molecular characterisation of variants on noncoding rna genes in the x-inactivation centre from three symptomatic carriers with severe haemophilia a (ha) and extremely skewed x-chromosome inactivation

CLAUDIA P. RADIC; MIGUEL M. ABELLEYRO; VANINA D. MARCHIONE; LAURA PRIMIANI; CANDELA, MIGUEL; DANIELA NEME; MIGUEL DE TEZANOS PINTO; LILIANA C. ROSSETTI; CARLOS D. DE BRASI

Berlin

Congreso; XXVI International Society on Thrombosis and Hemostasis Congress; 2017

International Society on Thrombosis and Hemostasis

Background: Random X­chromosome inactivation (XCI) of one X­chromosome in females achievesdosage equivalency for X­linked genes with males. Non­coding RNA genes were described in the X-chromosome inactivation centre (XIC, Xq13) associated with the inactivation process: XIST (X­inactivespecific transcript), JPX (just proximal to XIST) and FTX (five prime to XIST). We hypothesized thatSNPs (single nucleotide polymorphism) may modify XIC gene expression or function impacting its allelicability to inactivate.Aims: Study the association between SNP variants on relevant sequences of XIST, JPX and FTX withextremely skewed XCI in three symptomatic carriers with severe HA.Methods: An extensive genetic variant screening of XIST, JPX and FTX was performed in leukocyte-extracted DNA samples from three symptomatic carriers with severe HA and extremely skewed XCI(97­100%) and 11 controls with random XCI (50­55%) by CSGE (conformation sensitive gelelectrophoresis) and Sanger sequencing. Symptomatic carriers were previously F8 genotyped asheterozygous for severe HA mutations and the phenotypic expression resulted from their association incis with the preferential X­inactive (Radic et al., JTH 2015,13:530­9).Results: Analysis of the non­coding RNA genes on XIC from the three cases showed no deleteriousmutations, but 12 SNP variants out of 161 annotated in public databases: 5/80 SNPs on XIST, 4/46 onFTX and 3/35 JPX in heterozygous status (Table 1). Despite this observation, these variants were alsofound in controls (Table 1).Case #15 Case #29 Case #31 Controls (n)F8 genotypeHeterozygousc.4241C>AHeterozygousc.4825dupAHeterozygousc.325A>GCarriers or NotFVIII:C [IU/dl] 1.5 1.2