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This Article Full Text Full Text (PDF) 065425.Supplemental Data All Versions of this Article: clinchem.2005.065425v1 52/6/995    most recent Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (3) Citing Articles via Google Scholar Google Scholar Articles by Denlinger, L. C. Articles by Bertics, P. J. Search for Related Content PubMed PubMed Citation Articles by Denlinger, L. C. Articles by Bertics, P. J. Related Collections Molecular Diagnostics and Genetics

Human P2X₇ Pore Function Predicts Allele Linkage Disequilibrium

Departments of¹ Medicine,² Biomolecular Chemistry, and³ Anesthesiology, and⁴ Comprehensive Cancer Center, University of Wisconsin School of Medicine and Public Health, Madison, WI.

^aAddress correspondence to this author at: Section of Allergy, Pulmonary & Critical Care Medicine, University of Wisconsin School of Medicine and Public Health, 1300 University Ave., Rm 4285 MSC, Madison, WI 53705. Fax 608-263-4969; e-mail ldenling{at}wisc.edu.

Background: Innate immune response amplification is achieved by leukocyte expression of the purinergic nucleotide receptor P2X₇, an extracellular nucleotide-gated pore. Previously, low P2X₇ pore activity in whole blood was associated with loss-of-function genotypes in correlation with a decreased ratio of lipopolysaccharide-stimulated tumor necrosis factor- to interleukin-10, of relevance to a variety of infectious and inflammatory disorders. We hypothesized that evaluation of participants with discordance between the P2X7 genotype and pore status would disclose additional alleles, linkage disequilibrium, and novel functional correlates of genotype to phenotype.

Methods: Comparison of whole-blood pore results with restriction fragment length polymorphism data for known loss-of-function genotypes from 200 healthy participants optimized the diagnostic threshold for low pore activity by ROC curve analysis. We identified novel alleles and inferred haplotypes by sequencing outlier genomic templates and by linkage analysis.

Results: With a refined threshold of low activity, a normal pore result had only a 2% probability of association with known loss-of-function variants. By contrast, the positive predictive value of low pore activity was 59% for identifying known alleles. DNA samples from this discordant group contained 28 P2X7 sequence variations. Linkage analysis demonstrated that A1513C, T1729A, and G946A are inherited independently from one another, although these loss-of-function variants are in disequilibrium with other alleles. When we segregated pore activity data according to genotypes, nonsynonymous sequence variations (G474A and A1405G) appeared to exhibit modulatory effects on P2X₇ pore activity.

Conclusions: Direct analysis of pore activity demonstrates functional interactions between P2X7 alleles. The performance characteristics of the whole-blood pore assay enables correlation of genomic variation with concomitant investigation of functional performance in clinical studies.

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				L. C. Denlinger, L. Shi, A. Guadarrama, K. Schell, D. Green, A. Morrin, K. Hogan, R. L. Sorkness, W. W. Busse, and J. E. Gern Attenuated P2X7 Pore Function as a Risk Factor for Virus-induced Loss of Asthma Control Am. J. Respir. Crit. Care Med., February 15, 2009; 179(4): 265 - 270. [Abstract] [Full Text] [PDF]