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Objectives A combined digital droplet PCR (ddPCR)/pyrosequencing assay system was developed that demonstrated advantages applicable to multiple qualitative and quantitative molecular genetic diagnostic applications. Data for characterizing this combined approach for hematologic stem cell transplantation (HSCT) and allele quantification from graft-derived cell-free (cf) DNA in solid organ transplantation (SOT) is presented. Methods ddPCR and pyrosequencing assays targeting 32 SNPs/markers were established. ddPCR results from 72 gDNAs of 55 patients after allogeneic HSCT and 107 plasma-cfDNAs of 25 liver transplant recipients were compared with established methods/markers, i.e. short-tandem-repeat PCR and ALT, respectively. Results The ddPCR results were in good agreement with the established marker. The limit of detection was 0.02 % minor allele fraction. The relationship between ddPCR and STR-PCR was linear with R2=0.98 allowing to transfer previously established clinical STR-PCR cut-offs to ddPCR; 50-fold higher sensitivity and a variation coefficient of Conclusions Combining pyrosequencing for genotyping and ddPCR for minor allele quantification enhances sensitivity and precision for the patient after HSCT and SOT. The assay is designed for maximum flexibility. It is expected to be suitable for other applications (sample tracking, prenatal diagnostics, etc.).

Germline defects in the transcription factor GATA1 are known to cause dyserythropoiesis with(out) anemia and variable abnormalities in platelet count and function. However, damaging variants closely located to the C-terminal zinc finger domain of GATA1 are nearly unknown. In this study, a 36-year-old male index patient and his 4-year-old daughter suffered from moderate mucocutaneous bleeding diathesis since birth. Whole exome sequencing detected a novel hemizygous

Background Interpretation of genetic variants detected by sequencing of genomic DNA, which may cause splicing defects, regularly requires mRNA analysis. Usually, only bioinformatic testing is provided, because simple and non-invasive assay protocols are lacking. Furthermore, the detection of mis-splicing is often hampered by nonsense mediated mRNA decay (NMD). Methods Starting from a case of Pompe disease with two potential splicing variants an assay for the analysis of splice defects in general was developed. We analyzed the transcripts from the gene of interest by standard methods after short-term culture of the patient's lymphocytes in the presence and absence of a NMD inhibitor. Variant and wild type transcript expression were quantified by allele specific PCR in the patient and both parents and the expression ratio with/without NMD inhibition was calculated for each transcript. Results NMD detection in lymphocytes was optimized and evaluated by analyzing a naturally occurring NMD transcript. Several compounds inhibited NMD successfully, including potential therapeutic agents. Sample storage for up to 4 days at room temperature prior to lymphocyte isolation did not affect results. In a proof of concept we identified two candidate variants as severe splicing variants in a patient with Pompe disease, but the strategy can also be used to screen for any mis-spliced transcripts prone to NMD. Conclusions We developed a simple, non-invasive assay for the detection and characterization of potential splicing variants. This is essential, because early and near-term diagnosis and disease classification is required to facilitate therapy in many genetic diseases.

BACKGROUND Severe high-molecular-weight kininogen (HK) deficiency is a poorly studied autosomal recessive contact system defect caused by pathogenic, biallelic KNG1 variants. AIM We performed the first comprehensive analysis of diagnostic, clinical, genetic, and epidemiological aspects of HK deficiency. METHODS We collected clinical information and blood samples from a newly detected HK-deficient individual and from published cases identified by a systematic literature review. Activity and antigen levels of coagulation factors were determined. Genetic analyses of KNG1 and KLKB1 were performed by Sanger sequencing. The frequency of HK deficiency was estimated considering truncating KNG1 variants from GnomAD. RESULTS We identified 48 cases of severe HK deficiency (41 families), of these 47 have been previously published (n = 19 from gray literature). We genotyped 3 cases and critically appraised 10 studies with genetic data. Ten HK deficiency-causing variants (one new) were identified. All of them were truncating mutations, whereas the only known HK amino acid substitution with a relevant phenotype instead causes hereditary angioedema. Conservative estimates suggest an overall prevalence of severe HK deficiency of approximately one case per 8 million population, slightly higher in Africans. Individuals with HK deficiency appeared asymptomatic and had decreased levels of prekallikrein and factor XI, which could lead to misdiagnosis. CONCLUSION HK deficiency is a rare condition with only few known pathogenic variants. It has an apparently good prognosis but is prone to misdiagnosis. Our understanding of its clinical implications is still limited, and an international prekallikrein and HK deficiency registry is being established to fill this knowledge gap.

Ciliopathies often comprise retinal degeneration since the photoreceptors outer segment is an adapted primary cilium. CEP162 is a distal end centriolar protein required for proper transition zone assembly during ciliogenesis and whose loss causes ciliopathy in zebrafish. CEP162 has so far not been implicated in human disease. Here, we identified a homozygous CEP162 frameshift variant, c.1935dupA (p.(E646R*5)), in retinitis pigmentosa patients from two unrelated Moroccan families, likely representing a founder allele. We found that even though mRNA levels were reduced, the truncated CEP162-E646R*5 protein was expressed and localized to the mitotic spindle during mitosis, but not at the basal body of the cilium. In CEP162 knockdown cells, expression of the truncated CEP162-E646R*5 protein is unable to restore ciliation indicating its loss of function at the cilium. In patient fibroblasts, cilia overcome the absence of CEP162 from the primary cilium by delaying ciliogenesis through the persistence of CP110 at the mother centriole. The patient fibroblasts are ultimately able to extend some abnormally long cilia that are missing key transition zone components. Defective transition zone formation likely disproportionately affects the long-living ciliary outer segment of photoreceptors resulting in retinal dystrophy. CEP162 is expressed in human retina, and we show that wild-type CEP162, but not truncated CEP162-E646R*5, specifically localizes to the distal end of centrioles of mouse photoreceptor cilia. Together, our genetic, cell-based, and in vivo modeling establish that CEP162 deficiency causes retinal ciliopathy in humans. SIGNIFICANCE STATEMENTCiliopathies often comprise retinal degeneration since the photoreceptors outer segment is an adapted primary cilium. CEP162 is a basal body protein required for proper transition zone assembly during ciliogenesis and has so far not been implicated in human disease. Using genetic, cell-based, and in vivo studies, we show that a biallelic mutation of CEP162 causes late-onset human retinal degeneration. This mutation specifically hinders CEP162 function at the cilia, leading to impaired transition zone assembly and delayed formation of dysmorphic cilia. Studies in mouse photoreceptors support that absence of CEP162 could lead to defective outer segments. The discovery of novel ciliopathy genes, such as CEP162, advances our insight into cell-specific functions of the primary cilium.

Antiphospholipid antibodies (aPL) have been reported to activate platelets. This is considered to be one of the pathogenic properties of aPL. Even though aPL heterogeneity is quite well established, little is known, if the ability to activate platelets is common to all aPL or depends on antigen specificity. To further study this issue, we analyzed the ability of three human monoclonal aPL with distinctly different antigenic specificities to activate platelets in vitro. The results obtained with human monoclonal aPL were validated with immunoglobulin G (IgG) fractions obtained from patients with antiphospholipid syndrome (APS). A co-factor-independent human monoclonal anticardiolipin aPL had no discernible effect on human platelets. Two monoclonal aPL reactive against β2 glycoprotein I (β2GPI) induced platelet aggregation, integrin αIIbβ3 activation and P-selectin surface expression. These data could be confirmed with patient IgG fractions which could only induce aggregation, if they had anti-β2GPI activity. Anti-β2GPI aPL-induced platelet activation depended on interaction of aPL with the low affinity Fcγ-receptor IIa on the platelet surface. It was completely abolished by pretreatment of platelet-rich plasma with the mechanistic target of rapamycin (mTOR) inhibitors rapamycin or everolimus. This extends previous data showing that mTOR is involved in signaling of anti-β2GPI in monocytes and endothelial cells. In conclusion, anti-β2GPI aPL activate platelets while co-factor-independent anticardiolipin aPL have no effect. mTOR is involved in this signaling process which has implications beyond APS, because so far the role of mTOR signaling in platelets is incompletely explored and requires further study.

Several rapid antigen tests (RATs) for the detection of SARS-CoV-2 were evaluated recently. However, reliable performance data for laboratory-based, high-throughput antigen tests are lacking. Therefore and in response to a short-term shortage of PCR reagents, we evaluated DiaSorin's LIAISON SARS-CoV-2 antigen test in comparison to RT-qPCR, and concerning the application of screening non-COVID-19 patients on hospital admission. Applying the manufacturer-recommended cut-off of 200 arbitrary units (AU/mL) the specificity of the LIAISON Test was 100%, the overall analytical sensitivity 40.2%. Lowering the cut-off to 100 AU/mL increased the sensitivity to 49.7% and decreased the specificity to 98.3%. Confining the analysis to samples with an RT-qPCR result

A lipid-protein autoimmunity target Several autoimmune diseases, including systemic lupus erythematosus and primary antiphospholipid syndrome, are characterized by the presence of antiphospholipid antibodies (aPLs). These molecules can activate the complement and coagulation cascades, which contributes to pathologies such as thrombosis, stroke, and pregnancy complications. Müller-Calleja et al. found that endothelial protein C receptor (EPCR) in complex with lysobisphosphatidic acid (LBPA) is the cell-surface target for aPL and mediates its internalization (see the Perspective by Kaplan). aPL binding to EPCR-LBPA resulted in the activation of tissue factor–mediated coagulation and interferon-α production by dendritic cells. Interferon-α, in turn, fueled the expansion of B1a cells, which secrete aPLs. The specific blockade of this target in mice inhibited the development of aPL autoimmunity, offering hope for future therapies for these conditions. Science , this issue p. eaay1833 ; see also p. 1100

Background: Severe high molecular weight kininogen (HK) deficiency is an autosomal recessive defect of the contact system caused by mutations in KNG1. Limited scientific interest in HK deficiency due to the rarity of the seemingly asymptomatic condition may increase, as HK, the precursor of bradykinin, is now discussed as a therapeutic target e.g. in hereditary angioedema. Aims: We provide a comprehensive analysis of the diagnostic, clinical, and genetic features of HK deficiency and estimate its frequency. Methods: We identified a new case of HK deficiency, systematically review the literature, conduct new genetic studies of reported cases, and comprehensively analyze the clinical course and diagnostic criteria. Clotting activity of HK and prekallikrein (PK) (HK:C/PK:C) and antigen (HK:Ag/PK:Ag) were determined and genetic analyses of KNG1 and KLKB1 were performed by Sanger sequencing. Characteristics deduced from the known HK deficiency-causing variants were used to estimate the frequency of HK deficiency from the KNG1 variants aggregated in GnomAD. Results: 677 studies were identified by systematic review of the literature for HK deficiency. 27 of these contained individual cases of HK deficiency including 6 studies not listed in PubMed. Little-noticed cases from the gray literature account for more than one-third (16/39) of the extracted, unrelated cases. We genotyped one newly diagnosed HK-deficient case and 2 cases described in the literature and additionally evaluated all 10 studies reporting genetic data in HK-deficiency (including one case previously misdiagnosed as having PK deficiency). A total of 10 KNG1 variants causing HK deficiency (one new) were found, the most frequent being c.586C>T, p.Arg196* (4 unrelated families). Interestingly, all HK deficiency-causing variants are truncating, whereas two amino acid substitutions with presumed functional consequence, have been described as the cause of hereditary angioedema. Conservative prevalence estimates based on all known and putative HK deficiency-causing variants extracted from GnomAD (truncating variants in KNG1, including indels, nonsense and canonical splice site mutations located in that part of the gene, where relevant mutations have been described) revealed a frequency of 1 case of HK deficiency among 7,925,172 with slight differences in the analyzed ethnicities (see table). In addition, although not to the same extent as seen in PK deficiency, HK deficiency apparently is more prevalent in Africans. While it is already well known that HK deficiency causes decreased PK levels, our data indicate that factor XI levels are also frequently decreased, albeit to a lesser extent. The number of cases detected so far is too low for a more detailed analysis regarding bleeding, thrombotic, and cardiovascular events or immunological abnormalities. Conclusion: HK-deficiency is probably more frequent than previously thought. Suspected cases of contact phase defects should at least be analyzed for HK activity (besides factor XII, XI and PK activity) to facilitate conclusive evaluation of the clinical significance in the future. Figure 1 Figure 1. Disclosures Lämmle: Takeda: Membership on an entity's Board of Directors or advisory committees; Ablynx: Membership on an entity's Board of Directors or advisory committees, Other: Travel Support, Speakers Bureau; Baxter: Other: Travel Support, Speakers Bureau; Alexion: Other: Travel Support, Speakers Bureau; Siemens: Other: Travel Support, Speakers Bureau; Bayer: Other: Travel Support, Speakers Bureau; Roche: Other: Travel Support, Speakers Bureau; Sanofi: Other: Travel Support, Speakers Bureau.

Essentials Antiphospholipid antibodies (aPL) are heterogeneous and induce different cellular responses. We analyzed signaling events induced by different monoclonal and patient aPL in monocytes. Two major signaling pathways involving either NADPH-oxidase or LRP8 were identified. Our data suggest that these two pathways mediate the majority of aPL effects on monocytes. Summary Background Antiphospholipid antibodies (aPLs) contribute to the pathogenesis of the antiphospholipid syndrome (APS) by induction of an inflammatory and procoagulant state in different cell types, and several signaling pathways have been described. Objectives To investigate whether signaling depends on the epitope specificity of aPLs. Methods Cellular effects of three human monoclonal aPLs with distinctly different epitope specificities were analyzed in vitro. Expression of tumor necrosis factor-α mRNA by mouse and human monocytes was the major readout. Analysis included cells from genetically modified mice, and the use of specific inhibitors in human monocytes. Data were validated with IgG isolated from 20 APS patients. Results Cofactor-independent anticardiolipin aPLs activated monocytes by induction of endosomal NADPH oxidase. Activation could be blocked by hydroxychloroquine (HCQ). Anti-β2 -glycoprotein I aPL activated monocytes by interacting with LDL receptor-related protein 8 (LRP8). This could be blocked by rapamycin. Analysis of 20 APS patients' IgG showed that all IgG fractions activated the same two pathways as the monoclonal aPL, depending on their epitope patterns as determined by ELISA. Monocyte activation by APS IgG could be blocked completely by HCQ and/or rapamycin, suggesting that in most, if not all, APS patients there is no other relevant signaling pathway. Conclusions aPLs activate two major proinflammatory signal transduction pathways, depending on their epitope specificity. HCQ and rapamycin, either alone or in combination, completely suppress signaling by APS IgG. These observations may provide a rationale for specific treatment of APS patients according to their aPL profile.

BACKGROUND Severe plasma prekallikrein (PK) deficiency is an autosomal-recessive defect characterized by isolated activated partial thromboplastin time prolongation. To date, no comprehensive methodologically firm analysis has investigated the diagnostic, clinical, and genetic characteristics of PK deficiency, and its prevalence remains unknown. PATIENTS/METHODS We described new families with PK deficiency, retrieved clinical and laboratory information of cases systematically searched in the (gray) literature, and collected blood of these cases for complementary analyses. The Genome Aggregation Database (gnomAD) and the population-based Gutenberg Health Study served to study the prevalence of mutations and relevant genetic variants. RESULTS We assembled a cohort of 111 cases from 89 families and performed new genetic analyses in eight families (three unpublished). We identified new KLKB1 mutations, excluded the pathogenicity of some of the previously described ones, and estimated a prevalence of severe PK deficiency of 1/155 668 overall and 1/4725 among Africans. One individual reported with PK deficiency had, in fact, congenital kininogen deficiency associated with decreased PK activity. One quarter of individuals had factor XII clotting activity below the reference range. Four major bleeding events were described in 96 individuals, of which 3 were provoked, for a prevalence of 4% and an annualized rate of 0.1%. The prevalence of cardiovascular events was 15% (6% 65 years) for an annualized rate of 0.4%. CONCLUSIONS We characterized the genetic background of severe PK deficiency, critically appraised mutations, and provided prevalence estimates. Our data on laboratory characteristics and clinical course of severe PK deficiency may have clinical implications.

Genome-wide association studies have identified and repeatedly confirmed the association of rs3197999 in MST1 with inflammatory bowel disease (IBD). However, the underlying pathophysiology remains unclear. rs3197999 is a non-synonymous single-nucleotide polymorphism which modifies the function of macrophage stimulating protein-1 (MST1). We show by haplotyping that rs3197999 is in linkage disequilibrium with rs1050450 in GPX1, with almost complete cosegregation of the minor alleles. As shown by immunoassay, rs3197999 influences the MST-1 level in serum. But also rs1050450 causes an amino acid exchange in glutathione peroxidase 1 (GPx-1) and reduced activity of this antioxidant enzyme. The association of GPx deficiency and IBD in mice was already shown. We propose that GPx-1 is a better candidate than MST1 for the pathophysiologic link between IBD locus 12 and IBD.

Crohn's disease and ulcerative colitis, the two main types of inflammatory bowel disease (IBD), were reported to be associated with a variety of genetic polymorphisms. A subset of these polymorphisms was identified in both diseases and only three of them were found in primary sclerosing cholangitis (PSC). rs3197999 (Arg689Cys) located in the MST1 gene is one of the most convincingly replicated IBD/PSC-associated polymorphisms but its functional consequences have not been investigated, yet. We expressed both MST1 gene variants (Arg(689) (MSP(wt)) and Cys(689) (MSP(mut)) in a eukaryotic cell system and compared their stimulatory effects on macrophage-like THP-1 cells. Except for the rate of apoptosis that remained unchanged, MSP(mut) significantly increased the stimulatory effect of MSP (macrophage-stimulating protein) on chemotaxis and proliferation by THP-1 cells, indicating a gain of function associated with the Arg689Cys exchange. A broad set of evidence reported previously suggests that pro-inflammatory changes in macrophage function have a major role in the initiation of the inflammatory process in IBD and PSC. Therefore, the gain of function observed with rs3197999 in MST1 might provide a cellular mechanism for the consistent association of this polymorphism with an increased risk for IBD and PSC.

Antiphospholipid antibodies (aPL) are likely involved in the pathogenesis of the antiphospholipid syndrome (APS). This study analyzes the structural and functional characteristics of a human monoclonal aPL (HL7G) from the IgG2 subtype with λ light chains generated from a patient with primary APS and recurrent cerebral microemboli. DNA encoding the variable region of heavy and light chains of the antibody was sequenced, analyzed, and compared to HL5B a previously described monoclonal aPL from the same patient. Both antibodies are derived from the same germline genes. HL7G had similar but more extensive somatic mutations in the CDR1 and 2 regions than HL5B, indicating that both antibodies are closely related and derived by a T cell-dependent antigen driven process. In ELISA assays HL7G bound to cardiolipin and several other phospholipid antigens in the absence of protein cofactors. Different from HL5B this aPL bound to β2-glycoprotein I (β2GPII). This suggests that reactivity of aPL against β2GPI is determined by only few specific amino acid exchanges. HL7G was able to induce tissue factor (TF) as one of the procoagulant effects of aPL. Our data suggest that the binding specificity of aPL is only of limited value to predict the biological effect and the pathophysiological impact of the antibodies.

Background Hepatitis E virus (HEV) infection is a potential reason for elevated liver enzymes after liver transplantation (LT). Our aim was to analyze a real-world cohort of LT patients, who underwent liver biopsy for elevated transaminases and suspected acute rejection, to evaluate frequency of post-transplant HEV infection. Patients Data from 160 liver biopsies were analyzed. Seventy-one patients were biopsied on schedule after LT without elevated liver enzymes. A subgroup of 25 patients with elevated liver enzymes and suspected rejection was chosen for further analysis. Patient demographics and data were retrieved from a clinical database, patients' charts, and reports. Results Hepatitis E virus infection was diagnosed in five of 25 patients with suspected acute rejection (20%). HEV genotype 3 was detected in three of the five HEV-infected patients. Patients with HEV infection showed higher ALT levels (P = 0.014), lower De Ritis ratio (P = 0.021), and more frequent glucocorticoid therapy (P = 0.012) compared to HEV-negative patients. Conclusion We found a rate of 20% HEV infections in LT patients undergoing liver biopsy for elevated liver enzymes and suspected acute rejection. These data indicate the necessity for HEV testing in all LT patients with elevated liver enzymes and suspected acute rejection.

Aims Heme oxygenase-1 (HO-1) confers protection to the vasculature and suppresses inflammatory properties of monocytes and macrophages. It is unclear how HO-1 determines the extent of vascular dysfunction in mice and humans. Methods and results Decreased HO-1 activity and expression was paralleled by increased aortic expression and activity of the nicotinamide dinucleotide phosphate oxidase Nox2 in HO-1 deficient Hmox1 −/− and Hmox1 +/− compared with Hmox1 +/+ mice. When subjected to angiotensin II-infusion, streptozotocin-induced diabetes mellitus and aging, HO-1 deficient mice showed increased vascular dysfunction inversely correlated with HO activity. In a primary prevention population-based cohort, we assessed length polymorphisms of the HMOX1 promoter region and established a bipolar frequency pattern of allele length (long vs. short repeats) in 4937 individuals. Monocytic HMOX1 mRNA expression was positively correlated with flow-mediated dilation and inversely with CD14 mRNA expression indicating pro-inflammatory monocytes in 733 hypertensive individuals of this cohort. Hmox1 −/− mice showed drastically increased expression of the chemokine receptor CCR2 in monocytes and the aorta. Angiotensin II-infused Hmox1 −/− mice had amplified endothelial inflammation in vivo , significantly increased aortic infiltration of pro-inflammatory CD11b+Ly6Chi monocytes and Ly6G+ neutrophils and were marked by Ly6Chi monocytosis in the circulation and an increased blood pressure response. Finally, individuals with unfavourable HMOX1 gene promoter length had increased prevalence of arterial hypertension and reduced cumulative survival after a median follow-up of 7.23 years. Conclusions Heme oxygenase-1 is a regulator of vascular function in hypertension via determining the phenotype of inflammatory circulating and infiltrating monocytes with possible implications for all-cause mortality.

Background: Cystic fibrosis (CF) is a common autosomal recessive genetic disorder caused by a variety of sequence alterations in the CFTR gene [cystic fibrosis transmembrane conductance regulator (ATP-binding cassette sub-family C, member 7)]. Because the relative prevalence of mutations strongly depends on the ethnic background, first-level testing of CF as defined by recent consensus recommendations ought to be adaptable to the ethnicity of patients. Methods: We therefore developed and implemented a diagnostic approach to first-level testing for CF based on published mutation frequencies and Pyrosequencing (PSQ) technology that we complemented with standard procedures of mutation detection at the second level. Results: The current test system of PSQ assays for 46 target CF mutations [including CFTRdele2,3 (21 kb) and 1342-6 (T)n (5T/7T/9T)] permits recombinations of single assays to optimize sensitivities for certain ethnicities. By easy expansion of the original mutation panel, the first-level test sensitivities with other ethnic groups would be increased, provided that the mutation frequencies are known. The test was validated with our local, ethnically mixed, but mainly German population (155 patients). The mutation-detection rate for the 92 patients whose CF was confirmed by the sweat test was 89.0% for the patients of German descent (73 of the 92 patients) and 73.7% for the patients of any other origin (19 of the 92 patients). Ethnicity-adapted testing panels for our foreign CF patients would increase the sensitivities for the respective groups by approximately 5%. Conclusions: PSQ-based genotyping is a reliable, convenient, highly flexible, and inexpensive alternative to conventional methods for first-level testing of CFTR, facilitating flexible adaptation of the analyzed mutation panel to any local ethnic group.