One percent of human genes 'can be shut down without causing serious disease'

Twenty completely inactive genes have been identified by scientist studying so called 'loss of function' mutations in the human genome.

The team, from the Wellcome Trust Sanger Institute in the UK, believes this work could help to identify new, disease-causing genes.

The study compared 185 peoples' genomes, looking for instances where a change in the gene affects the function of the protein it codes for. They found nearly 1,300 loss of function variants, with around 100 being found in the average European's genome. While some of these affect only one copy of the gene, meaning there may still be some functionality, around 20 occurred in both copies, and so they are completely shut down.

Dr Daniel MacArthur, first author of the study, said: 'The key questions we focused on for this study were: how many of these loss of function variants were real and how large a role might they play in human disease?'

Such variations in crucial genes are the underlying cause of a range of human diseases such as cystic fibrosis and muscular dystrophy. However, disrupting the function of other, less crucial genes might have no profound or visible effect.

Previous studies have estimated that around 3,000 loss of function variants exist in humans. However, it is not always easy to identify these variants in human genome sequences, as the sequencing process is prone to errors. So in this study other methods were used to validate these predicted variants.

Professor Mark Gerstein, co-author from Yale University, USA, explained that they found that 'at least one percent of human genes can be shut down without causing serious disease'.

The fact not all loss of function variants affect our health will be an important consideration when genome sequencing becomes more common place, as geneticist Peter Visscher of the University of Queensland in Australia told Science Now: 'This shows how careful we need to be when drawing inferences about such mutations'.

The team believes a complete catalogue of these loss of function variants will help researchers understand the genetics of rare diseases.

The study was carried out as part of the 1000 Genomes Project and was published in the journal Science.