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Channel Gene (channel + gene)
Kinds of Channel Gene Selected AbstractsRelationship between Genetic Variants in Myocardial Sodium and Potassium Channel Genes and QT Interval Duration in Diabetics: The Diabetes Heart StudyANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 1 2009Allison B. Lehtinen Ph.D. Background: Genetic variants in myocardial sodium and potassium channel genes are associated with prolonged QT interval and increased risk of sudden death. It is unclear whether these genetic variants remain relevant in subjects with underlying conditions such as diabetes that are associated with prolonged QT interval. Methods: We tested single nucleotide polymorphisms (SNPs) in five candidate genes for association with QT interval in a family-based study of subjects with type 2 diabetes mellitus (T2DM). Thirty-six previously reported SNPs were genotyped in KCNQ1, HERG, SCN5A, KCNE1, and KCNE2 in 901 European Americans from 366 families. The heart rate-corrected (QTc) durations were determined using the Marquette 12SL program. Associations between the QTc interval and the genotypes were evaluated using SOLAR adjusting for age, gender, T2DM status, and body mass index. Results: Within KCNQ1 there was weak evidence for association between the minor allele of IVS12 +14T>C and increased QTc (P = 0.02). The minor allele of rs2236609 in KCNE1 trended toward significance with longer QTc (P = 0.06), while the minor allele of rs1805123 in HERG trended toward significance with shorter QTc (P = 0.07). However, no statistically significant associations were observed between the remaining SNPs and QTc variation. Conclusions: We found weak evidence of association between three previously reported SNPs and QTc interval duration. While it appears as though genetic variants in previously identified candidate genes may be associated with QT duration in subjects with diabetes, the clinical implications of these associations in diabetic subjects at high risk for sudden death remain to be determined. [source] Individual variation and hormonal modulation of a sodium channel , subunit in the electric organ correlate with variation in a social signalDEVELOPMENTAL NEUROBIOLOGY, Issue 10 2007He Liu Abstract The sodium channel ,1 subunit affects sodium channel gating and surface density, but little is known about the factors that regulate ,1 expression or its participation in the fine control of cellular excitability. In this study we examined whether graded expression of the ,1 subunit contributes to the gradient in sodium current inactivation, which is tightly controlled and directly related to a social behavior, the electric organ discharge (EOD), in a weakly electric fish Sternopygus macrurus. We found the mRNA and protein levels of ,1 in the electric organ both correlate with EOD frequency. We identified a novel mRNA splice form of this gene and found the splicing preference for this novel splice form also correlates with EOD frequency. Androgen implants lowered EOD frequency and decreased the ,1 mRNA level but did not affect splicing. Coexpression of each splice form in Xenopus oocytes with either the human muscle sodium channel gene, hNav1.4, or a Sternopygus ortholog, smNav1.4b, sped the rate of inactivation of the sodium current and shifted the steady-state inactivation toward less negative membrane potentials. The translational product of the novel mRNA splice form lacks a previously identified important tyrosine residue but still functions normally. The properties of the fish , and coexpressed ,1 subunits in the oocyte replicate those of the electric organ's endogenous sodium current. These data highlight the role of ion channel , subunits in regulating cellular excitability. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007. [source] An unusual distribution of the kdr gene among populations of Anopheles gambiae on the island of Bioko, Equatorial GuineaINSECT MOLECULAR BIOLOGY, Issue 6 2005L. J. Reimer Abstract In West Africa, Anopheles gambiae exists in discrete subpopulations known as the M and S molecular forms. Although these forms occur in sympatry, pyrethroid knock-down resistance (kdr) is strongly associated with the S molecular form. On the island of Bioko, Equatorial Guinea we found high frequencies of the kdr mutation in M form individuals (55.8%) and a complete absence of kdr in the S form. We also report the absence of the kdr allele in M and S specimens from the harbour town of Tiko in Cameroon, representing the nearest continental population to Bioko. The kdr allele had previously been reported as absent in populations of An. gambiae on Bioko. Contrary to earlier reports, sequencing of intron-1 of this sodium channel gene revealed no fixed differences between M form resistant and susceptible individuals. The mutation may have recently arisen independently in the M form on Bioko due to recent and intensive pyrethroid application. [source] Sodium channel gene expression in mosquitoes, Aedes albopictus (S.)INSECT SCIENCE, Issue 6 2006NANNAN LIU Abstract A mosquito strain of Aedes albopictus, HAmAalG0, from Huntsville, Alabama, USA, showed a normal susceptibility and low tolerance to permethrin and resmethrin (pyrethroid insecticides) compared to a susceptible Ikaken strain, even though these pyrethroid insecticides have been used in the field for a long period of time in Alabama. Recently, we treated HAmAalG0 in the laboratory with permethrin for five generations and detected no significant change in the level of resistance to permethrin in the selected mosquitoes, HAmAalG5, compared with the parental strain HAmAalG0. We then examined the allelic expression at the L-to-F kdr site of the sodium channel gene in the Aedes mosquitoes to address our hypothesis that the L-to-F kdr mutation was not present in HAmAalG0 and HAmAalG5 mosquitoes. We found that every tested individual in Ikaken, HAmAalG0, and HAmAalG5 populations expressed a codon of CTA at the L-to-F kdr site encoding Leu, strongly corresponding to their susceptibility to insecticides. [source] Atrial Fibrillation in the Goat Induces Changes in Monophasic Action Potential and mRNA Expression of Ion Channels Involved in RepolarizationJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 11 2000HUUB M.W. VAN DER VELDEN PH.D. MAP Changes and Ion Channel Expression in Goat AF. Introduction: Sustained atrial fibrillation (AF) is characterized by a marked shortening of the atrial effective refractory period (AKRP) and a decrease or reversal of its physiolonic adaptation to heart rate. The aim of the present study was to investigate whether the AF-induced changes in AKKP in the goat are associated with changes in the atrial monophasic action potential (MAP) and whether an abnormal expression of specific ion channels underlies such changes. Methods and Results: Following thoracotomy, MAPs were recorded from the free wall of the right atrium hoth before induction of AF (control) and after cardioversion of sustained AF (>2 months) in chronically instrumented goats. In control goats. MAP duration at 80% repolarization (MAPD80) shortened (P < 0.01) from 132 ± 4 msec during slow pacing (400-msec interval) to 86 ± 10 msec during fast pacing (180 msec). After cardioversion of sustained AF, the MAPD80, during slow pacing was as short as 67 ± 5 msec (electrical remodeling). Increasing the pacing rate resulted in prolongation (P = 0.02) of the MAPD80 to 91 ± 6 msec. Also. MAPD20 (20% repolarization) shortened (P = 0.05) from 32 ± 4 msec (400 msec) to 14 ± 7 msec (180 msec) in the control goats, whereas it prolonged (P = 0.03) from 20 ± 3 msec (400 msec) to 33 ± 5 msec (180 msec) in sustained AF, mRNA expression of the L-type Ca2+ channel ,1c gene and Kv1.5 potassium channel gene, which underlie Ica, and Ikur respectively, was reduced in sustained.AF compared with sinus rhythm hy 32% (P = 0.01) and 45% (P < 0.01). respectively. No significant changes were found in the mRNA levels of the rapid Na+ channel, the Na+/Ca2+ exchanger, or the Kv4.2/4.3 channels responsible for I10. Conclusion: AF-induced electrical remodeling in the goat comprises shortening of MAPD and reversal of its physiologic rate adaptation. Changes in the time course of reploarization of the action potential are associated with changes in mRNA expression of the , subunit genes of the L.-type Ca2+ channel and the Kvl.5 potassium channel. [source] Ethanol Tolerance Caused by slowpoke Induction in DrosophilaALCOHOLISM, Issue 5 2006Roshani. Background: The large-conductance calcium-activated potassium channel encoded by the slowpoke gene has recently been implicated in the ethanol response. Caenorhabditis elegans carrying mutations in this gene have altered ethanol sensitivity and Drosophila mutant for this gene are unable to acquire rapid tolerance to ethanol or anesthetics. In Drosophila, induction of slowpoke expression has been linked to anesthetic resistance. Methods: We used Drosophila as a model system to examine the relationship between slowpoke expression and ethanol tolerance. Real-time PCR and a reporter transgene were used to measure slowpoke induction after ethanol sedation. An inducible slowpoke transgene was used to manipulate slowpoke levels in the absence of ethanol sedation. Results: Ethanol sedation increased transcription from the slowpoke neural promoters but not from the slowpoke muscle/tracheal cell promoters. This neural-specific change was concomitant with the appearance of ethanol tolerance, leading us to suspect linkage between the two. Moreover, induction of slowpoke expression from a transgene produced a phenotype that mimics ethanol tolerance. Conclusions: In Drosophila, ethanol sedation induces slowpoke expression in the nervous system and results in ethanol tolerance. The induction of slowpoke expression alone is sufficient to produce a phenotype that is indistinguishable from true ethanol tolerance. Therefore, the regulation of the slowpoke BK-type channel gene must play an integral role in the Drosophila ethanol response. [source] Insecticide resistance in the malarial mosquito Anopheles arabiensis and association with the kdr mutationMEDICAL AND VETERINARY ENTOMOLOGY, Issue 1 2007T. S. MATAMBO Abstract A colony of Anopheles arabiensis Patton (Diptera: Culicidae) from the Sennar region of Sudan was selected for resistance to dichlorodiphenyltrichloroethane (DDT). Adults from the F-16 generation of the resistant strain were exposed to all four classes of insecticides approved for use in malaria vector control and showed high levels of resistance to them all (24-h mortalities: malathion, 16.7%; bendiocarb, 33.3%; DDT, 12.1%; dieldrin, 0%; deltamethrin, 24.0%; permethrin, 0%). Comparisons between the unselected base colony and the DDT-resistant strain showed elevated glutathione- S -transferase (P < 0.05) in both sexes and elevated esterases (P < 0.05) in males only. The Leu-Phe mutation in the sodium channel gene was detected by polymerase chain reaction and sequencing, but showed no correlation with the resistant phenotype. These results do not provide any explanation as to why this colony exhibits such widespread resistance and further studies are needed to determine the precise mechanisms involved. The implications for malaria vector control in central Sudan are serious and resistance management (e.g. through the rotational use of different classes of insecticides) is recommended. [source] Pyrethroid and DDT cross-resistance in Aedes aegypti is correlated with novel mutations in the voltage-gated sodium channel geneMEDICAL AND VETERINARY ENTOMOLOGY, Issue 1 2003C. Brengues Abstract. Samples of the dengue vector mosquito Aedes aegypti (L.) (Diptera: Culicidae) were collected from 13 localities between 1995 and 1998. Two laboratory strains, Bora (French Polynesia) and AEAE, were both susceptible to DDT and permethrin; all other strains, except Larentuka (Indonesia) and Bouaké (Ivory Coast), contained individual fourth-instar larvae resistant to permethrin. Ten strains were subjected to a range of biochemical assays. Many strains had elevated carboxylesterase activity compared to the Bora strain; this was particularly high in the Indonesian strains Salatiga and Semarang, and in the Guyane strain (Cayenne). Monooxygenase levels were increased in the Salatiga and Paea (Polynesia) strains, and reduced in the two Thai strains (Mae Kaza, Mae Kud) and the Larentuka strain. Glutathione S-transferase activity was elevated in the Guyane strain. All other enzyme profiles were similar to the susceptible strain. The presence of both DDT and pyrethroid resistance in the Semarang, Belem (Brazil) and Long Hoa (Vietnam) strains suggested the presence of a knock-down resistant (kdr)-type resistance mechanism. Part of the S6 hydrophobic segment of domain II of the voltage-gated sodium channel gene was obtained by RT-PCR and sequenced from several insects from all 13 field strains. Four novel mutations were identified. Three strains contained identical amino acid substitutions at two positions, two strains shared a different substitution, and one strain was homozygous for a fourth alteration. The leucine to phenylalanine substitution that confers nerve insensitivity to pyrethroids in a range of other resistant insects was absent. Direct neurophysiological assays on individual larvae from three strains with these mutations demonstrated reduced nerve sensitivity to permethrin or lambda cyhalothrin inhibition compared to the susceptible strains. [source] Genetic modifiers of the severity of sickle cell anemia identified through a genome-wide association study,AMERICAN JOURNAL OF HEMATOLOGY, Issue 1 2010Paola Sebastiani We conducted a genome-wide association study (GWAS) to discover single nucleotide polymorphisms (SNPs) associated with the severity of sickle cell anemia in 1,265 patients with either "severe" or "mild" disease based on a network model of disease severity. We analyzed data using single SNP analysis and a novel SNP set enrichment analysis (SSEA) developed to discover clusters of associated SNPs. Single SNP analysis discovered 40 SNPs that were strongly associated with sickle cell severity (odds for association >1,000); of the 32 that we could analyze in an independent set of 163 patients, five replicated, eight showed consistent effects although failed to reach statistical significance, whereas 19 did not show any convincing association. Among the replicated associations are SNPs in KCNK6 a K+ channel gene. SSEA identified 27 genes with a strong enrichment of significant SNPs (P < 10,6); 20 were replicated with varying degrees of confidence. Among the novel findings identified by SSEA is the telomere length regulator gene TNKS. These studies are the first to use GWAS to understand the genetic diversity that accounts the phenotypic heterogeneity sickle cell anemia as estimated by an integrated model of severity. Additional validation, resequencing, and functional studies to understand the biology and reveal mechanisms by which candidate genes might have their effects are the future goals of this work. Am. J. Hematol., 2010. © 2009 Wiley-Liss, Inc. [source] Secretion and cell volume regulation by salivary acinar cells from mice lacking expression of the Clcn3 Cl, channel geneTHE JOURNAL OF PHYSIOLOGY, Issue 1 2002Jorge Arreola Salivary gland acinar cells shrink when Cl, currents are activated following cell swelling induced by exposure to a hypotonic solution or in response to calcium-mobilizing agonists. The molecular identity of the Cl, channel(s) in salivary cells involved in these processes is unknown, although ClC-3 has been implicated in several tissues as a cell-volume-sensitive Cl, channel. We found that cells isolated from mice with targeted disruption of the Clcn3 gene undergo regulatory volume decrease in a fashion similar to cells from wild-type littermates. Consistent with a normal regulatory volume decrease response, the magnitude and the kinetics of the swell-activated Cl, currents in cells from ClC-3-deficient mice were equivalent to those from wild-type mice. It has also been suggested that ClC-3 is activated by Ca2+ -calmodulin-dependent protein kinase II; however, the magnitude of the Ca2+ -dependent Cl, current was unchanged in the Clcn3,/- animals. In addition, we observed that ClC-3 appeared to be highly expressed in the smooth muscle cells of glandular blood vessels, suggesting a potential role for this channel in saliva production by regulating blood flow, yet the volume and ionic compositions of in vivo stimulated saliva from wild-type and null mutant animals were comparable. Finally, in some cells ClC-3 is an intracellular channel that is thought to be involved in vesicular acidification and secretion. Nevertheless, the protein content of saliva was unchanged in Clcn3,/- mice. Our results demonstrate that the ClC-3 Cl, channel is not a major regulator of acinar cell volume, nor is it essential for determining the secretion rate and composition of saliva. [source] Gene Transfer in Human Vestibular Epithelia and the Prospects for Inner Ear Gene Therapy,,THE LARYNGOSCOPE, Issue 5 2008Bradley W. Kesser MD Abstract Transfer of exogenous genetic material into the mammalian inner ear using viral vectors has been characterized over the last decade. A number of different viral vectors have been shown to transfect the varying cell types of the nonprimate mammalian inner ear. Several routes of delivery have been identified for introduction of vectors into the inner ear while minimizing injury to existing structures and at the same time ensuring widespread distribution of the agent throughout the cochlea and the rest of the inner ear. These studies raise the possibility that gene transfer may be developed as a potential strategy for treating inner ear dysfunction in humans. Furthermore, a recent report showing successful transfection of excised human vestibular epithelia offers proof of principle that viralgene transfer is a viable strategy for introduction andexpression of exogenous genetic material to restore function to the inner ear. Human vestibular epithelia were harvested from patients undergoing labyrinthectomy, either for intractable Méničre's disease or vestibular schwannoma resection, and cultured for as long as 5 days. In those experiments, recombinant, multiply-deleted, replication-deficient adenoviral vectors were used to transfect and express a reporter gene as well as the functionally relevant gene, wild-type KCNQ4, a potassium channel gene that when mutated causes the autosomal dominant HL DFNA2. Here, we review the current state of viral-mediated gene transfer in the inner ear and discuss different viral vectors, routes of delivery, and potential applications of gene therapy. Emphasis is placed on experiments demonstrating viral transfection of human inner ear tissue and implications of these findings and for the future of gene therapy in the human inner ear. [source] Whole-body high-field MRI shows no skeletal muscle degeneration in young patients with recessive myotonia congenitaACTA NEUROLOGICA SCANDINAVICA, Issue 2 2010C. Kornblum Kornblum C, Lutterbey GG, Czermin B, Reimann J, von Kleist-Retzow J-C, Jurkat-Rott K, Wattjes MP. Whole-body high-field MRI shows no skeletal muscle degeneration in young patients with recessive myotonia congenita. Acta Neurol Scand: 2010: 121: 131,135. © 2009 The Authors Journal compilation © 2009 Blackwell Munksgaard. Background,,, Muscle magnetic resonance imaging (MRI) is the most sensitive method in the detection of dystrophic and non-dystrophic abnormalities within striated muscles. We hypothesized that in severe myotonia congenita type Becker muscle stiffness, prolonged transient weakness and muscle hypertrophy might finally result in morphologic skeletal muscle alterations reflected by MRI signal changes. Aim of the study,,, To assess dystrophic and/or non-dystrophic alterations such as fatty or connective tissue replacement and muscle edema in patients with severe recessive myotonia congenita. Methods,,, We studied three seriously affected patients with myotonia congenita type Becker using multisequence whole-body high-field MRI. All patients had molecular genetic testing of the muscle chloride channel gene (CLCN1). Results,,, Molecular genetic analyses demonstrated recessive CLCN1 mutations in all patients. Two related patients were compound heterozygous for two novel CLCN1 mutations, Q160H and L657P. None of the patients showed skeletal muscle signal changes indicative of fatty muscle degeneration or edema. Two patients showed muscle bulk hypertrophy of thighs and calves in line with the clinical appearance. Conclusions,,, We conclude that (i) chloride channel dysfunction alone does not result in skeletal muscle morphologic changes even in advanced stages of myotonia congenita, and (ii) MRI skeletal muscle alterations in myotonic dystrophy must be clear consequences of the dystrophic disease process. [source] Common variants in the ATP-sensitive K+ channel genes KCNJ11 (Kir6.2) and ABCC8 (SUR1) in relation to glucose intolerance: population-based studies and meta-analyses,DIABETIC MEDICINE, Issue 5 2005R. M. Van Dam Abstract Aims To evaluate the relation between common variants in the ATP-sensitive K+ channel genes and glucose intolerance. Methods We conducted a meta-analysis of reported association studies in Caucasian populations for common variants in the ABCC8 (exons 16 and 18) and the KCNJ11 (E23K) gene and examined sources of heterogeneity in the results. The meta-analysis was based on 7768,10216 subjects (depending on the gene variant), and included two new population-based studies in the Netherlands with 725 cases and 742 controls. Results For the KCNJ11 variant, the summary odds ratio (OR) for glucose intolerance was 1.12 (1.01,1.23, P = 0.03) for the EK genotype and 1.44 (1.17,1.78, P = 0.0007) for the KK genotype, as compared with the EE genotype. For the ABCC8 exon 16 variant, the OR was 1.06 (0.94,1.19, P = 0.34) for ct and 0.93 (0.71,1.20, P = 0.56) for tt, as compared with the cc genotype. For ABCC8 exon 18, the OR was 1.20 (0.97,1.49, P = 0.10) for CT/TT, as compared with the CC genotype. Studies of the ABCC8 variants that were published first or had smaller sample sizes (for the exon 18 variant) showed stronger associations, which may indicate publication bias. For the ABCC8 exon 18 and the KCNJ11 variant, associations were stronger for studies of clinical diabetes than newly detected glucose intolerance. The population attributable risk for clinical Type 2 diabetes was 6.2% for the KCNJ11 KK genotype and 10.1% for the KCNJ11 EK and KK genotype combined. Conclusions The common KCNJ11 E23K gene variant, but not the ABCC8 exon 16 or exon 18 variant, was consistently associated with Type 2 diabetes. [source] Ions, genes and insulin release: from basic science to clinical disease Based on the 1998 R. D. Lawrence LectureDIABETIC MEDICINE, Issue 2 2000M. J. Dunne Summary In 1968, reports of the first microelectrode recordings of insulin-secreting cells were published. Thirty years later it is now established that electrical responses of ,-cells play a critical role in stimulus-secretion coupling. It is now also clear that defects in ion channel genes compromise the mechanisms which govern secretion and lead to the onset of disease. Here, the physiology of insulin release is reviewed in the context of ion channels, the ionic control of insulin release and the pathophysiology of hyperinsulinism of infancy. [source] Cellular expression and functional characterization of four hyperpolarization-activated pacemaker channels in cardiac and neuronal tissuesFEBS JOURNAL, Issue 6 2001Sven Moosmang Hyperpolarization-activated cation currents (Ih) have been identified in cardiac pacemaker cells and a variety of central and peripheral neurons. Four members of a gene family encoding hyperpolarization-activated, cyclic nucleotide-gated cation channels (HCN1,4) have been cloned recently. Native Ih currents recorded from different cell types exhibit distinct activation kinetics. To determine if this diversity of Ih currents may be caused by differential expression of HCN channel isoforms, we investigated the cellular distribution of the transcripts of HCN1,4 in the murine sinoatrial node, retina and dorsal root ganglion (DRG) by in situ hybridization. In the sinoatrial node, the most prominently expressed HCN channel is HCN4, whereas HCN2 and HCN1 are detected there at moderate and low levels, respectively. Retinal photoreceptors express high levels of HCN1, whereas HCN2, 3 and 4 were not found in these cells. In DRG neurons, the dominant HCN transcript is HCN1, followed by HCN2. We next determined the functional properties of recombinant HCN1,4 channels expressed in HEK293 cells. All four channel types gave rise to Ih currents but displayed marked differences in their activation kinetics. Our results suggest that the heterogeneity of native Ih currents is generated, at least in part, by the tissue-specific expression of HCN channel genes. [source] The case for sequencing the genome of the electric eel Electrophorus electricusJOURNAL OF FISH BIOLOGY, Issue 2 2008J. S. Albert A substantial international community of biologists have proposed the electric eel Electrophorus electricus (Teleostei: Gymnotiformes) as an important candidate for genome sequencing. In this study, the authors outline the unique advantages that a genome sequencing project of this species would offer society for developing new ways of producing and storing electricity. Over tens of millions of years, electric fish have evolved an exceptional capacity to generate a weak (millivolt) electric field in the water near their body from specialized muscle-derived electric organs, and simultaneously, to sense changes in this field that occur when it interacts with foreign objects. This electric sense is used both to navigate and orient in murky tropical waters and to communicate with other members of the same species. Some species, such as the electric eel, have also evolved a strong voltage organ as a means of stunning prey. This organism, and a handful of others scattered worldwide, convert chemical energy from food directly into workable electric energy and could provide important clues on how this process could be manipulated for human benefit. Electric fishes have been used as models for the study of basic biological and behavioural mechanisms for more than 40 years by a large and growing research community. These fishes represent a rich source of experimental material in the areas of excitable membranes, neurochemistry, cellular differentiation, spinal cord regeneration, animal behaviour and the evolution of novel sensory and motor organs. Studies on electric fishes also have tremendous potential as a model for the study of developmental or disease processes, such as muscular dystrophy and spinal cord regeneration. Access to the genome sequence of E. electricus will provide society with a whole new set of molecular tools for understanding the biophysical control of electromotive molecules, excitable membranes and the cellular production of weak and strong electric fields. Understanding the regulation of ion channel genes will be central for efforts to induce the differentiation of electrogenic cells in other tissues and organisms and to control the intrinsic electric behaviours of these cells. Dense genomic sequence information of E. electricus will also help elucidate the genetic basis for the origin and adaptive diversification of a novel vertebrate tissue. The value of existing resources within the community of electric fish research will be greatly enhanced across a broad range of physiological and environmental sciences by having a draft genome sequence of the electric eel. [source] Regulation of membrane potential and fluid secretion by Ca2+ -activated K+ channels in mouse submandibular glandsTHE JOURNAL OF PHYSIOLOGY, Issue 2 2007Victor G. Romanenko We have recently shown that the IK1 and maxi-K channels in parotid salivary gland acinar cells are encoded by the KCa3.1 and KCa1.1 genes, respectively, and in vivo stimulated parotid secretion is severely reduced in double-null mice. The current study tested whether submandibular acinar cell function also relies on these channels. We found that the K+ currents in submandibular acinar cells have the biophysical and pharmacological footprints of IK1 and maxi-K channels and their molecular identities were confirmed by the loss of these currents in KCa3.1- and KCa1.1 -null mice. Unexpectedly, the pilocarpine-stimulated in vivo fluid secretion from submandibular glands was essentially normal in double-null mice. This result and the possibility of side-effects of pilocarpine on the nervous system, led us to develop an ex vivo fluid secretion assay. Fluid secretion from the ex vivo assay was substantially (about 75%) reduced in animals with both K+ channel genes ablated , strongly suggesting systemic complications with the in vivo assay. Additional experiments focusing on the membrane potential in isolated submandibular acinar cells revealed mechanistic details underlying fluid secretion in K+ channel-deficient mice. The membrane potential of submandibular acinar cells from wild-type mice remained strongly hyperpolarized (,55 ± 2 mV) relative to the Cl, equilibrium potential (,24 mV) during muscarinic stimulation. Similar hyperpolarizations were observed in KCa3.1- and KCa1.1 -null mice (,51 ± 3 and ,48 ± 3 mV, respectively), consistent with the normal fluid secretion produced ex vivo. In contrast, acinar cells from double KCa3.1/KCa1.1 -null mice were only slightly hyperpolarized (,35 ± 2 mV) also consistent with the ex vivo (but not in vivo) results. Finally, we found that the modest hyperpolarization of cells from the double-null mice was maintained by the electrogenic Na+,K+ -ATPase. [source] Gene Transfer of TRPC6DN (Dominant Negative) Restores Erectile Function in Diabetic RatsTHE JOURNAL OF SEXUAL MEDICINE, Issue 3 2010Jae Hun Jung MD ABSTRACT Introduction., Transient receptor potential (TRP) channels play an important role in modulating intracellular Ca2+ ([Ca2+]i) levels. Aim., We examined the hypothesis that overexpression of TRPC6DN (dominant negative) may contribute to decreased [Ca2+]i levels in corporal smooth muscle (CSM). We also investigated whether gene transfer of TRPC6DN could restore erectile function in diabetic rats. Methods., For the in vitro study, the KCa, KATP, and TRPC6DN channel genes were transferred using cDNA, into cultured human CSM cells and human embryonic kidney cells. For the in vivo study, young adult rats were divided into three groups: normal controls; diabetic controls transfected with vector only; and a diabetic group transfected with pcDNA of the TRPC6DN gene. Main Outcome Measures., After gene transfer, the effects of reducing [Ca2+]i levels were assessed by Fura-2-based imaging analysis. The intracavernosal pressure (ICP) response to cavernosal nerve stimulation was assessed after intracorporal injection of TRPC6DN pcDNA. The transgene expression of the TRPC6DN was examined by reverse transcription polymerase chain reaction (RT-PCR) in rats transfected with TRPC6DN pcDNA. Results., Gene transfer of ion channels effectively reduced [Ca2+]i. Among these channels, transfer of the TRPC6DN gene resulted in the greatest reduction of [Ca2+]i in human CSM. The mean (±standard error of the mean) ratio of ICP to mean arterial pressure (BP) in the gene-transfer rats was 79.4 ± 2.4% (N = 8). This was significantly higher than that in control rats (55.6 ± 3.7% [N = 8]), and similar to that in the young control rats (83 ± 2.2% [N = 12]). The RT-PCR showed expression of TRPC6DN genes in the transfected rats. Conclusion., Gene transfer of TRPC6DN not only reduced [Ca2+]i in human CSM but also restored erectile function in diabetic rats. These results suggest that pcDNA transfer of TRPC6DN may represent a promising new form of therapy for the treatment of male erectile dysfunction in the future. Jung JH, Kim BJ, Chae MR, Kam SC, Jeon J-H, So I, Chung KH, and Lee SW. Gene transfer of TRPC6DN (dominant negative) restores erectile function in diabetic rats. J Sex Med 2010;7:1126,1138. [source] Differential expression and regulation of K+ channels in the maize coleoptile: molecular and biophysical analysis of cells isolated from cortex and vasculatureTHE PLANT JOURNAL, Issue 2 2000Claudia S. Bauer Summary Recently, two K+ channel genes, ZMK1 and ZMK2, were isolated from maize coleoptiles. They are expressed in the cortex and vasculature, respectively. Expression in Xenopus oocytes characterized ZMK1 as an inwardly rectifying K+ channel activated by external acidification, while ZMK2 mediates voltage-independent and proton-inhibited K+ currents. In search of the related gene products in planta, we applied the patch,clamp technique to protoplasts isolated from the cortex and vasculature of Zea mays coleoptiles and mesocotyls. In the cortex, a 6,8 pS K+ channel gave rise to inwardly rectifying K+ currents. Like ZMK1, this channel was activated by apoplastic acidification. In contrast, protoplasts from vascular tissue expressing the sucrose transporter ZmSUT1 were dominated by largely voltage-independent K+ currents with a single-channel conductance of 22 pS. The pronounced sensitivity to the extracellular protons Ca2+, Cs+ and Ba2+ is reminiscent of ZMK2 properties in oocytes. Thus, the dominant K+ channels in cortex and vasculature most likely represent the gene products of ZMK1 and ZMK2. Our studies on the ZMK2-like channels represent the first in planta analysis of a K+ channel that shares properties with the AKT3 K+ channel family. Keywords: K+ channel, voltage-independent, proton block, maize coleoptile. [source] Relationship between Genetic Variants in Myocardial Sodium and Potassium Channel Genes and QT Interval Duration in Diabetics: The Diabetes Heart StudyANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 1 2009Allison B. Lehtinen Ph.D. Background: Genetic variants in myocardial sodium and potassium channel genes are associated with prolonged QT interval and increased risk of sudden death. It is unclear whether these genetic variants remain relevant in subjects with underlying conditions such as diabetes that are associated with prolonged QT interval. Methods: We tested single nucleotide polymorphisms (SNPs) in five candidate genes for association with QT interval in a family-based study of subjects with type 2 diabetes mellitus (T2DM). Thirty-six previously reported SNPs were genotyped in KCNQ1, HERG, SCN5A, KCNE1, and KCNE2 in 901 European Americans from 366 families. The heart rate-corrected (QTc) durations were determined using the Marquette 12SL program. Associations between the QTc interval and the genotypes were evaluated using SOLAR adjusting for age, gender, T2DM status, and body mass index. Results: Within KCNQ1 there was weak evidence for association between the minor allele of IVS12 +14T>C and increased QTc (P = 0.02). The minor allele of rs2236609 in KCNE1 trended toward significance with longer QTc (P = 0.06), while the minor allele of rs1805123 in HERG trended toward significance with shorter QTc (P = 0.07). However, no statistically significant associations were observed between the remaining SNPs and QTc variation. Conclusions: We found weak evidence of association between three previously reported SNPs and QTc interval duration. While it appears as though genetic variants in previously identified candidate genes may be associated with QT duration in subjects with diabetes, the clinical implications of these associations in diabetic subjects at high risk for sudden death remain to be determined. [source] Single Nucleotide Polymorphisms and Haplotype of Four Genes Encoding Cardiac Ion Channels in Chinese and their Association with ArrhythmiaANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2 2008Yu Zhang Ph.D. Background: Many studies revealed that variations in cardiac ion channels would cause cardiac arrhythmias or act as genetic risk factors. We hypothesized that specific single nucleotide polymorphisms in cardiac ion channels were associated with cardiac rhythm disturbance in the Chinese population. Method: We analyzed 160 nonfamilial cardiac arrhythmia patients and 176 healthy individuals from which 81 individuals were selected for association study, and a total of 19 previously reported SNPs in four cardiac ion channel genes (KCNQ1, KCNH2, SCN5A, KCNE1) were genotyped. Results: The frequency of KCNQ1 1638G>A, as well as the haplotype harboring KCNQ1 1638A, KCNQ1 1685 + 23G and 1732 + 43T (haplotype AGT) was significantly higher in healthy controls than in arrhythmia patients. This finding implicated that this haplotype (AGT) might be a protective factor against arrhythmias. Conclusions: Our study provided important information to elucidate the effect of SNPs of cardiac ion channel genes on channel function and susceptibility to cardiac arrhythmias in Chinese population. [source] Loss-of-function mutations in the Nav1.7 gene underlie congenital indifference to pain in multiple human populationsCLINICAL GENETICS, Issue 4 2007YP Goldberg Congenital indifference to pain (CIP) is a rare condition in which patients have severely impaired pain perception, but are otherwise essentially normal. We identified and collected DNA from individuals from nine families of seven different nationalities in which the affected individuals meet the diagnostic criteria for CIP. Using homozygosity mapping and haplotype sharing methods, we narrowed the CIP locus to chromosome 2q24,q31, a region known to contain a cluster of voltage-gated sodium channel genes. From these prioritized candidate sodium channels, we identified 10 mutations in the SCN9A gene encoding the sodium channel protein Nav1.7. The mutations completely co-segregated with the disease phenotype, and nine of these SCN9A mutations resulted in truncation and loss-of-function of the Nav1.7 channel. These genetic data further support the evidence that Nav1.7 plays an essential role in mediating pain in humans, and that SCN9A mutations identified in multiple different populations underlie CIP. [source] Functional implications for Kir4.1 channels in glial biology: from K+ buffering to cell differentiationJOURNAL OF NEUROCHEMISTRY, Issue 3 2008Michelle L. Olsen Abstract Astrocytes and oligodendrocytes are characterized by a very negative resting potential and a high resting permeability for K+ ions. Early pharmacological and biophysical studies suggested that the resting potential is established by the activity of inwardly rectifying, Ba2+ sensitive, weakly rectifying Kir channels. Molecular cloning has identified 16 Kir channels genes of which several mRNA transcripts and protein products have been identified in glial cells. However, genetic deletion and siRNA knock-down studies suggest that the resting conductance of astrocytes and oligodendrocytes is largely due to Kir4.1. Loss of Kir4.1 causes membrane depolarization, and a break-down of K+ and glutamate homeostasis which results in seizures and wide-spread white matter pathology. Kir channels have also been shown to act as critical regulators of cell division whereby Kir function is correlated with an exit from the cell cycle. Conversely, loss of functional Kir channels is associated with re-entry of cells into the cell cycle and gliosis. A loss of functional Kir channels has been shown in a number of neurological diseases including temporal lobe epilepsy, amyotrophic lateral sclerosis, retinal degeneration and malignant gliomas. In the latter, expression of Kir4.1 is sufficient to arrest the aberrant growth of these glial derived tumor cells. Kir4.1 therefore represents a potential therapeutic target in a wide variety of neurological conditions. [source] | ||||||||||||||||