New Gene Sequencing Technique of Individual Cells Developed

Helen Holmes January 08, 2013

In a paper published in the journal Science, a team of US researchers has developed a new technique for sequencing the DNA in individual cells. Unlike the traditional genome sequencing method, the new technique is better and more accurate, scientists say.

Cell groups can have different genomes because of the dynamic changes in the DNA. In the traditional method of gene sequencing, thousands of cells are required to be able to provide sufficient DNA evidence. One big problem with this method however is that the variations found in small groups of cells, such as cancer cells, are usually missed. The technique, called polymerase chain reaction (PCR), allowed scientists to produce copies of a genome with 40-70 percent accuracy. But there’s a problem with amplification bias – a condition when some parts of the genome tend to have more copies than the others. According to the researchers, this method does not only reduce the amount of genome that can be sequenced, but also makes it difficult for some parts of the genome to be copied.

Single Cell Sequencing

The new method developed by the researchers addresses the problem with the amplification bias. It is called Multiple Annealing and Looping-Based Amplification Cycles (MALBAC). The process involves isolating the genome from a cell. After which, the short segments of DNA (called primers) are added. Primers are segments of DNA with a common section of 27 nucleotides and a variable section of 8 nucleotides. The variable section binds with the DNA while the common section prevents the DNA from being copied too often, reducing the amplification bias. Through this technique, up to 93 percent of genome can be sequenced. It is because common segments in the genome tend to loop back on themselves, the paper reports. MALBAC is also easier to perform since only one cell is necessary.

Their first clinical trial using the new genome sequencing method was a success. The researchers used it to sequence the DNA in three groups of cells, including the DNA of 99 sperm cells in one Asian male. The team were able to identify genome variations using individual nucleotides.

More challenges to come

The development of MALBAC is a groundbreaking scientific advancement. However, there are several challenges yet to be met by future studies. For instance, it is still possible to miss variations in single nucleotides. The new method may also produce occasional copying errors. Nevertheless, it can have great use in different scientific explorations, such as in forensic science. More importantly, it widens the possibility of cancer prevention (as well as early treatment) because it allows comparisons to be made between individual cells.

Source of this article:

Genome-Wide Detection of Single-Nucleotide and Copy-Number Variations of a Single Human Cell