Biochemical features of primary cells from a pediatric patient with a gain-of-function ODC1 genetic mutation

2019 ◽  
Vol 476 (14) ◽  
pp. 2047-2057
Author(s):  
Chad R. Schultz ◽  
Caleb P. Bupp ◽  
Surender Rajasekaran ◽  
André S. Bachmann
Keyword(s):  
Pediatric Patient ◽  
De Novo ◽  
Genetic Disorder ◽  
Genetic Mutation ◽  
Dermal Fibroblasts ◽  
The Body ◽  
De Novo Mutation ◽  
Global Developmental Delay ◽  
Gain Of Function ◽  
Protein Variant

Abstract We recently described a new autosomal dominant genetic disorder in a pediatric patient caused by a heterozygous de novo mutation in the ornithine decarboxylase 1 (ODC1) gene. The new genetic disorder is characterized by global developmental delay, alopecia, overgrowth, and dysmorphic features. We hypothesized that this new mutation (c.1342 A>T) leads to a C-terminal truncation variant of the ODC protein that is resistant to normal proteasomal degradation, leading to putrescine accumulation in cells. ODC (E.C. 4.1.1.17) is a rate-limiting enzyme in the biosynthesis of polyamines (putrescine, spermidine, and spermine) that plays a crucial role during embryogenesis, organogenesis, and tumorigenesis. In this study, we show that primary dermal fibroblasts derived from a skin biopsy of a 3-year-old patient contain large amounts of ODC protein and putrescine compared with primary dermal (neonatal and adult) fibroblast control cells. Importantly, the accumulated ODC protein variant remained functionally active as we detected exceptionally high ODC enzyme activity in both primary dermal fibroblasts (12–17-fold of controls) and red blood cells (RBCs) (125–137-fold of controls), using a specific 14C radioactive ODC activity assay. Exposure of primary dermal fibroblasts to ODC inhibitor α-difluoromethylornithine (DFMO) reduced the ODC activity and putrescine to levels observed in controls without adversely affecting cell morphology or inducing cell death. In conclusion, our patient and potentially other patients that carry a similar ODC1 gain-of-function mutation might benefit from treatment with DFMO, a drug with a good safety profile, to suppress the exceptionally high ODC activity and putrescine levels in the body.

Hereditary angioedema: Differential diagnosis, diagnostic tests, and family screening

2020 ◽  
Vol 41 (6) ◽  
pp. S22-S25 ◽  
Author(s):  
Michael E. Manning
Keyword(s):  
Differential Diagnosis ◽  
Hereditary Angioedema ◽  
Diagnostic Tests ◽  
Autosomal Dominant ◽  
Genetic Disorder ◽  
Genetic Mutation ◽  
The Body ◽  
Laboratory Evaluation ◽  
Family Screening ◽  
Common Causes

Hereditary angioedema is a rare, autosomal dominant genetic disorder that leads to sporadic episodes of swelling, which can affect any part of the body. With a prevalence of 1 in 10,000 to 1 in 50,000, there are other, more common causes of angioedema. Differentiating between bradykinin-mediated and histamine-mediated causes of swelling remains a major challenge. It is critical to develop an appropriate differential diagnosis, work through the various conditions, and obtain the pertinent laboratory evaluation to rule in or out the proposed diagnosis. As an autosomal dominant genetic disorder, there is a 50% chance with each pregnancy of passing on the genetic mutation in the SERPING1 gene. This review addressed the differential diagnosis to consider, the appropriate laboratory evaluation, and the importance of family screening.

scholarly journals X-linked neonatal-onset epileptic encephalopathy associated with a gain-of-function variant p.R660T in GRIA3

PLoS Genetics ◽  
2021 ◽  
Vol 17 (6) ◽  
pp. e1009608
Author(s):  
Jia-Hui Sun ◽  
Jiang Chen ◽  
Fernando Eduardo Ayala Valenzuela ◽  
Carolyn Brown ◽  
Diane Masser-Frye ◽  
...  
Keyword(s):  
Developmental Delay ◽  
Prolonged Exposure ◽  
De Novo ◽  
Missense Variant ◽  
Epileptic Encephalopathy ◽  
Global Developmental Delay ◽  
Decay Kinetics ◽  
Gain Of Function ◽  
Ca1 Neurons ◽  
Pathogenic Variants

The X-linked GRIA3 gene encodes the GLUA3 subunit of AMPA-type glutamate receptors. Pathogenic variants in this gene were previously reported in neurodevelopmental diseases, mostly in male patients but rarely in females. Here we report a de novo pathogenic missense variant in GRIA3 (c.1979G>C; p. R660T) identified in a 1-year-old female patient with severe epilepsy and global developmental delay. When exogenously expressed in human embryonic kidney (HEK) cells, GLUA3_R660T showed slower desensitization and deactivation kinetics compared to wildtype (wt) GLUA3 receptors. Substantial non-desensitized currents were observed with the mutant but not for wt GLUA3 with prolonged exposure to glutamate. When co-expressed with GLUA2, the decay kinetics were similarly slowed in GLUA2/A3_R660T with non-desensitized steady state currents. In cultured cerebellar granule neurons, miniature excitatory postsynaptic currents (mEPSCs) were significantly slower in R660T transfected cells than those expressing wt GLUA3. When overexpressed in hippocampal CA1 neurons by in utero electroporation, the evoked EPSCs and mEPSCs were slower in neurons expressing R660T mutant compared to those expressing wt GLUA3. Therefore our study provides functional evidence that a gain of function (GoF) variant in GRIA3 may cause epileptic encephalopathy and global developmental delay in a female subject by enhancing synaptic transmission.

scholarly journals Case Report: A Novel de novo Mutation in DNM1L Presenting With Developmental Delay, Ataxia, and Peripheral Neuropathy

2021 ◽  
Vol 9 ◽  
Author(s):  
Yanping Wei ◽  
Min Qian
Keyword(s):  
Peripheral Neuropathy ◽  
Developmental Delay ◽  
De Novo ◽  
Refractory Epilepsy ◽  
De Novo Mutation ◽  
Global Developmental Delay ◽  
Missense Mutations ◽  
Related Protein ◽  
Resonance Imaging ◽  
Genetic Results

DNM1L encodes dynamin-related protein 1 (Drp1), which is a member of the dynamin superfamily of GTPases and mediates mitochondrial and peroxisomal fission. In humans, several de novo heterozygous missense mutations in DNM1L have been reported, which were characterized by devastating courses with refractory epilepsy, myoclonus, and brain atrophy on MRI. We describe a 4.5-year-old male child harboring a novel de novo mutation in DNM1L presenting a phenotype of developmental delay, ataxia, and peripheral neuropathy. The clinical features, magnetic resonance imaging findings, and genetic results were summarized. Meanwhile, all the cases of DNM1L mutations reported were reviewed. DNM1L variants may need to be considered in phenotypes that include global developmental delay, peripheral neuropathy, and ataxia.

scholarly journals Biophysical classification of a CACNA1D de novo mutation as a high-risk mutation for a severe neurodevelopmental disorder

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Nadja T. Hofer ◽  
Petronel Tuluc ◽  
Nadine J. Ortner ◽  
Yuliia V. Nikonishyna ◽  
Monica L. Fernándes-Quintero ◽  
...  
Keyword(s):  
High Risk ◽  
Neurodevelopmental Disorders ◽  
Developmental Disorder ◽  
De Novo ◽  
Disease Risk ◽  
Neurodevelopmental Disorder ◽  
Autism Spectrum ◽  
De Novo Mutation ◽  
Loss Of Function ◽  
Gain Of Function

Abstract Background There is increasing evidence that de novo CACNA1D missense mutations inducing increased Cav1.3 L-type Ca2+-channel-function confer a high risk for neurodevelopmental disorders (autism spectrum disorder with and without neurological and endocrine symptoms). Electrophysiological studies demonstrating the presence or absence of typical gain-of-function gating changes could therefore serve as a tool to distinguish likely disease-causing from non-pathogenic de novo CACNA1D variants in affected individuals. We tested this hypothesis for mutation S652L, which has previously been reported in twins with a severe neurodevelopmental disorder in the Deciphering Developmental Disorder Study, but has not been classified as a novel disease mutation. Methods For functional characterization, wild-type and mutant Cav1.3 channel complexes were expressed in tsA-201 cells and tested for typical gain-of-function gating changes using the whole-cell patch-clamp technique. Results Mutation S652L significantly shifted the voltage-dependence of activation and steady-state inactivation to more negative potentials (~ 13–17 mV) and increased window currents at subthreshold voltages. Moreover, it slowed tail currents and increased Ca2+-levels during action potential-like stimulations, characteristic for gain-of-function changes. To provide evidence that only gain-of-function variants confer high disease risk, we also studied missense variant S652W reported in apparently healthy individuals. S652W shifted activation and inactivation to more positive voltages, compatible with a loss-of-function phenotype. Mutation S652L increased the sensitivity of Cav1.3 for inhibition by the dihydropyridine L-type Ca2+-channel blocker isradipine by 3–4-fold. Conclusions and limitations Our data provide evidence that gain-of-function CACNA1D mutations, such as S652L, but not loss-of-function mutations, such as S652W, cause high risk for neurodevelopmental disorders including autism. This adds CACNA1D to the list of novel disease genes identified in the Deciphering Developmental Disorder Study. Although our study does not provide insight into the cellular mechanisms of pathological Cav1.3 signaling in neurons, we provide a unifying mechanism of gain-of-function CACNA1D mutations as a predictor for disease risk, which may allow the establishment of a more reliable diagnosis of affected individuals. Moreover, the increased sensitivity of S652L to isradipine encourages a therapeutic trial in the two affected individuals. This can address the important question to which extent symptoms are responsive to therapy with Ca2+-channel blockers.

The Clinical Picture of a Bilateral Perisylvian Syndrome as the Initial Symptom of Mega-Corpus-Callosum Syndrome due to a MAST1-Gene Mutation

2020 ◽  
Vol 51 (06) ◽  
pp. 435-439
Author(s):  
Laura Hecher ◽  
Jessika Johannsen ◽  
Tatjana Bierhals ◽  
Jan-Hendrik Buhk ◽  
Maja Hempel ◽  
...  
Keyword(s):  
Corpus Callosum ◽  
Clinical Picture ◽  
De Novo ◽  
De Novo Mutation ◽  
Global Developmental Delay ◽  
Initial Symptom ◽  
Imaging Features ◽  
Serine Threonine Kinase ◽  
Threonine Kinase ◽  
Migration Disorder

AbstractCongenital bilateral perisylvian syndrome (CBPS) is a rare neurological disorder associated with typical clinical and imaging features such as bilateral symmetrical polymicrogyria, either exclusively or mainly affecting the perisylvian region of the brain. We present a girl with the typical clinical picture of a CBPS and a complex migration disorder, predominantly presenting as bilateral symmetrical polymicrogyria associated with corpus callosum hyperplasia, ventricular dilation, and pontine hypoplasia. At the age of 6 months, the girl showed a profound global developmental delay, seizures refractory to treatment, and severe oromotor dysfunction. Exome analysis revealed a de novo mutation in microtubule-associated serine/threonine kinase 1 (MAST1). Recently, mutations in this gene were described in six patients with a cortical migration disorder named mega-corpus-callosum syndrome with cerebellar hypoplasia. Although all patients present the clinical and imaging features of CBPS, a clear assignment between CBPS and MAST1 mutations has not been reported yet.

scholarly journals A Novel de novo Mutation in EBF3 Associated With Hypotonia, Ataxia, and Delayed Development Syndrome in a Chinese Boy

2021 ◽  
Vol 12 ◽  
Author(s):  
Yanru Huang ◽  
Libin Mei ◽  
Yangdan Wang ◽  
Huiming Ye ◽  
Xiaomin Ma ◽  
...  
Keyword(s):  
Developmental Delay ◽  
Clinical Diagnosis ◽  
De Novo ◽  
Pathogenic Mutation ◽  
De Novo Mutation ◽  
Luciferase Reporter ◽  
Global Developmental Delay ◽  
Whole Exome ◽  
Development Delay ◽  
Delayed Development

ObjectiveGlobal developmental delay has markedly high phenotypic and genetic heterogeneity, and is a great challenge for clinical diagnosis. Hypotonia, ataxia, and delayed development syndrome (HADDS), first reported in 2017, is one type of global development delay. The aim of the present study was to investigate the genetic etiology of a Chinese boy with global developmental delay.MethodsWe combined clinical and imaging phenotyping with trio whole-exome sequencing and Sanger sequencing to the patient and his clinically unaffected parents. A luciferase reporter and immunofluorescence were performed to detect the effect of mutation on transcriptional activity and subcellular localization.ResultsThe patient presented with several previously unreported symptoms in the patients with HADDS, including hemangiomas, mild hearing abnormalities and tracheomalacia. A novel EBF3 c.589A > G missense mutation (p.Asn197Asp, p.N197D) was identified in the patient but not in his parents. By constructing the plasmid and transfecting HEK293T cells, EBF3-N197D mutant showed impaired activation of luciferase reporter expression of the p21 promoter, and the mutant affected its entry into the nucleus.ConclusionTo the best of our knowledge, this is the first report of EBF3 pathogenic mutation which associated with HADDS in the Chinese population. Our results expand the phenotypes and pathogenic mutation spectrum of HADDS, thus potentially facilitating the clinical diagnosis and genetic counseling of HADDS patients.

scholarly journals De novo mutation screening in childhood-onset cerebellar atrophy identifies gain-of-function mutations in the CACNA1G calcium channel gene

Brain ◽  
2018 ◽  
Vol 141 (7) ◽  
pp. 1998-2013 ◽  
Author(s):  
Jean Chemin ◽  
Karine Siquier-Pernet ◽  
Michaël Nicouleau ◽  
Giulia Barcia ◽  
Ali Ahmad ◽  
...  
Keyword(s):  
Calcium Channel ◽  
De Novo ◽  
Mutation Screening ◽  
Cerebellar Atrophy ◽  
De Novo Mutation ◽  
Childhood Onset ◽  
Gain Of Function ◽  
Channel Gene

The Sins of Our Forefathers: Paternal Impacts on De Novo Mutation Rate and Development

2020 ◽  
Vol 54 (1) ◽  
pp. 1-24 ◽  
Author(s):  
R. John Aitken ◽  
Geoffry N. De Iuliis ◽  
Brett Nixon
Keyword(s):  
Oxidative Dna Damage ◽  
De Novo ◽  
Hot Spot ◽  
Spontaneous Mutation ◽  
Genetic Diseases ◽  
Well Being ◽  
The Body ◽  
Apert Syndrome ◽  
De Novo Mutation ◽  
Chromosome 15

Spermatogonial stem cells (SSCs) are generally characterized by excellent DNA surveillance and repair, resulting in one of the lowest spontaneous mutation rates in the body. However, the barriers to mutagenesis can be overwhelmed under two sets of circumstances. First, replication errors may generate age-dependent mutations that provide the mutant cells with a selective advantage, leading to the clonal expansions responsible for dominant genetic diseases such as Apert syndrome and achondroplasia. The second mechanism centers on the vulnerability of the male germline to oxidative stress and the induction of oxidative DNA damage in spermatozoa. Defective repair of such oxidative damage in the fertilized oocyte results in the creation of mutations in the zygote that can influence the health and well-being of the offspring. A particular hot spot for such oxidative attack on chromosome 15 has been found to align with several mutations responsible for paternally mediated disease, including cancer, psychiatric disorders, and infertility.

scholarly journals Campomelic dysplasia: an overview of a rare genetic disorder

2019 ◽  
Vol 18 (3) ◽  
pp. 67-70
Author(s):  
N. Antonakopoulos ◽  
D. Vrachnis ◽  
N. Loukas ◽  
Ch. Christodoulaki ◽  
Z. Iliodromiti ◽  
...  
Keyword(s):  
De Novo ◽  
Pregnancy Termination ◽  
Genetic Disorder ◽  
Molecular Genetic ◽  
Ambiguous Genitalia ◽  
De Novo Mutation ◽  
Campomelic Dysplasia ◽  
Rare Genetic Disorder ◽  
Radiologic Evaluation ◽  
Increased Risk

Campomelic dysplasia is a rare and severe genetic condition that is characterized by shortening and bowing of the long bones, abnormal face, multiple congenital anomalies, and ambiguous genitalia. Having conducted a review of the existing literature on this rare genetic disorder, we herein present the most pertinent and essential data on the condition viewed from the clinical perspective. In the majority of cases when the neonate survives the condition, since the underlying cause is more often than not a de novo mutation of the SOX9 gene, there is no increased risk of recurrence. Diagnosis is tentatively made based on skeletal findings during routine prenatal ultrasound; it may subsequently be confirmed via either prenatal or postnatal molecular genetic testing or else radiologic evaluation. In general, the condition is considered to be lethal in the neonatal period, there is no prenatal treatment and pregnancy termination is an option.

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