scholarly journals Critical Role of E1623 Residue in S3-S4 Loop of Nav1.1 Channel and Correlation Between Nature of Substitution and Functional Alteration

2022 ◽  
Vol 14 ◽  
Author(s):  
Tao Su ◽  
Meng-Long Chen ◽  
Li-Hong Liu ◽  
Hen Meng ◽  
Bin Tang ◽  
...  

Objective: An overwhelming majority of the genetic variants associated with genetic disorders are missense. The association between the nature of substitution and the functional alteration, which is critical in determining the pathogenicity of variants, remains largely unknown. With a novel missense variant (E1623A) identified from two epileptic cases, which occurs in the extracellular S3-S4 loop of Nav1.1, we studied functional changes of all latent mutations at residue E1623, aiming to understand the relationship between substitution nature and functional alteration.Methods: Six latent mutants with amino acid substitutions at E1623 were generated, followed by measurements of their electrophysiological alterations. Different computational analyses were used to parameterize the residue alterations.Results: Structural modeling indicated that the E1623 was located in the peripheral region far from the central pore, and contributed to the tight turn of the S3-S4 loop. The E1623 residue exhibited low functional tolerance to the substitutions with the most remarkable loss-of-function found in E1623A, including reduced current density, less steady-state availability of activation and inactivation, and slower recovery from fast inactivation. Correlation analysis between electrophysiological parameters and the parameterized physicochemical properties of different residues suggested that hydrophilicity of side-chain at E1623 might be a crucial contributor for voltage-dependent kinetics. However, none of the established algorithms on the physicochemical variations of residues could well predict changes in the channel conductance property indicated by peak current density.Significance: The results established the important role of the extracellular S3-S4 loop in Nav1.1 channel gating and proposed a possible effect of local conformational loop flexibility on channel conductance and kinetics. Site-specific knowledge of protein will be a fundamental task for future bioinformatics.

2018 ◽  
Vol 56 (5) ◽  
pp. 332-339 ◽  
Author(s):  
Abolfazl Rad ◽  
Umut Altunoglu ◽  
Rebecca Miller ◽  
Reza Maroofian ◽  
Kiely N James ◽  
...  

BackgroundPutative nucleotidyltransferase MAB21L1 is a member of an evolutionarily well-conserved family of the male abnormal 21 (MAB21)-like proteins. Little is known about the biochemical function of the protein; however, prior studies have shown essential roles for several aspects of embryonic development including the eye, midbrain, neural tube and reproductive organs.ObjectiveA homozygous truncating variant in MAB21L1 has recently been described in a male affected by intellectual disability, scrotal agenesis, ophthalmological anomalies, cerebellar hypoplasia and facial dysmorphism. We employed a combination of exome sequencing and homozygosity mapping to identify the underlying genetic cause in subjects with similar phenotypic features descending from five unrelated consanguineous families.ResultsWe identified four homozygous MAB21L1 loss of function variants (p.Glu281fs*20, p.Arg287Glufs*14 p.Tyr280* and p.Ser93Serfs*48) and one missense variant (p.Gln233Pro) in 10 affected individuals from 5 consanguineous families with a distinctive autosomal recessive neurodevelopmental syndrome. Cardinal features of this syndrome include a characteristic facial gestalt, corneal dystrophy, hairy nipples, underdeveloped labioscrotal folds and scrotum/scrotal agenesis as well as cerebellar hypoplasia with ataxia and variable microcephaly.ConclusionThis report defines an ultrarare but clinically recognisable Cerebello-Oculo-Facio-Genital syndrome associated with recessive MAB21L1 variants. Additionally, our findings further support the critical role of MAB21L1 in cerebellum, lens, genitalia and as craniofacial morphogenesis.


2016 ◽  
Vol 310 (3) ◽  
pp. C233-C242 ◽  
Author(s):  
Erik Allman ◽  
Qian Wang ◽  
Rachel L. Walker ◽  
Molly Austen ◽  
Maureen A. Peters ◽  
...  

Calcineurin B homologous proteins (CHP) are N-myristoylated, EF-hand Ca2+-binding proteins that bind to and regulate Na+/H+ exchangers, which occurs through a variety of mechanisms whose relative significance is incompletely understood. Like mammals, Caenorhabditis elegans has three CHP paralogs, but unlike mammals, worms can survive CHP loss-of-function. However, mutants for the CHP ortholog PBO-1 are unfit, and PBO-1 has been shown to be required for proton signaling by the basolateral Na+/H+ exchanger NHX-7 and for proton-coupled intestinal nutrient uptake by the apical Na+/H+ exchanger NHX-2. Here, we have used this genetic model organism to interrogate PBO-1's mechanism of action. Using fluorescent tags to monitor Na+/H+ exchanger trafficking and localization, we found that loss of either PBO-1 binding or activity caused NHX-7 to accumulate in late endosomes/lysosomes. In contrast, NHX-2 was stabilized at the apical membrane by a nonfunctional PBO-1 protein and was only internalized following its complete loss. Additionally, two pbo-1 paralogs were identified, and their expression patterns were analyzed. One of these contributed to the function of the excretory cell, which acts like a kidney in worms, establishing an alternative model for testing the role of this protein in membrane transporter trafficking and regulation. These results lead us to conclude that the role of CHP in Na+/H+ exchanger regulation differs between apical and basolateral transporters. This further emphasizes the importance of proper targeting of Na+/H+ exchangers and the critical role of CHP family proteins in this process.


2021 ◽  
Author(s):  
Niklas Schwarz ◽  
Simone Seiffert ◽  
Manuela Pendziwiat ◽  
Annika Rademacher ◽  
Tobias Bruenger ◽  
...  

Background KCNC2 encodes a member of the shaw-related voltage-gated potassium channel family (KV3.2), which are important for sustained high-frequency firing and optimized energy efficiency of action potentials in the brain. Methods Individuals with KCNC2 variants detected by exome sequencing were selected for clinical, further genetic and functional analysis. The cases were referred through clinical and research collaborations in our study. Four de novo variants were examined electrophysiologically in Xenopus laevis oocytes. Results We identified novel KCNC2 variants in 27 patients with various forms of epilepsy. Functional analysis demonstrated gain-of-function in severe and loss-of-function in milder phenotypes as the underlying pathomechanisms with specific response to valproic acid. Conclusion These findings implicate KCNC2 as a novel causative gene for epilepsy emphasizing the critical role of KV3.2 in the regulation of brain excitability with an interesting genotype-phenotype correlation and a potential concept for precision medicine.


2021 ◽  
pp. mcs.a006122
Author(s):  
Mohammad Marhabaie ◽  
Scott E Hickey ◽  
Katherine E Miller ◽  
Olivia Grischow ◽  
Kathleen M Schieffer ◽  
...  

There is increasing recognition for the contribution of genetic mosaicism to human disease, particularly as high-throughput sequencing has enabled detection of sequence variants at very low allele frequencies. Here, we describe an infant male who presented at 9 months of age with hypotonia, dysmorphic features, congenital heart disease, hyperinsulinemic hypoglycemia, hypothyroidism, and bilateral sensorineural hearing loss. Whole-genome sequencing of the proband and the parents uncovered an apparent de novo mutation in the X-linked SMS gene. SMS encodes spermine synthase, which catalyzes the production of spermine from spermidine. Inactivation of the SMS gene disrupts the spermidine/spermine ratio, resulting in Snyder-Robinson syndrome. The variant in our patient is absent from the gnomAD and ExAC databases and causes a missense change (p.Arg130Cys) predicted to be damaging by most in silico tools. While Sanger sequencing confirmed the de novo status in our proband, PCR and deep targeted resequencing to ~84,000-175,000x depth revealed that the variant is present in blood from the unaffected mother at ~3% variant allele frequency. Our findings thus provided a long-sought diagnosis for the family while highlighting the role of parental mosaicism in severe genetic disorders.


PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e11929
Author(s):  
Gaoda Ju ◽  
Tianhao Zhou ◽  
Rui Zhang ◽  
Xiaozao Pan ◽  
Bing Xue ◽  
...  

Background Dual specificity protein phosphatase (DUSP)12 is an atypical member of the protein tyrosine phosphatase family, which are overexpressed in multiple types of malignant tumors. This protein family protect cells from apoptosis and promotes the proliferation and motility of cells. However, the pathological role of DUSP12 in hepatocellular carcinoma (HCC) is incompletely understood. Methods We analyzed mRNA expression of DUSP12 between HCC and normal liver tissues using multiple online databases, and explored the status of DUSP12 mutants using the cBioPortal database. The correlation between DUSP12 expression and tumor-infiltrating immune cells was demonstrated using the Tumor Immune Estimation Resource database and the Tumor and Immune System Interaction Database. Loss of function assay was utilized to evaluate the role of DUSP12 in HCC progression. Results DUSP12 had higher expression along with mRNA amplification in HCC tissues compared with those in normal liver tissues, which suggested that higher DUSP12 expression predicted shorter overall survival. Analyses of functional enrichment of differentially expressed genes suggested that DUSP12 regulated HCC tumorigenesis, and that knockdown of DUSP12 expression by short hairpin (sh)RNA decreased the proliferation and migration of HCC cells. Besides, DUSP12 expression was positively associated with the infiltration of cluster of differentiation (CD)4+ T cells (especially CD4+ regulatory T cells), macrophages, neutrophils and dendritic cells. DUSP12 expression was positively associated with immune-checkpoint moieties, and was downregulated in a C3 immune-subgroup of HCC (which had the longest survival). Conclusion These data suggest that DUSP12 may have a critical role in the tumorigenesis, infiltration of immune cells, and prognosis of HCC.


2021 ◽  
Vol 15 ◽  
Author(s):  
Nikolas Layer ◽  
Lukas Sonnenberg ◽  
Emilio Pardo González ◽  
Jan Benda ◽  
Ulrike B. S. Hedrich ◽  
...  

Dravet syndrome (DS) is a developmental epileptic encephalopathy mainly caused by functional NaV1.1 haploinsufficiency in inhibitory interneurons. Recently, a new conditional mouse model expressing the recurrent human p.(Ala1783Val) missense variant has become available. In this study, we provided an electrophysiological characterization of this variant in tsA201 cells, revealing both altered voltage-dependence of activation and slow inactivation without reduced sodium peak current density. Based on these data, simulated interneuron (IN) firing properties in a conductance-based single-compartment model suggested surprisingly similar firing deficits for NaV1.1A1783V and full haploinsufficiency as caused by heterozygous truncation variants. Impaired NaV1.1A1783V channel activation was predicted to have a significantly larger impact on channel function than altered slow inactivation and is therefore proposed as the main mechanism underlying IN dysfunction. The computational model was validated in cortical organotypic slice cultures derived from conditional Scn1aA1783V mice. Pan-neuronal activation of the p.Ala1783V in vitro confirmed a predicted IN firing deficit and revealed an accompanying reduction of interneuronal input resistance while demonstrating normal excitability of pyramidal neurons. Altered input resistance was fed back into the model for further refinement. Taken together these data demonstrate that primary loss of function (LOF) gating properties accompanied by altered membrane characteristics may match effects of full haploinsufficiency on the neuronal level despite maintaining physiological peak current density, thereby causing DS.


2007 ◽  
Vol 30 (4) ◽  
pp. 87
Author(s):  
A. E. Lin ◽  
A. Wakeham ◽  
A. You-Ten ◽  
G. Wood ◽  
T. W. Mak

Ubiquitination is a eukaryotic process of selective proteolysis, where a highly conserved ubiquitin protein is selectively added as a chain to the targeted to a protein for degradation. In recent years, the process of ubiquitination has been shown to be a critical mechanism that can affect essential signalling pathways, including apoptosis, cell cycle arrest and induction of the inflammatory response. Thus, alterations in the ubiquitination process can alter signalling pathways pivotal to numerous disease pathologies. This is clearly demonstrated in perturbations of ubiquitination in the NFκB giving rise to cancer and other immunological disease processes. To gain insight into pathways that require regulation by ubiquitination, our lab has directed focus on the highly conserved E3 ligase, Ariadne 2. Ariadne 2 is characterized as a putative RING finger E3 ligase and is part of the family of highly conserved RBR (RING-B-Box-RING) superfamily. The role of Ariadne 2 has been well studied in Drosophila melanogaster, however, little is known of the function of Ariadne 2 in mammalian systems. Therefore, the main objectives of the project are as follows: To determine the biological role of Ariadne 2, the role of Ariadne 2 in development and differentiation, and the consequences of in vivo loss of Ariadne 2 expression. We are currently investigating the role of Ariadne 2 as an E3 ligase and its involvement in the immune response. To date, we have shown that Ariadne 2 is ubiquitously expressed, especially in the brain, heart, spleen and thymus. For in vivo loss of function analysis, mice were generated by homologous recombination to be deficient for Ariadne 2. These deficient mice die prematurely soon after birth, suggesting a critical role for Ariadne 2 in development and survival. We are currently focusing on the role of Ariadne 2 in development and it’s role in immune pathologies, in particular, spontaneous autoimmunity, using both in vitro studies and in vivo models.


Development ◽  
1998 ◽  
Vol 125 (3) ◽  
pp. 393-406 ◽  
Author(s):  
V.E. Prince ◽  
C.B. Moens ◽  
C.B. Kimmel ◽  
R.K. Ho

The developing hindbrain is organized into a series of segments termed rhombomeres which represent lineage restricted compartments correlating with domains of gene expression and neuronal differentiation. In this study, we investigate the processes of hindbrain segmentation and the acquisition of segmental identity by analyzing the expression of zebrafish hox genes in the hindbrains of normal fish and fish with a loss-of-function mutation in the segmentation gene valentino (val, the homologue of mouse kreisler; Moens, C. B., Cordes, S. P. Giorgianni, M. W., Barsh, G. S. and Kimmel, C. B. (1998). Development 125, 381–391). We find that zebrafish hox genes generally have similar expression profiles to their murine and avian counterparts, although there are several differences in timing and spatial extent of expression which may underlie some of the functional changes that have occurred along the separate evolutionary lineages of teleosts and tetrapods. Our analysis of hox gene expression in val- embryos confirms that the val gene product is important for subdivision of the presumptive rhombomere 5 and 6 territory into definitive rhombomeres, suggests that the val gene product plays a critical role in regulating hox gene transcription, and indicates that some neural crest cells are inappropriately specified in val- embryos. Our analysis of gene expression at several developmental stages has allowed us to infer differences between primary and secondary defects in the val mutant: we find that extended domains of expression for some hox genes are secondary, late phenomena potentially resulting from inappropriate cell mixing or lack of normal inter-rhombomeric interactions in the caudal hindbrain.


2010 ◽  
Vol 30 (16) ◽  
pp. 3916-3928 ◽  
Author(s):  
Jamie R. Weaver ◽  
Garnik Sarkisian ◽  
Christopher Krapp ◽  
Jesse Mager ◽  
Mellissa R. W. Mann ◽  
...  

ABSTRACT Imprinted genes are expressed in a monoallelic, parent-of-origin-specific manner. Clusters of imprinted genes are regulated by imprinting control regions (ICRs) characterized by DNA methylation of one allele. This methylation is critical for imprinting; a reduction in the DNA methyltransferase DNMT1 causes a widespread loss of imprinting. To better understand the role of DNA methylation in the regulation of imprinting, we characterized the effects of Dnmt1 mutations on the expression of a panel of imprinted genes in the embryo and placenta. We found striking differences among imprinted domains. The Igf2 and Peg3 domains showed imprinting perturbations with both null and partial loss-of-function mutations, and both domains had pairs of coordinately regulated genes with opposite responses to loss of DNMT1 function, suggesting these domains employ similar regulatory mechanisms. Genes in the Kcnq1 domain were less sensitive to the absence of DNMT1. Cdkn1c exhibited imprinting perturbations only in null mutants, while Kcnq1 and Ascl2 were largely unaffected by a loss of DNMT1 function. These results emphasize the critical role for DNA methylation in imprinting and reveal the different ways it controls gene expression.


2008 ◽  
Vol 54 (2) ◽  
pp. 284-298 ◽  
Author(s):  
Charles R. Dietrich ◽  
Gongshe Han ◽  
Ming Chen ◽  
R. Howard Berg ◽  
Teresa M. Dunn ◽  
...  

Sign in / Sign up

Export Citation Format

Share Document