Retrospective analysis of the perioperative outcome in living donor kidney transplantation with multiple renal arteries: does accessory vessel ligation affect the outcome?

PURPOSE: Accurate surgical reconstruction of arterial vascular supply is a crucial part of living kidney transplantation (LDKT). The presence of multiple renal arteries (MRA) in grafts can be challenging. In the present study, we investigated the impact of ligation versus anastomosis of small accessory graft arteries on the perioperative outcome. METHODS: Clinical and radiological outcomes of 51 patients with MRA out of a total of 308 patients who underwent LDKT with MRA between 2011 and 2020 were stratified in two groups and analyzed. In group 1 (20 patients), ligation of accessory arteries (ARAs) and group 2 (31 patients) anastomosis of ARAs was performed. RESULTS: Significant differences were observed in the anastomosis-, surgery-, and warm ischemia time (WIT) in favor of group 1. Students t-test showed comparable serum creatinine levels of 2.33 (± 1.75) to 1.68 (± 0.83) mg/dL in group 1 and 2.63 (± 2.47) to 1.50 (± 0.41) mg/dL in group 2, were seen from 1 week to 1 year after transplant. No increased rates of Delayed graft function (DGF), primary transplant dysfunction and transplant rejection were seen, but graft loss and revision rates were slightly higher when the ARAs were ligated. Analysis of Doppler sonography revealed that segmental perfusion deficits tend to regenerate during the clinical course. CONCLUSION: Ligation of smaller accessory renal arteries may not affect the outcome of living kidney transplantation, except for a minor increase in the reoperation rate. Segmental perfusion deficits of the graft seem to regenerate in most cases as seen in Doppler sonography.

Transplant nephrectomy: indication, surgical approach and complications-experiences from a single transplantation center.

PURPOSE: Management of a failed kidney allograft, and the question whether it should be removed is a challenging task for clinicians. The reported risks for transplant nephrectomy (TN) vary, and there is no clear recommendation on indications or surgical approach that should be used. This study gives an overview of indications, compares surgical techniques, and identifies risk factors for higher morbidity. METHODS: Retrospective analysis was conducted on all transplant nephrectomies performed between 2005 and 2020 at Charité Hospital Berlin, Department of Urology. Patient demographics, laboratory parameters, graft survival data, indication for TN, and surgical complications were extracted from medical reports. RESULTS: A total of 195 TN were performed, with graft intolerance syndrome being the most common indication in 52 patients (26.7%), acute rejection in 36 (18.5%), acute infection in 30 (15.4%), and other reasons to stop immunosuppression in 26 patients (13.3%). Rare indications were vascular complications in 16 (8.2%) and malignancies in the allograft in six (3.1%) cases. Extracapsular surgical approach was significantly more often used in cases of vascular complications and earlier allograft removal, but there was no difference in complication rates between extra- and intracapsular approach. Acute infection was identified as an independent risk factor for a complication grade IIIb or higher according to Clavien-Dindo classification, with a HR of 12.3 (CI 2.2-67.7; p = 0.004). CONCLUSION: Transplant nephrectomy should only be performed when there is a good indication, and non-elective surgery should be avoided, when possible, as it increases morbidity.

Molecular determinants of the factor VIII/von Willebrand factor complex revealed by BIVV001 cryo-electron microscopy.

Interaction of factor VIII (FVIII) with von Willebrand factor (VWF) is mediated by the VWF D'D3 domains and thrombin-mediated release is essential for hemostasis after vascular injury. VWF-D'D3 mutations resulting in loss of FVIII binding are the underlying cause of von Willebrand disease (VWD) type 2N. Furthermore, the FVIII-VWF interaction has significant implications for the development of therapeutics for bleeding disorders, particularly hemophilia A, in which endogenous VWF clearance imposes a half-life ceiling on replacement FVIII therapy. To understand the structural basis of FVIII engagement by VWF, we solved the structure of BIVV001 by cryo-electron microscopy to 2.9 Å resolution. BIVV001 is a bioengineered clinical-stage FVIII molecule for the treatment of hemophilia A. In BIVV001, VWF-D'D3 is covalently linked to an Fc domain of a B domain-deleted recombinant FVIII (rFVIII) Fc fusion protein, resulting in a stabilized rFVIII/VWF-D'D3 complex. Our rFVIII/VWF structure resolves BIVV001 architecture and provides a detailed spatial understanding of previous biochemical and clinical observations related to FVIII-VWF engagement. Notably, the FVIII acidic a3 peptide region (FVIII-a3), established as a critical determinant of FVIII/VWF complex formation, inserts into a basic groove formed at the VWF-D'/rFVIII interface. Our structure shows direct interaction of sulfated Y1680 in FVIII-a3 and VWF-R816 that, when mutated, leads to severe hemophilia A or VWD type 2N, respectively. These results provide insight on this key coagulation complex, explain the structural basis of many hemophilia A and VWD type 2N mutations, and inform studies to further elucidate how VWF dissociates rapidly from FVIII upon activation.

BIVV001, a new class of factor VIII replacement for hemophilia A that is independent of von Willebrand factor in primates and mice.

Factor VIII (FVIII) replacement products enable comprehensive care in hemophilia A. Treatment goals in severe hemophilia A are expanding beyond low annualized bleed rates to include long-term outcomes associated with high sustained FVIII levels. Endogenous von Willebrand factor (VWF) stabilizes and protects FVIII from degradation and clearance, but it also subjects FVIII to a half-life ceiling of ∼15 to 19 hours. Increasing recombinant FVIII (rFVIII) half-life further is ultimately dependent upon uncoupling rFVIII from endogenous VWF. We have developed a new class of FVIII replacement, rFVIIIFc-VWF-XTEN (BIVV001), that is physically decoupled from endogenous VWF and has enhanced pharmacokinetic properties compared with all previous FVIII products. BIVV001 was bioengineered as a unique fusion protein consisting of a VWF-D'D3 domain fused to rFVIII via immunoglobulin-G1 Fc domains and 2 XTEN polypeptides (Amunix Pharmaceuticals, Inc, Mountain View, CA). Plasma FVIII half-life after BIVV001 administration in mice and monkeys was 25 to 31 hours and 33 to 34 hours, respectively, representing a three- to fourfold increase in FVIII half-life. Our results showed that multifaceted protein engineering, far beyond a few amino acid substitutions, could significantly improve rFVIII pharmacokinetic properties while maintaining hemostatic function. BIVV001 is the first rFVIII with the potential to significantly change the treatment paradigm for severe hemophilia A by providing optimal protection against all bleed types, with less frequent doses. The protein engineering methods described herein can also be applied to other complex proteins.

Comparison of PHI and PHI Density for Prostate Cancer Detection in a Large Retrospective Caucasian Cohort.

BACKGROUND: Beyond prostate-specific antigen (PSA), other biomarkers for prostate cancer (PCa) detection are available and need to be evaluated for clinical routine. OBJECTIVE: The aim of the study was to evaluate the Prostate Health Index (PHI) density (PHID) in comparison with PHI in a large Caucasian group >1,000 men. METHODS: PHID values were used from available patient data with PSA, free PSA, and [-2]pro-PSA and prostate volume from 3 former surveys from 2002 to 2014. Those 1,446 patients from a single-center cohort included 701 men with PCa and 745 with no PCa. All patients received initial or repeat biopsies. The diagnostic accuracy was evaluated by receiver operating characteristic (ROC) curves comparing area under the ROC curves (AUCs), precision-recall approach, and decision curve analysis (DCA). RESULTS: PHID medians differed almost 2-fold between PCa (1.12) and no PCa (0.62) in comparison to PHI (48.6 vs. 33; p always <0.0001). However, PHID and PHI were equal regarding the AUC (0.737 vs. 0.749; p = 0.226), and the curves of the precision-recall analysis also overlapped in the sensitivity range between 70 and 100%. DCA had a maximum net benefit of only ∼5% for PHID versus PHI between 45 and 55% threshold probability. Contrary, in the 689 men with a prostate volume ≤40 cm3, PHI (AUC 0.732) showed a significant larger AUC than PHID (AUC 0.69, p = 0.014). CONCLUSIONS: Based on DCA, PHID had only a small advantage in comparison with PHI alone, while ROC analysis and precision-recall analysis showed similar results. In smaller prostates, PHI even outperformed PHID. The increment for PHID in this large Caucasian cohort is too small to justify a routine clinical use.

Congenital oesophageal stenosis in oesophageal atresia: underrecognised and often missed?

PURPOSE: Congenital oesophageal stenosis (COS) is characterised by an intrinsic oesophageal narrowing that is present, but not necessarily symptomatic at birth. Small studies report an association of COS with oesophageal atresia (OA) in up to 14% of OA cases. Although OA is usually appreciated shortly after birth, the diagnosis of a concomitant COS is frequently delayed. This risk may be increased with the current movement away from routine postoperative upper gastrointestinal (GI) contrast study following OA repair. We performed a systematic review of the literature to assess the timing of diagnosis of COS in patients with COS and OA and how this impacted on patient outcomes. METHODS: A systematic review in accordance with PRISMA guidelines was undertaken. Only patients with OA associated with COS were included. Delayed diagnosis was defined as presentation > 1 month of age. RESULTS: 14 full-text studies with a total of 131 patients were included. Diagnosis of COS was delayed in 62/131 (47%) patients. These children presented with symptoms of dysphagia and aspiration at a median age of 13.5 months (IQR 7-30 months). In total, 18/131 patients were identified at the initial operation, due to difficulty passing a tube distally into the stomach. The data on timing of contrast studies were provided in 60/131 (46%) patients. A routine postoperative contrast study was performed in 39/60 (65%) of these, of which COS was identified immediately in 28/39 (72%). A diagnosis of COS could also be made on retrospective review of the early contrast study in a further 6/39 patients, giving an overall sensitivity of 87%. CONCLUSION: The association of COS and OA may be underrecognised and diagnosis delayed if routine contrast study is not performed. Contrast studies, performed in the neonatal period are effective at detecting a concomitant COS (sensitivity > 87%). This review supports routine early contrast study after OA repair with specific consideration of the presence of COS.

Gastrostomies in children requiring long-term ventilation.

PURPOSE: Children requiring long-term ventilation (LTV) via tracheostomy often require enteral tube feeding. We sought to investigate what proportion of these children underwent gastrostomy insertion to inform decision making at time of tracheostomy formation. METHODS: A retrospective review of all children commenced on LTV via a tracheostomy at Royal Manchester Children's Hospital over a 9-year period (2012-2020). Data are presented as median [IQR]. RESULTS: Forty-one LTV patients had tracheostomy insertion with an average age of 167 days [101-604]. Reasons for tracheostomy insertion were upper airway obstruction (18), central neurological condition (7), neuromuscular condition (12) and lower respiratory tract disease (4). Twenty-two patients were born preterm and chronic lung disease of prematurity was a contributory factor in their requirement for LTV. Eight children had gastrostomies inserted prior to tracheostomy formation. A further 22 children had a gastrostomy inserted at an average of 139 days [99-227] following tracheostomy. Four children remained on nasogastric feed and the rest were fed orally. Seventy-three percentage of LTV children with tracheostomy were gastrostomy fed. Neither indication for LTV nor prematurity predicted whether a child was gastrostomy fed. CONCLUSION: The large majority of children requiring LTV are tube fed and gastrostomy insertion should be considered at time of formation of tracheostomy.

The von Willebrand factor D'D3 assembly and structural principles for factor VIII binding and concatemer biogenesis.

D assemblies make up half of the von Willebrand factor (VWF), yet are of unknown structure. D1 and D2 in the prodomain and D'D3 in mature VWF at Golgi pH form helical VWF tubules in Weibel Palade bodies and template dimerization of D3 through disulfides to form ultralong VWF concatemers. D'D3 forms the binding site for factor VIII. The crystal structure of monomeric D'D3 with cysteine residues required for dimerization mutated to alanine was determined at an endoplasmic reticulum (ER)-like pH. The smaller C8-3, TIL3 (trypsin inhibitor-like 3), and E3 modules pack through specific interfaces as they wind around the larger, N-terminal, Ca2+-binding von Willebrand D domain (VWD) 3 module to form a wedge shape. D' with its TIL' and E' modules projects away from D3. The 2 mutated cysteines implicated in D3 dimerization are buried, providing a mechanism for protecting them against premature disulfide linkage in the ER, where intrachain disulfide linkages are formed. D3 dimerization requires co-association with D1 and D2, Ca2+, and Golgi-like acidic pH. Associated structural rearrangements in the C8-3 and TIL3 modules are required to expose cysteine residues for disulfide linkage. Our structure provides insight into many von Willebrand disease mutations, including those that diminish factor VIII binding, which suggest that factor VIII binds not only to the N-terminal TIL' domain of D' distal from D3 but also extends across 1 side of D3. The organizing principle for the D3 assembly has implications for other D assemblies and the construction of higher-order, disulfide-linked assemblies in the Golgi in both VWF and mucins.

Does the Side Matter? A Retrospective Cohort Study Comparing Left and Right Pure Laparoscopic Donor Nephrectomies.

OBJECTIVES: Right laparoscopic donor nephrectomy (RLDN) is no longer regarded inferior to left LDN (LLDN). However, this knowledge is based on many studies suffering from inherent learning curves, center-specific imbalances, and different laparoscopic techniques. METHODS: Pure LDNs at a high-volume referral center from 2011 to 2016 were retrospectively analyzed. Patient, graft characteristics, outcomes of LDNs, and corresponding open kidney transplantations were compared between LLDN and RLDN including a follow-up. RESULTS: 160 (78.4%) LLDNs and 44 (21.6%) RLDNs only differed regarding graft characteristics, as more right grafts had multiple veins (34.1 vs. 6.9%, p < 0.001) and worse scintigraphic function (44 vs. 51%, p < 0.001). RLDNs were shorter (201 vs. 220 min, p = 0.032) with longer warm ischemia time (165 vs. 140 s, p < 0.001), but left grafts were transplanted faster (160 vs. 171 min, p = 0.048). Recipients of right kidneys had more postoperative complications (grade 3: 25.6 vs. 11.3%, p = 0.020). At a follow-up of 45 (range 6-79) months, neither the kidney function, nor death-censored graft (5-year: LLDN 89 vs. 92%, p = 0.969) and patient survival (5-year: LLDN 95 vs. 98%, p = 0.747) differed. CONCLUSIONS: Pure LLDN and RLDN can have different outcomes at high-volume centers, especially higher complications for recipients of right grafts. However, long-term function and graft survival are the same irrespective of the chosen side.

Equivalence of Effective Non-Hermitian Hamiltonians in the Context of Open Quantum Systems and Strongly Correlated Electron Systems.

Recently, it has become clear that non-Hermitian phenomena can be observed not only in open quantum systems experiencing gain and loss but also in equilibrium single-particle properties of strongly correlated systems. However, the circumstances and requirements for the emergence of non-Hermitian phenomena in each field are entirely different. While the implementation of postselection is a significant obstacle to observe the dynamics governed by a non-Hermitian Hamiltonian in open quantum systems, it is unnecessary in strongly correlated systems. Until now, a relation between both descriptions of non-Hermitian phenomena has not been revealed. In this Letter, we close this gap and demonstrate that the non-Hermitian Hamiltonians emerging in both fields are identical, and we clarify the conditions for the emergence of a non-Hermitian Hamiltonian in strongly correlated materials. Using this knowledge, we propose a method to analyze non-Hermitian properties without the necessity of postselection by studying specific response functions of open quantum systems and strongly correlated systems.

Nephron Sparing Surgery in Renal Allograft in Recipients with de novo Renal Cell Carcinoma: Two Case Reports and Review of the Literature.

We report 2 cases of de novo renal cell carcinoma (RCC) in renal grafts after transplantation. Both patients underwent nephron sparing surgery (NSS) 211 and 167 months after transplantation, revealing papillary RCC with a tumour size >4 cm (pT1a). Within a follow-up of 25 and 32 months after NSS, a stable renal function without indication for dialysis was present. No recurrence of RCC in both cases was reported within the yearly routine examinations. NSS in kidney allografts is a safe procedure with preservation of renal function.

Is a Retroaortic Vein a Risk Factor in Laparoscopic Living Donor Nephrectomy?

INTRODUCTION: In living donor transplantation choosing the right donor and donor side for laparoscopic donor nephrectomy is a challenging task in clinical practice. Knowledge about anomalies in renal blood supply are crucial to evaluate the feasibility of the operative procedure. Few data so far exist whether the existence of a retroaortic left renal vein has an impact on living kidney transplantation outcome for donor and recipient. MATERIALS AND METHODS: We retrospectively analyzed 221 patients who underwent laparoscopic living donor nephrectomy between 2011 and 2017 for existence of a retroaortic left renal vein. Clinical characteristics and operative outcomes for donors and recipients were analyzed. RESULTS: 221 patients underwent donor nephrectomy between 2011 and 2017; 11 patients (4.98%) showed the feature of a retroaortic left renal vein, and in 8 patients (72.7%) out of those 11 the left kidney was chosen for transplantation. Mean preoperative serum creatinine was 0.77 (0.49-0.98) mg/dL and 1.28 (0.97-1.64) mg/dL at discharge. In recipients mean serum creatinine preoperatively, after 1 week, 1 month,1 year, 2 and 3 years of follow-up was 10.36 (6.09-20.77) mg/dL, 1.71 (0.67-2.72), 1.33 (0.70-1.89), 1.31 (0.95-2.13), 1.31 (0.98-2.13) and 1.33 (1.03-1.84), respectively. Neither donors nor recipients suffered from any operative complications. CONCLUSIONS: Laparoscopic living donor nephrectomy of a left kidney with retroaortic renal vein is safe for the donor, without limitation in the outcome for the recipient.

Improving HbA1c with Glucose Self-Monitoring in Diabetic Patients with EpxDiabetes, a Phone Call and Text Message-Based Telemedicine Platform: A Randomized Controlled Trial.

Background:We conducted a randomized controlled trial of EpxDiabetes, a novel digital health intervention as an adjunct therapy to reduce HbA1c and fasting blood glucose (FBG) among patients with type 2 diabetes mellitus (T2DM). In addition, we examined the effect of social determinants of health on our system.Methods:Sixty-five (n = 65) patients were randomized at a primary care clinic. Self-reported FBG data were collected by EpxDiabetes automated phone calls or text messages. Only intervention group responses were shared with providers, facilitating follow-up and bidirectional communication. ΔHbA1c and ΔFBG were analyzed after 6 months.Results:There was an absolute HbA1c reduction of 0.69% in the intervention group (95% confidence interval [CI], -1.41 to 0.02) and an absolute reduction of 0.03% in the control group (95% CI, -0.88 to 0.82). For those with baseline HbA1c >8%, HbA1c decreased significantly by 1.17% in the intervention group (95% CI, -1.90 to -0.44), and decreased by 0.02% in the control group (95% CI, -0.99 to 0.94). FBG decreased in the intervention group by 21.6 mg/dL (95% CI, -37.56 to -5.639), and increased 13.0 mg/dL in the control group (95% CI, -47.67 to 73.69). Engagement (proportion responding to ≥25% of texts or calls over 4 weeks) was 58% for the intervention group (95% CI, 0.373-0.627) and 48% for the control group (95% CI, 0.296-0.621). Smoking, number of comorbidities, and response rate were significant predictors of ΔHbA1c.Conclusions:EpxDiabetes helps to reduce HbA1c in patients with uncontrolled T2DM and fosters patient-provider communication; it has definite merit as an adjunct therapy in diabetes management. Future work will focus on improving the acceptability of the system and implementation on a larger scale trial.

Contrast-Enhanced Ultrasound (CEUS) and Quantitative Perfusion Analysis in Patients with Suspicion for Prostate Cancer.

PURPOSE: The aim of this study was to investigate contrast-enhanced ultrasound (CEUS) parameters acquired by software during magnetic resonance imaging (MRI) US fusion-guided biopsy for prostate cancer (PCa) detection and discrimination. MATERIALS AND METHODS: From 2012 to 2015, 158 out of 165 men with suspicion for PCa and with at least 1 negative biopsy of the prostate were included and underwent a multi-parametric 3 Tesla MRI and an MRI/US fusion-guided biopsy, consecutively. CEUS was conducted during biopsy with intravenous bolus application of 2.4 mL of SonoVue® (Bracco, Milan, Italy). In the latter CEUS clips were investigated using quantitative perfusion analysis software (VueBox, Bracco). The area of strongest enhancement within the MRI pre-located region was investigated and all available parameters from the quantification tool box were collected and analyzed for PCa and its further differentiation was based on the histopathological results. RESULTS: The overall detection rate was 74 (47 %) PCa cases in 158 included patients. From these 74 PCa cases, 49 (66 %) were graded Gleason ≥ 3 + 4 = 7 (ISUP ≥ 2) PCa. The best results for cancer detection over all quantitative perfusion parameters were rise time (p = 0.026) and time to peak (p = 0.037). Within the subgroup analysis (> vs ≤ 3 + 4 = 7a (ISUP 2)), peak enhancement (p = 0.012), wash-in rate (p = 0.011), wash-out rate (p = 0.007) and wash-in perfusion index (p = 0.014) also showed statistical significance. CONCLUSION: The quantification of CEUS parameters was able to discriminate PCa aggressiveness during MRI/US fusion-guided prostate biopsy.

Multispectral diffusion-weighted imaging near metal implants.

PURPOSE: The need for diffusion-weighted-imaging (DWI) near metallic implants is becoming increasingly relevant for a variety of clinical diagnostic applications. Conventional DWI methods are significantly hindered by metal-induced image artifacts. A novel approach relying on multispectral susceptibility artifact reduction techniques is presented to address this unmet need. METHODS: DWI near metal implants is achieved through a combination of several advanced MRI acquisition technologies. Previously described approaches to Carr-Purcell-Meiboom-Gill spin-echo train DWI sequences using the periodically rotated overlapping parallel lines with enhanced reconstruction are combined with multispectral-imaging metal artifact reduction principles to provide DWI with substantially reduced artifact levels. The presented methods are applied to limited sets of slices over areas of sarcoma risk near six implanted devices. RESULTS: Using the presented methods, DWI assessment without bulk image distortions is demonstrated in the immediate vicinity of metallic interfaces. In one subject, the apparent diffusion coefficient was reduced in a region of suspected sarcoma directly adjacent to fixation hardware. CONCLUSIONS: An initial demonstration of minimal-artifact multispectral DWI in the near vicinity of metallic hardware is described and successfully demonstrated on clinical subjects. Magn Reson Med 79:987-993, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Reduction of Topological Z Classification in Cold-Atom Systems.

One of the most challenging problems in correlated topological systems is a realization of the reduction of topological classification, but very few experimental platforms have been proposed so far. We here demonstrate that ultracold dipolar fermions (e.g., ^{167}Er, ^{161}Dy, and ^{53}Cr) loaded in an optical lattice of two-leg ladder geometry can be the first promising test bed for the reduction Z→Z_{4}, where solid evidence for the reduction is available thanks to their high controllability. We further give a detailed account of how to experimentally access this phenomenon; around the edges, the destruction of one-particle gapless excitations can be observed by the local radio frequency spectroscopy, while that of gapless spin excitations can be observed by a time-dependent spin expectation value of a superposed state of the ground state and the first excited state. We clarify that even when the reduction occurs, a gapless edge mode is recovered around a dislocation, which can be another piece of evidence for the reduction.

Bioavailability and costs of once-daily and twice-daily tacrolimus formulations in de novo kidney transplantation.

The use of once-daily tacrolimus in de novo kidney transplantation is increasingly common. Therefore, we were interested in bioavailability aspects of novel once-daily tacrolimus (LCPT, Envarsus) and once-daily tacrolimus extended-release formulation (ER-Tac, Advagraf) compared with twice-daily immediate-release tacrolimus (IR-Tac, Prograf). Furthermore, we calculated the costs. Kidney allograft recipients on tacrolimus-based immunosuppression within 2 clinical trials were included in a single-center analysis. The tacrolimus formulations were compared with respect to daily doses, doses per body weight, trough levels, and concentration-dose (C/D) ratio over 12 months. Intrapatient variability in trough levels and C/D ratios after 3 months was calculated. For the calculation of tacrolimus costs, German list prices were used. Eighty patients (21 with LCPT, 23 with IR-Tac, and 36 with ER-Tac) were analyzed. Pharmacokinetic comparisons revealed significantly higher bioavailability of LCPT at all visits. The variability of trough levels and C/D ratios in general was high and highest in LCPT patients. Different dose requirements translated into different costs. Median treatment costs during the first year were 7.825€ (IQR 6.195-8.892€) for LCPT, 9.813€ (IQR 7.630-16.832€) for IR-Tac, and 9.838€ (IQR 7.503- 13.541€) for ER-Tac (Kruskal-Wallis test, P = .003). The 3 tacrolimus formulations exhibit different dose requirements, exposure, and costs in favor of LCPT.

Single synonymous mutation in factor IX alters protein properties and underlies haemophilia B.

BACKGROUND: Haemophilia B is caused by genetic aberrations in the F9 gene. The majority of these are non-synonymous mutations that alter the primary structure of blood coagulation factor IX (FIX). However, a synonymous mutation c.459G>A (Val107Val) was clinically reported to result in mild haemophilia B (FIX coagulant activity 15%-20% of normal). The F9 mRNA of these patients showed no skipping or retention of introns and/or change in mRNA levels, suggesting that mRNA integrity does not contribute to the origin of the disease in affected individuals. The aim of this study is to elucidate the molecular mechanisms that can explain disease manifestations in patients with this synonymous mutation. METHODS: We analyse the molecular mechanisms underlying the FIX deficiency through in silico analysis and reproducing the c.459G>A (Val107Val) mutation in stable cell lines. Conformation and non-conformation sensitive antibodies, limited trypsin digestion, activity assays for FIX, interaction with other proteins and post-translation modifications were used to evaluate the biophysical and biochemical consequences of the synonymous mutation. RESULTS: The Val107Val synonymous mutation in F9 was found to significantly diminish FIX expression. Our results suggest that this mutation slows FIX translation and affects its conformation resulting in decreased extracellular protein level. The altered conformation did not change the specific activity of the mutated protein. CONCLUSIONS: The pathogenic basis for one synonymous mutation (Val107Val) in the F9 gene associated with haemophilia B was determined. A mechanistic understanding of this synonymous variant yields potential for guiding and developing future therapeutic treatments.