The Role of the Epinephrine Test in the Diagnosis and Management of Children Suspected of Having Congenital Long QT Syndrome

The epinephrine test has been shown to be a powerful tool to predict the genotype of congenital long QT syndrome (LQTS). The aim of this study was to evaluate its role in the diagnosis and management of LQTS in children. The test (using the Shimizu protocol) was conducted in patients with some evidence of LQTS but in whom clinical and management decisions were challenging (n = 41, age 9.6 ± 3.9 years, 19 female). LQT1, LQT2, and negative responses to epinephrine were obtained in 16, 5, and 20 subjects, respectively. LQTS gene positivity was obtained in two subjects. Beta-blocker therapy was started in all subjects with a positive epinephrine response (n = 21) and in some negative responders because of their strong LQTS phenotype (n = 10). No therapy was given to the subset with less convincing features of LQTS who had also responded negatively to epinephrine (n = 10). Follow-up for 3.0 ± 2 years was uneventful in both management groups. Due to the discordance with genotyping, the epinephrine test cannot be used to diagnose genotype-positive LQTS but when used in combination with phenotype assessment and genetic screening, it could enable better management decisions

Loss-of-function variants in CUL3 cause a syndromic neurodevelopmental disorder

Purpose De novovariants inCUL3(Cullin-3 ubiquitin ligase) have been strongly associated with neurodevelopmental disorders (NDDs), but no large case series have been reported so far. Here we aimed to collect sporadic cases carrying rare variants inCUL3,describe the genotype-phenotype correlation, and investigate the underlying pathogenic mechanism.MethodsGenetic data and detailed clinical records were collected via multi-center collaboration. Dysmorphic facial features were analyzed using GestaltMatcher. Variant effects on CUL3 protein stability were assessed using patient-derived T-cells.ResultsWe assembled a cohort of 35 individuals with heterozygousCUL3variants presenting a syndromic NDD characterized by intellectual disability with or without autistic features. Of these, 33 have loss-of-function (LoF) and two have missense variants.CUL3LoF variants in patients may affect protein stability leading to perturbations in protein homeostasis, as evidenced by decreased ubiquitin-protein conjugatesin vitro. Specifically, we show that cyclin E1 (CCNE1) and 4E-BP1 (EIF4EBP1), two prominent substrates of CUL3, fail to be targeted for proteasomal degradation in patient-derived cells.ConclusionOur study further refines the clinical and mutational spectrum ofCUL3-associated NDDs, expands the spectrum of cullin RING E3 ligase-associated neuropsychiatric disorders, and suggests haploinsufficiency via LoF variants is the predominant pathogenic mechanism

Biallelic variants in LIG3 cause a novel mitochondrial neurogastrointestinal encephalomyopathy

none67si: Abnormal gut motility is a feature of several mitochondrial encephalomyopathies, and mutations in genes such as TYMP and POLG, have been linked to these rare diseases. The human genome encodes three DNA ligases, of which only one, ligase III (LIG3), has a mitochondrial splice variant and is crucial for mitochondrial health. We investigated the effect of reduced LIG3 activity and resulting mitochondrial dysfunction in seven patients from three independent families, who showed the common occurrence of gut dysmotility and neurological manifestations reminiscent of mitochondrial neurogastrointestinal encephalomyopathy. DNA from these patients was subjected to whole exome sequencing. In all patients, compound heterozygous variants in a new disease gene, LIG3, were identified. All variants were predicted to have a damaging effect on the protein. The LIG3 gene encodes the only mitochondrial DNA (mtDNA) ligase and therefore plays a pivotal role in mtDNA repair and replication. In vitro assays in patient-derived cells showed a decrease in LIG3 protein levels and ligase activity. We demonstrated that the LIG3 gene defects affect mtDNA maintenance, leading to mtDNA depletion without the accumulation of multiple deletions as observed in other mitochondrial disorders. This mitochondrial dysfunction is likely to cause the phenotypes observed in these patients. The most prominent and consistent clinical signs were severe gut dysmotility and neurological abnormalities, including leukoencephalopathy, epilepsy, migraine, stroke-like episodes, and neurogenic bladder. A decrease in the number of myenteric neurons, and increased fibrosis and elastin levels were the most prominent changes in the gut. Cytochrome c oxidase (COX) deficient fibres in skeletal muscle were also observed. Disruption of lig3 in zebrafish reproduced the brain alterations and impaired gut transit in vivo. In conclusion, we identified variants in the LIG3 gene that result in a mitochondrial disease characterized by predominant gut dysmotility, encephalopathy, and neuromuscular abnormalities.This work was supported by Telethon Grant GGP15171 to E.B. and R.D.G. and by a donation from Kobe city to the Department of General Pediatrics, Kobe University Graduate School of Medicine (K550003302). S.C. was supported by a Dutch Cancer Foundation grant (KWF11011). V.C. and A.M. were supported by the Italian Ministry of Health (“Ricerca Corrente” funding). R.D.G. is the recipient of grants from University of Ferrara (FAR and FIR funds).openBonora, Elena; Chakrabarty, Sanjiban; Kellaris, Georgios; Tsutsumi, Makiko; Bianco, Francesca; Bergamini, Christian; Ullah, Farid; Isidori, Federica; Liparulo, Irene; Diquigiovanni, Chiara; Masin, Luca; Rizzardi, Nicola; Cratere, Mariapia Giuditta; Boschetti, Elisa; Papa, Valentina; Maresca, Alessandra; Cenacchi, Giovanna; Casadio, Rita; Martelli, Pierluigi; Matera, Ivana; Ceccherini, Isabella; Fato, Romana; Raiola, Giuseppe; Arrigo, Serena; Signa, Sara; Sementa, Angela Rita; Severino, Mariasavina; Striano, Pasquale; Fiorillo, Chiara; Goto, Tsuyoshi; Uchino, Shumpei; Oyazato, Yoshinobu; Nakamura, Hisayoshi; Mishra, Sushil K; Yeh, Yu-Sheng; Kato, Takema; Nozu, Kandai; Tanboon, Jantima; Morioka, Ichiro; Nishino, Ichizo; Toda, Tatsushi; Goto, Yu-Ichi; Ohtake, Akira; Kosaki, Kenjiro; Yamaguchi, Yoshiki; Nonaka, Ikuya; Iijima, Kazumoto; Mimaki, Masakazu; Kurahashi, Hiroki; Raams, Anja; MacInnes, Alyson; Alders, Mariel; Engelen, Marc; Linthorst, Gabor; de Koning, Tom; den Dunnen, Wilfred; Dijkstra, Gerard; van Spaendonck, Karin; van Gent, Dik C; Aronica, Eleonora M; Picco, Paolo; Carelli, Valerio; Seri, Marco; Katsanis, Nicholas; Duijkers, Floor A M; Taniguchi-Ikeda, Mariko; De Giorgio, RobertoBonora, Elena; Chakrabarty, Sanjiban; Kellaris, Georgios; Tsutsumi, Makiko; Bianco, Francesca; Bergamini, Christian; Ullah, Farid; Isidori, Federica; Liparulo, Irene; Diquigiovanni, Chiara; Masin, Luca; Rizzardi, Nicola; Cratere, Mariapia Giuditta; Boschetti, Elisa; Papa, Valentina; Maresca, Alessandra; Cenacchi, Giovanna; Casadio, Rita; Martelli, Pierluigi; Matera, Ivana; Ceccherini, Isabella; Fato, Romana; Raiola, Giuseppe; Arrigo, Serena; Signa, Sara; Sementa, Angela Rita; Severino, Mariasavina; Striano, Pasquale; Fiorillo, Chiara; Goto, Tsuyoshi; Uchino, Shumpei; Oyazato, Yoshinobu; Nakamura, Hisayoshi; Mishra, Sushil K; Yeh, Yu-Sheng; Kato, Takema; Nozu, Kandai; Tanboon, Jantima; Morioka, Ichiro; Nishino, Ichizo; Toda, Tatsushi; Goto, Yu-Ichi; Ohtake, Akira; Kosaki, Kenjiro; Yamaguchi, Yoshiki; Nonaka, Ikuya; Iijima, Kazumoto; Mimaki, Masakazu; Kurahashi, Hiroki; Raams, Anja; MacInnes, Alyson; Alders, Mariel; Engelen, Marc; Linthorst, Gabor; de Koning, Tom; den Dunnen, Wilfred; Dijkstra, Gerard; van Spaendonck, Karin; van Gent, Dik C; Aronica, Eleonora M; Picco, Paolo; Carelli, Valerio; Seri, Marco; Katsanis, Nicholas; Duijkers, Floor A M; Taniguchi-Ikeda, Mariko; De Giorgio, Robert

Epigenotype, phenotype, and tumors in patients with isolated hemihyperplasia

OBJECTIVE: To investigate whether epigenotyping of patients with isolated hemihyperplasia (IH) can, analogous to genetic screening of patients with Beckwith-Wiedemann syndrome, be used for the prediction of tumor risk and tumor type of individual patients. STUDY DESIGN: Methylation analysis of H19 and KCNQ1OT1 of 73 patients. Questionnaires were sent to referring clinicians. RESULTS: In 75% of the clinically confirmed patients with IH no epigenetic defect was detected. Paternal uniparental disomy was found in 15%, demethylation of KCNQ1OT1 in only 6%, and hypermethylation of H19 in 3% of isolated hemihyperplasia cases. Ten percent of the patients with IH had development of a childhood tumor associated with paternal uniparental disomy (2/8) or no methylation defect (2/30). No genetic defect was detected in 10 of 14 additional patients with cancer with IH. In these latter patients, a methylation defect of H19 was seen 3 times and a paternal uniparental disomy once. The female-to-male ratio was 6:1. CONCLUSIONS: Aberrant methylation of the 11p15 region is not common in patients with IH and can at present not be used for tumor risk determinatio

Recurrent GNAO1 Mutations Associated With Developmental Delay and a Movement Disorder

In 2 unrelated patients with axial hypotonia, developmental delay and a hyperkinetic movement disorder, a missense mutation was found in codon 209 of the GNAO1 gene. From the still scarce literature on GNAO1 mutations, a clear genotype-phenotype correlation emerged. From the 26 patients reported thus far, 12 patients had epileptic encephalopathy, and 14 had a developmental delay and a hyperkinetic movement disorder. All but 1 of the latter patients had missense mutations in GNAO1 codon 209 or 246, which thus appear to be mutation hotspots. At least 2 sibling pairs showed that the recurrence risk after 1 affected child with a GNAO1 mutation might be relatively high (5-15%), due to apparent gonadal mosaicism in the parent

Hematologic abnormalities in Shwachman Diamond syndrome: lack of genotype-phenotype relationship

Shwachman-Diamond syndrome (SIDS) is an autosomal-recessive disorder characterized by short stature, exocrine pancreatic insufficiency, and hematologic defects. The causative SBDS gene was sequenced in 20 of 23 unrelated patients with clinical SIDS. Mutations in the SBDS gene were found in 75 %, being identical in 11 patients. Hematologic parameters for all 3 lineages were determined over time such as absolute neutrophil counts (ANCs), granulocyte functions, and erythroid and myeloid colony formation (erythroid burst-forming unit [BFU-E] and granulocyte-monocyte colony-forming unit [CFU-GM]) from hematopoietic progenitor cells, percentage of fetal hemoglobin (HbF), and platelet counts. Persistent neutropenia was present in 43 % in the absence of apoptosis and unrelated to chemotaxis defects (in 65 %) or infection rate. Irrespective of the ANC in vivo, abnormal CFU-GM was observed in all patients with SIDS tested (14 of 14), whereas BFU-E was less often affected (9 of 14). Cytogenetic aberrations occurred in 5 of 19 patients in the absence of myelodysplasia. One child died during allogeneic bone marrow transplantation. In conclusion, neutropenia and defective chemotaxis did not result in severe clinical infection in SDS. CFU-GMs were impaired in all patients tested. From the SBDS sequence data, we conclude that in patients with genetically proven SDS a genotype-phenotype relationship in SDS does not exist in clinical and hematologic term

Contribution of inherited heart disease to sudden cardiac death in childhood

BACKGROUND. In children aged 1 to 18 years, the causes of sudden cardiac death may remain unresolved when autopsy results are negative. Because inherited cardiac diseases are likely, cardiologic and genetic investigations of relatives may still yield the diagnosis in these cases. Moreover, these investigations provide timely identification of relatives who are also at risk of sudden cardiac death. We aimed to establish the cause of sudden cardiac death in the children of whom the family was referred to our cardiogenetics department and the diagnostic yield of these investigations. METHODS AND RESULTS. We genetically counseled 25 consecutive, unrelated families after sudden cardiac death of a child ( aged 1 to 18 years) who was disease-free during lifetime and in whose family there was no known inherited heart disease. We performed cardiac investigation ( electrocardiography, exercise testing, and echocardiography) of first-degree and second-degree relatives and performed diagnosis-directed DNA analysis. Autopsy was performed in 20 case subjects. A diagnosis was identified in 14 of 25 families. In addition, we studied 10 children after aborted sudden cardiac death; in 6 of them, a diagnosis was made. Overall, in 17 of the 19 families in whom an inherited disease was diagnosed, a disease-causing mutation in either a first-degree relative or the index patient confirmed the diagnosis. CONCLUSIONS. Sudden cardiac death in children seems to be caused often by inherited cardiac diseases. Cardiac and genetic examination of relatives combined, if possible, with postmortem analysis after sudden cardiac death of a child has a high diagnostic yield ( 14 of 25), comparable to analysis in surviving victims of sudden cardiac death ( 6 of 10). Because sudden cardiac death can be prevented by timely treatment, these results warrant active family screening after unexplained sudden cardiac death of a chil

Mutation in the KCNQ1 gene leading to the short QT-interval syndrome

Background - The electrocardiographic short QT-interval syndrome forms a distinct clinical entity presenting with a high rate of sudden death and exceptionally short QT intervals. The disorder has recently been linked to gain-of-function mutation in KCNH2. The present study demonstrates that this disorder is genetically heterogeneous and can also be caused by mutation in the KCNQ1 gene. Methods and Results - A 70-year man presented with idiopathic ventricular fibrillation. Both immediately after the episode and much later, his QT interval was abnormally short without any other physical or electrophysiological anomalies. Analysis of candidate genes identified a g919c substitution in KCNQ1 encoding the K+ channel KvLQT1. Functional studies of the KvLQT1 V307L mutant ( alone or coexpressed with the wild-type channel, in the presence of IsK) revealed a pronounced shift of the half-activation potential and an acceleration of the activation kinetics leading to a gain of function in I-Ks. When introduced in a human action potential computer model, the modified biophysical parameters predicted repolarization shortening. Conclusions - We present an alternative molecular mechanism for the short QT-interval syndrome. Functional and computational studies of the KCNQ1 V307L mutation identified in a patient with this disorder favor the association of short QT with mutation in KCNQ