A common polymorphism decreases LRP1 mRNA stability and is associated with increased plasma factor VIII levels.

The low-density lipoprotein receptor-related protein 1 (LRP1) gene is associated with increased levels of plasma factor VIII (FVIII). We aimed to explore eight functional genetic LRP1 variants for their potential roles in regulating FVIII levels and acute ischemic stroke (AIS). This genetic association study enrolled 192 patients with AIS and 134 controls. There were no significant differences in the genetic frequency of the eight functional single-nucleotide polymorphisms (SNPs) between the control and AIS groups. However, while analyzing the association between the eight SNPs and plasma FVIII levels, subjects with T/T genotype of rs1800137 (vs. CC+CT) were found to be associated with higher FVIII levels (23.5IU/dL; 95% confidence interval, 7.4-39.5IU/dL; P=0.0044) after adjusting for age, gender, estimated glomerular filtration rate, O blood type, inflammatory state, and body mass index. An analysis of the mRNA stability and abundance was designed and performed using minigene system transfected into HepG2 cells to assess the possible differences in mRNA stabilities between rs1800137 CC (rs1800137C) and TT (rs1800137T) genotypes. Site-directed mutagenesis revealed that rs1800137T accounts for the observed decrease in mRNA stability. The SNP rs1800137, located in exon 8, has been identified as an exon-splicing enhancer in silico. However, alternative splicing of LRP1 without inclusion of exon 8 was not identified. In transfected HepG2 cells, cycloheximide slowed down the degradation of the rs1800137T-containing minigene. These results demonstrate that synonymous SNP rs1800137 can lead to increased plasma FVIII levels due to decreased mRNA stability via translation-dependent mRNA degradation associated with codon optimality.

Multiplex polymerase chain reaction assay developed to diagnose adult bacterial meningitis in Taiwan.

Acute bacterial meningitis causes high morbidity and mortality; the associated clinical symptoms often are insensitive or non-specific; and the pathogenic bacteria are geographically diverse. Clinical diagnosis requires a rapid and accurate methodology. This study aimed to develop a new multiplex polymerase chain reaction (mPCR) assay to detect simultaneously six major bacteria that cause adult bacterial meningitis in Taiwan: Klebsiella pneumoniae, Pseudomonas aeruginosa, Streptococcus pneumoniae, Staphylococcus aureus, Escherichia coli, and Acinetobacter baumannii. Species-specific primers for the six bacteria were developed using reference strains. The specificities of the mPCRs for these bacteria were validated, and the sensitivities were evaluated via serial dilutions. The mPCR assay specifically detected all of the six pathogens, particularly with sensitivities of 12 colony forming units (CFU)/mL, 90 CFU/mL, and 390 CFU/mL for E. coli, S. pneumoniae, and K. pneumoniae, respectively. This mPCR assay is a rapid and specific tool to detect the six major bacterial pathogens that cause acute adult meningitis in Taiwan, particularly sensitive for detecting E. coli, S. pneumoniae, and K. pneumoniae. The assay may facilitate early diagnosis and guidance for antimicrobial therapy for adult patients with this deadly disease in Taiwan.

Mutual effect of rs688 and rs5925 in regulating low-density lipoprotein receptor splicing.

Analysis of the low-density lipoprotein receptor (LDLR) gene based on the rs688 and rs5925 genetic polymorphisms has provided evidence suggesting that haplotypes related to rs688 and rs5925 are associated with ischemic cerebrovascular diseases. Both rs688 and rs5925 have been empirically identified as exon-splicing enhancers in silico, and rs688 has been shown to be a functional polymorphism that modulates LDLR exon 12 splicing efficiency both in vitro and in vivo. The aim of this study was to evaluate whether rs688 and rs5925 and their haplotypes may alter the splicing efficiency of exons 12 and 13 both in vivo and in vitro. When the minigenes were evaluated for splicing efficiency, we found that converting rs688C to the T allele reduced exon 12 splicing efficiency. In parallel, converting rs688T to the C allele increased the efficiency of exon 12 inclusion. The apparent difference in splicing efficiency was 9.36%±2.58% between the C and T alleles. When rs688C existed in the minigene, the major and minor rs5925 alleles were also sufficient to account for the differences in splicing efficiency of LDLR involving exon 13. The apparent splicing efficiency difference was 5.43%±2.87%. Sequential mutations of rs688 and rs5925 were performed to generate four different haplotypes in the LDLR minigene system. The splicing efficiencies for the haplotypes CC, CT, TC, and TT were 79.60%±1.38%, 76.68%±0.85%, 69.02%±1.79%, and 68.54%±1.38%, respectively. The splicing efficiency of the four haplotype groups differed significantly. In vivo analysis of human leukocyte samples was also compatible with in vitro analysis, indicating a mutual effect between rs688 and rs5925 in regulating LDLR splicing efficiency.

The homeobox transcription factor Irxl1 negatively regulates MyoD expression and myoblast differentiation.

Irxl1/Mkx (Iroquois homeobox-like 1/Mohawk) encodes a member of the TALE subfamily of homeodomain proteins. It is expressed in multiple mesoderm-derived tissues and has recently been shown to regulate tendon differentiation during mouse embryonic development. Previously we showed that knockdown of Irxl1 in zebrafish caused a deficit in neural crest cells which consequently resulted in deformation of craniofacial muscles and arch cartilages. Here, we further demonstrate that loss of Irxl1 function results in deformed somites with disordered muscle fibers and myotendinous junctions. Because expression of myoD is increased in the somites of Irxl1 knockdown morphants, we test whether Irxl1 negatively regulates myoD expression. When stable C2C12 myoblasts overexpressing Irxl1/Mkx were induced to differentiate, myotube formation was inhibited and protein levels of myoD and myosin heavy chain were decreased accordingly. A series of deletion constructs of myoD promoter fragments were tested by luciferase reporter assays, which identified a promoter fragment that is necessary and sufficient for Irxl1-mediated repression. Direct interaction of Irxl1 and myoD promoter was subsequently elucidated by yeast one-hybrid assays, electrophoretic mobility shift assays and chromatin immunoprecipitation analysis. Furthermore, mouse Mkx also binds to and represses myoD promoter. These results indicate that Irxl1/Mkx can repress myoD expression through direct binding to its promoter and may thus play a negative regulatory role in muscle differentiation.

Genetic polymorphism of LDLR (rs688) is associated with primary intracerebral hemorrhage.

Intracranial hemorrhage is the third most common cause of cerebrovascular disease. Some polymorphisms that affect clotting factors increase the risk of thrombosis. However, few reports have analyzed the effect of polymorphisms on the hemostatic state in bleeding disorders. The low-density lipoprotein receptor (LDLR) has been shown to contribute to factor VIII (FVIII) homeostasis, which represents a link between LDLR and hemostasis. FVIII plays a pivotal role in the coagulation cascade. Patients with high levels of FVIII are at an increased risk of arterial and venous thrombosis. On the other hand, patients with insufficient FVIII tend to bleed excessively, such as in hemophilia A. In a previous study, analysis of the genetic LDLR variant rs688 provided evidence suggesting that genetic polymorphisms of rs688 are associated with thrombotic cardiovascular diseases. The current study aimed to investigate the potential role of rs688 in primary intracerebral hemorrhage (PICH). This genetic association study was conducted within an isolated Taiwanese population (447 PICH patients and 430 controls). Genotypes C/C and C/T were used as the reference genotypes, and the genotype T/T was found to be associated with a 73% decreased risk of PICH. The preliminary evidence suggests that genetic polymorphisms of LDLR are associated with PICH.

Molecular characterization of toxicity mechanism of single-walled carbon nanotubes.

Carbon nanotubes (CNTs) are one of widely used nanomaterials in industry and biomedicine. The potential impact of single-walled carbon nanotubes (SWCNTs) was evaluated using Caenorhabditis elegans (C. elegans) as a toxicological animal model. SWCNTs are extremely hydrophobic to form large agglomerates in aqueous solutions. Highly soluble amide-modified SWCNTs (a-SWCNTs) were therefore used in the present study so that the exact impact of SWCNTs could be studied. No significant toxicity was observed in C. elegans due to the amide modification. a-SWCNTs were efficiently taken up by worms and caused acute toxicity, including retarded growth, shortened lifespan and defective embryogenesis. The resulting toxicity was reversible since C. elegans could recover from a-SWCNT-induced toxicity once the exposure terminates. Chronic exposure to low doses of a-SWCNTs during all development stages could also cause a toxic accumulation in C. elegans. Genome-wide gene expression analysis was performed to investigate the toxic molecular mechanisms. Functional genomic analysis and molecular biology validation suggest that defective endocytosis, the decreased activity of the citrate cycle and the reduced nuclear translocation of DAF-16 transcription factor play key roles in inducing the observed a-SWCNT toxicity in worms. The present study presents an integrated approach to evaluating the toxicity of nanomaterials at the organism and molecular level for human and environmental health and demonstrates that traditional toxicological endpoints associated with functional genomic analysis can provide global and thorough insight into toxicity.

Calcium content of different compositions of gallstones and pathogenesis of calcium carbonate gallstones.

BACKGROUND/OBJECTIVES: Our aim was to investigate the calcium content of different gallstone compositions and the pathogenic mechanisms of calcium carbonate gallstones. METHODS: Between August 2001 and July 2007, gallstones from 481 patients, including 68 calcium carbonate gallstones, were analyzed for total calcium content. Gallbladder bile samples from 33 cases and six controls were analyzed for pH, carbonate anion level, free-ionized calcium concentration and saturation index for calcium carbonate. RESULTS: Total calcium content averaged 75.6 %, 11.8 %, and 4.2 % for calcium carbonate, calcium bilirubinate and cholesterol gallstones. In 29.4 % of patients, chronic and/or intermittent cystic duct obstructions were caused by polypoid lesions in the neck region and 70.6 % were caused by stones. A total of 82 % of patients had chronic low-grade inflammation of the gallbladder wall and 18.0 % had acute inflammatory exacerbations. In the bile, we found the mean pH, mean carbonate anion, free-ionized calcium concentrations, and mean saturation index for calcium carbonate to be elevated in comparison to controls. CONCLUSION: From our study, we found chronic and/or intermittent cystic duct obstructions and low-grade GB wall inflammation lead to GB epithelium hydrogen secretion dysfunction. Increased calcium ion efflux into the GB lumen combined with increased carbonate anion presence increases SI_CaCO(3) from 1 to 22.4. Thus, in an alkaline milieu with pH 7.8, calcium carbonate begins to aggregate and precipitate.

Polymorphisms at the LDLR locus may be associated with ischemic cerebrovascular disease independent of lipid profile.

The low-density lipoprotein receptor (LDLR) gene has been reported to be associated with cerebral infarction. This study aimed to explore 2 genetic LDLR variants, rs688 and rs5925, for their potential roles in cerebral infarction. This genetic association study was conducted within an isolated Taiwanese population; 815 ischemic stroke patients (431 with atherothrombotic stroke and 384 with lacunar infarction) and 430 normal controls were enrolled. There was no significant difference in the genetic frequency of rs688 and rs5925 between the control group and overall ischemic stroke, atherothrombotic stroke, or lacunar infarct groups. However, when analyzing the association between the haplotypes related to rs688 and rs5925 and cerebral ischemic stroke, the most common haplotype allele CT was used as the reference allele, and the haplotype TC associated with a 65% increased risk of overall ischemic stroke, 72% increased risk of atherothrombotic stroke, and 70% increased risk of lacunar infarction; this indicated a synergistic effect between these 2 single-nucleotide polymorphisms. The LDLR analysis based on the haplotypes rs688 and rs5925 was conducted in a Taiwanese population and provided preliminary evidence suggesting that genetic polymorphisms of LDLR are associated with cerebral infarction.

ALOX5AP genetic variants and risk of atherothrombotic stroke in the Taiwanese population.

We explored the role of variants of the arachidonate 5-lipoxygenase-activating protein (ALOX5AP) gene as factors for atherothrombotic stroke (ATS). A HapMap-based haplotype-tagging single nucleotide polymorphism (htSNP) association study was conducted in an isolated Taiwanese population. Multivariate logistic regression analyses revealed that patients with the GG/CG genotype of rs4293222 and the AA/AG genotype of rs4360791 had a 1.61-fold (odds ratio [OR]=1.61; 95% confidence interval [CI]=1.02-2.56, p=0.042) and a 1.69-fold (OR=1.69; 95% CI=1.00-2.86, p=0.047) increased risk of ATS, compared with patients with the CC/GG genotype, respectively. The most common haplotype allele, GTA, was used as a reference when analyzing the association between the haplotypes related to rs4293222, rs10507391, rs12429692 and ATS. The combined frequencies of all minor variant alleles of the three selected htSNP were associated with a 44% decreased risk of ATS (OR=0.56; 95% CI=0.37-0.84, p=0.005). This study provides preliminary evidence suggesting that genetic polymorphisms of ALOX5AP are associated with ATS.

Long tract of untranslated CAG repeats is deleterious in transgenic mice.

The most frequent trinucleotide repeat found in human disorders is the CAG sequence. Expansion of CAG repeats is mostly found in coding regions and is thought to cause diseases through a protein mechanism. Recently, expanded CAG repeats were shown to induce toxicity at the RNA level in Drosophila and C. elegans. These findings raise the possibility that CAG repeats may trigger RNA-mediated pathogenesis in mammals. Here, we demonstrate that transgenic mice expressing EGFP transcripts with long CAG repeats in the 3' untranslated region develop pathogenic features. Expression of the transgene was directed to the muscle in order to compare the resulting phenotype to that caused by the CUG expansion, as occurs in myotonic dystrophy. Transgenic mice expressing 200, but not those expressing 0 or 23 CAG repeats, showed alterations in muscle morphology, histochemistry and electrophysiology, as well as abnormal behavioral phenotypes. Expression of the expanded CAG repeats in testes resulted in reduced fertility due to defective sperm motility. The production of EGFP protein was significantly reduced by the 200 CAG repeats, and no polyglutamine-containing product was detected, which argues against a protein mechanism. Moreover, nuclear RNA foci were detected for the long CAG repeats. These data support the notion that expanded CAG repeat RNA can cause deleterious effects in mammals. They also suggest the possible involvement of an RNA mechanism in human diseases with long CAG repeats.

Overcoming the difficulties in laparoscopic management of contracted gallbladders with gallstones: possible role of fundus-down approach.

BACKGROUND: The aim of this study is to compare efficacy and complications between fundus-down and conventional laparoscopic cholecystectomy (LC) in treating contracted gallbladders with gallstones. METHODS: Between January 1999 and May 2008, 64 patients with contracted gallbladders and gallstones were included in the study. Main outcome measures included conversion rate, complication rate, bile duct injury rate, operation time, and postoperative stay. RESULTS: The average postoperative hospital stay for fundus-down technique was 5 ± 3 days, and 7 ± 3 days for conventional technique (P = 0.003). The conversion rate and complication rate were 0% (0/33) and 3.00% (1/33) for fundus-down technique, and 32.3% (10/31) and 22.6% (7/31) for conventional technique (P = 0.0009 and 0.02, respectively). In subgroup analysis, fundus-down LC seemed to lower the bile duct injury rate from 2/31 (6.5%) to 0/33 (0%) compared with 6/1,468 (0.4%) (P = 0.01 between 6.5% and 0.4% vs. P = 1.00 between 0% and 0.4%). CONCLUSIONS: It appears that fundus-down laparoscopic cholecystectomy is associated with lower conversion and complication rates and shorter postoperative hospital stay as compared with conventional laparoscopic cholecystectomy when used to treat patients with contracted gallbladders and gallstones.

Muscleblind participates in RNA toxicity of expanded CAG and CUG repeats in Caenorhabditis elegans.

We have utilized Caenorhabditis elegans as a model to investigate the toxicity and underlying mechanism of untranslated CAG repeats in comparison to CUG repeats. Our results indicate that CAG repeats can be toxic at the RNA level in a length-dependent manner, similar to that of CUG repeats. Both CAG and CUG repeats of toxic length form nuclear foci and co-localize with C. elegans muscleblind (CeMBL), implying that CeMBL may play a role in repeat RNA toxicity. Consistently, the phenotypes of worms expressing toxic CAG and CUG repeats, including shortened life span and reduced motility rate, were partially reversed by CeMbl over-expression. These results provide the first experimental evidence to show that the RNA toxicity induced by expanded CAG and CUG repeats can be mediated, at least in part, through the functional alteration of muscleblind in worms.

Pathophysiological significance of gallbladder volume changes in gallstone diseases.

AIM: To study the pathophysiological significance of gallbladder volume (GBV) and ejection fraction changes in gallstone patients. METHODS: The fasting GBV of gallstone patients with acute cholecystitis (n = 99), chronic cholecystitis (n = 85) and non-gallstone disease (n = 240) were measured by preoperative computed tomography. Direct saline injection measurements of GBV after cholecystectomy were also performed. The fasting and postprandial GBV of 65 patients with gallstones and chronic cholecystitis and 53 healthy subjects who received health examinations were measured by abdominal ultrasonography. Proper adjustments were made after the correction factors were calculated by comparing the preoperative and postoperative measurements. Pathological correlations between gallbladder changes in patients with acute calculous cholecystitis and the stages defined by the Tokyo International Consensus Meeting in 2007 were made. Unpaired Student's t tests were used. P < 0.05 was deemed statistically significant. RESULTS: The fasting GBV was larger in late stage than in early/second stage acute cholecystitis gallbladders (84.66 +/- 26.32 cm(3), n = 12, vs 53.19 +/- 33.80 cm(3), n = 87, P = 0.002). The fasting volume/ejection fraction of gallbladders in chronic cholecystitis were larger/lower than those of normal subjects (28.77 +/- 15.00 cm(3) vs 6.77 +/- 15.75 cm(3), P < 0.0001)/(34.6% +/- 10.6%, n = 65, vs 53.3% +/- 24.9%, n = 53, P < 0.0001). CONCLUSION: GBV increases as acute cholecystitis progresses to gangrene and/or empyema. Gallstone formation is associated with poorer contractility and larger volume in gallbladders that contain stones.

Functional study of CLC-1 mutants expressed in Xenopus oocytes reveals that a C-terminal region Thr891-Ser892-Thr893 is responsible for the effects of protein kinase C activator.

ClC-1 plays an important part in the maintenance of membrane potential in the mammalian skeletal muscle. To investigate the phosphorylation sites responsible for the effect of PKC (protein kinase C) activator, we constructed 21 different ClC-1 mutants with mutations at predicted phosphorylation sites for PKC. The functional experiments were performed on both wild-type and mutant proteins (17 point mutants and 4 double mutants) expressed in Xenopus oocytes with two-electrode voltage-clamp recording. PMA (12-myristate 13-acetate), a PKC activator, caused a right shift of half-maximum activation potential (V(1/2)) significantly in the wild-type (from -42.9+/-4.4 to -13.7+/-1.7 mV; n = 8, P < 0.05) and most of the single mutants except the S892P (from -39.5+/-4.5 to -35.7+/-5.7 mV; n = 6) and S892D (from -10.2+/-4.9 to -9.6+/-3.5 mV; n = 4). S892D, a mutant mimicking PKC-mediated phosphorylation at position 892, can also mimic the effect of wild-type treated with PMA in V(1/2) value (-10.2+/-4.9 mV vs -13.7+/-1.7 mV, n = 4 - 8). However, S892A still had a significant response to PMA indicating that other sites responsible for PMA might exist. Thus double mutants are generated for the following analysis. The V(1/2) of double mutants, T891A/S892A, S892A/T893A and T891A/T893A, show no significant difference between before and after PMA treatment. We hypothesize that this structural modification results in the observed alteration of the gating properties of ClC-1 by PMA. In summary, our observations show that a C-terminal region Thr891-Ser892-Thr893, at least in part, responsible for the effect of PMA on ClC-1.

Laparoscopic primary closure of common bile duct combined with percutaneous cholangiographic drainage for treating choledocholithiasis.

The aim of this study was to compare the efficacy and safety of laparoscopic primary closure of the common bile duct (CBD) combined with percutaneous transhepatic cholangiographic drainage (PTCD) and laparoscopic choledocholithotomy with T-tube placement for the treatment of CBD stones. Between January 1991 and July 2002, 50 patients with choledocholithiasis and a CBD diameter larger than or equal to 1 cm underwent laparoscopic CBD explorations. The study group consisted of 10 patients undergoing laparoscopic primary closure of the CBD combined with PTCD. The control group consisted of 40 patients undergoing laparoscopic choledocholithotomy with T-tube placement. Parameters were compared statistically. The study group showed higher female/male ratio (6/4 vs. 8/32, P = 0.02), less stone numbers (1.90 +/- 0.88 vs. 3.40 +/- 1.65, P = 0.0078), shorter operation time (138 +/- 37 minutes vs. 191 +/- 75 minutes, P = 0.014), and shorter postoperative stays (7 +/- 3 days vs. 10 +/- 3 days, P = 0.0013). It seems that laparoscopic primary closure of the CBD combined with PTCD can shorten the operation time and postoperative stays as compared with laparoscopic choledocholithotomy with T-tube placement for the treatment of CBD stones.

The zebrafish homeobox gene irxl1 is required for brain and pharyngeal arch morphogenesis.

Iroquois homeobox-like 1 (irxl1) is a novel member of the TALE superfamily of homeobox genes that is most closely related to the Iroquois class. We have identified the zebrafish irxl1 gene and characterized its structure. The protein contains a homeodomain that shares 100% sequence identity with other vertebrate orthologs. During embryogenesis, irxl1 is expressed from 18 hours postfertilization onward and prominent expression is detected in the pharyngeal arches. Knockdown of irxl1 by morpholinos results in malformed brain and arch structures, which can be partially rescued by cRNA injection. The heads of the morphants become small and flat, and extensions along the anterior-posterior/dorso-ventral axes are reduced without affecting regional specification. Loss of irxl1 function also causes deficit in neural crest cells which consequently results in partial loss of craniofacial muscles and severe deformation of arch cartilages. These observations suggest that irxl1 may regulate factors involved in brain and pharyngeal arch development.

Zebrafish muscleblind-like genes: identification, structural features and expression.

Muscleblind-like (MBNL) proteins are a family of RNA-binding proteins that participate in the regulation of tissue-specific alternative splicing. Misregulation of MBNL activity in humans leads to pathogenesis. Here, we report upon the identification and characterization of three muscleblind-like genes in zebrafish (zmbnl1, zmbnl2 and zmbnl3). Alternative splicing of the three zmbnl primary transcripts gives rise to at least four protein isoforms for zmbnl1, four for zmbnl2 and five for zmbnl3, respectively. All of the zmbnl proteins contain the characteristic CCCH zinc fingers required for RNA binding. In addition, several structural motifs, including a C-terminal Ser/Thr-rich region, are conserved among Mbnl orthologs in vertebrates, but not invertebrates. These genes are broadly expressed in most adult tissues. However, the relative expression levels of specific spliceforms vary across different tissues. During embryogenesis, zmbnl1 and zmbnl2 are both maternally and zygotically expressed. In contrast, zmbnl3 transcripts are not detected until the late pharyngula stage. Our results reveal the expression pattern of various mbnl spliceforms for the first time and suggest that they may play specific roles during fish development.

Growth-dependent effect of muscleblind knockdown on Caenorhabditis elegans.

The muscleblind-like (MBNL) proteins are tissue-specific alternative splicing regulators. Dysfunction of MBNL has been implicated in the pathogenesis of expanded CUG repeats-associated myotonic dystrophy (DM). In this study, we describe the identification and functional characterization of a Caenorhabditis elegans muscleblind (CeMbl) gene. CeMbl is a single gene alternatively spliced to generate two isoforms (CeMBL-A and CeMBL-B). It displays a high homology with human MBNL1 in the C3H1 zinc finger domains. CeMbl transcripts are detected in larval and adult stages. However, inactivation of CeMbl by RNA-mediated interference results in muscle phenotype only at adulthood. Immunofluorescence staining using anti-vinculin antibody reveals that the organization of dense body is disrupted in affected worms. Our results demonstrate a growth-dependent requirement of CeMbl on muscle structure and function. They also provide a possible molecular basis for the developmentally regulated toxicity of expanded CUG repeats.

Functional studies of the effect of NO donor on human CLCN1 polymorphism/mutants expressed in Xenopus laevis oocytes.

In this study, we investigated the effect of NO donor, diethylamine/nitric oxide (DEA/NO), on the electrophysiological behavior of human skeletal muscle chloride channel (CLCN1). The wild-type and variants of CLCN1, including one polymorphism (P727L) and four mutants (T631I, D644G, G482R, and S471F), were expressed in Xenopus oocytes and the ionic current was measured by two-electrode voltage-clamp method. Our results revealed that there is no significant difference in the current-voltage relationships and half-voltage values of open probability between wild-type and variants of CLCN1 except for G482R. Application of the DEA-NO (0.1mM) significantly increases the channel conductance of wild-type, T631I, D644G, and S471F, but not P727L. This indicates that P727L polymorphism causes loss of sensitivity of CLCN1 to the DEA/NO treatment, which could be due to a conformational change caused by proline substitution. The data suggest that the polymorphic changes may affect the function of CLCN1 in response to the treatment of chemical compounds.

Phenotypic variability of autosomal dominant myotonia congenita in a Taiwanese family with muscle chloride channel (CLCN1) mutation.

BACKGROUND: Myotonia congenita (MC), whether inherited in autosomal dominant or recessive form, is caused by mutation of CLCN1 on chromosome 7 and associated with impaired skeletal muscle relaxation after contraction. The basic pathophysiology is the reduction of chloride conductance in skeletal muscles caused by various molecular mechanisms. The cause of the wide phenotypic variability in both dominant and recessive MC remains unclear. METHODS: A family clinically diagnosed with autosomal dominant myotonia congenita was enrolled. Three family members underwent a detailed neurological examination, eletromyography, and genetic analysis. RESULTS: A G230E mutation of CLCN1 was confirmed in these three family members. One of them was completely asymptomatic and the electromyographic studies were normal. A great variability of clinical presentation was found in these family members with MC. CONCLUSIONS: We report the first autosomal dominant MC family with G230E mutation in oriental countries. Most of the previously reported MC families with G230E mutation were autosomal dominant pedigrees, and only 1 out of 20 heterozygous family members was asymptomatic. The reduced penetrance in this family indicates a less "dominant negative effect" of the G230E mutation.