Depletion of the RNA-binding protein PURA triggers changes in posttranscriptional gene regulation and loss of P-bodies

The RNA-binding protein PURA has been implicated in the rare, monogenetic, neurodevelopmental disorder PURA Syndrome. PURA binds both DNA and RNA and has been associated with various cellular functions. Only little is known about its main cellular roles and the molecular pathways affected upon PURA depletion. Here, we show that PURA is predominantly located in the cytoplasm, where it binds to thousands of mRNAs. Many of these transcripts change abundance in response to PURA depletion. The encoded proteins suggest a role for PURA in immune responses, mitochondrial function, autophagy and processing (P)-body activity. Intriguingly, reduced PURA levels decrease the expression of the integral P-body components LSM14A and DDX6 and strongly affect P-body formation in human cells. Furthermore, PURA knockdown results in stabilization of P-body-enriched transcripts, whereas other mRNAs are not affected. Hence, reduced PURA levels, as reported in patients with PURA Syndrome, influence the formation and composition of this phase-separated RNA processing machinery. Our study proposes PURA Syndrome as a new model to study the tight connection between P-body-associated RNA regulation and neurodevelopmental disorders.

Impact of different factor VIII inhibitor kinetic profiles on the inhibitor titer quantification using the modified Nijmegen–Bethesda assay

Background

Coagulation factor VIII (FVIII) inhibitor titer quantification is vital for optimizing care in people with hemophilia A.

Objectives

This study analyzed the impact of the different kinetic profiles of four FVIII monoclonal antibodies on inhibitor titer quantification using the modified Nijmegen–Bethesda assay.

Methods

Concentration‐related and time‐related profiles of FVIII antibodies (4A4, BO2C11, 2‐54, ESH‐8) were evaluated in vitro. FVIII residual activity was measured using a one‐stage clotting assay and chromogenic substrate assay. Profiles of the FVIII antibodies were compared with the theoretical kinetic model: the ideal log (residual activity)‐linear (inhibitor concentration) relationship. Different theoretical kinetic model–dependent and –independent criteria to calculate FVIII inhibitor titer were compared.

Results

Factor VIII monoclonal antibodies had different concentration‐related and time‐related profiles, ideal for comparative analysis using the modified Nijmegen–Bethesda assay. The kinetic profile of 4A4 was similar to the theoretical kinetic model, while BO2C11 showed a steeper curve, and 2‐54 and ESH‐8 a flatter curve, than the model. In the modified Nijmegen–Bethesda assay, conversion of measured FVIII residual activities for different inhibitor dilutions into FVIII inhibitor titer is based on the theoretical kinetic model. Therefore, titer calculations for FVIII inhibitors that deviate from the model are prone to underestimation or overestimation. Calculating a theoretical dilution at 50% FVIII residual activity by sigmoidal regression reflecting different kinetic inhibition profiles can provide a more accurate titer result.

Conclusion

Kinetic profiles of FVIII antibodies can deviate from the theoretical kinetic model in the modified Nijmegen–Bethesda assay, leading to differences in FVIII inhibitor titer quantification.

Monitoring of different factor VIII replacement products using a factor VIII one-stage clotting assay on cobas t 511/711 analysers

INTRODUCTION

Recombinant coagulation factor VIII (FVIII) products are the standard of care for patients with haemophilia A. The development of modified FVIII products has provided benefit for patients but presented challenges for monitoring FVIII activity.

AIM

This single-centre study evaluated the Roche FVIII one-stage clotting assay (OSA) in measuring FVIII activity in plasma samples spiked with seven FVIII products at clinically relevant concentrations.

METHODS

FVIII-deficient plasma samples were spiked with two batches of recombinant FVIII products (octocog alfa, moroctocog alfa, simoctocog alfa, efmoroctocog alfa, damoctocog alfa pegol, rurioctocog alfa pegol, lonoctocog alfa) at 1-120 IU/dL FVIII activity, according to their labelled potency. Measurement was conducted on the cobas t 511/711 analysers using the Roche FVIII OSA and the Technoclone TECHNOCHROM FVIII:C chromogenic substrate assay (CSA).

RESULTS

Using the OSA, FVIII activity was close to labelled potency for most analysed FVIII products including a recombinant FVIII Fc fusion protein. PEGylated FVIII product, damoctocog alfa pegol, was marginally above and single-chain product, lonoctocog alfa, below the predefined acceptance criteria: for FVIII activity < 25 IU/dL: ± 5 IU/dL; for FVIII activity ≥ 25 IU/dL: ± 20% (relative). The different principles of OSA and CSA led to discrepancies in the estimation of all analysed FVIII products. Additionally, in vitro recovery was increased at lower levels of FVIII activity using the OSA, whereas recovery was more consistent using the CSA.

CONCLUSION

These data allow the interpretation of FVIII activity results for different FVIII products using the Roche FVIII OSA on the cobas t 511/711 analysers.

The Dynamics of Heparin-Binding Protein in Cardiothoracic Surgery-A Pilot Study

OBJECTIVES

To explore the preoperative, intraoperative, and postoperative dynamics of heparin-binding protein (HBP) in cardiothoracic surgery.

DESIGN

This was a prospective, observational study.

SETTING

The study was conducted at a single university hospital.

PARTICIPANTS

Thirty patients undergoing cardiac surgery with cardiopulmonary bypass (CPB) were included, 15 of whom underwent coronary artery bypass grafting surgery and 15 of whom underwent complex procedures. Ten patients undergoing lung surgery also were included as a conventional surgery reference group.

INTERVENTIONS

No interventions were performed.

MEASUREMENTS AND MAIN RESULTS

HBP was measured at nine different perioperative times. HBP levels increased immediately after heparin administration, further increased during CPB, but decreased rapidly after protamine administration. At arrival to the intensive care unit, median HBP levels were 24.8 (15.6-38.1) ng/mL for coronary artery bypass grafting patients and 51.2 (34.0-117.7) ng/mL for complex surgery patients (p = 0.011). One day after surgery, HBP levels in all three groups were below the proposed cutoff of 30 ng/mL, which previously was found to predict development of organ dysfunction in patients with infection.

CONCLUSIONS

HBP levels are elevated by the administration of heparin and the use of CPB but reduced by protamine administration. At postoperative day one, HBP levels were less than the threshold for organ dysfunction in patients with infection. The usefulness of HBP for predicting postoperative infections in cardiothoracic surgery should be investigated in future studies.