545A Poster - 07. Chromatin, epigenetics and genomics
Thursday April 07, 2:00 PM - 4:00 PM

Authors:
Nathan Dupre ^1,2; Shyanne Abbott ^1,2; Safiyo Aden ^1,2; Ashlyn Anderson ^1,2; Solomon Aviles ^1,2; Deneisha Bergquist ^1,2; Derrick Carper ^1,2; Rhianna Coffey ^1,2; Max Her ^1,2; Clara Hovland ^1,2; Marayan Ibrahim ^1,2; Hunter Lindsay ^1,2; Heidi Pipkin ^1,2; Kyle Reichstadt ^1,2; Anthony Ruiz ^1,2; Melissa Sawyer ^1,2; Christina Yang ^1,2; Emily Yang ^1,2; Andrew Arsham ^1,2

Affiliations:
1) Bemidji State University; 2) North Hennepin Community College

Keywords:
e. heterochromatin; v. RNA transport and localization

Highly repetitive DNA sequences are often associated with invasive or pathogenic DNA, and can also be found in gene-poor regions of eukaryotic genomes like centromeres and telomeres. Genomes often defensively package repeats in dense, transcriptionally refractory, stably heritable heterochromatin which plays a crucial role in the regulation of gene expression through transcriptional silencing. How these sequences trigger the establishment and maintenance of heterochromatin remains poorly understood, but repeats appear to serve as a signal of foreignness to host genomes and can activate the siRNA, miRNA, or piRNA silencing pathways. Silencing of repetitive DNA is implicated in the formation and function of centromeres and telomeres, in defense against transposons and viruses, and in human trinucleotide repeat expansion diseases like Friedreichs Ataxia and Fragile X syndrome. To investigate the mechanism and regulation of repeat-triggered silencing, undergraduate students participating in a classroom research experience (CURE) carried out a transposition mutagenesis to investigate the effects of large tracts of repetitive DNA on gene expression and chromatin state. Students mobilized a p-element containing a 256-copy tandem array of the E. coli lac operator (LacO), flanked by white and yellow reporter genes. After setting up mobilization crosses, students screened F2 progeny for changes in eye or body color indicating expression of either or both reporter genes (287/14137 or 2% of all male F2 screened). Of transgene-expressing flies, wild type expression of yellow and white comprised 82% of all mutants and indicate presumed euchromatic insertions resulting in high reporter gene expression. The white gene alone was silenced in 11% of identified mutants; the yellow gene alone was silenced in 4%, demonstrating a surprising decoupling of reporter gene silencing. 3% of mutants showed variegation of the white gene and full expression of the yellow gene, but the converse was not observed, nor was variegation of body color. Molecular mapping of insertion sites with inverse PCR suggest that LacO repeat insertion can trigger silencing even in gene-rich euchromatic locations.