all cases of 13q14 loss examined, the first exon of both genes, which are only 300 bp apart, were deleted. The LEU2 gene is highly conserved between humans and mouse and is expressed as two alternatively spliced transcripts, one of which contains an exon located at a CpG island found methylated in 40% of heterozygously deleted patients. It is concluded that LEUI, and in particular LEU2 are strong candidates for the tumour suppressor gene(s) involved in B-CLL leukaemogenesis.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available