The Drosophila Mutagen-Sensitivity Gene mus109 Encodes DmDNA2.

The identification of mutants through forward genetic screens is the backbone of Drosophila genetics research, yet many mutants identified through these screens have yet to be mapped to the Drosophila genome. This is especially true of mutants that have been identified as mutagen-sensitive (mus), but have not yet been mapped to their associated molecular locus. Our study addressed the need for additional mus gene identification by determining the locus and exploring the function of the X-linked mutagen-sensitive gene mus109 using three available mutant alleles: mus109D1, mus109D2, and mus109lS. After first confirming that all three mus109 alleles were sensitive to methyl methanesulfonate (MMS) using complementation analysis, we used deletion mapping to narrow the candidate genes for mus109. Through DNA sequencing, we were able to determine that mus109 is the uncharacterized gene CG2990, which encodes the Drosophila ortholog of the highly conserved DNA2 protein that is important for DNA replication and repair. We further used the sequence and structure of DNA2 to predict the impact of the mus109 allele mutations on the final gene product. Together, these results provide a tool for researchers to further investigate the role of DNA2 in DNA repair processes in Drosophila.

Medical morbidities and DNA methylation of NR3C1 in preterm infants.

BACKGROUND: Although there are no accepted "normal" levels of circulating cortisol in preterm infants, critically ill preterm infants show lower cortisol levels than healthy preterm infants. The regulation of cortisol reactivity by epigenetic changes in glucocorticoid receptor gene (NR3C1) expression has been demonstrated. This study aims to examine the relationship between medical morbidities in preterm infants and DNA methylation of NR3C1. METHODS: Pyrosequencing was used to determine DNA methylation in CpG sites 1-4 of promoter region 1F of NR3C1. Cluster analysis placed 67 preterm infants born <1,500 g into groups based on medical morbidities. The DNA methylation pattern was compared across groups. RESULTS: Cluster analysis identified a high medical risk cluster and a low medical risk cluster. A Mann-Whitney U-test showed lower methylation at CpG1 for infants in the high-risk group (M = 0.336, SE = 0.084) than infants in the low-risk group (M = 0.617, SE = 0.109, P = 0.032). The false discovery rate was low (q = 0.025). Cohen's D effect size was moderate (0.525). CONCLUSION: Decreased DNA methylation of CpG1 of NR3C1 in high-risk infants may allow for increased binding of transcription factors involved in the stress response, repair and regulation of NR3C1. This may ensure healthy growth in high-risk preterm infants over increasing cortisol levels.