scholarly journals CACNA1A Mutations Causing Early Onset Ataxia: Profiling Clinical, Dysmorphic and Structural-Functional Findings

2021 ◽  
Vol 22 (10) ◽  
pp. 5180
Author(s):  
Antonio F. Martínez-Monseny ◽  
Albert Edo ◽  
Dídac Casas-Alba ◽  
Mercè Izquierdo-Serra ◽  
Mercè Bolasell ◽  
...  
Keyword(s):  
Neurodevelopmental Disorder ◽  
Functional Characterization ◽  
Cerebellar Atrophy ◽  
Structural Data ◽  
Loss Of Function ◽  
Nasal Bridge ◽  
Structural Localization ◽  
Dysmorphic Features ◽  
New Variant ◽  
Evolutionary Features

The CACNA1A gene encodes the pore-forming α1A subunit of the voltage-gated CaV2.1 Ca2+ channel, essential in neurotransmission, especially in Purkinje cells. Mutations in CACNA1A result in great clinical heterogeneity with progressive symptoms, paroxysmal events or both. During infancy, clinical and neuroimaging findings may be unspecific, and no dysmorphic features have been reported. We present the clinical, radiological and evolutionary features of three patients with congenital ataxia, one of them carrying a new variant. We report the structural localization of variants and their expected functional consequences. There was an improvement in cerebellar syndrome over time despite a cerebellar atrophy progression, inconsistent response to acetazolamide and positive response to methylphenidate. The patients shared distinctive facial gestalt: oval face, prominent forehead, hypertelorism, downslanting palpebral fissures and narrow nasal bridge. The two α1A affected residues are fully conserved throughout evolution and among the whole human CaV channel family. They contribute to the channel pore and the voltage sensor segment. According to structural data analysis and available functional characterization, they are expected to exert gain- (F1394L) and loss-of-function (R1664Q/R1669Q) effect, respectively. Among the CACNA1A-related phenotypes, our results suggest that non-progressive congenital ataxia is associated with developmental delay and dysmorphic features, constituting a recognizable syndromic neurodevelopmental disorder.

scholarly journals A mutation in CaV2.1 linked to a severe neurodevelopmental disorder impairs channel gating

2019 ◽  
Vol 151 (6) ◽  
pp. 850-859 ◽  
Author(s):  
Sidharth Tyagi ◽  
Tyler R. Bendrick ◽  
Dilyana Filipova ◽  
Symeon Papadopoulos ◽  
Roger A. Bannister
Keyword(s):  
Action Potential ◽  
Neuromuscular Junctions ◽  
Neurodevelopmental Disorder ◽  
Cerebellar Atrophy ◽  
Global Developmental Delay ◽  
Loss Of Function ◽  
Open Probability ◽  
Mutant Channel ◽  
Axon Terminals ◽  
Central Synapses

Ca2+ flux into axon terminals via P-/Q-type CaV2.1 channels is the trigger for neurotransmitter vesicle release at neuromuscular junctions (NMJs) and many central synapses. Recently, an arginine to proline substitution (R1673P) in the S4 voltage-sensing helix of the fourth membrane-bound repeat of CaV2.1 was linked to a severe neurological disorder characterized by generalized hypotonia, ataxia, cerebellar atrophy, and global developmental delay. The R1673P mutation was proposed to cause a gain of function in CaV2.1 leading to neuronal Ca2+ toxicity based on the ability of the mutant channel to rescue the photoreceptor response in CaV2.1-deficient Drosophila cacophony larvae. Here, we show that the corresponding mutation in rat CaV2.1 (R1624P) causes a profound loss of channel function; voltage-clamp analysis of tsA-201 cells expressing this mutant channel revealed an ∼25-mV depolarizing shift in the voltage dependence of activation. This alteration in activation implies that a significant fraction of CaV2.1 channels resident in presynaptic terminals are unlikely to open in response to an action potential, thereby increasing the probability of synaptic failure at both NMJs and central synapses. Indeed, the mutant channel supported only minimal Ca2+ flux in response to an action potential–like waveform. Application of GV-58, a compound previously shown to stabilize the open state of wild-type CaV2.1 channels, partially restored Ca2+ current by shifting mutant activation to more hyperpolarizing potentials and slowing deactivation. Consequently, GV-58 also rescued a portion of Ca2+ flux during action potential–like stimuli. Thus, our data raise the possibility that therapeutic agents that increase channel open probability or prolong action potential duration may be effective in combatting this and other severe neurodevelopmental disorders caused by loss-of-function mutations in CaV2.1.

scholarly journals Characterization of a KCNB1 variant associated with autism, intellectual disability, and epilepsy

2017 ◽  
Vol 3 (6) ◽  
pp. e198 ◽  
Author(s):  
Jeffrey D. Calhoun ◽  
Carlos G. Vanoye ◽  
Fernando Kok ◽  
Alfred L. George ◽  
Jennifer A. Kearney
Keyword(s):  
Protein Expression ◽  
Exome Sequencing ◽  
Biochemical Characterization ◽  
Neurodevelopmental Disorder ◽  
Functional Characterization ◽  
Loss Of Function ◽  
Phenotypic Spectrum ◽  
Whole Exome ◽  
Protein Dysfunction

Objective:To perform functional characterization of a potentially pathogenic KCNB1 variant identified by clinical exome sequencing of a proband with a neurodevelopmental disorder that included epilepsy and centrotemporal spikes on EEG.Methods:Whole-exome sequencing identified the KCNB1 variant c.595A>T (p.Ile199Phe). Biochemical and electrophysiologic experiments were performed to determine whether this variant affected protein expression, trafficking, and channel functional properties.Results:Biochemical characterization of the variant suggested normal protein expression and trafficking. Functional characterization revealed biophysical channel defects in assembled homotetrameric and heterotetrameric channels.Conclusions:The identification of the KCNB1 variant c.595A>T (p.Ile199Phe) in a neurodevelopmental disorder that included epilepsy with centrotemporal spikes expands the phenotypic spectrum of epilepsies associated with KCNB1 variants. The KCNB1-I199F variant exhibited partial loss of function relative to the wild-type channel. This defect is arguably less severe than previously reported KCNB1 variants, suggesting the possibility that the degree of KCNB1 protein dysfunction may influence disease severity.

scholarly journals SAT-077 Two Cases of Hypoparathyroidism Due to Activating Calcium Sensing Receptor Mutation

2020 ◽  
Vol 4 (Supplement_1) ◽  
Author(s):  
Ahmed Badran ◽  
Vivian Chin
Keyword(s):  
Genetic Testing ◽  
Gene Mutation ◽  
Functional Characterization ◽  
Heterozygous Mutation ◽  
Calcium Sensing Receptor ◽  
Dysmorphic Features ◽  
High Phosphorus ◽  
Casr Gene ◽  
Calcium Sensing ◽  
New Variant

Abstract Introduction The extracellular calcium-sensing receptor (CaSR) expressed mainly in the parathyroid gland and kidneys regulates calcium (Ca+2) homeostasis through parathyroid hormone (PTH) secretion. Activating mutations of CaSR can lead to autosomal dominant hypocalcemia and severe congenital hypoparathyroidism. Constitutively activated CaSR receptors blocks PTH release leading to hypocalcemia, hyperphosphatemia and decreased Ca+2 reabsorption from the kidney. Case 1: 14 year old male presented for an evaluation of hypocalcemia and hyperphosphatemia found on routine blood work. He denied symptoms of hypocalcemia. He had normal vital signs, positive Chovstek sign but rest of exam was unremarkable. His lab results showed low Ca+2 8.1 mg/dl (8.6–10 mg/dl), high phosphorus 6 mg/dl (2.7–4.5 mg/dl) and inappropriately normal PTH 26.8 pg/ml (10–65 pg/ml). FISH was negative for DiGeorge. Genetic testing showed heterozygous CaSR gene mutation I822T, variant of uncertain significance. His father with primary hypoparathyroidism has the same CaSR gene mutation; mother is healthy and tested negative for this variant. Given the inheritance pattern of the mutation, it is likely a pathologic mutation. He is maintained on Calcium (1500 mg BID) and Calcitriol (0.5 mcg PO BID) and is doing well. Case 2: One day old premature 32-week old infant girl was found to have early onset neonatal hypocalcemia 6.1 mg/dl (6.2–11 mg/dl) during NICU admission for respiratory distress, inappropriately normal PTH 18.5 pg/ml and high phosphorus 8.8 mg/dl (4.6–7.9 mg/dl). She had no symptoms of hypocalcemia in the NICU or at home. She did not have any dysmorphic features. FISH was negative for DiGeorge. Genetic testing to sequence genes including AIRE, AP2S1, CASR, GNAS, HADHA, HADHB, PTH1R, SOX3, STX16, TBCE was done and revealed a novel heterozygous mutation in the CaSR gene for a missense variant c.2495T>C (p.lle832Thr) and STX16 c.644A>T, possibly benign variant. Unfortunately, the parents have not consented to testing yet. Further familial and functional characterization of this new variant is necessary to confirm its possible pathogenetic role in this hypocalcemic patient. Currently she is maintained on ergocalciferol 800 IU, calcitriol 0.25 mcg and sevelamer 3 packets daily and is doing well. Conclusion: In the workup for primary hypoparathyroidism without dysmorphic features and tests negative for DiGeorge, CaSR mutations should be investigated as part of the differential as we have identified variants in the CaSR gene in 2 children with asymptomatic hypocalcemia, one of which is a novel mutation which has never been reported before.

scholarly journals Functional Characterization of KCNMA1 mutation associated with dyskinesia, seizure, developmental delay, and cerebellar atrophy

2021 ◽  
Author(s):  
Emrah Yucesan ◽  
Beyza Goncu ◽  
Cemil Ozgul ◽  
Arda Kebapci ◽  
Ayca Dilruba Aslanger ◽  
...  
Keyword(s):  
Functional Characterization ◽  
Cerebellar Atrophy ◽  
Bk Channels ◽  
Bk Channel ◽  
Functional Study ◽  
Loss Of Function ◽  
Gain Of Function ◽  
Α Subunit ◽  
Truncating Mutation

Abstract KCNMA1 located on chromosome 10q22.3, encodes the pore-forming α subunit of the “Big K+” (BK) large conductance calcium and voltage-activated K + channel. BK channels are widely distributed across tissues, including both excitable and non excitable cells. Numerous evidence suggests the functional BK channel alterations produced by different KCNMA1 alleles may associate with different symptoms, such as paroxysmal non kinesigenic dyskinesia with gain of function and ataxia with loss of function. Functional classifications revealed two major patterns, gain of function and loss of function effects on channel properties in different cell lines. In the literature, two mutations have been shown to confer gain of function properties to BK channels: D434G and N995S. On the other hand 10 mutations have been classified as loss of function (S351Y,G354S, G356R, G375R, C413Y/N449fs, I663V, P805L, and D984N) or putative loss of function (premature truncation mutations: Y676Lfs*7 and Arg458Ter). In this study, we report the functional characterization of a variant which was previously reported the whole exome sequencing revealed bi-allelic nonsense variation (NM_001161352.1 (ENST00000286628.8):c.1372C > T; Arg458*) of the cytoplasmic domain of calcium-activated potassium channel subunit alpha-1 protein. To detect functional consequences of the variation immunostaining and electrophysiological studies were conducted. In this study, we conducted patch-clamp recordings on WT and R458X mutant cells. We found the gain of function effect for the mutation. This is the first functional study observing an increased current in the KCNMA1 gene resulting from a truncating mutation

Coffin-Lowry Syndrome

2017 ◽  
Author(s):  
Michael V. Johnston
Keyword(s):  
Neurodevelopmental Disorder ◽  
Camp Response Element Binding ◽  
Loss Of Function ◽  
Camp Response Element ◽  
S6 Kinase ◽  
Dysmorphic Features ◽  
Skeletal Changes ◽  
Severe Intellectual Disability ◽  
Element Binding Protein ◽  
Phosphorylated Creb

Coffin-Lowry syndrome (CLS) is a relatively rare (1:50,000-100,000 incidence) sex-linked neurodevelopmental disorder that includes severe intellectual disability, dysmorphic features including facial and digital abnormalities, growth retardation, and skeletal changes. Most cases are sporadic with only 20% to 30% of cases having an additional family member. CLS is caused by variable loss of function mutations in the RPS6KA3 gene that maps to Xp22.2 and codes for the hRSK2 S6 kinase that phosphorylates the transcription factor CREB (cAMP response element binding protein) as well as other nuclear transcription factors. Phosphorylated CREB (pCREB) plays a major role in memory formation in fruit flies and mammals by activating specific genes through epigenetic histone acetylation.

scholarly journals Functional Characterization of the Adenylyl Cyclase Genesgs-1by Analysis of a Mutational Spectrum inCaenorhabditis elegans

Genetics ◽  
2002 ◽  
Vol 161 (1) ◽  
pp. 133-142 ◽  
Author(s):  
Celine Moorman ◽  
Ronald H A Plasterk
Keyword(s):  
Life Span ◽  
Adenylyl Cyclase ◽  
Neuronal Degeneration ◽  
Functional Characterization ◽  
Adenylyl Cyclases ◽  
Loss Of Function ◽  
C Elegans ◽  
Larval Stages ◽  
Pharyngeal Pumping

AbstractThe sgs-1 (suppressor of activated Gαs) gene encodes one of the four adenylyl cyclases in the nematode C. elegans and is most similar to mammalian adenylyl cyclase type IX. We isolated a complete loss-of-function mutation in sgs-1 and found it to result in animals with retarded development that arrest in variable larval stages. sgs-1 mutant animals exhibit lethargic movement and pharyngeal pumping and (while not reaching adulthood) have a mean life span that is >50% extended compared to wild type. An extensive set of reduction-of-function mutations in sgs-1 was isolated in a screen for suppressors of a neuronal degeneration phenotype induced by the expression of a constitutively active version of the heterotrimeric Gαs subunit of C. elegans. Although most of these mutations change conserved residues within the catalytic domains of sgs-1, mutations in the less-conserved transmembrane domains are also found. The sgs-1 reduction-of-function mutants are viable and have reduced locomotion rates, but do not show defects in pharyngeal pumping or life span.

scholarly journals Emerging Role of ODC1 in Neurodevelopmental Disorders and Brain Development

Genes ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 470
Author(s):  
Jeremy W. Prokop ◽  
Caleb P. Bupp ◽  
Austin Frisch ◽  
Stephanie M. Bilinovich ◽  
Daniel B. Campbell ◽  
...  
Keyword(s):  
Brain Development ◽  
Neural Progenitor Cells ◽  
Neurodevelopmental Disorder ◽  
Fetal Brain ◽  
Missense Variant ◽  
Neural Progenitor ◽  
Loss Of Function ◽  
Gain Of Function ◽  
Systematic Analysis ◽  
Function Expression

Ornithine decarboxylase 1 (ODC1 gene) has been linked through gain-of-function variants to a rare disease featuring developmental delay, alopecia, macrocephaly, and structural brain anomalies. ODC1 has been linked to additional diseases like cancer, with growing evidence for neurological contributions to schizophrenia, mood disorders, anxiety, epilepsy, learning, and suicidal behavior. The evidence of ODC1 connection to neural disorders highlights the need for a systematic analysis of ODC1 genotype-to-phenotype associations. An analysis of variants from ClinVar, Geno2MP, TOPMed, gnomAD, and COSMIC revealed an intellectual disability and seizure connected loss-of-function variant, ODC G84R (rs138359527, NC_000002.12:g.10444500C > T). The missense variant is found in ~1% of South Asian individuals and results in 2.5-fold decrease in enzyme function. Expression quantitative trait loci (eQTLs) reveal multiple functionally annotated, non-coding variants regulating ODC1 that associate with psychiatric/neurological phenotypes. Further dissection of RNA-Seq during fetal brain development and within cerebral organoids showed an association of ODC1 expression with cell proliferation of neural progenitor cells, suggesting gain-of-function variants with neural over-proliferation and loss-of-function variants with neural depletion. The linkage from the expression data of ODC1 in early neural progenitor proliferation to phenotypes of neurodevelopmental delay and to the connection of polyamine metabolites in brain function establish ODC1 as a bona fide neurodevelopmental disorder gene.

scholarly journals CATH functional families predict functional sites in proteins

2020 ◽  
Author(s):  
Sayoni Das ◽  
Harry M Scholes ◽  
Neeladri Sen ◽  
Christine Orengo
Keyword(s):  
Functional Characterization ◽  
Functional Site ◽  
Training Data ◽  
Supplementary Information ◽  
Conserved Residues ◽  
Functional Sites ◽  
Protein Protein Interaction ◽  
Evolutionary Features ◽  
Functional Families

Abstract Motivation Identification of functional sites in proteins is essential for functional characterization, variant interpretation and drug design. Several methods are available for predicting either a generic functional site, or specific types of functional site. Here, we present FunSite, a machine learning predictor that identifies catalytic, ligand-binding and protein–protein interaction functional sites using features derived from protein sequence and structure, and evolutionary data from CATH functional families (FunFams). Results FunSite’s prediction performance was rigorously benchmarked using cross-validation and a holdout dataset. FunSite outperformed other publicly available functional site prediction methods. We show that conserved residues in FunFams are enriched in functional sites. We found FunSite’s performance depends greatly on the quality of functional site annotations and the information content of FunFams in the training data. Finally, we analyze which structural and evolutionary features are most predictive for functional sites. Availabilityand implementation https://github.com/UCL/cath-funsite-predictor. Contact [email protected] or [email protected] Supplementary information Supplementary data are available at Bioinformatics online.

scholarly journals The de novo CACNA1A pathogenic variant Y1384C associated with hemiplegic migraine, early onset cerebellar atrophy and developmental delay leads to a loss of Cav2.1 channel function

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Maria A. Gandini ◽  
Ivana A. Souza ◽  
Laurent Ferron ◽  
A. Micheil Innes ◽  
Gerald W. Zamponi
Keyword(s):  
Developmental Delay ◽  
Early Onset ◽  
Structural Damage ◽  
De Novo ◽  
Splice Variants ◽  
Cerebellar Atrophy ◽  
Familial Hemiplegic Migraine ◽  
Significant Loss ◽  
Loss Of Function ◽  
Hemiplegic Migraine

AbstractCACNA1A pathogenic variants have been linked to several neurological disorders including familial hemiplegic migraine and cerebellar conditions. More recently, de novo variants have been associated with severe early onset developmental encephalopathies. CACNA1A is highly expressed in the central nervous system and encodes the pore-forming CaVα1 subunit of P/Q-type (Cav2.1) calcium channels. We have previously identified a patient with a de novo missense mutation in CACNA1A (p.Y1384C), characterized by hemiplegic migraine, cerebellar atrophy and developmental delay. The mutation is located at the transmembrane S5 segment of the third domain. Functional analysis in two predominant splice variants of the neuronal Cav2.1 channel showed a significant loss of function in current density and changes in gating properties. Moreover, Y1384 variants exhibit differential splice variant-specific effects on recovery from inactivation. Finally, structural analysis revealed structural damage caused by the tyrosine substitution and changes in electrostatic potentials.

scholarly journals HINT1 neuropathy in Norway: clinical, genetic and functional profiling

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Silvia Amor-Barris ◽  
Helle Høyer ◽  
Lin V. Brauteset ◽  
Els De Vriendt ◽  
Linda Strand ◽  
...  
Keyword(s):  
Axonal Neuropathy ◽  
Functional Characterization ◽  
Treatment Strategies ◽  
Central Nervous System Involvement ◽  
Sensory Neuropathy ◽  
Muscle Stiffness ◽  
Compound Heterozygous ◽  
Clinical Genetic ◽  
Cellular Models ◽  
New Variant

Abstract Background Autosomal recessive axonal neuropathy with neuromyotonia has been linked to loss of functional HINT1. The disease is particularly prevalent in Central and South-East Europe, Turkey and Russia due to the high carrier frequency of the c.110G > C (p.Arg37Pro) founder variant. Results In a cohort of 748 Norwegian patients with suspected peripheral neuropathy, we identified two seemingly unrelated individuals, compound heterozygous for a new variant (c.284G > A, p.Arg95Gln) and the most common pathogenic founder variant (c.110G > C, p.Arg37Pro) in the HINT1 gene. Probands presented with motor greater than sensory neuropathy of various onset, accompanied by muscle stiffness and cramps in the limbs. Furthermore, they displayed non-classical symptoms, including pain in the extremities and signs of central nervous system involvement. Haplotype analysis in both patients revealed a common chromosomal background for p.Arg95Gln; moreover, the variant was identified in Swedish carriers. Functional characterization in HINT1-knockout and patient-derived cellular models, and in HNT1-knockout yeast, suggested that the new variant is deleterious for the function of HINT1 and provided mechanistic insights allowing patient stratification for future treatment strategies. Conclusion Our findings broaden the genetic epidemiology of HINT1-neuropathy and have implications for molecular diagnostics of inherited peripheral neuropathies in Scandinavia.

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