Kai Kupferschmidt, 26 May 2016, Science Magazine, http://www.sciencemag.org/news/2016/05/genome-editor-crispr-helps-trace-growth-embryos-and-maybe-cancer-next
Tracing cells lineages from fertilization to adulthood has traditionally proven extremely challenging. However McKenna et al. (http://science.sciencemag.org/content/early/2016/05/25/science.aaf7907) have now developed a technique named GESTALT (Genome Editing of Synthetic Target Arrays for Lineage Tracing) that uses CRISPR to create a unique barcode that can be followed through development. The technique was developed in zebra fish by injecting the Cas9 enzyme and 10 unique gRNAs into single-celled embryos. The Cas9/gRNA complexes can then cleave the targeted sequences through the first rounds of cell divisions over ~4 hours. Each time a cleavage event occurs a unique InDel is created, thus allowing the lineage of organs and tissues to be determined from the sequence of the fully developed zebra fish.