Phenotypic associations with the HMOX1 GT(n) promoter repeat in European populations

HO-1 is a key enzyme in the management of heme in humans. A GT(n) repeat length in the gene HMOX1, has previously been widely associated with a variety of phenotypes, including susceptibility and outcomes in diabetes, cancer, infections, and neonatal jaundice. However, studies are generally small and results inconsistent. In this study, we imputed the GT(n) repeat length in two European cohorts (UK Biobank, n = 463,005; and Avon Longitudinal Study of Parents and Children (ALSPAC n = 937), with the reliability of imputation tested in other cohorts (1000 Genomes, HGDP, and UK-PGP). Subsequently, we measured the relationship between repeat length and previously identified associations (diabetes, COPD, pneumonia and infection related mortality in UK Biobank; neonatal jaundice in ALSPAC) and performed a phenome-wide association study (PheWAS) in UK Biobank. Despite high quality imputation (correlation between true repeat length and imputed repeat length >0.9 in test cohorts), no clinical associations were identified in either the PheWAS or specific association studies. These findings were robust to definitions of repeat length and sensitivity analyses. Despite multiple smaller studies identifying associations across a variety of clinical settings; we could not replicate or identify any relevant phenotypic associations with the HMOX1 GT(n) repeat.