Enrichment of FLI1 and RUNX1 mutations in families with excessive bleeding and platelet dense granule secretion defects

Abstract

Key Points• Novel FLI1 and RUNX1alterations were identified in 6 of 13 patients with excessive bleeding and platelet granule secretion defects.• Two FLI1 alterations predicting amino acid substitutions in the DNAbinding domain of FLI1 abolished transcriptional activity of FLI1.We analyzed candidate platelet function disorder genes in 13 index cases with a history of excessive bleeding in association with a significant reduction in dense granule secretion and impaired aggregation to a panel of platelet agonists. Five of the index cases also had mild thrombocytopenia. Heterozygous alterations in FLI1 and RUNX1, encoding Friend leukemia integration 1 and RUNT-related transcription factor 1, respectively, which have a fundamental role in megakaryocytopoeisis, were identified in 6 patients, 4 of whom had mild thrombocytopenia. Two FLI1 alterations predicting p.Arg337Trp and p.Tyr343Cys substitutions in the FLI1 DNA-binding domain abolished transcriptional activity of FLI1. A 4-bp deletion in FLI1, and 2 splicing alterations and a nonsense variation in RUNX1, which were predicted to cause haploinsufficiency of either FLI1 or RUNX1, were also identified. Our findings suggest that alterations in FLI1 and RUNX1 may be common in patients with platelet dense granule secretion defects and mild thrombocytopenia. (Blood. 2013; 122(25):4090-4093)

Whole exome sequencing identifies genetic variants in inherited thrombocytopenia with secondary qualitative function defects

“…Seven variants have previously been published as part of two separate publications from the UK-GAPP study group. 8,15 Classification of the 28 variants occurring within the known IT-related genes, following the interpretation guidelines set out by Richards et al, 17 revealed four variants to be "pathogenic", 13 to be "likely pathogenic" and 11 to be of "uncertain significance". Variants classified as "pathogenic" were either already known to be a genetic cause of IT; ANKRD26; c.-126T>G in F2.I and MYH9; p.Arg1165Cys in F9.I, or were predicted to be loss-of-function variants in genes for which a loss of function is known to cause disease; FLI1; p.Asn331Thr fs*4, in F4.I and F4.II and RUNX1; pTrp79* in P12.I.…”

“…An in-house flowcytometry assay was developed to assess platelet function in patients with platelet counts in platelet-rich plasma <1x10 8 /mL (n=22). Platelets from individuals with borderline platelet counts in platelet-rich plasma, between 1.0 and 1.5x10 8 /mL, were assessed using both assays (n=16).…”

“…Platelet function was assessed by light transmission aggregometry, including lumiaggregometry, for samples with platelet counts in platelet-rich plasma of >1x10 8 /mL (n=13). An in-house flowcytometry assay was developed to assess platelet function in patients with platelet counts in platelet-rich plasma <1x10 8 /mL (n=22).…”

“…WES and bioinformatics analysis were performed as described previously 8,15,16 ( Figure 1). The pathogenicity of variants was determined and called using the consensus guidelines as set out by the American College of Medical Genetics and Genomics and the Association for Molecular Pathology (ACMG guidelines).…”

“…However, some protein functions currently remain unknown (SLFN14 and GNE). [4][5][6][7][8][9] . Although our knowledge of the causes of IT continues to grow, presently a genetic diagnosis is only reported in approximately 50% of individuals.…”