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This Week in Nature: Apr 22, 2010

In an advance, online publication of Nature this week, researchers report that microRNAs 165 and 166 differentially distribute "target mRNAs in the vascular cylinder determines xylem cell types in a dosage-dependent manner." This, the team writes, is itself mediated by the cell-to-cell movement of the transcription factors Short Root and Scarecrow. "To our knowledge, this is the first solid evidence that microRNAs can move from one cell to another," Philip Benfey, study co-author, says in a statement.

In a paper published in Nature Genetics online, investigators report RAD51C as a human breast and ovarian cancer susceptibility gene. The team identified germline mutations — including two frameshift-causing insertions, two splice-site mutations, and two nonfunctional missense mutations — in cases from 1,100 families with gynecological malignancies. "These results reinforce our assumption that various rare gene mutations contribute to hereditary breast and ovarian cancer," Alfons Meindl, lead author of the study, says in a statement. "The now known genes that predispose women to breast and/or ovarian cancer only explain 60 percent of the high-risk families."

A team of researchers led by investigators at the University of California, Riverside, Institute for Integrative Genome Biology reports that a Pol II and AGO4-associated protein, RDM1, "acts in RNA-directed DNA methylation" in Arabidopsis. Loss-of-function mutations in the gene encoding for RDM1 impairs "the accumulation of 24-nucleotide siRNAs, reduce DNA methylation, and release transcriptional gene silencing." The authors suggest that their results implicate a potential role for RDM1 in linking siRNA production with cytosine methylation.

Meanwhile, in Nature Methods, researchers at the University of Washington School of Medicine and their colleagues describe a "method to accurately genotype … new insertions by mapping next-generation sequencing data sets to the breakpoint, thereby providing a means to characterize copy-number status for regions previously inaccessible to single-nucleotide polymorphism arrays." Using their approach, the team sequenced 156 copy-number polymorphic insertions and identified new exons and non-coding sequences "not yet represented in the reference genome."

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.