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This Week in Science: Jun 12, 2009

In Science's early online edition, researchers performed a genome-wide RNAi screen in Drosophila to find genes for susceptibility or resistance to intestinal infection by the bacteria Serratia marcescens. Screening on organism- and tissue-specific levels, they found that the JAK-STAT signaling pathway "controls host defense in the gut by regulating stem cell proliferation and thus epithelial cell homeostasis," they say.

Two papers in this week's issue study gene imprinting in plants, which occurs in the endosperm and acts to silence either a maternal or paternal gene through DNA methylation. In one, led by HHMI researcher Steven Henikoff, they performed a genome-wide DNA methylation analysis in Arabidopsis embryo and endosperm and found that many transposable element fragments are "extensively demethylated" in the endosperm, suggesting that "imprinting in plants evolved from targeted methylation of transposable element insertions near genic regulatory elements." Likewise, in the second, Berkeley scientists found that "virtually the entire endosperm genome is demethylated," and that there is hypermethylation of transposable elements.

Work led by William Paul Hanage at Imperial College London studied the effect of homologous recombination on antibiotic resistance in bacteria. Looking at 1,930 pneumococcal genotypes from six housekeeping genes of Streptococcus pneumoniae and 94 genotypes from related species, they found a group of strains in which a sequence of housekeeping genes appeared to have been acquired through horizontal gene transfer and was linked to antibiotic resistance. This suggests that "hyper-recombination" is important for the development of antibiotic resistance, they say.

Finally, a policy article looks at what might help revamp the drug discovery and development process. The authors' "novel approach ... involves profound changes in the way postmarketing surveillance data are gathered and used" and would take advantage of consumer activism, genetic information, and social networking technologies to repurpose drugs.

The Scan

Pig Organ Transplants Considered

The Wall Street Journal reports that the US Food and Drug Administration may soon allow clinical trials that involve transplanting pig organs into humans.

'Poo-Bank' Proposal

Harvard Medical School researchers suggest people should bank stool samples when they are young to transplant when they later develop age-related diseases.

Spurred to Develop Again

New Scientist reports that researchers may have uncovered why about 60 percent of in vitro fertilization embryos stop developing.

Science Papers Examine Breast Milk Cell Populations, Cerebral Cortex Cellular Diversity, Micronesia Population History

In Science this week: unique cell populations found within breast milk, 100 transcriptionally distinct cell populations uncovered in the cerebral cortex, and more.