Novel Mutations in the TMPRSS3 Gene may Contribute to Taiwanese Patients with Nonsyndromic Hearing Loss.

A previous study indicated that mutations in the transmembrane protease serine 3 (TMPRSS3) gene, which encodes a transmembrane serine protease, cause nonsyndromic hearing loss (NSHL). This was the first description of a serine protease involved in hearing loss (HL). In Taiwan, however, data on the TMPRSS3 gene's association with NSHL is still insufficient. In this study, we described 10 mutations of TMPRSS3 genes found in 14 patients after screening 230 children with NSHL. The prevalence of the TMPRSS3 mutation appeared to be 6.09% (14/230). Of the 10 mutations, three were missense mutations: c.239G>A (p.R80H), c.551T>C (p.L184S), and 1253C>T (p.A418V); three were silent mutations, and four were mutations in introns. To determine the functional importance of TMPRSS3 mutations, we constructed plasmids carrying TMPRSS3 mutations of p.R80H, p.L184S, and p.A418V. TMPRSS3 function can be examined by secretory genetic assay for site-specific proteolysis (sGASP) and Xenopus oocyte expression system. Our results showed that p.R80H, p.L184S, and p.A418V TMPRSS3 mutations gave ratios of 19.4%, 13.2%, and 27.6%, respectively, via the sGASP system. Moreover, these three TMPRSS3 mutations failed to activate the epithelial sodium channel (ENaC) in the Xenopus oocyte expression system. These results indicate that the p.R80H, p.L184S, and p.A418V missense mutations of TMPRSS3 resulted in greatly diminishing the proteolytic activity of TMPRSS3. Our study provides information for understanding the importance of TMPRSS3 in the NSHL of Taiwanese children and provides a novel molecular explanation for the role of TMPRSS3 in HL.

An Application of NGS for WDR36 Gene in Taiwanese Patients with Juvenile-Onset Open-Angle Glaucoma.

Primary open-angle glaucoma (POAG) is one of the most important disease in ophthalmology with high prevalence and risk of irreversible blindness. If diagnosed before the age of 35, it is usually categorized as juvenile open-angle glaucoma (JOAG). The WDR36 gene is reckoned as one of the major causative genes of POAG, and had been studied to be related to the pathogenesis of POAG in the literature. We have selected 61 JOAG patients and 61 JOAG-free individuals, and by next-generation sequencing method, the WDR36 gene of the subjects were analyzed. We identified 26 variations exclusively in JOAG group. Among these 26 variations, there were 3 noteworthy variations. First, a novel variation c.460-650A>G was found in our study which might cause premature termination of splicing of the conserved domain in WDR36; second, c.1494+1111G>T (rs13178997) had significantly different frequency in our JOAG patients compared to the reference frequency on NCBI; third, a variation c.710+30C>T (rs10038177) was found in our study, which had already been reported to be related to high-pressure glaucoma. We offer the profile of WDR36 in JOAG in Taiwan population, and we suggest that WDR36 gene is involved in the pathogenesis of JOAG as a subordinate modifier gene.

Functional analysis of a nonsyndromic hearing loss-associated mutation in the transmembrane II domain of the GJC3 gene.

In a previous study, we identified a novel missense mutation, p.W77S, in the GJC3 gene encoding connexin30.2/connexin31.3 (CX30.2/CX31.3) from patients with hearing loss. The functional alteration of CX30.2/CX31.3 caused by the p.W77S mutant of GJC3 gene, however, remains unclear. In the current study, our result indicated that the p.W77 is localized at the second membrane-spanning segments (TM2) and near border of the E1 domain of the CX30.2/CX31.3 protein and highly conserved (Conseq score = 8~9) in all species. The p.W77S missense mutation proteins in the intracellular distribution are different CX30.2/CX31.3WT and an accumulation of the mutant protein in the endoplasmic reticulum (ER) of the HeLa cell. Furthermore, co-expression of WT and p.W77S mutant chimerae proteins showed that the heteromeric connexon accumulated in the cytoplasm, thereby impairing the WT proteins' expression in the cell membranes. In addition, we found that CX30.2/CX31.3W77S missense mutant proteins were degraded by lysosomes and proteosomes in the transfected HeLa cell. Based on these findings, we suggest that p.W77S mutant has a dominant negative effect on the formation and function of the gap junction. These results give a novel molecular elucidation for the mutation of GJC3 in the development of hearing loss.

A KCNQ2 E515D mutation associated with benign familial neonatal seizures and continuous spike and waves during slow-wave sleep syndrome in Taiwan.

BACKGROUND/PURPOSE: Pediatric epilepsy caused by a KCNQ2 gene mutation usually manifests as benign familial neonatal seizures (BFNS) during the 1st week of life. However, the exact mechanism, phenotype, and genotype of the KCNQ2 mutation are unclear. METHODS: We studied the KCNQ2 genotype from 75 nonconsanguineous patients with childhood epilepsy without an identified cause (age range: from 2 days to 18 years) and from 55 healthy adult controls without epilepsy. KCNQ2 mutation variants were transfected into HEK293 cells to investigate what functional changes they induced. RESULTS: Four (5%) of the patients had the E515D KCNQ2 mutation, which the computer-based PolyPhen algorithm predicted to be deleterious. Their seizure outcomes were favorable, but three had an intellectual disability. Two patients with E515D presented with continuous spikes and waves during slow-wave sleep (CSWS), and the other two presented with BFNS. We also analyzed 10 affected family members with the same KCNQ2 mutation: all had epilepsy (8 had BFNS and 2 had CSWS). A functional analysis showed that the recordings of the E515D currents were significantly different (p<0.05), which suggested that channels with KCNQ2 E515D variants are less sensitive to voltage and require stronger depolarization to reach opening probabilities than those with the wild type or N780T (a benign polymorphism). CONCLUSION: KCNQ2 mutations can cause various phenotypes in children: they lead to BFNS and CSWS. We hypothesize that patients with the KCNQ2 E515D mutation are susceptible to seizures.

Novel mutations in the connexin43 (GJA1) and GJA1 pseudogene may contribute to nonsyndromic hearing loss.

Connexins (CXs), a large family of membrane proteins, are key components of gap junction channels. Among a cohort of patients with nonsyndromic hearing loss, we have recently identified three novel missense mutations in the GJA1 gene and GJA1 pseudogene (rhoGJA1) as likely being causally related to hearing loss. However, the functional alteration of CX43 caused by the mutations of GJA1 and rhoGJA1 gene remains unclear. This study compares the intracellular distribution and assembly of three CX43 mutants expressed in HeLa cells with their wild-type (WT) counterparts and the effects of the mutant proteins on those cells. Localization assay of WT CX43 reveals a typical punctuate fluorescence pattern of a gap junction channel between neighboring expression cells. Additionally, immunoblotting analysis of the transfectants confirms the production of mutant proteins, in which their distributions along appositional membranes are determined using immunofluorescent staining procedures. Furthermore, dye transfer assay results demonstrate that gap junctional intercellular communication is less in HeLa cells carrying mutant GJA1 or rhoGJA1 gene than in WT-expressing cells. The results of this study suggest that the three mutations in GJA1 or rhoGJA1 that we previously reported result in at least partial loss of normal functions carried out by CX43, which may form a basis for the mechanism contributing to hearing loss in patients.

A novel mutation in the connexin 29 gene may contribute to nonsyndromic hearing loss.

Connexins (Cxs) are homologous four-transmembrane domain proteins and constitute the major components of gap junctions. Among a cohort of patients with nonsyndromic hearing loss, we recently identified a novel missense mutation, E269D, in the GJC3 gene encoding connexin 29 (Cx29), as being causally related to hearing loss. The functional alteration of Cx29 caused by the mutant GJC3 gene, however, remains unknown. This study compared the intracellular distribution and assembly of mutant Cx29 (Cx29E269D) with that of the wild-type Cx29 (Cx29WT) in HeLa cells and the effect the mutant protein had on those cells. Cx29TW showed continuous staining along apposed cell membranes in the fluorescent localization assay. In contrast, the p.E269D missense mutation resulted in accumulation of the Cx29 mutant protein in the endoplasmic reticulum (ER) rather than in the cytoplasmic membrane. Co-expression of Cx29WT and Cx29E269D proteins by a bi-directional tet-on expression system demonstrated that the heteromeric connexon accumulated in the cytoplasm, thereby impairing the formation of the gap junction. Based on these findings, we suggest that Cx29E269D has a dominant negative effect on the formation and function of the gap junction. These results provide a novel molecular explanation for the role Cx29 plays in the development of hearing loss.

Prospective variants screening of connexin genes in children with hearing impairment: genotype/phenotype correlation.

The crucial role of gap junctions, which are composed of connexin (CX) protein, in auditory functions has been confirmed by numerous studies. In this study, we investigate the prevalence and phenotype/genotype correlation of connexin (CX) gene family variants in a cohort of children with nonsyndromic hearing loss (HL). A total of 253 unrelated children with nonsyndromic HL were screened for the presence of variants in 6 genes of the CX gene family. The prevalence of CX gene variants in 253 patients was 19.7% (50/253). We found the frequency of a sloping audiometric configuration was significantly higher for children with GJB2 and GJB3 variants than for those with GJB4 and GJC3 variants (Adjusted OR = 4.89, p < 0.001). Conversely, the frequency of a flat audiometric configuration was significantly higher for children with GJB4 and GJC3 variants than for those with GJB2 and GJB3 variants (adjusted OR = 7.76, p < 0.001). The relative frequencies of multiplex families was significantly higher for children with GJB3 variants than for those with GJB2, GJB4, and GJC3 variants (Adjusted OR = 11.33, p = 0.003). Our results suggest the variants of GJC3, GJB4, and GJB3 may be the common genetic risk factor, after variants of GJB2, for the development of nonsyndromic HL in Taiwan. These data can be effectively applied to direct the clinical evaluation of children with CX gene variants.

Identification of novel variants in the Cx29 gene of nonsyndromic hearing loss patients using buccal cells and restriction fragment length polymorphism method.

The crucial role of gap junctions, which are composed of connexin (Cx) protein, in auditory functions has been confirmed by numerous studies. Cx29 is a relatively new member of the Cx protein family. In this article, we report variants of the Cx29 gene in 253 unrelated Taiwanese patients with nonsyndromic hearing loss. Thirteen (5.14%) of the 253 patients had variants of Cx29. Five sequence changes (c.43C-->G, c.230G-->C, c.525T-->G, c.781 + 62G-->A and c.*2T-->G) in the Cx29 gene were detected in the study, of which 3 (c.43C-->G, c.230G-->C and c.525T-->G) were novel variants. One novel compound heterozygote missense variant, c.[43C-->G(+) 230G-->C], was identified in the Cx29 gene carried by 1 patient, and this variant appears to have been inherited from the mother's chromosome. In addition, for diagnostic purposes, we developed a restriction fragment length polymorphism method using NaeI and StyI to identify c.43C-->G and c.525T-->G specific variants of the Cx29 gene, respectively. On the basis of the above results, we suggest that the c.[43C-->G(+)230G-->C] compound heterozygous variant of Cx29 may be a risk factor for the development of hearing loss in Taiwanese and that the restriction fragment length polymorphism method developed will be clinically useful in identifying variants of the Cx29 gene in patients with hearing loss.

Polymorphisms of the RET gene in hirschsprung disease, anorectal malformation and intestinal pseudo-obstruction in Taiwan.

BACKGROUND/PURPOSE: Mutations in the receptor tyrosine kinase RET gene are associated with Hirschsprung disease (HD), which is also known as congenital intestinal aganglionosis. We found an association with specific alleles in five single nucleotide polymorphism (SNP) sites of the RET gene in our HD patients. METHODS: We compared the association of specific RET SNP alleles in patients with severe GI disorders such as anorectal malformation (ARM) or pediatric intestinal pseudo-obstruction (IPO) to that in HD patients. Sixty-four HD, 23 ARM and 35 IPO patients were included. Genomic DNA extracted from blood samples was analyzed by polymerase chain reaction and DNA sequencing analysis. RESULTS: The allele distributions of all five RET SNPs in the HD patients deviated from those in the normal population (p < 0.05), whereas those of the ARM patients did not. The allele distributions of these RET SNPs in the IPO patients were all significantly different from those in the HD patients. Allele distributions of exon 2 and 13 in the IPO patients were also significantly different from those of the normal population. The frequencies of all the HD-predominant alleles were lower in the HD patients than the normal population, and were even lower in the IPO patients. CONCLUSION: This study strengthens the association of specific RET SNP alleles with typical HD in Taiwan.

A Wide Spectrum of Genetic Disorders Causing Severe Childhood Epilepsy in Taiwan: A Case Series of Ultrarare Genetic Cause and Novel Mutation Analysis in a Pilot Study.

BACKGROUND: Pediatric epileptic encephalopathy and severe neurological disorders comprise a group of heterogenous diseases. We used whole-exome sequencing (WES) to identify genetic defects in pediatric patients. METHODS: Patients with refractory seizures using ≥2 antiepileptic drugs (AEDs) receiving one AED and having neurodevelopmental regression or having severe neurological or neuromuscular disorders with unidentified causes were enrolled, of which 54 patients fulfilled the inclusion criteria, were enrolled, and underwent WES. RESULTS: Genetic diagnoses were confirmed in 24 patients. In the seizure group, KCNQ2, SCN1A, TBCID 24, GRIN1, IRF2BPL, MECP2, OSGEP, PACS1, PIGA, PPP1CB, SMARCA4, SUOX, SZT2, UBE3A, 16p13.11 microdeletion, [4p16.3p16.1(68,345-7,739,782)X1, 17q25.1q25.3(73,608,322-81,041,938)X3], and LAMA2 were identified. In the nonseizure group, SCN2A, SPTBN2, DMD, and FBN1 were identified. Ten novel mutations were identified. The recurrent genes included SCN1A, KCNQ2, and TBCID24. Male pediatric patients had a significantly higher (57% vs. 29%; p < 0.05, odds ratio = 3.18) yield than their female counterparts. Seventeen genes were identified from the seizure groups, of which 82% were rare genetic etiologies for childhood seizure and did not appear recurrently in the case series. CONCLUSIONS: Wide genetic variation was identified for severe childhood seizures by WES. WES had a high yield, particularly in male infantile patients.

Heteromeric Kv7.2 current changes caused by loss-of-function of KCNQ2 mutations are correlated with long-term neurodevelopmental outcomes.

Pediatric epilepsy caused by KCNQ2 mutations can manifest benign familial neonatal convulsions (BFNC) to neonatal-onset epileptic encephalopathy (EE). Patients might manifest mild to profound neurodevelopmental disabilities. We analysed c.853C > A (P285T) and three mutations that cause KCNQ2 protein changes in the 247 position: c.740C > T (S247L), c.740C > A (S247X), and c.740C > G (S247W). S247L, S247W, and P285T cause neonatal-onset EE and poor neurodevelopmental outcomes; S247X cause BFNC and normal outcome. We investigated the phenotypes correlated with human embryonic kidney 293 (HEK293) cell functional current changes. More cell-current changes and a worse conductance curve were present in the homomeric transfected S247X than in S247L, S247W, and P285T. But in the heteromeric channel, S247L, S247W and P285T had more current impairments than did S247X. The protein expressions of S247X were nonfunctional. The outcomes were most severe in S247L and S247W, and severity was correlated with heteromeric current. Current changes were more significant in cells with homomeric S247X, but currents were "rescued" after heteromeric transfection of KCNQ2 and KCNQ3. This was not the case in cells with S247L, S247W. Our findings support that homomeric current changes are common in KCNQ2 neonatal-onset EE and KCNQ2 BFNC; however, heteromeric functional current changes are correlated with long-term neurodevelopmental outcomes.

The Functional Role of CONNEXIN 26 Mutation in Nonsyndromic Hearing Loss, Demonstrated by Zebrafish Connexin 30.3 Homologue Model.

Nonsyndromic hearing loss (NSHL) is of great clinical importance, and mutations in the GJB2 gene and the encoded human CONNEXIN 26 (CX26) protein play important roles in the genetic pathogenesis. The CX26 p.R184Q mutation was shown to be a dominant-negative effect in our previous study. Previously, we also demonstrated that zebrafish Cx30.3 is orthologous to human CX26. In the present study, we established transgenic zebrafish models with mutated Cx30.3 specifically expressed in the supporting cells of zebrafish inner ears driven by the agr2 promoter, to demonstrate and understand the mechanism by which the human CX26 R.184 mutation causes NSHL. Our results indicated that significant structural changes in the inner ears of transgenic lines with mutations were measured and compared to wild-type zebrafish. Simultaneously, significant alterations of transgenic lines with mutations in swimming behavior were analyzed with the zebrafish behavioral assay. This is the first study to investigate the functional results of the CX26 p.R184Q mutation with in vivo disease models. Our work supports and confirms the pathogenic role of the CX26 p.R184Q mutation in NSHL, with a hypothesized mechanism of altered interaction among amino acids in the connexins.

Functional study of the effect of phosphatase inhibitors on KCNQ4 channels expressed in Xenopus oocytes.

AIM: KCNQ4 channels play an important part in adjusting the function of cochlear outer hair cells. The aim of this study was to investigate the effects of ser/thr phosphatase inhibitors on human KCNQ4 channels expressed in Xenopuslaevis oocytes. METHODS: Synthetic cRNA encoding human KCNQ4 channels was injected into Xenopus oocytes. We used a two-electrode voltage clamp to measure the ion currents in the oocytes. RESULTS: Wild-type KCNQ4 expressed in Xenopus oocytes showed the typical properties of slow activation kinetics and low threshold activation. The outward K(+) current was almost completely blocked by a KCNQ4 blocker, linopirdine (0.25 mmol/L). BIMI (a PKC inhibitor) prevented the effects of PMA (a PKC activator) on the KCNQ4 current, indicating that PKC may be involved in the regulation of KCNQ4 expressed in the Xenopus oocyte system. Treatment with the ser/thr phosphatase inhibitors, cyclosporine (2 micromol/L), calyculin A (2 micromol/L) or okadaic acid (1 micromol/L), caused a significant positive shift in V(1/2) and a decrease in the conductance of KCNQ4 channels. The V(1/2) was shifted from -14.6+/-0.5 to -6.4+/-0.4 mV by cyclosporine, -18.8+/-0.5 to -9.2+/-0.4 mV by calyculin A, and -14.1+/-0.5 to -0.7+/-0.6 mV by okadaic acid. Moreover, the effects of these phosphatase inhibitors (okadaic acid or calyculin A) on the induction of a positive shift of V(1/2) were augmented by further addition of PMA. CONCLUSION: These results indicate that ser/thr phosphatase inhibitors can induce a shift to more positive potentials of the activation curve of the KCNQ4 current. It is highly likely that the phosphatase functions to balance the phosphorylated state of substrate protein and thus has an important role in the regulation of human KCNQ4 channels expressed in Xenopus oocytes.

Expansion of CAG repeats in the spinocerebellar ataxia type 1 (SCA1) gene in idiopathic oligozoospermia patients.

PURPOSE: The lengths of CAG repeats in two spinocerebellar ataxia genes, SCA1 and SCA3, were analyzed to determine whether such repeats exist in higher numbers in infertile males. METHODS: Blood samples were collected from healthy controls, oligozoospermia patients, and azoospermia patients. DNA fragments containing target CAG repeats were amplified by PCR with template DNA purified from the blood samples. CAG repeats in PCR fragments were determined, using ABI PRISM 310 Gene Analyzer. RESULTS: In SCA1, the distribution of CAG repeats in oligozoospermic males was different from that of the control group: More alleles had a repeat number that exceeded 32. Conversely, for SCA3, the examined oligozoospermia and azoospermia patients exhibited no differences in distribution of CAG repeats in comparison with the control group. CONCLUSIONS: SCA1 in a subset of oligozoospermia patients has an increased number of CAG repeats.

KCNQ2 mutations in childhood nonlesional epilepsy: Variable phenotypes and a novel mutation in a case series.

BACKGROUND: Epilepsy caused by a KCNQ2 gene mutation usually manifests as neonatal seizures during the first week of life. The genotypes and phenotypes of KCNQ2 mutations are noteworthy. METHODS: The KCNQ2 sequencings done were selected from 131 nonconsanguineous pediatric epileptic patients (age range: 2 days to 18 years) with nonlesional epilepsy. RESULTS: Seven (5%) index patients had verified KCNQ2 mutations: c.387+1 G>T (splicing), c.1741 C>T (p.Arg581*), c.740 C>T p.(Ser247Leu), c.853 C>A p.(Pro285Thr), c.860 C>T p.(Thr287Ile), c.1294 C>T p.(Arg432Cys), and c.1627 G>A p.(Val543Met). We found, after their paternity had been confirmed, that three patients had de novo p.(Ser247Leu), p.(Pro285Thr), and p.(Thr287Ile) mutations and neonatal-onset epileptic encephalopathy; however, their frequent seizures remitted after they turned 6 months old. Those with the c.387+1G>T (splicing), (p.Arg581*), and p.(Val543Met) mutations presented with benign familial neonatal convulsions. In addition to their relatives, 14 patients had documented KCNQ2 mutations, and 12 (86%) had neonatal seizures. The seizures of all five patients treated with oxcarbazepine remitted. CONCLUSION: KCNQ2-related epilepsy led to varied outcomes (from benign to severe) in our patients. KCNQ2 mutations accounted for 13% of patients with seizure onset before 2 months old in our study. KCNQ2 mutations can cause different phenotypes in children. p.(Pro 285Thr) is a novel mutation, and the p.(Pro 285Thr), p.(Ser247Leu), and p.(Thr287Ile) variants can cause neonatal-onset epileptic encephalopathy.

Absence of optineurin (OPTN) gene mutations in Taiwanese patients with juvenile-onset open-angle glaucoma.

PURPOSE: To investigate sequence variants in the optineurin (OPTN) gene in patients with juvenile-onset open-angle glaucoma (JOAG) in Taiwan. METHODS: We analyzed the sequence variants of OPTN in 51 unrelated Taiwanese probands with JOAG and in 51 control group subjects who did not have JOAG. Genomic DNA was extracted from the individuals and subjected to polymerase chain reaction (PCR) to amplify all 16 exons and flanking introns of OPTN. The amplified products were then screened for base variants by autosequence. Data from the two study groups were then compared using Fisher's exact test and Armitage's trend test. RESULTS: Fifteen variants of OPTN were found in the 51 JOAG patients and 51 unrelated normal controls. Two were missense variants (M98K and K322E), one was a synonymous codon change (T34T), and 12 were changes in the noncoding sequences. Seven of the variants have been reported and eight were novel. All of the sequence changes were found in patients with JOAG and in the normal controls except for variant c.-233+25C>G, which was found only in the control group. Allelic frequencies of these sequence changes did not differ significantly between patients and controls (p>0.05) except for the variant c.-233+25C>G (p<0.001). Genotype frequencies of c.-233+25C>G was shown to be significant between the two groups using Fisher's two-tailed exact test (p<0.001) and Armitage's trend test (p=6.815e(-06)). CONCLUSIONS: Our data indicate that none of the mutations in OPTN are associated with JOAG. The variant M98K is not a risk factor and the variant c.-233+25C>G may be protective against glaucoma in Taiwanese.

Identification of mutations in the myocilin (MYOC) gene in Taiwanese patients with juvenile-onset open-angle glaucoma.

PURPOSE: To investigate mutations in the promoter and coding regions of the myocilin (MYOC) gene in Taiwanese patients suffering from juvenile-onset open-angle glaucoma (JOAG). METHODS: MYOC was analyzed for mutations in 48 unrelated Taiwanese probands with JOAG and in 100 healthy control subjects. Genomic DNA was extracted from peripheral blood leukocytes and then subjected to PCR to amplify exons, flanking introns and promoter regions of the MYOC gene. The amplified products were screened for base mutations by autosequence. Data from the two groups were then compared using the chi(2) test. Finally, the levels of MYOC transcripts were predicted by a neural network prediction system to study whether the intron mutations have any effect on the level of mRNA expression. RESULTS: The analysis revealed four MYOC mutations and six polymorphisms. The prevalence of MYOC gene mutations in this study was 12.5% (6/48). The mutations included one nonsense mutation (Arg46Stop; 3/6), one missense mutation (Val56Ala; 1/6), one intron mutation (c.604+228A>T; 1/6) as well as one mutation in the 3'-untranslated region (c.1515+73G>C; 1/6). In addition, although c.604+228A>T is an intron mutation and does not alter the content of the amino acid residue, the neural network prediction system revealed that it can potentially create a novel accept splice site during transcription. This mutation might affect the protein structure and consequently the normal function of myocilin. CONCLUSIONS: Our results indicate that the c.136C>T (Arg46Stop), c.158T>C (Val56Ala), c.604+228A>T, and c.1515+73G>C mutations of MYOC may be associated with JOAG. In addition, we suggest that the c.136C>T (Arg46Stop) mutation of MYOC is a hot spot in Taiwanese patients with JOAG.

Identification of mutations in members of the connexin gene family as a cause of nonsyndromic deafness in Taiwan.

Connexins (Cx), a large family of membrane proteins, are key components of gap junction channels. These channels are critical intercellular pathways through which ions or small molecules are passed, regulating a variety of physiological and developmental processes. One of these processes is hearing. In the current study, a genetic survey was made on 380 Taiwanese individuals, 260 with nonsyndromic deafness and 120 with normal hearing. All the 380 Taiwanese were screened for the presence of mutations in 8 genes of the Cx gene family. These genes included Cx26 (GJB2), Cx29 (GJE1), Cx30 (GJB6), Cx30.3 (GJB4), Cx31 (GJB3), Cx32 (GJB1), Cx43 (GJA1) and pseudogene [rho] of Cx43 (rho GJA1). Mutations were identified in 7 out of the 8 screened genes of the Cx family from 62 of the 260 deaf subjects (23.85%). Of the 17 mutations observed in the Cx gene family, 11 were novel mutations. Fourteen polymorphisms that were not associated with hearing loss were identified in the Cx gene family. The first 2 most frequently occurring mutations were found in the Cx26 (28/62; 45.16%) and the rho Cx43 (17/62; 27.42%), respectively. Nine cases of mutations were found in the Cx30.3 (9/62; 14.52%). In the Cx30, 1 novel mutation was identified in 1 case (1/62; 1.61%). Two patients with mutations of each of Cx29 and Cx43 were found (2/62; 3.23%). One novel mutation of Cx31 was identified in 3 patients with nonsyndromic deafness (3/62; 4.84%). The Cx32 was the only gene without detecting any mutation or polymorphism.Our study provides information for understanding the importance of genetic factors in nonsyndromic deafness of the Taiwanese and may be of use in the improvement of genetic diagnosis of hearing loss in Taiwan.

Mutations and new polymorphic changes in the TCOF1 gene of patients with oculo-auriculo-vertebral spectrum and Treacher-Collins syndrome.

Oculo-auriculo-vertebral spectrum, the exact genetic predisposition of which has not yet been resolved, is characterized by varying degrees of the prevalently unilateral underdevelopment of craniofacial structures and spinal anomalies. Here, we analyzed four cases exhibiting multiple features of oculo-auriculo-vertebral spectrum and one case with Treacher-Collins syndrome. The cranium was analyzed using three-dimensional computed tomography, which reliably identifies craniofacial malformations. We detected one typical oculo-auriculo-vertebral spectrum patient who had a missense mutation in exon 9 of the TCOF1 gene complex and two silent mutations in exons 10 and 23, three partial oculo-auriculo-vertebral spectrum patients who had no detectable mutations in the TCOF1 gene complex, and one Treacher-Collins syndrome patient who had a nonsense mutation in exon 14. All five patients had eight previously reported polymorphic changes in the TCOF1 exons 10, 11, 12, 16, 21, 22, and 23, and four unreported polymorphisms in exons 9, 17, and 22 that were also detected in 51 Taiwanese control patients. These observations strongly suggest that the TCOF1 genetic changes observed in these five patients might be related to oculo-auriculo-vertebral spectrum symptoms.

Seizure Recurrence in Children after Stopping Antiepileptic Medication: 5-Year Follow-Up.

BACKGROUND: We wanted to identify in children with epilepsy the factors associated with seizure control and recurrence after a 2-year remission. METHODS: We did a 5-year follow-up of epileptic children whose antiepileptic medication had been stopped. Bivariate and multivariate analyses were used to compare features of electroencephalograms (EEGs) and clinical findings. In this study, 43 patients with and 64 without a seizure recurrence (SR) were enrolled. RESULTS: Clinical features strongly associated with SR in the univariate analysis included a symptomatic etiology for seizures, a history of status epilepticus, treatment duration before stopping antiepileptic drugs, and abnormal EEG findings at the time of stopping antiepileptic drugs. CONCLUSION: We found that a history of status epilepticus, symptomatic partial epilepsy, treatment duration before stopping antiepileptic drugs, and an abnormal EEG when the medication was stopped are important predictors of SR. The risk factors of SR after discontinuing antiepileptic drugs have been investigated in several studies. However, a history of status epilepticus as a predictive factor is rarely mentioned.