A California company says it can decipher almost all the DNA code of a days-old embryo created through in vitro fertilization (IVF)—a challenging feat because of the tiny volume of genetic material available for analysis. The advance depends on fully sequencing both parents’ DNA and “reconstructing” an embryo’s genome with the help of those data. And the company suggests it could make it possible to forecast risk for common diseases that develop decades down the line. Currently, such genetic risk prediction is being tested in adults, and sometimes offered clinically. The idea of applying it to IVF embryos has generated intense scientific and ethical controversy. But that hasn’t stopped the technology from galloping ahead.

Heart conditions, autoimmune diseases, cancer, and many other adult ailments have complex and often mysterious origins, fueled by a mix of genetic and environmental influences. Hundreds of variations in the human genome can collectively raise or lower risk of a particular disease, sometimes by a lot. Predicting a person’s chance of a specific illness by blending this genetic variability into what’s called a “polygenic risk score” remains under study in adults, in part because our understanding of how gene variants come together to drive or protect against disease remains a work in progress. In embryos it’s even harder to prove a risk score’s accuracy, researchers say. “Ultimately, how are we going to validate this in embryos?” says Norbert Gleicher, an infertility specialist at the Center for Human Reproduction in New York City who was not involved in the research. “We’ll have to wait for 40 or 50 years” to find out whether a person develops the diseases they were screened for as an embryo.

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