A GENETIC SCREEN TO UNCOVER MnSOD MICRO REGION IN DROSOPHILA GENOME





C.Martin, A.Duttaroy *

Biology Department, Howard University, Washington DC 20059



Oxygen (O2) is an essential resource to virtually all living organisms because it can release a vast amount of free energy inside their cell when it is reduced in the mitochondrial electron transport chain. A small percentage (1-3%) of the consumed O2 however, escapes the chain as incomplete reduction products known as superoxide radicals (O2.-). Mounting evidence now points to the fact that superoxide radical and its intracellular derivatives, hydrogen peroxide and hydroxyl radicals that are collectively termed as reactive oxygen species (ROS), are capable of inflicting global damage to the living cell because proteins, nucleic acids, and lipids, are all vulnerable to ROS attack. A living organism can not sustain without a continuous supply of O2, but its consumption generates more ROS, and therefore cellular damages almost invariably accrue . ROS induced cellular damages are random, progressive and cumulative events that have long been pointed out as one of the major causes of natural aging. Besides natural aging, ROS are now related to various late onset degenerative diseases such as cancer, atherosclerosis, arthritis, and neurodegenerative disorders.

The fruitfly Drosophila melanogaster deploys a defense system to fight against ROS that is very similar to that of humans. Manganese superoxide dismutase (MnSOD) activity plays a vital role in this defense system. It is active in mitochondria in which 90% of the consumed oxygen is utilized and therefore where most ROS are produced. My lab is interested in investigating the effects of missense mutations in MnSOD gene in Drosophila, testing the hypothesis that like in familial amyotrophic lateral sclerosis (FALS) patients, altered MnSOD activity could cause neuropathology and degenerative tissue damages. In addition, an MnSOD loss of function allele would allow us to investigate the effect of loss of MnSOD function in specific tissue or cell types, testing the hypothesis that loss of MnSOD function is associated with increased oxidative stress causing accelerated tissue damages. The MnSOD gene is located between the polytene interval 53D6-12 in Drosophila melanogaster genome. To pursue mutational analysis of the Drosophila MnSOD gene, a genomic deletion is necessary that uncovers the MnSOD gene. To obtain such a deletion, we initiated a genetic screen whereby two P element transposons flanking the MnSOD gene are used. Pairing and subsequent genetic exchanges between these two P insertions will cause genomic deletions to happen including the MnSOD locus. So far, this screen has yielded several putative deletions that are being characterized now.






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