Functional quantification of cyclosporine A and FK506 in human whole blood by flow cytometry, using the green fluorescent protein as an interleukin-2 reporter gene

Combined cis-regulator elements as important mechanism affecting FXII plasma levels

INTRODUCTION

Factor XII (FXII) deficiency is a recessive Mendelian trait due to mutations in the F12 gene. There is no bleeding associated with FXII deficiency, but FXII deficiency has been reported to be associated with risk of thrombosis in some studies.

MATERIAL AND METHODS

We examined the functional effect of two naturally-occurring mutations in two Spanish FXII deficient families: a C/G substitution at position -8, and a C/T substitution at position -13. Both mutations were located on a putative HNF4 binding site of F12 gene promoter. We also analyzed the F12 C46T polymorphism (rs1801020), associated with a decrease in the FXII levels, which also segregated in both families. A fragment containing each one of both -8 and -13 mutations, was cloned 5' of a reporter gene. We compared the in vitro expression of these constructs to the wild type expression.

RESULTS

Our analyses confirm that the -8C/G and the -13C/T mutations decreased expression levels, demonstrating that both mutations are involved in the observed FXII deficiency. In addition, electrophoretic shift analyses suggest that they alter the union of nuclear proteins to the promoter. Coinheritance of these mutations with the C46T polymorphism, result in a significant genotype-phenotype correlation.

CONCLUSIONS

We have identified two naturally-occurring mutations in the F12 promoter that drastically reduce FXII levels. Knowing rare genetic alterations in the F12 gene, together with the C46T common variant, may yield further understanding about the genetic architecture of FXII levels, which may have a role in the risk of thrombosis.

Functional analysis of the genetic variability in the F7 gene promoter

The FVII level is considered a risk factor for cardiovascular disease. Some of the polymorphic differences in the promoter of the F7 gene have been associated with variations in FVII levels. However, linkage disequilibrium among those polymorphisms has made it difficult to pinpoint the true functional variants, so contradictory results have often appeared among various studies. We provide new findings of the effect of the polymorphisms in the promoter region of F7. In vitro transfection of 15 plasmids containing different combinations of F7 promoter polymorphisms was performed in HepG2 cells. We found that allelic variants -323ins10 and -122C strongly reduced promoter activity and that allelic variant -402A significantly increased promoter activity. We report the effect of a novel variant (-2989A) that significantly increases F7 expression levels. However, this novel allelic variant is in strong linkage disequilibrium with the -323ins10 variant in our Spanish population, which has a clear dominant effect over the -2989A variant and completely masks its effect. Our results have important implications for mapping genes affecting complex diseases using association studies. That is, they imply that true functional variants should be chosen to confirm the analyses and to ensure that the results can be reproduced in other populations. In addition, our results suggest that it would be informative to screen for the -2989A variant in other populations, since it may well be a risk factor for cardiovascular disease in populations where it does not appear with the decanucleotide insertion.

In vitro evaluation of the effects of candidate immunosuppressive drugs: flow cytometry and quantitative real-time PCR as two independent and correlated read-outs

BACKGROUND

Immune monitoring may use flow cytometry or molecular biology techniques. Flow cytometry assays cells that are phenotypically characterized, whereas TaqMan RT-PCR starts with RNA extraction from unfractionated heterogeneous cell populations. We therefore wondered how the effects of immunosuppressive drugs on cytokine production in stimulated whole blood, as determined by flow cytometry, would correlate with those obtained with quantitative real-time PCR (TaqMan RT-PCR).

METHODS

Blood drawn from naive cynomolgus monkeys was exposed to incremental amounts of cyclosporine (CsA; 300, 600, 900 and 1200 ng/ml) or tacrolimus (TRL; 8, 20, 40 and 80 ng/ml) before lectin stimulation in vitro. Blood was then either stained for CD3, IFN-gamma, IL-2, IL-4, and TNF-alpha and analyzed on a flow cytometer with various gating strategies, or submitted to RNA extraction for analysis of the above mentioned cytokines mRNA transcripts using TaqMan RT-PCR.

RESULTS

Both methods revealed a parallel dose-dependent inhibition of cytokine production in stimulated blood. The 50% inhibitory concentrations (IC(50)'s) ranged from 511-771 ng/ml (CsA) and 15-29 ng/ml (TRL) with flow cytometry, and from 275-529 ng/ml (CsA) and 11-48 ng/ml (TRL) with TaqMan RT-PCR for T-helper 1 cytokines. Both assays correlated well with a Pearson product moment correlation of 0.76. Extending gating from a CD3(+) gate to a lymphocyte gate improved correlation (r = 0.85) for all cytokines investigated (except IL-2; unchanged) whereas further extending gating resulted, to the contrary, in lower correlations. Independent of gating strategy a high correlation (r = 0.97) was observed when drug IC(50)'s were considered.

CONCLUSIONS

Flow cytometry and TaqMan RT-PCR may be used interchangeably to monitor the effects of candidate immunosuppressive drugs on cytokine mRNA production in lectin-stimulated whole blood.