Platelet activation in cystic fibrosis

Cystic fibrosis (CF) is caused by a mutation of the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR). We examined platelet function in CF patients because lung inflammation is part of this disease and platelets contribute to inflammation. CF patients had increased circulating leukocyte-platelet aggregates and increased platelet responsiveness to agonists compared with healthy controls. CF plasma caused activation of normal and CF platelets; however, activation was greater in CF platelets. Furthermore, washed CF platelets also showed increased reactivity to agonists. CF platelet hyperreactivity was incompletely inhibited by prostaglandin E(1) (PGE(1)). As demonstrated by Western blotting and reverse-transcriptase-polymerase chain reaction (RT-PCR), there was neither CFTR nor CFTR-specific mRNA in normal platelets. There were abnormalities in the fatty acid composition of membrane fractions of CF platelets. In summary, CF patients have an increase in circulating activated platelets and platelet reactivity, as determined by monocyte-platelet aggregation, neutrophil-platelet aggregation, and platelet surface P-selectin. This increased platelet activation in CF is the result of both a plasma factor(s) and an intrinsic platelet mechanism via cyclic adenosine monophosphate (cAMP)/adenylate cyclase, but not via platelet CFTR. Our findings may account, at least in part, for the beneficial effects of ibuprofen in CF

Excluding Digenic Inheritance of <i>PGAP2</i> and <i>PGAP3</i> Variants in Mabry Syndrome (OMIM 239300) Patient: Phenotypic Spectrum Associated with <i>PGAP2</i> Gene Variants in Hyperphosphatasia with Mental Retardation Syndrome-3 (HPMRS3)

We present a case report of a child with features of hyperphosphatasia with neurologic deficit (HPMRS) or Mabry syndrome (MIM 239300) with variants of unknown significance in two post-GPI attachments to proteins genes, PGAP2 and PGAP3, that underlie HPMRS 3 and 4. Background: In addition to HPMRS 3 and 4, disruption of four phosphatidylinositol glycan (PIG) biosynthesis genes, PIGV, PIGO, PIGW and PIGY, result in HPMRS 1, 2, 5 and 6, respectively. Methods: Targeted exome panel sequencing identified homozygous variants of unknown significance (VUS) in PGAP2 c:284A>G and PGAP3 c:259G>A. To assay the pathogenicity of these variants, we conducted a rescue assay in PGAP2 and PGAP3 deficient CHO cell lines. Results: Using a strong (pME) promoter, the PGAP2 variant did not rescue activity in CHO cells and the protein was not detected. Flow cytometric analysis showed that CD59 and CD55 expression on the PGAP2 deficient cell line was not restored by variant PGAP2. By contrast, activity of the PGAP3 variant was similar to wild-type. Conclusions: For this patient with Mabry syndrome, the phenotype is likely to be predominantly HPMRS3: resulting from autosomal recessive inheritance of NM_001256240.2 PGAP2 c:284A>G, p.Tyr95Cys. We discuss strategies for establishing evidence for putative digenic inheritance in GPI deficiency disorders