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Title: Characterisation of l(3)IX-14, a novel mitotic mutant in Drosophila melanogaster
Author: McHugh, Brian
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2001
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I have characterised alleles of the late larval lethal mutation l(3)IX-14, which was previously observed to disrupt mitotic and polytene chromosome structure. Mitotic chromosomes from homozygous mutant larval neuroblasts appear hypercondensed in length and surrounded by a halo of loosely condensed chromatin. Polytene chromosomes from homozygous mutant larval salivary glands also display a chromatin packaging problem and lack the characteristic banding patterns normally observed in wild type polytene chromosomes. Further phenotypic characterisation of l(3)IV-14 has shown that several other cell division processes as defective, mainly the duplication of centrosomes and the establishment of a bipolar mitotic spindle. BrdU labelling of larval brains has indicated that replication may be processing at a slower rate than in wild type. Also, despite the almost normal level of cells committed to mitosis, the mitotic index of l(3)IX-14 is low, and elevated levels of TUNEL labelling has suggesting that many cells are switching to an apoptotic pathway. I have cloned a novel full length cDNA for the putative IX-14 gene by inverse PCR, utilising a P-element allele of l(3)IX-14. The surrounding genomic region has also been characterised in detail, and I have determined that the P insertion site is 40 bp upstream of the putative IX-14 gene. Northern blot analysis using the cDNA from this gene reveals a message of 3.6 kb present in wild type and heterozygous larvae but absent in homozygous mutants. The predicted IX-14 gene product is 684 amino acids in length containing a well conserved zinc-metalloprotease motif, and has homologues in several higher eukaryotes but no in lower eukaryotes or prokaryotes. RNAi of IX-14 in cultured Drosophila cells has given similar phenotypes to those observed in the late larval lethal alleles, providing further evidence that this novel metalloprotease is responsible for the phenotypes observed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available