title: Assessment of genetic linkage and parent-of-origin effects on obesity.
abstract: BACKGROUND
  Obesity is a growing health care problem worldwide and is a major underlying risk factor for common diseases such as diabetes. Parent-of-origin effect has been reported to be involved in the development of obesity. But the genes with imprinting effects related to obesity are largely unknown.
  
  
  OBJECTIVE
  The objective of the study was to identify obesity-related genetic loci, both with and without imprinting effects.
  
  
  METHODS
  We conducted genome-wide linkage analyses for obesity with and without consideration of imprinting effects in a large sample including more than 4000 individuals. In addition to body mass index (BMI), we also used a more stringent and accurate obesity definition, which simultaneously considers BMI and percentage of fat mass (PFM) in a gender-specific manner. Simulations were performed to identify the genome-wide significant and suggestive significant thresholds.
  
  
  RESULTS
  In nonimprinted linkage analyses, we detected suggestive linkage at 2q31 (LOD = 2.23) and 16q22 (LOD = 1.87) for BMI and 2q37 (LOD = 2.23) for BMI and PFM. Interestingly, 2q37 also achieved a significant maternal linkage with BMI and PFM (LOD=3.34) in imprinted linkage analyses. Imprinted linkage analyses revealed suggestive linkage evidence for BMI at three additional genomic regions, including 3p14 (LOD = 2.20, paternal), 3q24 (LOD = 1.97, maternal), and 19q13 (LOD = 1.81, maternal).
  
  
  CONCLUSIONS
  We reported linkage and imprinting effects for obesity on several chromosome regions and suggested the potential importance of parent-of-origin effects and phenotype definition of obesity in delineating the genetic basis of obesity.
authors.affiliation: Key Laboratory of Biomedical Information Engineering, Ministry of Education and Institute of Molecular Genetics, School of Life Science and Technology, Xi'an Jiantong University, Xi'an 710049, People's Republic of China.
authors.forename: Yan-Fang
authors.initials: YF
authors.lastname: Guo
authors.forename: Hui
authors.initials: H
authors.lastname: Shen
authors.forename: Yong-jun
authors.initials: YJ
authors.lastname: Liu
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.forename: Dong-hai
authors.initials: DH
authors.lastname: Xiong
authors.forename: Peng
authors.initials: P
authors.lastname: Xiao
authors.forename: Yao-zhong
authors.initials: YZ
authors.lastname: Liu
authors.forename: Lan-juan
authors.initials: LJ
authors.lastname: Zhao
authors.forename: Robert R
authors.initials: RR
authors.lastname: Recker
authors.forename: Hong-wen
authors.initials: HW
authors.lastname: Deng
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism; D001823:Body Composition; D015992:Body Mass Index; D002874:Chromosome Mapping; D005260:Female; D008040:Genetic Linkage; D006801:Humans; D008126:Lod Score; D008297:Male; D009765:Obesity / Q000235:genetics*; D010290:Parents