OBJECTIVE: To investigate the effect of calmodulin (CaM) and its mutants on binding to voltage-gated Na channel isoleucine-glutamine domain (Na1.2 IQ). METHODS: The cDNA of Na1.2 IQ was constructed by PCR technique, CaM mutants CaM, CaM and CaM were constructed with Quickchange site-directed mutagenesis kit (QIAGEN). The binding of Na1.2 IQ to CaM and CaM mutants under calcium and calcium free conditions were detected by pull-down assay. RESULTS: Na1.2 IQ and CaM were bound to each other at different calcium concentrations, while GST alone did not bind to CaM. The binding affinity of CaM and Na1.2 IQ at [Ca]-free was greater than that at 100 nmol/L [Ca] ( < 0.05). In the absence of calcium, the binding amount of CaM wild-type to Na1.2 IQ was greater than that of its mutant, and the binding affinity of CaM to Na1.2 IQ was the weakest among the three mutants ( < 0.05). CONCLUSIONS The binding ability of CaM and CaM mutants to Na1.2 IQ is Ca-dependent. This study has revealed a new mechanism of Na1.2 regulated by CaM, which would be useful for the study of ion channel related diseases.
Calcium ; metabolism ; Calmodulin ; genetics ; metabolism ; Mutation ; NAV1.2 Voltage-Gated Sodium Channel ; metabolism ; Protein Binding ; genetics

OBJECTIVE: To report on a family which has two siblings with SCN2A mutation caused by germline mosaicism suffering from autism spectrum disorder/development delay (ASD/DD). METHODS: Clinical data was collected for the proband and his parents. Next generation sequencing (NGS) was carried out on the proband and his parents. Suspected mutations were verified by Sanger sequencing of the proband, his parents and brother. To detect whether there is a low proportion of somatic mosaicism in the parents, a droplet digital PCR was conducted. The result of ddPCR showed that the father was germline mosaicism (0.233%). RESULTS: NGS has identified a de novo splicing mutation of the SCN2A gene, c.605+1G>A, in the proband and his brother. Combined with its clinical phenotype and inheritance pattern, SCN2A was judged to be the pathogenic gene. Above findings strongly suggested parental germline mosaicism. CONCLUSION ASD/DD in siblings with SCN2A mutations caused by germline mosaicism. Paternal mosaicism should be considered as one of the important inheritance patterns for counseling parents with a child carrying SCN2A mutation. The ddPCR can help to reveal very low proportion of germline mosaicism.
Autism Spectrum Disorder ; Germ Cells ; Humans ; Male ; Mosaicism ; Mutation ; NAV1.2 Voltage-Gated Sodium Channel/genetics* ; Siblings

Epilepsy is one of the most common and debilitating neurological diseases that affects more than 40 million people worldwide. Genetic factors contribute to the pathogenesis of epilepsy. Molecular genetic studies have identified 15 disease-causing genes for epilepsy. The majority of the genes encode ion channels, including voltage-gated potassium channels KCNQ2 and KCNQ3, sodium channels SCN1A, SCN2A, and SCN1B, chloride channels CLCN2, and ligand-gated ion channels CHRNA4, CHRNB2, GABRG2, and GABRA1. Interestingly, non-ion channel genes have also been identified as epilepsy genes, and these genes include G-protein-coupled receptor MASS1/VLGR1, GM3 synthase, and proteins with unknown functions such as LGI1, NHLRC1, and EFHC1. These studies make genetic testing possible in some patients, and further characterization of the identified epilepsy genes may lead to the development of new drugs and new treatments for patients with epilepsy.
Chloride Channels ; genetics ; Epilepsies, Myoclonic ; genetics ; Epilepsy ; genetics ; Epilepsy, Absence ; genetics ; Humans ; KCNQ2 Potassium Channel ; genetics ; KCNQ3 Potassium Channel ; genetics ; NAV1.1 Voltage-Gated Sodium Channel ; NAV1.2 Voltage-Gated Sodium Channel ; Nerve Tissue Proteins ; genetics ; Sodium Channels ; genetics

A new method of axon recording through axon bleb has boosted the studies on the functional role of central nervous system (CNS) axons. Using this method, we have revealed the mechanisms underlying the initiation and propagation of the digital-mode signal, all-or-none action potentials (APs), in neocortical pyramidal neurons. Accumulation of the low-threshold Na(+) channel subtype Na(v)1.6 at the distal end of the axon initial segment (AIS) determines the lowest threshold for AP initiation, whereas accumulation of the high-threshold subtype Na(v)1.2 at the proximal region of the AIS promotes AP backpropagation to the soma and dendrites. Through dual recording from the soma and the axon, we have showed that subthreshold membrane potential (V(m)) fluctuations in the soma propagate along the axon to a long distance and probably reach the axon terminals. Paired recording from cortical neurons has revealed that these V(m) changes in the soma modulate AP-triggered synaptic transmission. This new V(m)-dependent mode of synaptic transmission is called analog communication. Unique properties of axonal K(+) channels (K(v)1 channels) may contribute to shaping the AP waveform, particularly its duration, and thus controlling synaptic strength at different levels of presynaptic V(m). The level of background Ca(2+) may also participate in mediating the analog signaling. Together, these findings enrich our knowledge on the principles of neuronal signaling in the CNS and help understand how the brain works.
Action Potentials ; physiology ; Animals ; Axons ; physiology ; Central Nervous System ; cytology ; physiology ; Humans ; Membrane Potentials ; physiology ; NAV1.2 Voltage-Gated Sodium Channel ; physiology ; NAV1.6 Voltage-Gated Sodium Channel ; physiology ; Neocortex ; cytology ; physiology ; Patch-Clamp Techniques ; Pyramidal Cells ; physiology ; Sodium Channels ; physiology

Objective: To explore the clinical manifestations and genetic characteristics of patients with epilepsy and episodic ataxia caused by SCN2A gene variation. Methods: The clinical data of seizure manifestation, imaging examination and genetic results of 5 patients with epilepsy and (or) episodic ataxia because of SCN2A gene variation admitted to the Department of Pediatrics, the Third Affiliated Hospital of Zhengzhou University from July 2017 to January 2021 were analyzed retrospectively. Results: Among 5 patients, 4 were female and 1 was male. The onset age of epilepsy ranged from 4 days to 8 months. There were 2 cases of benign neonatal or infantile epilepsy and 3 cases of epileptic encephalopathy, in whom 1 case had development retardation,1 case transformed from West syndrome to infantile spasm and another one transformed from infantile spasm to Lennox-Gastaut syndrome. One case of benign neonatal-infantile epilepsy was characterized by neonatal onset seizures and episodic ataxia developed at the age of 78 months. Electroencephalograms at first visit of 5 cases showed that 2 cases were normal, 1 case had focal epileptic discharge, and 2 cases had multi-focal abnormal discharge with peak arrhythmia. The brain magnetic resonance imaging (MRI) of 3 cases were nomal, 1 case was abnormal (brain atrophy with decreased white matter) and the results of 1 case was unknown. The follow-up time ranged from 17 months to 89 months. Four cases of epilepsy were controlled and 1 case died at 2 years of age. Two cases had normal intelligence and motor development, 2 had moderate to severe intelligence retardation and motor critical state, and 1 had moderate to severe intelligence and motor development retardation. SCN2A gene variations were identified in all cases. There were 4 missense variations and 1 frameshift variation. Three variations had not been reported so far, including c.4906A>G,c.3643G>T,c.638delT. Conclusions: Variations in SCN2A gene can cause benign neonatal or infantile epilepsy and epileptic encephalopathy. Some children develop episodic ataxia with growing age. The variation of SCN2A gene is mainly missense variation.
Ataxia/genetics* ; Child ; Electroencephalography ; Epilepsy/genetics* ; Female ; Humans ; Infant ; Infant, Newborn ; Male ; Mutation ; NAV1.2 Voltage-Gated Sodium Channel/genetics* ; Retrospective Studies ; Spasms, Infantile/genetics*

Objective: Due to genetic factors might increase the risk of depression, this study investigated the genetic risk factors of depression in Chinese Han population by analyzing the association between 13 candidate genes and depression. Methods: 439 depression patients and 464 healthy controls were included in this case-control study. Case group consisted of 158 males and 281 females, aged (29.84±14.91) years old, who were hospitalized in three departments of the affiliated Brain Hospital of Guangzhou Medical University including Affective Disorders Department, Adult Psychiatry Department and Geriatrics Department, from February 2020 to September 2021. The control group consisted of 196 males and 268 females, aged (30.65±12.63) years old. 20 loci of 13 candidate genes in all subjects were detected by MALDI-TOF mass spectrometry. Age difference was compared using the student's t-test, the distributions of gender and genotype were analyzed with Pearson's Chi-square test. The analyses of Hardy-Weinberg equilibrium, allele frequency and the genetic association of depression were conducted using the corresponding programs in PLINK software. Results: PLINK analysis showed that SCN2A rs17183814, ABCB1 rs1045642, CYP2C19*3 rs4986893 and NAT2*5A rs1799929 were associated with depression before Bonferroni correction (χ²=10.340, P=0.001; χ²=11.010, P=0.001; χ²=9.781, P=0.002; χ²=4.481, P=0.034). The frequencies of minor alleles of above loci in the control group were 12.07%, 43.64%, 2.59% and 3.88%, respectively. The frequencies of minor alleles of loci mentioned above in the case group were 17.43%, 35.99%, 5.47% and 6.04%, respectively. OR values were 1.538, 0.726, 2.178 and 1.592, respectively. After 1 000 000 permutation tests using Max(T) permutation procedure, the four loci were still statistically significant, the empirical P-value were 0.002, 0.001, 0.003 and 0.042, respectively. However, only three loci including SCN2A rs17183814, ABCB1 rs1045642 and CYP2C19 rs4986893 had statistical significance after Bonferroni correction, the adjusted P-value were 0.026, 0.018 and 0.035, respectively. Conclusion: SCN2A rs17183814, ABCB1 rs1045642 and CYP2C19*3 rs4986893 were associated with depression's susceptibility in Chinese Han population. The A allele of SCN2A rs17183814 and CYP2C19*3 rs4986893 were risk factors for depression, while the T allele of ABCB1 rs1045642 was a protective factor for depression.
ATP Binding Cassette Transporter, Subfamily B/genetics* ; Adolescent ; Adult ; Alleles ; Arylamine N-Acetyltransferase/genetics* ; Case-Control Studies ; Clopidogrel ; Cytochrome P-450 CYP2C19/genetics* ; Depressive Disorder, Major/genetics* ; Female ; Gene Frequency ; Genetic Predisposition to Disease ; Genotype ; Humans ; Male ; NAV1.2 Voltage-Gated Sodium Channel ; Polymorphism, Single Nucleotide ; Young Adult