Abstract 2020 Perinatal Brain Injury: Patterns and Mechanisms Platform, Tuesday, 5/4

Background: The ability to tolerate a low-Oxygen environment varies considerably among animals. We have previously shown that the Drosophila melanogaster, a well studied genetic model, has an extraordinary ability to tolerate a complete lack of Oxygen (anoxia) for prolonged periods (e.g. hours) without apparent tissue injury. To determine the genetic basis for this inherent ability, we performed a genetic screen in Drosophila to identify loci responsible for anoxia tolerance. Methods: Mutagenized (X-ray, 4000 rads) wild type male flies, which were crossed to attached-X females (c[1]ywf), transmitted their mutagenized X-chromosome to the male offspring. More than 20,000 flies resulting from this cross have so far been screened in a specially designed chamber where flies were exposed to anoxic conditions (0% Oxygen) for a 5 min period before allowing recovery in room air. Recovery time, or the time that it took flies to recover from anoxic stupor, was measured. Results: Ten anoxia-sensitive mutants (loss-of-function mutants), belonging to 8 complementation groups, were isolated. The identified mutations were X-linked recessive and dominant and flies carrying these mutations showed marked delay in recovery from anoxia (mean recovery time more than 50-300% of wild type). Electrophysiologic studies on the Drosophila Giant Fiber System corroborated the behavioral delay in the mutants' recovery from anoxia: evoked potentials in the jump and flight muscles elicited by stimulating central pathways showed major delays in recovery from anoxia. Electronmicroscopic analysis of the fly CNS showed that, while wild type flies demonstrated chromatin condensation only after 3 hours of anoxia, a severe mutant's CNS studied after the same period of anoxia showed evidence of severe cellular destruction, plasmalemmal disruption, vacuolization and mitochondrial swelling. Chromosomal mapping of these mutations was performed using multiply-marked X-chromosomes, complementation testing, and specific deficiencies. Cloning is being done using PCR-based techniques, Southern analysis and genomic sequences obtained from the Berkeley/European Genome Project or by P-element jumping. Conclusions: a) a number of genes seem to underly the inherent cellular responses to anoxia; b) the genetic screen is not yet saturated and c) the Drosophila can provide a model in which we can dissect the genetic basis for tissue tolerance/susceptibility to anoxia.

Supported by PO1 HD-32573 and T32 HL-07778