Functional significance of gene polymorphisms in the promoter of myeloid differentiation-2.
OBJECTIVE
To investigate the functional significance of the reported single nucleotide polymorphisms (SNPs) in the promoter of the myeloid differentiation-2 (MD-2) gene.


BACKGROUND
Functional gene polymorphisms of innate immune receptors have been shown to be critical determinants of the immune inflammatory response. MD-2 is an important signaling enhancer protein in the endotoxin (LPS) receptor complex. Although a total of 156 SNPs have been identified within the whole MD-2 gene, little is known about the functional significance of these SNPs.


METHODS
: The possible biosignificance of 8 reported SNPs was analyzed using on-line software tools. The selected SNPs were then genotyped using a restriction fragment length polymorphism method applied to 711 healthy Chinese volunteers. Their functional effects were assessed by the observation of transcription activity, MD-2 mRNA expression, and leukocyte response to ex vitro LPS stimulation. Moreover, the clinical relevance of these SNPs was investigated in 105 patients with major trauma.


RESULTS
Three SNPs (C-1625G, A-1064G, and A-475T) in the MD-2 promoter were selected based on bio-informatic analysis. Both -1625 and -1064 SNPs, rather than -475, were seen in the Chinese population, with frequencies of 19.8% (-1625G) and 34.7% (-1064G). But only the -1625 polymorphism was found to affect MD-2 promoter activity. Moreover, the expression of MD-2 mRNA and the production of TNF-alpha in whole blood leukocytes, in response to LPS stimulation, were significantly increased in subjects with the -1625 G allele. Patients who possessed the -1625 G allele were more likely to experience complications with organ dysfunction and sepsis after major trauma. All these associations were in allele-dose dependent effect.


CONCLUSIONS
The MD-2/-1625 polymorphism is an important functional variant.
Gu
Wei
W
State Key Laboratory of Trauma, Burns and Combined Injury, Institute of Surgery Research, Chongqing, China.
Shan
You-an
YA
Zhou
Jian
J
Jiang
Dong-po
DP
Zhang
Lianyang
L
Du
Ding-yuan
DY
Wang
Zheng-guo
ZG
Jiang
Jian-xin
JX
D000293:Adolescent; D000328:Adult; D000368:Aged; D000483:Alleles; D002681:China; D005260:Female; D015870:Gene Expression; D005838:Genotype; D006801:Humans; D007249:Inflammation / Q000235:genetics* / Q000276:immunology; D008070:Lipopolysaccharides / Q000494:pharmacology; D051218:Lymphocyte Antigen 96 / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics*; D012016:Reference Values; D012189:Retrospective Studies; D014158:Transcription, Genetic
D008070:Lipopolysaccharides; D051218:Lymphocyte Antigen 96; D012333:RNA, Messenger