Characterization of two polymorphisms in the leukotriene C4 synthase gene in an Australian population of subjects with mild, moderate, and severe asthma.
BACKGROUND
The cysteinyl-leukotrienes (cys-LTs) are proinflammatory mediators that are important in the pathophysiology of asthma. LTC(4) synthase is a key enzyme in the cys-LT biosynthetic pathway, and studies in small populations have suggested that a promoter polymorphism (A(-444)C) in the gene might be associated with asthma severity and aspirin intolerance.


OBJECTIVE
We sought to screen the LTC(4) synthase gene for polymorphisms and to determine whether there is an association between these polymorphisms and asthma severity or aspirin sensitivity in a large, well-phenotyped population and to determine whether this polymorphism is functionally relevant.


METHODS
The coding regions of the LTC(4) synthase gene were screened for polymorphisms and the A(-444)C polymorphism was analyzed in a large Australian white adult population of mild (n=282), moderate (n=236), and severe asthmatic subjects (n=86) and nonasthmatic subjects (n=458), as well as in aspirin-intolerant asthmatic subjects (n=67). The functional activity of the promoter polymorphism was investigated by transient transfection of HL-60 cells with a promoter construct.


RESULTS
A new polymorphism was identified in intron 1 of the gene (IVS1-10c>a) but was not associated with asthma. Association studies showed that the A(-444)C polymorphism was weakly associated with asthma per se, but there was no association between the C(-444) allele and chronic asthma severity or aspirin intolerance. A meta-analysis of all the genetic studies conducted to date found significant between-study heterogeneity in C(-444) allele frequencies within different clinical subgroups. In vitro functional studies showed no significant differences in transcription efficiency between constructs containing the A(-444) allele or the C(-444) allele.


CONCLUSIONS
Our data confirm that, independent of transcriptional activity, the C(-444) allele in the LTC(4) synthase gene is weakly associated with the asthma phenotype, but it is not related to disease severity or aspirin intolerance.
Kedda
Mary-Anne
MA
Co-operative Research Centre for Asthma and the Asthma and Allergy Research Institute (Inc), Sir Charles Gairdner Hospital, University of Western Australia, Perth, WA 6009, Australia.
Shi
Jing
J
Duffy
David
D
Phelps
Stephanie
S
Yang
Ian
I
O'Hara
Kirrily
K
Fong
Kwun
K
Thompson
Philip J
PJ
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000483:Alleles; D001241:Aspirin; D001249:Asthma / Q000201:enzymology* / Q000235:genetics*; D001315:Australia; D016022:Case-Control Studies; D004361:Drug Tolerance / Q000235:genetics; D005260:Female; D005982:Glutathione Transferase / Q000235:genetics* / Q000378:metabolism; D018922:HL-60 Cells; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D011110:Polymorphism, Genetic; D012150:Polymorphism, Restriction Fragment Length; D018807:Polymorphism, Single-Stranded Conformational; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D014162:Transfection
D011994:Recombinant Proteins; D005982:Glutathione Transferase; C041116:leukotriene-C4 synthase; D001241:Aspirin