Qiulan Ding

Impact of polymorphisms in genes involved in autoimmune disease on inhibitor development in Chinese patients with haemophilia A

One of the most severe and important complication in the treatment of haemophilia A (HA) patients is the formation of inhibitors. The mechanism that leads to factor (F)VIII inhibitor formation is complicated. Both genetic and environmental factors have been mentioned to play decisive roles. Recently, polymorphisms in the genes encoding interleukin-10 (IL-10), tumour necrosis factor-alpha (TNF-α), cytotoxic T-lymphocyte antigen-4 (CTLA-4), have been suggested to be contributing determinants of the inhibitor risk. In order to investigate the influence of the single nucleotide polymorphisms (SNPs) in the genes encoding for cytokines to the inhibitors development in Chinese HA patients, we genotyped 10 SNPs with high heterozygote rates in Chinese and a CA repeat microsatellite at the gene loci IL-10 as well in a separate, unrelated case-controlled cohort of 122 affected HA patients; 63 with inhibitors and 59 without inhibitors. The particular SNPs included in this study were as follows: -592C/A and -819C/T in IL-10, -590C/T in IL-4, -318C/T and 49A/G in CTLA-4, -827C/T in TNF-α, -1112C/T and 2044G/A in IL-13, 874A/T in interferon (IFN)-γ and -295T/C in IL-16. Our results demonstrated that -819T and -592A alleles in IL-10 were observed more frequently in patients with inhibitors. This indicated that -819C/T and -592A/C in IL-10 may influence the inhibitors development in HA patients. Furthermore, we concluded that the haplotype in IL-10 (TA, CA, CC at positions -819 and -582, respectively) may predispose FVIII inhibitor development in HA patients. In conclusion, the data reported in our study clearly highlight the participation of IL-10 in inhibitors formation in Chinese HA patients.

Characterisation of large F9 deletions in seven unrelated patients with severe haemophilia B

Large deletions in the F9 gene are detected in approximately 5% of patients with severe haemophilia B, but only a few deletion breakpoints have been characterised precisely until now. In this study we identified a total of seven large F9 deletions in the index patients and nine female carriers by the AccuCopy technique. We also successfully characterised the exact breakpoints for each large deletion including four deletions encompassing the entire F9 gene by the genome walking method combined with primer walking strategy. The extents of deletion regions ranged from 11.1 to 884 kb. Microhomologies ranged from 2 to 6 bp were identified in the breakpoint junctions of six deletions. The other deletion occurred between two highly homologous sequences of the same long interspersed nuclear element 1 (LINE/L1). Non-homologous end joining (NHEJ) and microhomology-mediated break-induced replication (MMBIR) may be the main causative mechanisms for the six large deletions with microhomologies. Non-allelic homologous recombination (NAHR) may mediate the deletion occurred between the two tandem LINEs in the other large deletion. Repetitive elements and non-B DNA forming motifs identified in the junction regions may contribute to DNA breakage leading to large deletions.

Maternal chromosome 4 heterodisomy/isodisomy and Bβ chain Trp323X mutation resulting in severe hypodysfibrinogenaemia.

We report a rare case of congenital hypodysfibrinogenaemia due to maternal uniparental disomy of chromosome 4 (mat UPD 4) and a maternally inherited novel nonsense mutation Trp323X in the fibrinogen Bβ chain (FGB) gene. Western blot analysis of patients plasma revealed an abnormal fibrinogen which consisted of truncated Bβ chain and normal Aα and γ chains. Patients clinical history and laboratory evidence are presented. Microsatellite genotyping analysis revealed a mixed nature of heterodisomy and isodisomy along chromosome 4. High density SNP genotyping array analysis further confirmed the mat UPD 4 and defined two segments of chromosome 4 (4pter-p15.33 and 4q31.21-4q32.3) as maternal isodisomy (iUPD4) and the remaining regions as maternal heterodisomy (hUPD4), with the FGB gene carrying the mutation resided in the iUPD4 region on the long (q) arm. It was predicted that the segmental nature of iUPD and hUPD was caused by three recombination events at positions around 167.96 cM, 145.51 cM and 14.40 cM on chromosome 4 followed by a meiosis I non-disjunction. This case is clinically and molecularly unique and offers an opportunity for understanding novel mechanisms of congenital hypodysfibrinogenaemia associated with complex UPD and fibrinogen secretion.

Occurence of haemophilia A and B in a Chinese family with mosaicism of the F9 gene mutation in the HB index's maternal grandfather

Occurence of haemophilia A and B in a Chinese family with mosaicism of the F9 gene mutation in the HB indexs maternal grandfather -

Clinical features and molecular basis of 102 Chinese patients with congenital dysfibrinogenemia

INTRODUCTION Congenital dysfibrinogenemia (CD) is a rare qualitative disorder of fibrinogen (Fg) with heterogeneous clinical manifestations. We aimed to analyze clinical phenotype and molecular basis of 102 Chinese CD patients and to evaluate the application of thromboelastography (TEG). MATERIALS AND METHODS Clinical manifestations were recorded and quantified using the consensus ISTH bleeding assessment tool. Kaolin activated TEG and functional Fg TEG were applied in 30 patients. Genetic analysis of Fg genes were performed by direct sequencing. RESULTS 27.5% patients experienced bleeding, 3.9% had thrombosis and 68.6% were asymptomatic. Females were more prone to experience bleeding (P=0.01). Significant difference (P<0.05) in TEG results were found between patients with hot-spot mutations at AαArg35(16) and γArg301(275), but were not identified between patients with and without bleeding. Normal TEG results were found in patients with mutations at AαArg35(16), AαPro37(18) or AαArg38(19). Six novel mutations were identified, including AαGly33(14)del, AαAsp57(38)_Trp60(41)delIVS2+1_+2GTdel, AαPhe742(723)Tyr, γAsn334(308)Thr, γGly335(309)Cys and γTrp395(369)Leu. CONCLUSIONS CD patients have similar clinical manifestations and hot-spot mutations worldwide with no ethnic difference. TEG results could not indicate the bleeding risk in patients, but priority of mutation screening at thrombin cleavage site or polymerization site on Aа chain may be given if TEG results are normal.

Clinical and genetic features of protein C deficiency in 23 unrelated Chinese patients

In this study, we investigated the clinical and genetic features of protein C deficiency in the Chinese population. A total of 23 symptomatic patients with protein C deficiency were identified by thrombophilic assays. Detailed clinical data about the patients with respect to their personal and family history of venous thromboembolism (VTE) were collected. Mutational analysis was then performed by direct sequencing of the protein C gene (PROC) in the patients and their family members. Of the 23 patients, 30.4% (7/23) had additional risk factors, 51.2% (12/23) suffered from recurrent thrombotic episodes, and 50.0% (6/12) of the patients with recurrent thrombosis had more than one heterozygous mutation in PROC itself or combined with protein S gene (PROS). The sex distribution of male:female was 19:4 in the 23 symptomatic patients and 10:2 in the 12 recurrent patients. Almost all patients (22/23) had lower extremity deep vein thrombosis (DVT) and one had pulmonary embolism (PE) only. A total of 15 different causative mutations were identified from the 23 subjects with 6 (40.0%) of the mutations being novel. Among the mutations identified, the Arg147Trp substitution was hotspot mutation in the Chinese population with a high frequency of 43.5%. Our finding suggests that complex genotypes of PROC or combined with protein S deficiency are primarily responsible for an increased risk of recurrent VTE. Our data further provides a framework for correlating the clinical pathogenesis of protein C deficiency to ethnic backgrounds in the Chinese population.

Molecular mechanisms of antithrombin deficiency in two Chinese families One novel and one recurrent point mutation in the antithrombin gene causing venous thrombosis

We investigated the molecular mechanisms responsible for type I congenital antithrombin (AT) deficiency in two unrelated Chinese pedigrees manifesting multiple site venous thrombosis. Phenotype analysis showed both probands had almost 50% of normal AT levels. Direct sequencing of amplified DNA revealed 2757C > T in proband 1 and 13328G > A in proband 2, predicting a heterozygous Thr98Ile (T981) and Ala404Thr (A404T), respectively. No proband had 20210A allele or factor V Leiden mutation. Transient expression of complementary DNA coding for the mutations in COS-7 cells showed impaired secretion of the mutant molecules. Real-time quantitative PCR indicated that the mutant AT mRNA was transcribed at a similar or even higher level as that of wild-type (wt). Pulse-chase labeling studies suggested both AT variants did not accumulate, but degraded intracellularly. Immunohistochemical staining of the transfected cells revealed that CHO cells expressing the AT-198 mutant were stained diffusely without perinuclear enhancement and cells expressing AT-T404 mutant mainly in the whole cytoplasm with weaker perinuclear enhancement. We conclude that the impaired secretion of the mutant AT molecules, due to intracellular degradation, is the molecular pathogenesis of AT deficiency caused by T981 and A404T mutation for the two families, respectively.

Six novel missense mutations causing factor X deficiency and application of thrombin generation test

INTRODUCTION Inherited factor X (FX) deficiency is a rare hemorrhagic condition characterized by a variable clinical presentation weakly correlating with laboratory phenotype and genotype. Thrombin generation test (TGT) offers potential clinical advantages in the evaluation of hypocoagulable states. MATERIALS AND METHODS Five FX assays were performed using clotting, chromogenic and immunological methods. The factor X gene (F10) defects were analyzed by direct sequencing. Thrombin generation (TG) was measured using a standard procedure with commercial reagents at 1 pM and 5 pM of tissue factor (TF). The influence of contact activation on TG at the two TF concentrations was analyzed by the addition of corn trypsin inhibitor (CTI). RESULTS Seven missense mutations were identified in the F10 of the four probands with FX deficiency, six of which (Ser425Pro, Ala-29Pro, Phe324Leu, Ala235Thr, Cys111Arg and Met362Thr) were novel and associated with type I FX deficiency. TG measurements at 1 pM TF need the addition of CTI in both healthy individuals and FX-deficient patients. TG parameters of ETP, Peak and Rate correlated well with the FX:C levels and the clinical expressions of the FX-deficient patients at 1 pM TF with CTI. There is a higher sensitivity for FX deficiency at 1 pM TF compared with 5 pM TF in FX-deficient patients. CONCLUSIONS TGT may serve as a useful laboratory tool to assess the individual clinical manifestation of the patients with FX deficiency and 1 pM TF concentration in the presence of CTI is recommended.

Molecular basis and thrombotic manifestations of antithrombin deficiency in 15 unrelated Chinese patients

INTRODUCTION Antithrombin (AT) deficiency is associated with an increasing risk of thrombosis. MATERIALS AND METHODS 15 unrelated patients with AT deficiency defined by thrombophilic assays were recruited and detailed clinical information about patients, focusing on the personal and family history of thromboembolism (TE), were recorded. Mutation analysis was performed by direct sequencing of an AT gene (SERPINC1) in the patients and their family members. RESULTS A total of 15 heterozygous causative mutations, each being identified in one family, were identified. Five mutations (33.3%) were reported here for the first time, including three null mutations (Ser36X, Lys70X and Try307X) and two missense mutations (Phe123Cys and Leu340Phe) probably impairing the structural integrity and stability of protein based on the AT structural analysis. Of the 15 patients, 33.3% (5/15) had additional risk factors and only one patient presented with additional genetic alteration causing an early onset of thrombosis. Fourteen patients (93.9%) suffered from multisite recurrent thrombotic episodes after a first episode of thrombosis. 93.3% of the patients experienced deep vein thrombosis (DVT) and 40.0% presented with mesenteric venous thrombosis (MVT). In addition, both venous and arterial thrombosis was present in two unrelated patients. 51.0% subjects with AT deficiency in the 15 unrelated pedigrees experienced TE events. CONCLUSIONS Prophylactic anticoagulation may be suggested in AT-deficient patients to avoid the recurrent and multisite thrombosis. The association of primary MVT and AT deficiency is highlighted.

Haemophilia A in two unrelated females due to F8 gene inversions combined with skewed inactivation of X chromosome

Haemophilia A in two unrelated females due to F8 gene inversions combined with skewed inactivation of X chromosome -