At a time when the longtime goal of a $1,000 genome is still just out of reach, a Harvard University physicist is promising an even cheaper price–the ability to sequence a human genome for just $30. David Weitz and his team are adapting microfluidics technology that uses tiny droplets, a strategy developed in his lab, to DNA sequencing. While the researchers have not yet sequenced DNA, they have successfully demonstrated parts of the process and formed a startup, GnuBio, to commercialize the technology. Weitz presented the findings at the Consumer Genomics Conference in Boston last week.
Weitz’s team had previously developed a way to create picoliter droplets of water, which act as tiny test tubes. The droplets can be precisely moved around on a microfluidics chip, injected with chemicals and sorted based on color. (The technology has been commercialized by RainDance Technologies, which Weitz cofounded in 2004. The company markets the droplet technology to amplify select regions of DNA.)
Because the droplets are so small, they require much smaller volumes of the chemicals used in the sequencing reaction than do current technologies. These reagents comprise the major cost of sequencing, and most estimates of the cost to sequence a human genome with a particular technology are calculated using the cost of the chemicals. Based solely on reagents, Weitz estimates that they will be able to sequence a human genome 30 times for $30. (Because sequencing is prone to errors, scientist must sequence a number of times to generate an accurate read.)
The cost of sequencing has dropped exponentially over the last five years, enabling much broader application of the technology to study human health and disease, agriculture, and microbial diversity. The current cost to sequence a human genome is just a few thousand dollars, though companies that perform the service charge $20,000 to $48,000. A number of companies are racing to develop even cheaper technologies.
In Weitz’s approach, droplets are injected with short strands of DNA of a known sequence, and these strands are labeled with an optical bar code. Pieces of the sample with an unknown sequence are also injected into the droplets–if the sample has a stretch of sequence complementary to the known strand, the two pieces will bind, triggering a change in color. Repeat this 1,000 times with 1,000 different known strands and you can generate the sequence of 1,000 letters of DNA, says Weitz.