In this week's Science, an team of scientists from industry and academia reports a draft genome sequence of the opium poppy, revealing the genetic basis for the flower's pain-killing ability. The investigators find that repetitive elements — in particularly long terminal repeat retrotransposons — account for a substantial part of the opium poppy's genome, and uncover a whole-genome duplication event from around 7.8 million years ago. Just before this duplication event, the authors write, a gene fusion occurred that enabled morphine biosynthesis in the plant.
Also in Science, a University of Texas Southwestern Medicine Center-led group describes using CRISPR-Cas9 genome editing to treat Duchenne muscular dystrophy (DMD) in a large animal model. DMD is caused by a mutation that prevents expression of the protein dystrophin, which is key for muscle function. The scientists systemically delivered a CRISPR payload designed to correct the defect into a dog model of the disease and were able to restore normal dystrophin levels by up to 70 percent in skeletal muscle and 92 percent in cardiac tissue. This compares with a recently approved DMD gene therapy that increases dystrophin levels less than 1 percent. The findings suggest that "with further development, gene editing approaches may prove clinically useful for the treatment of DMD," the scientists conclude.
Finally in Science, a multi-institute research team publishes a study showing that bursts of complex, loop-like genetic rearrangements — called chromoplexy — as often responsible for the gene fusions that characterize Ewing sarcomas (ES). By sequencing and analyzing ES tumors and their matched normal DNA, and comparing the results to another ES dataset, the scientists find that chromoplexy was responsible for disease-causing gene fusion in 42 percent of tumors studies. The loops "always contained the disease-defining fusion at the center, but they disrupted multiple additional genes," the team writes. They also occurred "preferentially in early replicating and transcriptionally active genomic regions." Notably, chromoplexy-generated fusions appear to be associated with an aggressive form of ES. A related Perspective piece discusses the findings and their clinical implications.