Sex differences important for medical research

The sex of animals frequently has an effect in biomedical research and therefore should be considered in scientific studies, according to UCL scientists. In the largest study of its kind, researchers from 10 centres that form the International Mouse Phenotyping Consortium (IMPC) found that differences between male and female mice had significant effects that could impact research results in many biomedical studies. Led by the Wellcome Trust Sanger Institute and published today , the study quantified the differences between males and females (known as sexual dimorphism) by analysing up to 234 physical characteristics of more than 50,000 mice (14,250 control mice and 40,192 mutant mice). By studying the control mice, they found that sex impacted on 56.6% of the 'quantitative traits' analysed such as body composition, metabolic profile, blood components and behavioural traits, and 9.9% of 'qualitative traits' such as the normality of their head shape, coat and paws. In the mutant mice that had a gene switched off, sex modified the effect of the mutation in 13.3% of qualitative traits and up to 17.7% of quantitative traits. Professor Judith Mank (UCL Genetics, Evolution & Environment), co-author of the study, said: 'This study illustrates how often sex differences occur in traits that we would otherwise assume to be the same in males and females. More importantly, the fact that a mouse's sex influenced the effects of genetic modification indicates that males and females differ right down to the underlying genetics behind many traits.