title: Genetic risk factors for type 2 diabetes: a trans-regulatory genetic architecture?
abstract: To date, 68 loci have been associated with type 2 diabetes (T2D) or glucose homeostasis traits. We report here the results of experiments aimed at functionally characterizing the SNPs replicated for T2D and glucose traits. We sought to determine whether these loci were associated with transcript levels in adipose, muscle, liver, lymphocytes, and pancreatic β-cells. We found an excess of trans, rather than cis, associations among these SNPs in comparison to what was expected in adipose and muscle. Among transcripts differentially expressed (FDR < 0.05) between muscle or adipose cells of insulin-sensitive individuals and those of insulin-resistant individuals (matched on BMI), trans-regulated transcripts, in contrast to the cis-regulated ones, were enriched. The paucity of cis associations with transcripts was confirmed in a study of liver transcriptome and was further supported by an analysis of the most detailed transcriptome map of pancreatic β-cells. Relative to location- and allele-frequency-matched random SNPs, both the 68 loci and top T2D-associated SNPs from two large-scale genome-wide studies were enriched for trans eQTLs in adipose and muscle but not in lymphocytes. Our study suggests that T2D SNPs have broad-reaching and tissue-specific effects that often extend beyond local transcripts and raises the question of whether patterns of cis or trans transcript regulation are a key feature of the architecture of complex traits.
authors.affiliation: Section on Endocrinology and Metabolism, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC 27157, USA.
authors.forename: Steven C
authors.initials: SC
authors.lastname: Elbein
authors.forename: Eric R
authors.initials: ER
authors.lastname: Gamazon
authors.forename: Swapan K
authors.initials: SK
authors.lastname: Das
authors.forename: Neda
authors.initials: N
authors.lastname: Rasouli
authors.forename: Philip A
authors.initials: PA
authors.lastname: Kern
authors.forename: Nancy J
authors.initials: NJ
authors.lastname: Cox
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism; D000328:Adult; D003924:Diabetes Mellitus, Type 2 / Q000235:genetics*; D005260:Female; D020869:Gene Expression Profiling / Q000379:methods; D005786:Gene Expression Regulation; D005947:Glucose / Q000378:metabolism; D006801:Humans; D007333:Insulin Resistance / Q000235:genetics; D050417:Insulin-Secreting Cells / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009132:Muscles / Q000378:metabolism; D009928:Organ Specificity; D020641:Polymorphism, Single Nucleotide; D040641:Quantitative Trait Loci; D012307:Risk Factors; D059467:Transcriptome; D055815:Young Adult
chemical_list: D005947:Glucose