Underbites are when the lower jaw protrudes further than the upper jaw and can lead to respiratory and feeding complications. One method currently used to correct underbites is the reverse pull facemask which puts tensile strain on the nasofrontal suture to promote growth of the upper jaw. The reverse pull facemask has major shortcomings such as a long duration of the treatment (12-18 months 16-18 hours a day), and is aesthetically unappealing. An alternative treatment that may produce faster results is to use an oscillatory cyclic load on the nasofrontal suture to increase the growth rate of the upper jaw to correct the underbite in less time than the reverse pull facemask. However to know how effective this method is for underbite correction it is vital to understand how the cyclic treatment changes the nasofrontal suture. My question is how the cyclic load changes the suture gap and growth rate (Mineral Apposition Rate MAR) of the nasofrontal suture in farm pigs. To measure the effectiveness of this treatment, the nasofrontal suture was extracted from farm pigs after they had been treated with the cyclic load for 30 minutes for 5 days. The sutures were then embedded, sectioned and examined under a fluorescent microscope to measure the MAR and suture gap for the control, and cyclic treated pigs. The control pigs had a suture gap range of 157-179 µm (n=5) and a MAR range of 7.75-15.25 µm/day (n=4). The cyclic loaded pigs had a suture gap range of 326-383 µm (n=2) and a MAR range of 29.9-33.2 µm/day (n=2). These data suggest that our cyclic treatment increases the suture gap and MAR of the nasofrontal suture. However, more data will need to be collected to validate our preliminary findings.

DNA replication is the process by which genetic information is duplicated and passed from cell to cell. The process of DNA replication occurs with the assistance of various enzymes, including DNA polymerases, which synthesize new DNA molecules using template DNA and deoxyribonucleotides (dNTPs). Faithful DNA replication is vital for population survival and protected by exonuclease domains on the major DNA polymerases, which proofread replication errors. A secondary error-correction pathway known as mismatch repair (MMR) also scans the genome for replication errors. Defects in proofreading and MMR lead to "mutator phenotypes" marked by elevated mutation rates and increased cellular mutation burden.  In microbial populations, mutators spontaneously emerge and can increase adaptation to new environments by fueling genetic diversity. However, at extreme mutation rates, the accumulation of harmful mutations can also drive extinction of mutators.  Some mutator cells survive this "error-induced extinction" (EEX) by acquiring antimutator mutations that suppress the mutator phenotype. We have identified Saccharomyces cerevisiae strains that suppress elevated mutation rates through a screen for mutants that survive EEX. Using these eex mutant strains, we are currently mapping the genetic changes responsible for the antimutator phenotypes. Changes in mutation rates in haploid spores derived from these eex suppressor strains are being tracked to identify antimutator segregants, which are then being subjected to whole genome sequencing. As mutator phenotypes are important drivers in cancer, our analyses may reveal novel pathways that influence cancer evolution.

This abstract is no longer available. Please contact urp@uw.edu if you have any questions.

This abstract is no longer available. Please contact urp@uw.edu if you have any questions.

Cancer survivors often experience memory and thinking problems after treatment. Cognitive rehabilitation has been shown to improve function in head injury patients. This study examined behavioral and neural responses to a group-based cognitive training intervention in cancer survivors with cognitive symptoms. Gynecologic cancer survivors (n=23) were randomized to treatment group (15) or attention control (8). A subset of participants were eligible for scanning from the treatment (6) and control (5) groups. Both groups attended a 7-session, weekly group-based workshop. The treatment group received education and practice in skills (e.g. method of loci), and the attention control group received only education on cognition and information processing. Prior to and following the 7-session group-based workshops, participants were evaluated with a comprehensive cognitive battery along with an in-scanner verbal memory task where they studied word-pairs (e.g. star–couch) for later recall. During the test phase of the word-pairs task, participants were shown original word-pairs, novel word-pairs, shuffled (old and new) word-pairs, or recombined (two old words not previously paired) word-pairs. Recall during the test phase was assessed at an item level, where responses were yes/no to the query “both old?” or at the relational level, where responses were yes/no to the query “together previously?” Participants in the treatment group showed significant improvement for in-scanner responses in accuracy in the Relational condition, p < .04. Image analysis of group comparison at second level revealed decreased activation in one region in anterior cingulate for the treatment group for item recall. Cognitive training in cancer survivors can improve both attention and verbal memory. Pre to post change in the anterior cingulate for the treatment group suggests additional attention recruitment, consistent with improvements in attention observed with out-of-scanner tasks (e.g. digit span). Overall, cognitive training may be a useful treatment for cancer patients suffering from cognitive symptoms.

Mutator phenotypes due to mutations in genes encoding DNA polymerases or mismatch repair proteins lead to increased error rates during DNA replication that accelerate the evolution of cancer cells and contribute to chemotherapy resistance. Work in the yeast Saccharomyces cerevisae indicates that excessive DNA replication errors can lead to error-induced extinction (EEX), where every cell within the population dies due to a random lethal mutation. Thus, a possible direction for cancer therapy may be to modulate mutation rates of mutator cells – to either increase mutation rates to a lethal level or suppress mutation rates to their baseline levels in order to slow the rate of tumor evolution. Genetic pathways that may be targeted to modulate mutator phenotypes have yet to be fully elucidated. To identify such pathways, we isolated spontaneous haploid yeast eex mutants that escaped from error-induced extinction caused by combining a mismatch repair defect (msh2Δ) with the pol2-L439V allele, which models a human cancer mutation affecting DNA polymerase epsilon. We crossed the eex mutants to wild type yeast, generating diploid strains that were heterozygous for msh2Δ, pol2-L439V, and the eex mutation. Following sporulation, we measured the mutation rates of haploid MMR-proficient pol2-L439V progeny in order to assess the presence or absence of the antimutator mutation. For each mapping experiment, cells showing evidence of suppressed mutation rates were pooled separately from those exhibiting the normal pol2-L439V mutator phenotype. Unique mutations present only in the antimutator pool were identified by Illumina Next Generation Sequencing. Candidate eex mutations were engineered into fresh strains to assess the antimutator phenotype. Our compiled list of antimutator mutations and their functions in yeast may allow us to identify analogous mutations in the human genome and explore new methods of cancer therapy by which specific genes can be targeted to lower mutation rates to normal levels.

DNA polymerase (Pol) proofreading and mismatch repair (MMR) cooperatively guard against DNA replication errors and cancer. Defects in these activities produce “mutator” phenotypes characterized by elevated levels of base-substitutions and frameshifts. Haploid yeast with combined defects in these activities rapidly go extinct, with some strains failing to even form visible colonies - a process termed error-induced extinction (EEX). Haploid eex mutants escape extinction by acquiring antimutator mutations that suppress the mutator phenotype; however, sixty percent of eex mutants escape extinction through spontaneous polyploidization, which insulates them from mutation accumulation by doubling their number of chromosomes. In evolution experiments with pol2-4 msh2Δ strains, which display a synthetic-sick phenotype due to Pol ε proofreading and MMR defects, polyploids routinely beat out antimutator mutants, which maintain haploidy. Whether strong diploid mutators also escape EEX by polyploidization is unknown. To investigate whether polyploids arise during the evolution of mutator diploid strains, we propagated pol3-01/pol3-01 msh6Δ/msh6Δ diploids (Pol δ proofreading and base-base MMR defective) with a mutation rate an order of magnitude below the diploid error threshold. Mathematical modeling suggests that although these diploid mutators are not immediately inviable, they should be overtaken by an antimutator or tetraploid after 200 generations. We found a single tetraploid culture in 89 independent cultures propagated for 300 generations. We measured mutation rates of isolates from cultures that remained diploid and repeatedly found antimutator phenotypes. Thus, spontaneous antimutator alleles and polyploidization rescues haploid and diploid cells from EEX with markedly different efficiencies. Differences in the relative frequency of each escape mechanism may reflect the nature of the mutator alleles, the starting ploidy of the cells, or the magnitude of the initial mutation rate. Our findings in diploids suggest that mutator cancer cells near the edge of error-induced extinction may similarly be under selection for spontaneous antimutator mutations and polyploidization.