Heidi Ledford in Nature:
The day when human sperm and eggs can be grown in the laboratory has inched a step closer, with the discovery of a way to recreate a crucial developmental step in a dish1. The advance, described 20 May in Nature, addresses a major hurdle: how to ensure that the chemical tags on the DNA and associated proteins in artificially produced sperm and eggs are placed properly. These tags are part of a cell’s ‘epigenome’ and can influence whether genes are turned on or off. The epigenome changes over a person’s lifetime; during the development of the cells that will eventually give rise to sperm or eggs, these marks must be wiped clean and then reset to their original state.
“Epigenetic reprogramming is key to making the next generation,” says Mitinori Saitou, a stem-cell biologist at Kyoto University in Japan, and a co-author of the paper. He and his team worked out how to activate this reprogramming — something that had been one of the biggest challenges in generating human sperm and eggs in the laboratory, he says. But Saitou is quick to note that there are further steps left to conquer, and that the epigenetic reprogramming his lab has achieved is not perfect. “There is still much work to be done and considerable time required to address these challenges,” agrees Fan Guo, a reproductive epigeneticist at the Chinese Academy of Sciences Institute of Zoology in Beijing.
More here.