In Nature Biotechnology this week, researchers from the Broad Institute and the Massachusetts Institute of Technology describe a technique for inducible gene editing using a modified CRISPR/Cas9 system. The approach involves breaking the Cas9 nuclease, which is responsible for the DNA double-strand breaks triggered by the technology, into two pieces that reconstitute in the presence of a specific chemical. This split Cas9 architecture could enable a variety of experiments such as ones where synchronized transcriptional activation is beneficial. GenomeWeb has more on this here.
Meanwhile, in Nature Genetics, a group led by scientists from the Hospital for Sick Children report on the discovery of genetic mutations responsible for a hyper-mutated form of childhood brain cancer. A condition called biallelic mismatch repair deficiency (bMMRD) is caused by the inheritance of two mutated copies of one of two key DNA repair genes and predisposes children to cancer, most commonly ones of the blood and brain. However, not all children with bMMRD develop cancer. In studying bMMRD patients with aggressive brain tumors, the investigators found that the cancers were hyper-mutated and that they all carried mutations in one of two DNA repair genes that are in a different pathway than the ones responsible for bMMRD. This, the study's authors state, is responsible for the rapid progression of these brain tumors.