Methylation profiling in individuals with uniparental disomy identifies novel differentially methylated regions on chromosome 15.

The maternal and paternal genomes possess distinct epigenetic marks that distinguish them at imprinted loci. In order to identify imprinted loci, we used a novel method, taking advantage of the fact that uniparental disomy (UPD) provides a system that allows the two parental chromosomes to be studied independently. We profiled the paternal and maternal methylation on chromosome 15 using immunoprecipitation of methylated DNA and hybridization to tiling oligonucleotide arrays. Comparison of six individuals with maternal versus paternal UPD15 revealed 12 differentially methylated regions (DMRs). Putative DMRs were validated by bisulfite sequencing, confirming the presence of parent-of-origin-specific methylation marks. We detected DMRs associated with known imprinted genes within the Prader-Willi/Angelman syndrome region, such as SNRPN and MAGEL2, validating this as a method of detecting imprinted loci. Of the 12 DMRs identified, eight were novel, some of which are associated with genes not previously thought to be imprinted. These include a site within intron 2 of IGF1R at 15q26.3, a gene that plays a fundamental role in growth, and an intergenic site upstream of GABRG3 that lies within a previously defined candidate region conferring an increased maternal risk of psychosis. These data provide a map of parent-of-origin-specific epigenetic modifications on chromosome 15, identifying DNA elements that may play a functional role in the imprinting process. Application of this methodology to other chromosomes for which UPD has been reported will allow the systematic identification of imprinted sites throughout the genome.

Effect of static electric field treatment on multiple antibiotic-resistant pathogenic strains of Escherichia coli and Staphylococcus aureus.

This study evaluated the effect of a (4.5 kV/cm, 50 Hz) static electric field (SEF) on pathogenic strains of Escherichia coli and Staphylococcus aureus with multiple antibiotic resistance. The bacteria were grown overnight at 37 degrees C in a nutrient broth medium, then inoculated in 5 mL fresh nutrient broth medium and incubated for 2 h at 25 degrees C with continuous shaking at 190 rpm. 10 x colony-forming units/mL of these bacteria were subjected to a 4.5 kV/cm, 50 Hz, SEF for various time periods. The effects of 5 different SEF exposure times (30, 60, 90, 120 and 150 min) on the bacteria were evaluated by the plate count agar method. The growth percentages of SEF treatment groups were significantly less than that of the control group. Inactivation significantly increased with the duration of SEF exposure. The results indicate that growth inhibition by SEF in the Gram-negative bacteria, E. coli, was greater than that in the Gram-positive bacteria, S. aureus. This study has demonstrated the antimicrobial effects of SEF treatment on 2 important pathogens, suggesting its potential for application as a method for controlling microbial population growth within in a variety of environments.