RT Journal Article SR Electronic T1 Genetic variants in CHI3L1 influencing YKL-40 levels: resequencing 900 individuals and genotyping 9000 individuals from the general population JF Journal of Medical Genetics JO J Med Genet FD BMJ Publishing Group Ltd SP 831 OP 837 DO 10.1136/jmedgenet-2013-101908 VO 50 IS 12 A1 Alisa D Kjaergaard A1 Julia S Johansen A1 Børge G Nordestgaard A1 Stig E Bojesen YR 2013 UL http://jmg.bmj.com/content/50/12/831.abstract AB Background Despite its important role in many serious diseases, the genetic background for plasma YKL-40 has still not been systematically catalogued. Therefore, we aimed at identifying genetic variants in CHI3L1 influencing plasma YKL-40 levels in the general population. Methods We resequenced the promoter, all 10 exons and exon-flanking intron segments of CHI3L1 in 904 individuals from the Danish general population (n=8899) with extreme plasma YKL-40 levels, adjusted for age. To potentially identify clinically important genetic variants with elevated plasma YKL-40 levels, we included twice as many individuals with the highest plasma YKL-40 levels (n=603) compared with the lowest plasma YKL-40 levels (n=301). Next, we mapped linkage disequilibrium for all variants with a minor allele frequency (MAF)>0.005. Finally, all participants were genotyped for eight variants that had divergent MAFs in the two extreme plasma YKL-40 groups. Results We identified 59 genetic variants in CHI3L1. Fifteen of the genetic variants were associated with plasma YKL-40 levels. Three promoter SNPs, 1 non-synonymous SNP, and four intronic SNPs in CHI3L1 were associated with plasma YKL-40 levels at or below genome-wide association significance levels (unadjusted p for trend: from 4 × 10−8 to 6 × 10−243; age adjusted percentiles p for trend: from 3 × 10−12 to 2 × 10−304). Conclusions In a systematic search to identify genetic variants influencing plasma YKL-40 levels, we identified eight SNPs associated with plasma YKL-40 levels in the general population.