title: An upstream polymorphism associated with lactase persistence has increased enhancer activity.
abstract: OBJECTIVE
  Intestinal lactase activity declines during childhood in some humans. This phenotypic polymorphism of lactase persistence or nonpersistence into adult life has been shown in a recent study to be 100% associated with a T/C nucleotide polymorphism at position -13910 and approximately 97% with an A/G nucleotide polymorphism at position -22018. The aim of this study was to investigate the role of these nucleotide polymorphisms for lactase-phlorizin hydrolase (LPH) gene expression.
  
  
  METHODS
  The -13910 and -22018 regions were cloned from lactase-persistent and -nonpersistent individuals, and the regions were analyzed for gene regulatory activity of a luciferase reporter gene by transfection experiments using the intestinal cell line Caco-2. Electrophoretic mobility shift assays (EMSAs) were used to investigate protein/DNA interactions with the -13910 sequence.
  
  
  RESULTS
  We show that the -13910 region contains a strong enhancer. The -13910 regions from both lactase persistent (-13910T variant) and lactase nonpersistent (-13910C variant) have enhancer activity. However, the -13910T variant enhances the LPH promoter approximately 4 times more than the -13910C variant when analyzed in differentiated Caco-2 cells. A nuclear factor from both an intestinal and a nonintestinal extract binds strongly to the -13910T variant whereas the binding to the -13910C variant is much weaker.
  
  
  CONCLUSIONS
  The discovery of a functional difference between the 2 alleles at position -13910 supports the notion that the molecular difference between lactase persistence and nonpersistence is caused by the mutation at position -13910.
authors.affiliation: Department of Medical Biochemistry and Genetics, Biochemical Laboratory C, The Panum Institute, University of Copenhagen, Denmark. troelsen@imbg.ku.dk
authors.forename: Jesper T
authors.initials: JT
authors.lastname: Troelsen
authors.forename: Jørgen
authors.initials: J
authors.lastname: Olsen
authors.forename: Jette
authors.initials: J
authors.lastname: Møller
authors.forename: Hans
authors.initials: H
authors.lastname: Sjöström
mesh_terms: D018938:Caco-2 Cells; D004742:Enhancer Elements, Genetic; D006367:HeLa Cells; D006801:Humans; D010694:Lactase-Phlorizin Hydrolase / Q000235:genetics*; D007787:Lactose Intolerance / Q000235:genetics*; D011110:Polymorphism, Genetic; D011401:Promoter Regions, Genetic; D013394:Sucrase-Isomaltase Complex / Q000235:genetics
chemical_list: D013394:Sucrase-Isomaltase Complex; D010694:Lactase-Phlorizin Hydrolase