HIDDEN VARIANT OF ANTITHROMBIN DETECTED THROUGH COMPLETE GENOME SEQUENCING THAT MODULATES THE EFFECTIVENESS OF N-GLYCOSYLATION. CLINICAL AND BASIC IMPLICATIONS

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ALG12‐CDG: An unusual patient without intellectual disability and facial dysmorphism, and with a novel variant

Background Congenital disorder of glycosylation (CDG) type I is a group of rare disorders caused by recessive mutations in up to 25 genes that impair theN-glycan precursor formation and its transfer to proteins resulting in hypoglycosylation of multiple proteins. Congenital disorder of glycosylation causes multisystem defects usually with psychomotor delay that is diagnosed in the infancy. We aim to supply further evidences supporting that CDG may be underestimated. Methods Antithrombin and factor XI were studied by chromogenic and coagulometric methods. Hypoglycosylation of plasma proteins was evaluated by western blot, HPLC, Q-TOF, and RP-LC-MRM-MS. Genetic analysis included whole exome, Sanger sequencing, and PCR-allele specific assay. Results We here present an intriguing patient with an exceptional phenotype: 25-year-old women with a ventricular septal defect and severe idiopathic scoliosis but no facial dysmorphism, who dances as a professional, and has a University degree. Congenital disorder of glycosylation diagnosis started through the identification of antithrombin deficiency withoutSERPINC1defect and the detection of hypoglycosylated forms. Increased levels of hypoglycosylated forms of F XI (also with significant deficiency) and transferrin were also detected. Whole exome analysis showed a novel homozygousALG12variant c.77T>A, p.(Val26Asp) supporting an ALG12-CDG diagnosis. It also showed three new variants inKMT2D, and a mild, knownALG6variant. Conclusions This novel ALG12-CDG patient (the 13th reported) underlines the heterogeneity of this CDG and broadens its phenotypical spectrum, supports that these disorders are underestimated, and suggests that combination of global hypoglycosylation with specific gene defects might determine the clinical manifestations of CDG patients.Afdeling Klinische Chemie en Laboratoriumgeneeskunde (AKCL

ALG12-CDG: An unusual patient without intellectual disability and facial dysmorphism, and with a novel variant

Background Congenital disorder of glycosylation (CDG) type I is a group of rare disorders caused by recessive mutations in up to 25 genes that impair theN-glycan precursor formation and its transfer to proteins resulting in hypoglycosylation of multiple proteins. Congenital disorder of glycosylation causes multisystem defects usually with psychomotor delay that is diagnosed in the infancy. We aim to supply further evidences supporting that CDG may be underestimated. Methods Antithrombin and factor XI were studied by chromogenic and coagulometric methods. Hypoglycosylation of plasma proteins was evaluated by western blot, HPLC, Q-TOF, and RP-LC-MRM-MS. Genetic analysis included whole exome, Sanger sequencing, and PCR-allele specific assay. Results We here present an intriguing patient with an exceptional phenotype: 25-year-old women with a ventricular septal defect and severe idiopathic scoliosis but no facial dysmorphism, who dances as a professional, and has a University degree. Congenital disorder of glycosylation diagnosis started through the identification of antithrombin deficiency withoutSERPINC1defect and the detection of hypoglycosylated forms. Increased levels of hypoglycosylated forms of F XI (also with significant deficiency) and transferrin were also detected. Whole exome analysis showed a novel homozygousALG12variant c.77T>A, p.(Val26Asp) supporting an ALG12-CDG diagnosis. It also showed three new variants inKMT2D, and a mild, knownALG6variant. Conclusions This novel ALG12-CDG patient (the 13th reported) underlines the heterogeneity of this CDG and broadens its phenotypical spectrum, supports that these disorders are underestimated, and suggests that combination of global hypoglycosylation with specific gene defects might determine the clinical manifestations of CDG patients.Afdeling Klinische Chemie en Laboratoriumgeneeskunde (AKCL

Long-Read Sequencing Identifies the First Retrotransposon Insertion and Resolves Structural Variants Causing Antithrombin Deficiency

The identification of inherited antithrombin deficiency (ATD) is critical to prevent potentially life-threatening thrombotic events. Causal variants in SERPINC1 are identified for up to 70% of cases, the majority being single-nucleotide variants and indels. The detection and characterization of structural variants (SVs) in ATD remain challenging due to the high number of repetitive elements in SERPINC1. Here, we performed long-read whole-genome sequencing on 10 familial and 9 singleton cases with type I ATD proven by functional and antigen assays, who were selected from a cohort of 340 patients with this rare disorder because genetic analyses were either negative, ambiguous, or not fully characterized. We developed an analysis workflow to identify disease-associated SVs. This approach resolved, independently of its size or type, all eight SVs detected by multiple ligation-dependent probe amplification, and identified for the first time a complex rearrangement previously misclassified as a deletion. Remarkably, we identified the mechanism explaining ATD in 2 out of 11 cases with previous unknown defect: the insertion of a novel 2.4 kb SINE-VNTR-Alu retroelement, which was characterized by de novo assembly and verified by specific polymerase chain reaction amplification and sequencing in the probands and affected relatives. The nucleotide-level resolution achieved for all SVs allowed breakpoint analysis, which revealed repetitive elements and microhomologies supporting a common replication-based mechanism for all the SVs. Our study underscores the utility of long-read sequencing technology as a complementary method to identify, characterize, and unveil the molecular mechanism of disease-causing SVs involved in ATD, and enlarges the catalogue of genetic disorders caused by retrotransposon insertions

Hypoglycosylation is a common finding in antithrombin deficiency in the absence of a SERPINC1 gene defect

Essentials We investigated the molecular base of antithrombin deficiency in cases without SERPINC1 defects. 27% of cases presented hypoglycosylation, transient in 62% and not restricted to antithrombin. Variations in genes involved in N-glycosylation underline this phenotype. These results support a new form of thrombophilia. Click here to listen to Dr Huntington's perspective on thrombin inhibition by the serpins SUMMARY: Background Since the discovery of antithrombin deficiency, 50 years ago, few new thrombophilic defects have been identified, all with weaker risk of thrombosis than antithrombin deficiency. Objective To identify new thrombophilic mechanisms. Patients/methods We studied 30 patients with antithrombin deficiency but no defects in the gene encoding this key anticoagulant (SERPINC1). Results A high proportion of these patients (8/30: 27%) had increased hypoglycosylated forms of antithrombin. All N-glycoproteins tested in these patients (alpha1-antitrypsin, FXI and transferrin) had electrophoretic, HPLC and Q-TOF patterns indistinguishable from those of the congenital disorders of glycosylation (rare recessive multisystem disorders). However, all except one had no mental disability. Moreover, intermittent antithrombin deficiency and hypoglycosylation was recorded in five out of these eight patients, all associated with moderate alcohol intake. Genetic analysis, including whole exome sequencing, revealed mutations in different genes involved in the N-glycosylation pathway. Conclusions Our study provides substantial and novel mechanistic insights into two disease processes, with potential implications for diagnosis and clinical care. An aberrant N-glycosylation causing a recessive or transient antithrombin deficiency is a new form of thrombophilia. Our data suggest that congenital disorders of glycosylation are probably underestimated, especially in cases with thrombosis as the main or only clinical manifestation

International clinical guidelines for the management of phosphomannomutase 2-congenital disorders of glycosylation: Diagnosis, treatment and follow up

Contains fulltext : 203022.pdf (publisher's version ) (Closed access)Phosphomannomutase 2 (PMM2-CDG) is the most common congenital disorder of N-glycosylation and is caused by a deficient PMM2 activity. The clinical presentation and the onset of PMM2-CDG vary among affected individuals ranging from a severe antenatal presentation with multisystem involvement to mild adulthood presentation limited to minor neurological involvement. Management of affected patients requires a multidisciplinary approach. In this article, a systematic review of the literature on PMM2-CDG was conducted by a group of international experts in different aspects of CDG. Our managment guidelines were initiated based on the available evidence-based data and experts' opinions. This guideline mainly addresses the clinical evaluation of each system/organ involved in PMM2-CDG, and the recommended management approach. It is the first systematic review of current practices in PMM2-CDG and the first guidelines aiming at establishing a practical approach to the recognition, diagnosis and management of PMM2-CDG patients

Atención integral del neonato con encefalopatía hipóxico-isquémica en España

Introducción Apenas conocemos cómo es la asistencia de los recién nacidos (RN) con encefalopatía hipóxico-isquémica (EHI) en hipotermia terapéutica (HT), especialmente si existen protocolos asistenciales, la neuromonitorización que se realiza o cómo es la aproximación al pronóstico neurológico. Este conocimiento permite detectar e implementar áreas de mejora asistencial. Método Estudio transversal de los 57 hospitales españoles que realizaban HT en 2015, mediante cuestionario sobre: 1) la disponibilidad de protocolos y de recursos tecnológicos; 2) el uso de herramientas de neuromonitorización; 3) los conocimientos de los profesionales; 4) la información pronóstica que se da los padres, y 5) el informe al alta y del plan de seguimiento. Resultados El 95% utiliza enfriamiento corporal-total servocontrolado y dispone de protocolos específicos de actuación. El 70% utiliza sedación y el 68% deja al paciente a dieta absoluta. La monitorización con electroencefalografía integrada por amplitud se utiliza en más del 80% de los centros, aunque solo en el 50% la enfermera es capaz de interpretarlo. La saturación de oxígeno cerebral es escasamente monitorizada (16%). Entre los estudios diagnóstico-pronósticos, la neuroimagen es universal, pero los neurobiomarcadores apenas se utilizan (29%). Solo el 21% ofrece información pronóstica antes de las 72 h de vida; sin presencia de la enfermera en el 70%. El seguimiento lo realiza el neuropediatra (84%), con una duración desigual entre centros. Conclusiones La asistencia del RN con EHI en España es adecuada, con áreas de mejora en: neuromonitorización, sedación, marco temporal de la información pronóstica, trabajo en equipo y estandarización de la duración del seguimiento