In this week's Science, Harvard Medical School's George Church and his colleagues publish a study demonstrating the use of the genome-editing technology CRISPR to inactivate a retrovirus in a pig cell line, marking a step forward to the generation of pig organs for transplantation. Though pig organs are viable as replacements in humans, retroviruses in porcine DNA can be transmitted to humans, potentially causing disease. Using CRISPR, the researchers were able to shut down all copies of a retrovirus by inactivating a gene critical for its replication. Importantly, CRISPR did not appear to cause detrimental genomic rearrangements. GenomeWeb has more on this here.
Also in Science, a multi-institute research team reports new details about the Piwi-interacting RNA (piRNA) pathway, a system of non-coding RNAs that play a key role in protecting the genomes of reproductive cells from transposon-related mutations. PiRNAs are known to function by repressing transposons at the transcriptional level, the mechanism that triggers this silencing has been unknown. The investigators identified a protein, called CG9754 that's expressed exclusively in the female gonad, as a component of Piwi and its binding partner in transcriptional silencing. Further experimentation led the team to propose that the protein bridges interactions between the piRNA pathway and the silencing machinery used for transcriptional repression.