Keegan McDonough
Research Mentor(s): Joann Sekiguchi
Mentor Department: Internal Medicine and Department of Human Genetics
Authors: Keegan McDonough, Steven Orban, Andrea Hartledrode, McKenna DeFoer, JoAnn Sekiguchi
Session: Session 3 (11:00am – 11:50am)
Presentation Type: Poster 113
Abstract
The DNA Damage Response (DDR) is an essential pathway in the management and maintenance of the genome of all living organisms.The DDR is activated when the MRN complex binds to double strand break (DSB) ends and recruits and activates the ATM kinase to initiate the response. The MRN (MRE11, RAD50, NBS1) complex is a protein complex highly conserved across all eukaryotes. Ataxia telangiectasia-like disorder (ATLD) is a disease resulting from the mutation of the MRE11 gene, with major symptoms such as cerebellar degeneration, developmental defects, and possible cancer predisposition. The first ATLD allele discovered in humans (ATLD1) causes a truncation of the MRE11 protein, and also causes the protein to be expressed at low levels. We seek to distinguish the effects of both of these impacts. To address this, the lab has created 4 mouse models. These models express either WT or ATLD1 at high or low levels. My position in the lab has me investigating the mutation and its effects on genome instability. Splenocytes are taken from each genotype of mouse. They are then arrested in the metaphase step of the cell division cycle and “dropped†onto a microscope slide. After being fixed, dyed, and dropped on a slide so that they lyse, the chromosomes are visible under a fluorescence microscope at 100x amplification. The metaphases are then imaged, and the images can then be “scoredâ€, where visual aberrations in the chromosomes are counted and divided by the total number of chromosomes present to create an aberrations/chromosome rate. This gives us a metric for the chromosomal instability of each genotype. This is done across every genotype and compared to assess the effect of low expression of MRE11 and c-terminus truncation on the genome. So far, experiments have indicated that both low expression and truncation result in higher rates of damage, but that low expression has much more damage. This suggests that the low expression leads to higher genomic instability.
