title: p21 gene polymorphisms in systemic lupus erythematosus.
abstract: OBJECTIVE
  Cyclin-dependent kinase inhibitor 1A (p21) is a negative regulator in the cell cycle. Development of sex-linked lupus-like syndrome in p21-/- mice and reduced p21 gene expression in patients with systemic lupus erythematosus (SLE) compared with those in healthy controls suggested that p21 is a susceptibility gene of SLE. We investigated the same by a case-control association study.
  
  
  METHODS
  Six single nucleotide polymorphisms, p21US G/A, p21DS C/A, p21-1022 G/A, p21C31 C/A, p21In2 G/C and p21UTR T/C, were genotyped in 516 SLE patients and 693 healthy controls. Association of genotypes and alleles with disease, disease phenotypes, haplotypes construction, linkage disequilibrium analysis and p21 mRNA expression were performed.
  
  
  RESULTS
  We found a significant association of p21US A allele (OR = 0.23, 95% CI: 0.14-0.38, P < 0.001) and p21-1022 A allele (OR = 1.95, 95% CI: 1.37-2.78, P < 0.001) with SLE. We identified significant differences in the frequencies of haplotypes ht1-ACACCC, which contains p21US A allele, and ht2-GCACCC, which contains p21-1022 A allele, between SLE patients and controls (P < 0.0001). Besides, the p21US GA was associated with SLE patients suffering from arthritis (P = 0.003). We also observed differential p21 mRNA expressions among different genotypes of p21US and p21-1022 which were statistically significant.
  
  
  CONCLUSIONS
  Our results suggested that the p21US A allele and p21-1022 A allele were both associated with the development of SLE, and the p21US A allele was associated with arthritis in SLE patients.
authors.affiliation: Department of Paediatrics and Adolescent Medicine, The University of Hong Kong, Pokfulam, Hong Kong SAR, China.
authors.forename: E K-P
authors.initials: EK
authors.lastname: Kong
authors.forename: W-P
authors.initials: WP
authors.lastname: Chong
authors.forename: W H-S
authors.initials: WH
authors.lastname: Wong
authors.forename: C-S
authors.initials: CS
authors.lastname: Lau
authors.forename: T-M
authors.initials: TM
authors.lastname: Chan
authors.forename: P K-M
authors.initials: PK
authors.lastname: Ng
authors.forename: Y-Q
authors.initials: YQ
authors.lastname: Song
authors.forename: W
authors.initials: W
authors.lastname: Mak
authors.forename: Y-L
authors.initials: YL
authors.lastname: Lau
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000096:biosynthesis / Q000235:genetics*; D005260:Female; D015870:Gene Expression; D005787:Gene Frequency; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006239:Haplotypes; D006801:Humans; D015810:Linkage Disequilibrium; D008180:Lupus Erythematosus, Systemic / Q000097:blood / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide; D012333:RNA, Messenger / Q000235:genetics
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D012333:RNA, Messenger