title: Genotype-phenotype correlation for histamine N-methyltransferase in a Chinese Han population.
abstract: BACKGROUND
  Two potential single-nucleotide polymorphisms (SNP) (C314T and A595G) exist in the gene for human histamine N-methyltransferase (HNMT).
  
  
  METHODS
  A radiochemical microassay was used to measure the erythrocyte HNMT activities, whereas the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was employed to perform the genetic analysis in 247 unrelated Chinese Han subjects.
  
  
  RESULTS
  All subjects had detectable HNMT activity. The activity of HNMT was gender related (males>females, p<0.0001), with a 5.5-fold individual variation. The distribution of HNMT activity was compatible with a normal distribution. There were 28 heterozygotes for the variant T314 allele among the 247 subjects, whereas no A595G transition was observed. All heterozygotes for the T314 allele displayed an intermediate or low HNMT activity, with an average HNMT activity being 34.0% lower than those with wild-type genotype (623.1+/-136.0 vs. 944.8+/-249.3 U/ml red blood cells [RBC], p<0.0001).
  
  
  CONCLUSIONS
  The C314T polymorphism was functionally important and contributes in part to phenotypic variance of HNMT activity in Chinese Han population. Additional unknown genetic or epigenetic factors should also play important roles in the regulation of HNMT activity.
authors.affiliation: Pharmacogenetics Research Institute, Institute of Clinical Pharmacology, Central South University, Hunan 410078, Changsha, PR China.
authors.forename: Guo Lin
authors.initials: GL
authors.lastname: Chen
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.forename: Zhen Hua
authors.initials: ZH
authors.lastname: Xu
authors.forename: Bing
authors.initials: B
authors.lastname: Zhu
authors.forename: Lian Sheng
authors.initials: LS
authors.lastname: Wang
authors.forename: Gan
authors.initials: G
authors.lastname: Zhou
authors.forename: Dan
authors.initials: D
authors.lastname: Wang
authors.forename: Hong Hao
authors.initials: HH
authors.lastname: Zhou
mesh_terms: D000293:Adolescent; D000328:Adult; D002681:China; D004912:Erythrocytes / Q000201:enzymology; D005260:Female; D005838:Genotype; D006637:Histamine N-Methyltransferase / Q000737:chemistry* / Q000235:genetics*; D006801:Humans; D008297:Male; D010641:Phenotype; D012150:Polymorphism, Restriction Fragment Length; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D006637:Histamine N-Methyltransferase