In this week’s Nature, researchers from the University of Massachusetts Medical School reported on the silencing of a third copy of chromosome 21 that causes Down’s syndrome in a cell culture model of the disorder, marking a step forward towards “chromosome therapy.” The scientists used zinc finger nucleases to insert an inducible transgene version of a gene called XIST into cultured stem cells from Down’s syndrome patients. “The XIST non-coding RNA coats chromosome 21 and triggers stable heterochromatin modifications, chromosome-wide transcriptional silencing, and DNA methylation,” effectively silencing genes on the chromosome and correcting the unusual pattern of cell growth and differentiation seen in cells derived from patients.
In Nature Genetics, a team from the University of Zurich published the draft genome of the fungal pathogen wheat powdery mildew, or Blumeria graminis forma specialis tritici, as well as the resequencing of three additional isolates and a comparative analysis with the barley powdery mildew genome. The researchers identified more than 600 candidate effector genes, many showing evidence of positive selection. Characterization of genetic diversity patterns suggested that mildew genomes are “mosaics of ancient haplogroups that existed before wheat domestication,” and that the adaptation of the pathogen to new host species was “based on a diverse haplotype pool that provided great genetic potential for pathogen variation.”