Researchers at the US Rensselaer Polytechnic Institute have created a new and very sensitive technique to detect the glycans (sugars) in living organisms. Dubbed glyco-qPCR, this uses quantitative PCR (qPCR; real-time PCR) techniques.
The genome (the whole of a cell, tissue or organism’s DNA or RNA), exome (all the coding portions of the genome), and proteome (all the proteins expressed by the genome) are all familiar terms. The glycome (all the sugars or carbohydrates in a cell or organism) is less well known, but it may actually tell us more, according to Robert Linhardt at Rensselaer.
“The glycome is richer in information than the genome or the proteome. A cancer cell, for example, might have the same genome as a non-cancer cell, but it produces different sugars,” said Linhardt.
As he explains further, the genes are the blueprints of the organism, and these code for proteins. The genome and proteome can be identical in two different cells, but their glycomes may differ, and this could affect how the cells function and how they react to external stimuli. However, studying glycans has proved difficult so far as they are at very low levels, so the team created a new PCR-based technique designed to be rapid and highly sensitive.
PCR, sometimes calls ‘molecular photocopying’, amplifies small quantities of DNA, creating up to a billion copies over 30 or 40 cycles. The team adapted this prinle to amplify and identify glycans – while glycans can’t be amplified directly, the researchers tagged these sugar molecules using specific DNA sequences, and then used qPCR to amplify and quantify these DNA tags. By identifying the tags and measuring the amounts they could establish which glycans were in a sample, and in what proportions.
“We don’t really detect the molecule, we detect the DNA that’s attached to it,” Linhardt said. “The DNA tags are cleverly designed so that they only attach to certain molecules. We can then amplify the DNA, see what kind of DNA it is, and then infer the molecule that it’s attached to.”
Currently available techniques, such as mass spectrometry or high-performance liquid chromatography, can detect a few billion glycan molecules. In contracts, glyco-qPCR can detect as few as a few hundred. The research has been published in Angewandte Chemie International, and Linhardt believes that it could prove very useful in studying complex multisystem diseases, such as cancer and diabetes.
“This gives us a new tool to study fundamental biology and chemistry,” he said. “It allows us a higher resolution view into the functions of a cell than the genome or proteome. With this tool we can go inside a cell, poke around, and understand how to predict the behaviour of that cell and ultimately control it.”
Suzanne Elvidge is a freelance science, biopharma, business and health writer with more than 20 years of experience. She is editor of Genome Engineering, a blog that monitors the latest developments in genome engineering and that aims to educate (and sometimes to entertain!) and has written for a range of online and print publications including FierceBiomarkers, FierceDrugDelivery, European Life Science, the Journal of Life Sciences (now the Burrill Report), In Vivo, Life Science Leader, Nature Biotechnology, PR Week and Start-Up. She specialises in writing on pharmaceuticals, biotechnology, healthcare, science, lifestyle and green living, but can write on any topic given enough tea and chocolate biscuits. She lives just beyond the neck end of nowhere in the Peak District with her second-hand bookseller husband and two second-hand cats.