title: Genome-wide linkage scan for maximum and length-dependent knee muscle strength in young men: significant evidence for linkage at chromosome 14q24.3.
abstract: BACKGROUND
  Maintenance of high muscular fitness is positively related to bone health, functionality in daily life and increasing insulin sensitivity, and negatively related to falls and fractures, morbidity and mortality. Heritability of muscle strength phenotypes ranges between 31% and 95%, but little is known about the identity of the genes underlying this complex trait. As a first attempt, this genome-wide linkage study aimed to identify chromosomal regions linked to muscle and bone cross-sectional area, isometric knee flexion and extension torque, and torque-length relationship for knee flexors and extensors.
  
  
  METHODS
  In total, 283 informative male siblings (17-36 years old), belonging to 105 families, were used to conduct a genome-wide SNP-based multipoint linkage analysis.
  
  
  RESULTS
  The strongest evidence for linkage was found for the torque-length relationship of the knee flexors at 14q24.3 (LOD = 4.09; p<10(-5)). Suggestive evidence for linkage was found at 14q32.2 (LOD = 3.00; P = 0.005) for muscle and bone cross-sectional area, at 2p24.2 (LOD = 2.57; p = 0.01) for isometric knee torque at 30 degrees flexion, at 1q21.3, 2p23.3 and 18q11.2 (LOD = 2.33, 2.69 and 2.21; p<10(-4) for all) for the torque-length relationship of the knee extensors and at 18p11.31 (LOD = 2.39; p = 0.0004) for muscle-mass adjusted isometric knee extension torque.
  
  
  CONCLUSIONS
  We conclude that many small contributing genes rather than a few important genes are involved in causing variation in different underlying phenotypes of muscle strength. Furthermore, some overlap in promising genomic regions were identified among different strength phenotypes.
authors.affiliation: Department of Biomedical Kinesiology, Research Center for Exercise and Health, Faculty of Kinesiology and Rehabilitation Sciences, Katholieke Universiteit Leuven, Leuven, Belgium.
authors.forename: G
authors.initials: G
authors.lastname: De Mars
authors.forename: A
authors.initials: A
authors.lastname: Windelinckx
authors.forename: W
authors.initials: W
authors.lastname: Huygens
authors.forename: M W
authors.initials: MW
authors.lastname: Peeters
authors.forename: G P
authors.initials: GP
authors.lastname: Beunen
authors.forename: J
authors.initials: J
authors.lastname: Aerssens
authors.forename: R
authors.initials: R
authors.lastname: Vlietinck
authors.forename: M A I
authors.initials: MA
authors.lastname: Thomis
mesh_terms: D000293:Adolescent; D000328:Adult; D002883:Chromosomes, Human, Pair 14; D008040:Genetic Linkage; D014644:Genetic Variation; D015894:Genome, Human; D006801:Humans; D007717:Knee / Q000502:physiology*; D008297:Male; D053580:Muscle Strength / Q000235:genetics*; D010641:Phenotype