VWF-Gly2752Ser, a novel non-cysteine substitution variant in the CK domain, exhibits severe secretory impairment by hampering C-terminal dimer formation

BACKGROUND

Von Willebrand factor (VWF) is a multimeric glycoprotein that plays important roles in hemostasis and thrombosis. C-terminal interchain-disulfide bonds in the cystine knot (CK) domain are essential for VWF dimerization. Previous studies have reported that missense variants of cysteine in the CK domain disrupt the intrachain-disulfide bond and cause type 3 von Willebrand disease (VWD). However, type 3 VWD-associated noncysteine substitution variants in the CK domain have not been reported.

OBJECTIVE

To investigate the molecular mechanism of a novel non-cysteine variant in the CK domain, VWF c.8254 G>A (p.Gly2752Ser), which was identified in a patient with type 3 VWD as homozygous.

METHODS

Genetic analysis was performed by whole exome sequencing and Sanger sequencing. VWF multimer analysis was performed using SDS-agarose electrophoresis. VWF production and subcellular localization were analyzed using ex vivo endothelial colony forming cells (ECFCs) and an in vitro recombinant VWF (rVWF) expression system.

RESULTS

The patient was homozygous for VWF-Gly2752Ser. Plasma VWF enzyme-linked immunosorbent assay showed that the VWF antigen level of the patient was 1.2% compared with healthy subjects. A tiny amount of VWF was identified in the patient's ECFC. Multimer analysis revealed that the circulating VWF-Gly2752Ser presented only low molecular weight multimers. Subcellular localization analysis of VWF-Gly2752Ser-transfected cell lines showed that rVWF-Gly2752Ser was severely impaired in its ER-to-Golgi trafficking.

CONCLUSION

VWF-Gly2752Ser causes severe secretory impairment because of its dimerization failure. This is the first report of a VWF variant with a noncysteine substitution in the CK domain that causes type 3 VWD.

Vwf K1362A resulted in failure of protein synthesis in mice

Von Willebrand factor (VWF) is synthesized in megakaryocytes and endothelial cells (ECs) and has two main roles: to carry and protect coagulation factor VIII (FVIII) from degradation by forming VWF-FVIII complex; and to mediate platelet adhesion and aggregation at sites of vascular injury. Previous research using the HEK293 cell line revealed that the VWF K1362 mutation interacted directly with platelet glycoprotein Ib (GPIb). Vwf K1362A knock-in (KI) mice were therefore generated to verify the in vivo function of residue 1362 in binding to platelet GPIb. The Cre-loxP system was employed to introduce the Vwf K1362A mutation systemically in mice. In blood coagulation analysis, the VWF antigen (VWF:Ag) of Lys1362Ala KI homozygous (homo) mice was below the sensitivity of detection by enzyme-linked immunosorbent assay. FVIII activities (FVIII:C) were 47.9 ± 0.3 and 3.3 ± 0.3% (K1362A heterozygous (hetero) and K1362A KI homo mice, respectively) compared to wild-type mice. Immunohistochemical staining analysis revealed that VWF protein did not exist in ECs of K1362A KI homo mice. These results indicated that VWF protein synthesis of K1362A was impaired after transcription in mice. K1362 seems to represent a very important position not only for VWF function, but also for VWF synthesis in mice.

Impact of thrombolysis in acute ischaemic stroke without occlusion: an observational comparative study

BACKGROUND AND PURPOSE

The impact of intravenous recombinant tissue plasminogen activator (IV-rtPA) in patients with acute ischaemic stroke (AIS) but no arterial occlusion is currently a matter of debate. This study aimed to assess functional outcome of such patients with respect to IV-rtPA use.

METHODS

A retrospective case-control analysis was performed comparing the outcome of AIS patients without arterial occlusion with or without IV-rtPA use. Patients were selected from prospective consecutive observational registries of five European university hospitals. The primary study outcome was excellent outcome at 3 months after stroke, as defined by a modified Rankin Scale (mRS) 0-1.

RESULTS

A total of 488 patients without arterial occlusion documented by angiography were included in the present study; 300 received IV-rtPA and 188 did not. No between-group difference was found for excellent outcome before and after adjustment for baseline characteristics (adjusted odds ratio for no IV-rtPA use 0.79, 95% confidence interval 0.51-1.24, P = 0.31). Similar results were found for favourable outcome (defined as a 90-day mRS of 0-2) whereas a higher rate of early neurological improvement was found in IV-rtPA-treated patients (adjusted odds ratio 1.99; 95% confidence interval 1.29-3.07, P = 0.002). Sensitivity analyses yielded similar results.

CONCLUSIONS

Our study suggests that AIS patients without visible arterial occlusion treated with IV-rtPA may have no better outcome at 3 months than those untreated. However, only a randomized controlled trial would provide a definitive answer about the impact of rtPA in acute stroke patients without occlusion. Until then, these patients should be treated by rtPA as recommended.

Down-regulation of PROS1 gene expression by 17beta-estradiol via estrogen receptor alpha (ERalpha)-Sp1 interaction recruiting receptor-interacting protein 140 and the corepressor-HDAC3 complex

Pregnant women show a low level of protein S (PS) in plasma, which is known to be a risk for deep venous thrombosis. 17Beta-estradiol (E(2)), an estrogen that increases in concentration in the late stages of pregnancy, regulates the expression of various genes via the estrogen receptor (ER). Here, we investigated the molecular mechanisms behind the reduction in PS levels caused by E(2) in HepG2-ERalpha cells, which stably express ERalpha, and also the genomic ER signaling pathway, which modulates the ligand-dependent repression of the PSalpha gene (PROS1). We observed that E(2) repressed the production of mRNA and antigen of PS. A luciferase reporter assay revealed that E(2) down-regulated PROS1 promoter activity and that this E(2)-dependent repression disappeared upon the deletion or mutation of two adjacent GC-rich motifs in the promoter. An electrophoretic mobility shift assay and DNA pulldown assay revealed that the GC-rich motifs were associated with Sp1, Sp3, and ERalpha. In a chromatin immunoprecipitation assay, we found ERalpha-Sp protein-promoter interaction involved in the E(2)-dependent repression of PROS1 transcription. Furthermore, we demonstrated that E(2) treatment recruited RIP140 and the NCoR-SMRT-HDAC3 complex to the PROS1 promoter, which hypoacetylated chromatin. Taken together, this suggested that E(2) might repress PROS1 transcription depending upon ERalpha-Sp1 recruiting transcriptional repressors in HepG2-ERalpha cells and, consequently, that high levels of E(2) leading to reduced levels of plasma PS would be a risk for deep venous thrombosis in pregnant women.

L1503R is a member of group I mutation and has dominant-negative effect on secretion of full-length VWF multimers: an analysis of two patients with type 2A von Willebrand disease

Type 2A von Willebrand disease (VWD) is characterized by decreased platelet-dependent function of von Willebrand factor (VWF); this in turn is associated with an absence of high-molecular-weight multimers. Sequence analysis of the VWF gene from two unrelated type 2A VWD patients showed an identical, novel, heterozygous T-->G transversion at nucleotide 4508, resulting in the substitution of L1503R in the VWF A2 domain. This substitution, which was not found in 60 unrelated normal individuals, was introduced into a full-length VWF cDNA and subsequently expressed in 293T cells. Only trace amount of the mutant VWF protein was secreted but most of the same was retained in 293T cells. Co-transfection experiment of both wild-type and mutant plasmids indicated the dominant-negative mechanism of disease development; as more of mutant DNA was transfected, VWF secretion was impaired in the media, whereas more of VWF was stored in the cell lysates. Molecular dynamic simulations of structural changes induced by L1503R indicated that the mean value of all-atom root-mean-squared-deviation was shifted from those with wild type or another mutation L1503Q that has been reported to be a group II mutation, which is susceptible to ADAMTS13 proteolysis. Protein instability of L1503R may be responsible for its intracellular retention and perhaps the larger VWF multimers, containing more mutant VWF subunits, are likely to be mal-processed and retained within the cell.

Molecular defects associated with antithrombin deficiency and dilated cardiomyopathy in a Japanese patient

OBJECTIVE

The molecular basis for the antithrombin (AT) deficiency and dilated cardiomyopathy (DCM) combined in a Japanese patient was investigated.

METHODS

We analyzed candidate genes -SERPINC1 for AT deficiency, and TNNT2 and LMNA for DCM. In addition, we examined the characteristics of recombinant mutant AT and evaluated the LMNA mutation associated with DCM by molecular modeling.

RESULTS

Genome sequencing of SERPINC1 revealed a C-to-A transversion in exon 6 that resulted in a p.Pro439Thr mutation of AT, which was previously reported as a pleiotropic effect type II AT deficiency (AT Budapest5). However, expression experiments with recombinant 439Thr-AT showed normal heparin affinity, slightly reduced secretion, and low specific activity, which suggested that this mutation exhibits an intermediate feature of type I and type II AT deficiencies. In a survey of gene abnormalities causing DCM, we found no causative gene defect in TNNT2; however, we identified a G-to-C transversion in LMNA that resulted in a novel p.Asp357His mutation in lamin A/C. This acidic-to-basic residue substitution might have impaired the head-to-tail association of two lamin dimers leading to DCM. Further, we identified both SERPINC1 and LMNA mutations in the patient's daughter and son, both of whom had AT deficiency. These data suggested that a p.Pro439Thr mutation in SERPINC1 and a p.Asp357His mutation in LMNA might have cosegregated in this family, associated with AT deficiency and DCM, respectively.

CONCLUSIONS

We identified missense mutations in SERPINC1 and LMNA genes to be associated with AT deficiency and DCM, respectively, which might have cosegregated in the family of the patient.

Tubular seminoma of the testis

A case of tubular seminoma in a 33-year-old man is reported. The tumor occurred in his right testis, measuring 7 x 6 x 6 cm in size. Microscopically, most of the tumor cells were arranged in solid or hollow tubular patterns. The tumor cells had round nuclei with vesicular chromatin and clear or granular cytoplasm, characteristic features of seminoma cells. A classic seminoma component and intratubular atypical germ cells occupying approximately 5% of the tumor area were noted. Immunohistochemical staining revealed that the tumor cells were diffusely placental alkaline phosphatase and vimentin positive, and focally cytokeratin positive. These findings are consistent with a tubular seminoma. The differential diagnoses are discussed.

Solitary fibrous tumor of the prostate

A case of solitary fibrous tumor of the prostate is reported. A 42-year-old man had been complaining of difficult voiding and constipation for 8 years. Urological and radiological examinations showed a large prostatic mass, and a total cystectomy and prostatectomy were performed. The tumor was 14 x 13 x 11 cm in size, solid with a fibromuscular capsule, and gray-tan in color. Histologically, the tumor was composed of short spindle-shaped and polygonal cells with mild to moderate nuclear atypia, predominantly arranged in the so-called 'patternless pattern' in a fibrocollagenous background. Mitoses were occasionally seen. Vascular invasion was also observed. Immunohistochemically, these cells were strongly positive for CD34 and vimentin, and occasionally for desmin. The maximum Ki-67 labeling index of the tumor cells was 4.5%. These findings are consistent with a solitary fibrous tumor. To our knowledge, this is the first report of a solitary fibrous tumor of the prostate in the English medical literature.

Rupture of pararenal pseudocyst in a patient with Down's syndrome

A rare case of Down's syndrome with spontaneous rupture of a pararenal pseudocyst has been reported. The rupture of the pararenal pseudocyst was treated nonsurgically. The presence of this cyst in conjunction with Down's syndrome may be due, in part, to muscular hypotonia.

[Studies on the usefulness of a long-term, high-dose treatment of methylcobalamin in patients with oligozoospermia]

Methylcobalamin (CH3-B12) was administrated in a dose of 6 mg per day (group A, 16 cases) or 12 mg per day (group B, 23 cases) for 16 weeks to patients with oligozoospermia. There was no difference between group A and group B regarding vitamin B12 concentrations in the serum or seminal fluid. CH3-B12 appeared to be transported to seminal fluid very efficiently. However, results from group A and group B did not differ with respect to this parameter. The efficacy rate for group A was 37.5% and that for group B was 39.1%. From these results, it was concluded that a long-term, high dose treatment of CH3-B12 was useful for the treatment of patients with oligozoospermia. Since the efficacy rates were not different between the two groups, 6 mg per day would be the recommended dose. Clinical adverse reactions were observed in one patient in each group. Drug-related laboratory adverse reactions were observed in only one patient in group B.

[Combined administration of human chorionic gonadotropin and human menopausal gonadotropin in idiopathic male infertility]

Clinical experiences of HCG-HMG therapy for 56 cases of idiopathic male infertility were studied. Serum levels of LH, FSH and testosterone were measured before therapy. Sperm density improved in 25% of all cases. In the low FSH group, sperm density showed a high rate of improvement. The basal FSH was the best indicator to predict the prognosis of fertility. Additional measurements of LH and FSH response to GnRH gave further information on the prospect of fertility.