Advanced Imaging


Advanced Imaging Magazine

Updated: July 8th, 2008 05:26 PM CDT

Imaging Solutions of the Year: Visible DNA Sequencing

Category: Microscopy
Color-coded, one-micron diameter acrylamide-coated spheres.
Specialized microscope stage.
The system: including Nikon Instruments' inverted, epifluorescence microscope.

By Advanced Imaging Editorial Staff

Harvard Medical School (Boston, MA)
Nikon Instruments Inc. (Melville, NY)
(Nominated by Norman Booth, Keating and Company, Florham Park, NJ)

The Challenge:

The expense of decoding the blueprint of life on Earth is enormous. Laboratories trying to decipher genomes usually outsource the work to sequencing centers where expensive DNA electrophoresis is performed. Faced with the prospect of spending a great deal of time and money to sequence large sections of DNA, scientists frequently make do with a “ready to wear” approach, taking what is available and tailoring it to their needs.

The Solution:

A genetics research team at Harvard Medical School developed a novel means for sequencing entire genomes, not simply DNA segments. The practice utilizes special fluorochrome-activated beads. In contrast to existing methods which suspend DNA strands in gel and decode them via electrophoresis, the Harvard procedure packs thousands of DNA fragments onto fourteen million one-micron diameter acrylamide-coated spheres. Each bead represents one snippet of DNA. One of four fluorescent dyes—corresponding to the four nucleotide bases­­binds to a specific location, depending on which base is present. This allows scientists to image the sample with an epifluorescence microscope and directly visualize the nucleotide sequence.

The Tools Used:

  • Hamamatsu (Bridgewater, NJ) 1000×1000-pixel Electron Multiplier CCD camera
  • Nikon Instruments epifluorescence inverted microscope
  • Prior Scientific (Rockland, MA) motorized translation stage
  • Sutter Instrument (Novato, CA) Lambda xenon illuminator, Lambda excitation and emission filter wheels and SmartShutter

The Difference It Made:

The Human Genome Project (National Human Genome Research Institute, Bethesda, MD) spent $2.7 billion to map the complete genome. Harvard Medical School’s fluorescence imaging methodology embodied an ultra-fast approach, which radically decreased the cost—by one order of magnitude—to sequence an individual gene. Further reductions are on the horizon which could bring down the price tag to about $200,000 per full human genome.

The image-based technique can compare differences among previously sequenced genomes, useful to determine how the one-tenth of one percent genetic variability among humans is expressed. And, its high accuracy, low cost and ability to decode more than thirty million bases at once (versus current technologies which manage about 196,000 base pairs) are revolutionizing many biomedical disciplines and heralding a new era of “personalized” medicine and custom-tailored prescriptions. The information garnered by such DNA sequencing also might enable doctors to predict an individual’s future risk of disease and to intervene with preventive measures.

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