Bioengineer Stephen Quake, PhD, has been in the news a lot lately. Earlier this month, his lab reported the first non-invasive whole-genome sequencing of a fetus using only the mother's blood. Now he's broken new ground again by sequencing the whole genomes of single sperm cells. The research is published today in Cell. As I explain in our release:
The entire genomes of 91 human sperm from one man have been sequenced by Stanford University researchers. The results provide a fascinating glimpse into naturally occurring genetic variation in one individual, and are the first to report the whole-genome sequence of a human gamete — the only cells that become a child and through which parents pass on physical traits.
Quake and his colleagues, including Barry Behr, PhD, HCLD, the director of Stanford's In Vitro Fertilization Laboratory, were able to identify places in each sperm genome where sections of chromosomes had been swapped in a natural process called recombination. The exact locations and number of times the swaps occur vary in each cell. When the process goes well, it's an important way to add genetic variation and ensure that a child is a blend of DNA from all four grandparents. When it goes awry, it can lead to infertility or genetic problems in the fetus.
More from the release:
The Stanford study showed that the previous, population-based estimates were, for the most part, surprisingly accurate: on average, the sperm in the sample had each undergone about 23 recombinations, or mixing events. However, individual sperm varied greatly in the degree of genetic mixing and in the number and severity of spontaneously arising genetic mutations. Two sperm were missing entire chromosomes. The study has long-ranging implication for infertility doctors and researchers.
“For the first time, we were able to generate an individual recombination map and mutation rate for each of several sperm from one person,” said [Behr]. “Now we can look at a particular individual, make some calls about what they would likely contribute genetically to an embryo and perhaps even diagnose or detect potential problems.”
Previously: New techniques to diagnose disease in a fetus