Analysing genes in individual cells is now simpler, cheaper and more effective thanks to US researchers.

Many diseases are linked to abnormal cellular events, which are governed by the cell's genes. But while the human genome has now been sequenced, the functions of these genes and how they interact is still largely unknown. Current techniques to analyse cells' genes use either bulk measurements, for an average from many cells, or expensive and labour intensive single cell measurements. Now, a new microfludic processor can be used to profile gene-gene interactions at the single cell level simply and more efficiently.

Genes are essentially a code, read by RNA polymerase enzymes, to make messenger RNA (mRNA), small fragments of RNA which are then used to assemble proteins. The level of an individual mRNA, therefore, depends upon the activity of its coding gene. The new microfluidic processor, developed by Jiang Zhong at the University of Southern California in Los Angeles and colleagues, was designed to study these mRNAs in large numbers of single cells.

The cellular mRNAs are studied indirectly: cells are broken down to capture the mRNA which is then used to make complementary DNA (cDNA). The cDNA can then be amplified and it is this that is detected. Zhong explained that existing methods to study single cells' mRNA 'suffer from low efficiency in converting mRNA to cDNA,' as well as being expensive and difficult. By extracting the mRNA and producing the cDNA on the same device in nanolitre volumes, the processor is much simpler and more efficient to use.

'Microfluidic and nanolitre scale biochemical reactions will greatly facilitate biological studies, particularly single cell analysis,' said Zhong. The team suggests that the processor could be used to investigate many different areas, from organ formation to aging and disease development, and is already making the device easier for biologists to use in the lab by introducing computer automation.

Laura Howes