The genetic definition of a ‘normal’ human being

UK scientists have completed one of the first studies to define how unique we are on the genetic level. We all share the same genetic code, but a team from the Institute of Food Research (IFR) has found that the way our genes function varies significantly between individuals, particularly in some key areas including the immune system.

On the other hand, the functioning of the code over time in any one individual varies very little.

Research leader Dr Ruan Elliott said: “We are all unique, and the way our genes work is one source of our individuality. This presents challenges for scientists in developing medicines and dietary advice. We are confident that our study provides a valuable resource by defining normal variability between healthy humans. This may allow even the very earliest signs of disease to be identified.”

The scientists studied “gene expression”, the process by which genes are activated to make proteins that in turn carry out a whole range of functions in the body. Differences in gene expression can translate into visible characteristics such as eye and hair colour. They can also affect how we respond to different medicines and what each of us needs to eat to achieve our own optimal health.

“Our bodies constantly seek to regulate their internal environment though ‘homeostasis’”, said Dr Elliott. “What we eat can contribute to that balance, or it can stretch the homeostatic limits. Knowing what the limits are will help us to detect early signs or even predisposition to disease.”

The team studied gene expression in white blood cells, which are involved in disease response. Research scientist John Eady said: “These cells can alert us to minor changes that occur before disease sets in. Our study has defined the normal level of variability of gene expression in healthy people so those minor changes can be detected.”

The study design allowed for maximum variation by taking a total of five samples from each of 18 individuals, sampling every eight days. In this way, it captured the possible effects of activities such as exercise, going to the pub or hormonal effects due to the menstrual cycle.

“As with the human genome project, our research involved relatively few people, but it tells an important story that will help scientists all over the world accurately make sense of genetic information”, said Eady. “We have made the data freely available.”

Of the 14,000 genes analysed, 3,302 were identified as varying significantly in their expression between human volunteers. Some of the variation was what might have been expected due to age, gender and body mass index. But there was also considerable variation in the expression of genes covering a wide range of biological functions, such as those regulating antibody production - a vital part of a healthy immune system.

The fact that day-to-day variation within individuals was so low suggests that detecting even small changes elicited by dietary interventions should be feasible.

“We are the same, but different, and the validity of nutrition research is dependent on knowing just how different we are”, said Eady. “With this research, the impact of diet can be more accurately measured and early signs of disease can be more easily predicted.”

The research was funded by the IFR’s core strategic grant from the Biotechnology and Biological Sciences Research Council and is part of ongoing work to investigate diet-gene interactions. It will be published in Physiological Genomics and is available on ‘Articles in Press’ from 12 July 2005, http://physiolgenomics.physiology.org/papbyrecent.shtml

Notes to Editors

Please contact Zoe Dunford for more information, photos and to arrange interviews: 01603 255111 / 07768 164185 / zoe.dunford@ifr.ac.uk
The mission of the Institute of Food Research (www.ifr.ac.uk) is to carry out independent basic, and strategic research on food safety, quality, nutrition and health. It is a company limited by guarantee, with charitable status, grant aided by the Biotechnology and Biological Sciences Research Council (www.bbsrc.ac.uk).

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