Tracing the genetic origins of the earliest farmers

Early farming practices developed in parallel among at least two groups, and the techniques of farming spread more quickly than the farmers themselves, according to two new analyses of ancient DNA. The discoveries lend credence to the idea that farming spread from multiple groups rather than a single population, as some have suggested. The studies—of early farmers in what is modern-day Turkey and of farmers found across the Fertile Crescent—agree that early farming communities remained genetically isolated for millennia before waves of migration led to genetic mixing of the groups. The studies applied improved methods for extracting and analyzing DNA from skeletons of the Near and Middle East, where the hot climate degrades genetic material. The larger of the studies, published in Nature, compared 44 ancient human DNA samples from what is modern-day Iran and the region encompassing Israel and Jordan to a DNA database of contemporary individuals from the region. The investigators found that early farming occurred between 10,000–9,000 BC in at least two separate populations in the Middle and Near East, suggesting that groups began practicing agriculture independently. A second study of samples from nine individuals, appearing in Current Biology, revealed that early farmers in Anatolia (Turkey) remained relatively genetically isolated during the Neolithic period, from around 9500–6000 BC. The international research team from Turkey and Sweden proposes that early farming populations maintained a relatively stable population structure during the transition to agriculture. Once established, farming techniques spread faster than the farmers, the researchers speculated. The two research teams independently concluded that early farmers descended from local hunter–gatherers and did not mix extensively with other groups until around the Bronze Age, when waves of migration led to genetic mixing among farmers and rapid expansion into western Europe, Asia, and Africa. —Karyn Hede, News Editor

New gene associated with risk of aortic rupture identified

Mutation of a protein known to help maintain the integrity of vascular connective tissue has now been shown to cause an inherited form of thoracic aortic aneurysms and dissections (TAAD). The finding adds to a growing list of genes that can underlie familial forms of TAAD, although a pathogenic mutation in this gene has been found in only one family to date. The study, led by researchers at Washington University School of Medicine in St. Louis, in collaboration with Brigham and Women’s Hospital in Boston, identified an autosomal dominant missense mutation in the lysyl oxidase (LOX) gene and generated a mouse model that confirmed that LOX underlies the disease. The LOX protein, which normally helps cross-link networks of elastic and collagen fibers that line blood vessels, leads to a weakened aorta when mutated. Several individuals in the family studied had a history of aortic aneurysm and other physical features that suggested Marfan syndrome, but tested negative for that disease. The study was published 18 July in the Proceedings of the National Academy of Sciences. Using CRISPR genome engineering tools, the research team introduced the human mutation into mice, which developed a condition that mimicked the human form of the disease. Mutation carriers have weakened vessel walls that may predispose them to TAAD. The researchers suggest that clinical sequencing for LOX mutations may help provide diagnoses to families that currently have unexplained familial TAAD. —Karyn Hede, News Editor