Genetic variants that affect more than one human disease or trait are reported in a study published online this week in Nature Genetics. The study shows how seemingly unrelated traits - such as migraine and coronary artery disease - can have partially overlapping underlying genetic factors and identifies some cases where traits may have a causal effect on other traits.
Genome-wide association studies can identify genetic variants that are statistically associated with a trait and that could potentially be involved in causing that trait. Variants that are associated with multiple traits can provide insight into the molecular functions of genes and the relationship between different traits. Most studies of multiple traits, however, have focussed on traits already thought to be related.
Joseph Pickrell and colleagues analyzed genome-wide association data for 42 traits or diseases for which large-scale data sets exist to identify genetic overlap. The traits included anthropometric traits (for example, height, BMI and nose size), neurological diseases (for example, Alzheimer disease and Parkinson disease) and susceptibility to infection (for example, childhood ear infections and tonsillectomy). They found 341 locations of genomic variation associated with at least two traits. For example, several variants associated with later age at menarche in girls (indicating the onset of puberty) were also associated with later age at voice drop in boys, lower BMI, increased height in both sexes and reduced risk of male-pattern baldness. The study found statistical evidence for a causal role of the timing of puberty in these related traits.
The authors also found a small association between individual genetic variants that increase risk of schizophrenia and two autoimmune diseases - Crohn’s disease and ulcerative colitis.