Attempted replication of 50 reported asthma risk genes identifies a SNP in RAD50 as associated with childhood atopic asthma.

OBJECTIVES Asthma is a childhood disease that is strongly influenced by genetic factors. We sought to replicate an association between single nucleotide polymorphisms (SNPs) of the top-ranked candidate genes and childhood atopic asthma in Perinatal Risk of Asthma in Infants of Asthmatic Mothers (PRAM) study subjects. METHODS Using data from a systematic literature search and an exploratory genome-wide association study conducted in a subset of the PRAM cohort, we followed a strict procedure to generate a ranked list of candidate genes. SNPs in the top 50 genes were genotyped in the full PRAM cohort (n = 103 cases with doc- tor-diagnosed atopic asthma at age 6, and n = 499 controls). RESULTS The literature search identified 251 prior risk genes from 469 publications. RAD50 (rs2706347) and PTPRE (rs10830196) revealed crude associations with asthma at a Bonferroni-corrected level of significance (p < 0.0011). IL4R (rs1801275), CCL5 (rs2280788), and TBXA2R (rs4523) revealed nominal significance (p < 0.05). When adjusted for race and gender, only rs2706347 in RAD50 remained significantly associated with asthma. SNPs in frequently replicated asthma risk genes, including TNF, IL13, ADAM33, TGFB1, and MS4A2, revealed no association. CONCLUSION RAD50 may be a promising candidate asthma risk gene. Lack of evidence of highly reported polymorphisms in the present study highlights the genetic heterogeneity of asthma and emphasizes the need for robust replication of candidate genes.