No abstract

Genetic reduction is of great significance in many biological pathways. In particular, aneuploid cancerous cells typically undergo genetic reduction to obtain a diploid state, a process accompanied by apoptotic programmed cell death. A tetraploid strain of Candida albicans, when grown on a diploid specific pre‐sporulation media, undergoes random chromosome loss, becoming diploid to near‐diploid in DNA content and undergoing significant cell death as part of the completion of a parasexual cycle. Cell death measurements were made for cells grown on pre‐sporulation media plates. Measurements of viability were made with a methylene blue stain, showing significantly lower tetraploid viability. Assays done to determine levels of reactive oxygen species present showed increased concentration in tetraploid cells undergoing genome reduction. Similar results were found in an assay for caspase These results indicate high ROS levels and high levels of caspase activity in the reducing tetraploid, suggestive of apoptosis‐like programmed cell death accompanying genome reduction. Similar results are seen in diploid Saccharomyces cerevisiae. Further research is currently being done with both tetraploid and diploid strands with apoptotic gene knockouts to further understand the mechanism of death, and understanding of these results could aid in understanding of cancerous and other biological mechanisms in humans.

Genome reduction is often associated with cell death. For example, in the yeast, Candida albicans, tetraploid strains undergo significant cell death when cultured on media that induce them to reduce their genomes to the diploid state. To investigate the mechanism of death in these cells, we have examined them to determine if the manifest any of the markers associated with programmed cell death. Dying cells were stained with dihydrorhodamine 123 and the FLICA reagent and imaged with a Zeiss 700 LSM confocal microscope. Both assays revealed that these dying cells contained reactive oxygen species (ROS) and activated caspases ‐‐ two markers for apoptotic cell death in yeast ‐‐ suggesting that these dying tetraploid cells are undergoing programmed cell death. Similarly, we have discovered that diploid Saccharomyces cells undergoing sporulation also stain positive for increased ROS and caspase activation. To better understand the mechanism of death, we are currently testing the ability of mutants lacking several apoptosis‐related genes to die as they undergo genome reduction.This research has been funded by the following grants to N. Austriaco: a faculty research (CAFR) award from Providence College, a faculty development award from the Rhode Island‐INBRE program, and by grant R15 GM094712 from the NIGMS.