SLC26A4 Mutations Research Articles

Rescue of mis-splicing of a common SLC26A4 mutant associated with sensorineural hearing loss by antisense oligonucleotides

A wide spectrum of SLC26A4 mutations causes Pendred syndrome and enlarged vestibular aqueduct, both associated with sensorineural hearing loss (SNHL). A splice-site mutation, c.919-2A>G (A-2G), which is common in Asian populations, impairs the 3′ splice site of intron 7, resulting in exon 8 skipping during pre-mRNA splicing and a subsequent frameshift that creates a premature termination codon in the following exon. Currently, there is no effective drug treatment for SHNL. For A-2G-triggered SNHL, molecules that correct mis-splicing of the mutant hold promise to treat the disease. Antisense oligonucleotides (ASOs) can promote exon inclusion when targeting specific splicing silencers. Here, we systematically screened a large number of ASOs in a minigene system and identified a few that markedly repressed exon 8 skipping. A lead ASO, which targets a heterogeneous nuclear ribonucleoprotein (hnRNP) A1/A2 intronic splicing silencer (ISS) in intron 8, promoted efficient exon 8 inclusion in cultured peripheral blood mononuclear cells derived from two homozygous patients. In a partially humanized Slc26a4 A-2G mouse model, two subcutaneous injections of the ASO at 160 mg/kg significantly rescued exon 8 splicing in the liver. Our results demonstrate that the ISS-targeting ASO has therapeutic potential to treat genetic hearing loss caused by the A-2G mutation in SLC26A4.

Maternally transmitted nonsyndromic hearing impairment may be associated with mitochondrial tRNAAla 5601C>T and tRNALeu(CUN) 12311T>C mutations.

BackgroundSequence alternations in mitochondrial genomes, especially in genes encoding mitochondrial tRNA (mt‐tRNA), were the important contributors to nonsyndromic hearing loss (NSHL); however, the molecular mechanisms remained largely undetermined.MethodsA maternally transmitted Chinese pedigree with NSHL underwent clinical, genetic, and biochemical assessment. PCR and direct sequence analyses were performed to detect mitochondrial DNA (mtDNA), GJB2, and SLC26A4 gene mutations from matrilineal relatives of this family. Mitochondrial functions including mitochondrial membrane potential (MMP), ATP, and ROS were evaluated in polymononuclear leukocytes (PMNs) derived from three deaf patients and three controls from this pedigree.ResultsFour of nine matrilineal relatives developed hearing loss at the variable age of onset. Two putative pathogenic mutations, m.5601C>T in tRNAAla and m.12311T>C in tRNALeu(CUN), were identified via PCR‐Sanger sequencing, as well as 34 variants that belonged to mtDNA haplogroup G2b2. Intriguingly, m.5601C>T mutation resided at very conserved nucleotide in the TψC loop of tRNAAla (position 59), while the T‐to‐C substitution at position 12311 located at position 48 in the variable stem of tRNALeu(CUN) and was believed to alter the aminoacylation and the steady‐state level of tRNA. Biochemical analysis revealed the impairment of mitochondrial functions including the significant reductions of ATP and MMP, whereas markedly increased ROS levels were found in PMNs derived from NSHL patients with m.5601C>T and m.12311T>C mutations. However, we did not detect any mutations in GJB2 and SLC26A4 genes.ConclusionOur data indicated that mt‐tRNAAla m.5601C>T and tRNALeu(CUN) 12311T>C mutations were associated with NSHL.

The H+ Transporter SLC4A11: Roles in Metabolism, Oxidative Stress and Mitochondrial Uncoupling.

Solute-linked cotransporter, SLC4A11, a member of the bicarbonate transporter family, is an electrogenic H+ transporter activated by NH3 and alkaline pH. Although SLC4A11 does not transport bicarbonate, it shares many properties with other members of the SLC4 family. SLC4A11 mutations can lead to corneal endothelial dystrophy and hearing deficits that are recapitulated in SLC4A11 knock-out mice. SLC4A11, at the inner mitochondrial membrane, facilitates glutamine catabolism and suppresses the production of mitochondrial superoxide by providing ammonia-sensitive H+ uncoupling that reduces glutamine-driven mitochondrial membrane potential hyperpolarization. Mitochondrial oxidative stress in SLC4A11 KO also triggers dysfunctional autophagy and lysosomes, as well as ER stress. SLC4A11 expression is induced by oxidative stress through the transcription factor NRF2, the master regulator of antioxidant genes. Outside of the corneal endothelium, SLC4A11’s function has been demonstrated in cochlear fibrocytes, salivary glands, and kidneys, but is largely unexplored overall. Increased SLC4A11 expression is a component of some “glutamine-addicted” cancers, and is possibly linked to cells and tissues that rely on glutamine catabolism.

A case of Landau-Kleffner syndrome with SLC26A4-related hearing impairment

BackgroundLandau-Kleffner syndrome (LKS) is an acquired aphasia and electroencephalogram (EEG) abnormalities mainly in temporoparietal areas. SLC26A4 mutations can cause hearing loss associated with enlarged vestibular aqueduct (EVA).Case presentationsWe report a case of LKS in a 5-year-old boy with non-syndromic EVA due to homozygous mutations of c.919-2A>G (IVS7-2A>G) in SLC26A4. He had normal language development before 2 years old. At the age of 2.5 years, he was admitted to the hospital due to remarkable language delay, and diagnosed with hearing loss with EVA. The seizures started at 4.4 years of age and EEG recording showed electrical status epilepticus during sleep (ESES) with a posterior-temporal predominance. He received cochlear implantation in the right ear at 4.7 years of age, which improved his hearing and language skills. The nocturnal focal motor seizures recurred at 4.9 years of age. Then a remarkable inability to respond to calls and reduction in spontaneous speech were noticed. He was treated with methylprednisolone at 5 years old, which controlled the seizures, suppressed ESES, and remarkably improved the language ability. The absence of seizures maintained until the last follow-up at 5.3 years of age, with further improvements in EEG recording and language ability.ConclusionsThe co-existence of LKS and hearing loss caused by SLC26A4 mutations increases the difficulty of LKS diagnosis, especially in the presence of hearing loss and impaired language skills. EEG discharges predominantly in temporoparietal areas, the occurrence of ESES, and language improvement after antiepileptic medications are potential indicators for LKS diagnosis.

Novel CRISPR/Cas12a-based genetic diagnostic approach for SLC26A4 mutation-related hereditary hearing loss

Hereditary hearing loss is a common defect of the auditory nervous system with high-incidence, seriously affecting the quality of life of the patients. The clinical manifestations of SLC26A4 mutation-related hearing loss are congenital sensorineural or mixed deafness. Sensitive and specific SLC26A4 mutation detection in the early clinical stage is key for the early indication of potential hearing loss in the lack of effective treatment. Using clustered regularly interspaced short palindromic repeats (CRISPR)-based nucleic acid detection technology, we designed a fast and sensitive detection system for SLC26A4 pathogenic mutations (c.919-2A > G, c.2168A > G and c.1229C > T). This recombinase-aided amplification-based detection system allows rapid target gene amplification and, in combination with the CRISPR-based nucleic acid testing (NAT) system, mutation site detection. Moreover, mismatches were introduced in CRISPR-derived RNA (crRNA) to increase signal differences between the wild-type genes and mutant genes. A total of 64 samples were examined using this approach and all results were verified using Sanger sequencing. The detection results were consistent with the polymerase chain reaction-Sanger sequencing results. Overall, this CRISPR-based NAT technology provides a sensitive and fast new approach for the detection of hereditary deafness and provides a crRNA optimization strategy for single-nucleotide polymorphism detection, which could be helpful for the clinical diagnosis of SLC26A4 mutation-related hereditary hearing loss.

Molecular screening of patients with profound hearing loss from Chengdu, China

Background The rate of genetic deafness in Chengdu is still underestimated. Objective To investigate patients’ molecular etiology with profound hearing loss and facilitate genetic counseling for their families, we screened deafness-related genes of profound hearing loss in the population. Methods A total of 1427 unrelated patients with profound hearing loss containing all age groups in the administrative area of City Chengdu (Sichuan, China) were enrolled in this study, and the average examination rate is 81.13%. Nine loci of four deaf-associated genes (GJB2, GJB3, SLC26A4, and mitochondrial 12SrRNA gene) were analyzed. Then we examined all the deaf-associated mutations and compared them between groups. Results The average age of all subjects is 48.537 ± 19.077 years, peak range in 41–70 years (985/1427, 69.03%). The positive mutation rates of patients in GJB2, SLC26A4, and 12S rRNA are respectively 8.90%, 4.84%, and 5.96%, and GJB3 none. In group A the GJB2 and SLC26A4 mutation rate is 14.17% (36/254), which is remarkably higher than group B (6.14%, 72/1173). The frequency of 12SrRNA mutations is 3.15% (8/254) in group A, which is significantly different (χ 2 = 4.34, p < .05) from that of group B (6.56%, 77/1173). Conclusions and significance The mutation rate of mtDNA 12SrRNA is higher than SLC26A4 gene in our study, which is different from other parts of China. And the deaf-related gene mutation spectrums have a distinct age difference.

Different Rates of the SLC26A4-Related Hearing Loss in Two Indigenous Peoples of Southern Siberia (Russia).

Hereditary hearing loss (HL) is known to be highly locus/allelic heterogeneous, and the prevalence of different HL forms significantly varies among populations worldwide. Investigation of region-specific landscapes of hereditary HL is important for local healthcare and medical genetic services. Mutations in the SLC26A4 gene leading to nonsyndromic recessive deafness (DFNB4) and Pendred syndrome are common genetic causes of hereditary HL, at least in some Asian populations. We present for the first time the results of a thorough analysis of the SLC26A4 gene by Sanger sequencing in the large cohorts of patients with HL of unknown etiology belonging to two neighboring indigenous Turkic-speaking Siberian peoples (Tuvinians and Altaians). A definite genetic diagnosis based on the presence of biallelic SLC26A4 mutations was established for 28.2% (62/220) of all enrolled Tuvinian patients vs. 4.3% (4/93) of Altaian patients. The rate of the SLC26A4-related HL in Tuvinian patients appeared to be one of the highest among populations worldwide. The SLC26A4 mutational spectrum was characterized by the presence of Asian-specific mutations c.919-2A>G and c.2027T>A (p.Leu676Gln), predominantly found in Tuvinian patients, and c.2168A>G (p.His723Arg), which was only detected in Altaian patients. In addition, a novel pathogenic variant c.1545T>G (p.Phe515Leu) was found with high frequency in Tuvinian patients. Overall, based on the findings of this study and our previous research, we were able to uncover the genetic causes of HL in 50.5% of Tuvinian patients and 34.5% of Altaian patients.

Altered gene expression in slc4a11\u2212/\u2212 mouse cornea highlights SLC4A11 roles

SLC4A11 is a H+/NH3/water transport protein, of corneal endothelial cells. SLC4A11 mutations cause congenital hereditary endothelial dystrophy and some cases of Fuchs endothelial corneal dystrophy. To probe SLC4A11’s roles, we compared gene expression in RNA from corneas of 17-week-old slc4a11−/− (n = 3) and slc4a11+/+ mice (n = 3) and subjected to RNA sequencing. mRNA levels for a subset of genes were also assessed by quantitative real-time reverse transcription PCR (qRT RT-PCR). Cornea expressed 13,173 genes, which were rank-ordered for their abundance. In slc4a11−/− corneas, 100 genes had significantly altered expression. Abundant slc14a1 expression, encoding the urea transporter UT-A, suggests a significant role in the cornea. The set of genes with altered expression was subjected to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses, revealing that alterations clustered into extracellular region, cytoskeleton, cell adhesion and plasma membrane functions. Gene expression changes further clustered into classes (with decreasing numbers of genes): cell fate and development, extracellular matrix and cell adhesion, cytoskeleton, ion homeostasis and energy metabolism. Together these gene changes confirm earlier suggestions of a role of SLC4A11 in ion homeostasis, energy metabolism, cell adhesion, and reveal an unrecognized SLC4A11 role in cytoskeletal organization.

Cochlear Pathomorphogenesis of Incomplete Partition Type II in Slc26a4-Null Mice.

Incomplete partition type II (IP-II) is frequently identified in ears with SLC26A4 mutations. Cochleae with IP-II are generally observed to have 1½ turns; the basal turns are normally formed, and the apical turn is dilated or cystic. The objective of this study was to characterize the pathomorphogenesis of the IP-II cochlear anomaly in Slc26a4-null mice. Otic capsules were dissected from Slc26a4Δ/+ and Slc26a4Δ/Δ mice at 1 and 8days of age and at 1 and 3months of age. X-ray micro-computed tomography was used to image samples. We used a multiplanar view and three-dimensional reconstructed models to calculate the cochlear duct length, cochlear turn rotation angle, and modiolus tilt angle. The number of inner hair cells was counted, and the length of the cochlear duct was measured in a whole-mount preparation of the membranous labyrinth. X-ray micro-computed tomography mid-modiolar planar views demonstrated cystic apical turns in Slc26a4Δ/Δ mice resulting from the loss or deossification of the interscalar septum, which morphologically resembles IP-II in humans. Planes vertical to the modiolus showed a similar mean rotation angle between Slc26a4Δ/+ and Slc26a4Δ/Δ mice. In contrast, the mean cochlear duct length and mean number of inner hair cells in Slc26a4Δ/Δ mice were significantly smaller than in Slc26a4Δ/+ mice. In addition, there were significant differences in the mean tilt angle and mean width of the modiolus. Our analysis of Slc26a4-null mice suggests that IP-II in humans reflects loss or deossification of the interscalar septum but not a decreased number of cochlear turns.

Pendred Syndrome, or Not Pendred Syndrome? That Is the Question.

Pendred syndrome (PDS) is the most common form of syndromic Hearing Loss (HL), characterized by sensorineural HL, inner ear malformations, and goiter, with or without hypothyroidism. SLC26A4 is the major gene involved, even though ~50% of the patients carry only one pathogenic mutation. This study aims to define the molecular diagnosis for a cohort of 24 suspected-PDS patients characterized by a deep radiological and audiological evaluation. Whole-Exome Sequencing (WES), the analysis of twelve variants upstream of SLC26A4, constituting the “CEVA haplotype” and Multiplex Ligation Probe Amplification (MLPA) searching for deletions/duplications in SLC26A4 gene have been carried out. In five patients (20.8%) homozygous/compound heterozygous SLC26A4 mutations, or pathogenic mutation in trans with the CEVA haplotype have been identified, while five subjects (20.8%) resulted heterozygous for a single variant. In silico protein modeling supported the pathogenicity of the detected variants, suggesting an effect on the protein stabilization/function. Interestingly, we identified a genotype-phenotype correlation among those patients carrying SLC26A4 mutations, whose audiograms presented a characteristic slope at the medium and high frequencies, providing new insights into PDS. Finally, an interesting homozygous variant in MYO5C has been identified in one patient negative to SLC26A4 gene, suggesting the identification of a new HL candidate gene.

Mutation Screening and Functional Study of SLC26A4 in Chinese Patients with Congenital Hypothyroidism

Objective:Defects in the human solute carrier family 26 member 4 (SLC26A4) gene are reported to be one of the causes of congenital hypothyroidism (CH). We aimed to identify SLC26A4 mutations in Chinese patients with CH and analyze the function of the mutations.Methods:Patients with primary CH were screened for 21 CH candidate genes mutations by targeted next-generation sequencing. All the exons and exon-intron boundaries of SLC26A4 were identified and analyzed. The function of six missense mutation in SLC26A4 were further investigated in vitro.Results:Among 273 patients with CH, seven distinct SLC26A4 heterozygous mutations (p.S49R, p.I363L, p.R409H, p.T485M, p.D661E, p.H723R, c.919-2A>G) were identified in 10 patients (3.66%, 10/273). In vitro experiments showed that mutation p.I363L, p.R409H, p.H723R affect the membrane location and ion transport of SLC26A4, while p.S49R did not. Mutation p.T485M and p.D661E only affected ion transport, but had no effect on the membrane location.Conclusion:The prevalence of SLC26A4 mutations was 3.66% in Chinese patients with CH. Five mutations (p.I363L, p.R409H, p.T485M, p.D661E and p.H723R) impaired the membrane location or ion transport function of SLC26A4, suggesting important roles for Ile363, Arg409, Thr485, Asp661, and His723 residues in SLC26A4 function. As all variants identified were heterozygous, the pathogenesis of these patients cannot be explained, and the pathogenesis of these patients needs further study.

Genetic architecture and phenotypic landscape of SLC26A4-related hearing loss.

Mutations of coding regions and splice sites of SLC26A4 cause Pendred syndrome and nonsyndromic recessive hearing loss DFNB4. SLC26A4 encodes pendrin, a transmembrane exchanger of anions and bases. The mutant SLC26A4 phenotype is characterized by inner ear malformations, including an enlarged vestibular aqueduct (EVA), incomplete cochlear partition type II and modiolar hypoplasia, progressive and fluctuating hearing loss, and vestibular dysfunction. A thyroid iodine organification defect can lead to multinodular goiter and distinguishes Pendred syndrome from DFNB4. Pendred syndrome and DFNB4 are each inherited as an autosomal recessive trait caused by biallelic mutations of SLC26A4 (M2). However, there are some EVA patients with only one detectable mutant allele (M1) of SLC26A4. In most European-Caucasian M1 patients, there is a haplotype that consists of 12 variants upstream of SLC26A4, called CEVA (Caucasian EVA), which acts as a pathogenic recessive allele in trans to mutations affecting the coding regions or splice sites of SLC26A4. This combination of an M1 genotype with the CEVA haplotype is associated with a less severe phenotype than the M2 genotype. The phenotype in EVA patients with no mutant alleles of SLC26A4 (M0) has a very low recurrence probability and is likely to be caused by other factors.

Interpreting pendred syndrome as a foetal hydrops: Clinical and animal model evidence.

Menière disease (MD) and SLC26A4 related deafness (Pendred syndrome (PS) or DFNB4) are two different inner ear disorders which present with fluctuating and progressive hearing loss, which could be a direct consequence of endolymphatic hydrops. To present similarities between both pathologies and explore how the concept of hydrops may be applied to PS/DFNB4. Review of the literature on MD, PS/DFNB4 and mouse model of PS/DFNB4. MD and PS/DFNB4 share a number of similarities such as fluctuating and progressive hearing loss, acute episodes with vertigo and tinnitus, MRI and histological evidence of endolymphatic hydrops (although with different underlying mechanisms). MD is usually diagnosed during the fourth decade of life whereas PS/DFNB4 is congenital. The PS/DFNB4 mouse models have shown that biallelic slc26a4 mutations lead to Na+ and water retention in the endolymph during the perinatal period, which in turn induces degeneration of the stria vascularis and hearing loss. Crossing clinical/imagery characteristics and animal models, evidence seems to support the hypothesis of PS being a foetal hydrops. When understanding PS/DFNB4 as a developmental hydrops, treatments used in MD could be repositioned to PS.

Multi-Center in-Depth Screening of Neonatal Deafness Genes: Zhejiang, China.

PurposeThe conventional genetic screening for deafness involves 9–20 variants from four genes. This study expands screening to analyze the mutation types and frequency of hereditary deafness genes in Zhejiang, China, and explore the significance of in-depth deafness genetic screening in newborns.MethodsThis was a multi-centre study conducted in 5,120 newborns from 12 major hospitals in the East-West (including mountains and islands) of Zhejiang Province. Concurrent hearing and genetic screening was performed. For genetic testing, 159 variants of 22 genes were screened, including CDH23, COL11A1, DFNA5, DFNB59, DSPP, GJB2, GJB3, KCNJ10, MT-RNR1, MT-TL1, MT-TS1, MYO15A, MYO7A, OTOF, PCDH15, SLC26A4, SOX10, TCOF1, TMC1, USH1G, WFS1, and WHRN using next-generation sequencing. Newborns who failed to have genetic mutations or hearing screening were diagnosed audiologically at the age of 6 months.ResultsA total of 4,893 newborns (95.57%) have passed the initial hearing screening, and 7 (0.14%) have failed in repeated screening. Of these, 446 (8.71%) newborns carried at least one genetic deafness-associated variant. High-risk pathogenic variants were found in 11 newborns (0.21%) (nine homozygotes and two compound heterozygotes), and eight of these infants have passed the hearing screening. The frequency of mutations in GJB2, GJB3, SLC26A4, 12SrRNA, and TMC1 was 5.43%, 0.59%, 1.91%, 0.98%, and 0.02%, respectively. The positive rate of in-depth screening was significantly increased when compared with 20 variants in four genes of traditional testing, wherein GJB2 was increased by 97.2%, SLC26A4 by 21% and MT-RNR1 by 150%. The most common mutation variants were GJB2c.235delC and SLC26A4c.919-2A > G, followed by GJB2c.299_300delAT. Homoplasmic mutation in MT-RNR1 was the most common, including m.1555A > G, m.961T > C, m.1095T > C. All these infants have passed routine hearing screening. The positive rate of MT-RNR1 mutation was significantly higher in newborns with high-risk factors of maternal pregnancy.ConclusionThe positive rate of deafness gene mutations in the Zhejiang region is higher than that of the database, mainly in GJB2c.235delC, SLC26A4 c.919-2A > G, and m.1555A > G variants. The expanded genetic screening in the detection rate of diseasecausing variants was significantly improved. It is helpful in identifying high-risk children for follow-up intervention.

Autosomal recessive congenital hereditary corneal dystrophy associated with a novel SLC4A11 mutation in two consanguineous Tunisian families

BackgroundAutosomal recessive congenital hereditary corneal dystrophy (CHED) is a rare isolated developmental anomaly of the eye characterised by diffuse bilateral corneal clouding that may lead to visual impairment requiring corneal...

Genetic mutations in patients with nonsyndromic hearing impairment of minority and Han Chinese ethnicities in Qinghai, China.

ObjectiveMutations in GJB2, SLC26A4, and mitochondrial (mt)DNA 12S rRNA genes are the main cause of nonsyndromic hearing impairment. The present study analyzed these mutations in ethnic minority and Han Chinese patients with nonsyndromic hearing impairment from Qinghai, China.MethodsThe SNPscan assay was used to analyze mutation spectra and frequencies in the two patient groups.ResultsGJB2 mutations were detected in 9.5% (20/210) of minority patients and 20.88% (48/230) of Han Chinese patients. The most common Han Chinese GJB2 variants were c.235delC and c.299_300delAT, whereas c.235delC and c.109G > A were the most prevalent in minority patients. SLC26A4 mutations were detected in 5.71% (12/210) of minority patients and 14.35% (33/230) of Han Chinese patients, and mtDNA 12S rRNA mutations were detected in 4.28% (9/210) of minority patients and 9.13% (21/230) of Han Chinese patients.ConclusionsThese data indicate that the mutation frequencies of three deafness-associated genes were significantly higher in Han Chinese patients than in minority patients. Moreover, the GJB2 mutation spectrum was shown to differ between these two patient groups.

Enhanced expression of SLC4A11 by tert-Butylhydroquinone is mediated by direct binding of Nrf2 to the promoter of SLC4A11

BackgroundSLC4A11, a Na + dependent OH− transporter, is highly expressed in the epithelium and endothelium of the cornea. Mutations in SLC4A11 cause congenital hereditary endothelial dystrophy (CHED), a progressive disease with gradual loss of vision and characterized by degeneration and dysfunction of corneal endothelial cells. SLC4A11 expression is also responsive to oxidative stress. Thus, understanding of SLC4A11 gene regulation is of utmost importance for therapeutic interventions. However, it remains elusive how SLC4A11 is regulated at transcriptional and translational level. MethodsBioinformatics analysis of the SLC4A11 promoter was performed using TRANSFAC. SLC4A11 promoter constructs were generated and exposed to tert-Butylhydroquinone (tBHQ) or cotransfected with Nuclear factor erythroid 2-related factor 2 (Nrf2) expression plasmid and promoter activity was determined. The expression of SLC4A11 was also determined by quantitative PCR and immunoblot analysis. The binding of Nrf2 to the promoter of SLC4A11 was validated by chromatin immunoprecipitation assay. ResultsInduction of Nrf2 by tBHQ or overexpression of Nrf2 caused increased expression of SLC4A11 in HeLa and human corneal endothelial cells. A conserved Nrf2 binding sequence was found in the promoter of SLC4A11 of several mammalian species. Reporter gene assays showed transcriptional activation of the SLC4A11 promoter in response to tBHQ treatment and Nrf2 overexpression. ChIP analysis validated Nrf2 binding to the conserved sequence of the SLC4A11 promoter. Induction of the Nrf2 pathway also resulted in increased endogenous SLC4A11 protein abundance. On the other hand, depletion of Nrf2 inhibited both transcriptional and translational activities of SLC4A11. ConclusionIn summary, we determined direct Nrf2 binding to antioxidant responsive element site within the SLC4A11 promoter, and observed increased expression of SLC4A11 by Nrf2 inducers. To the best of our knowledge, this is the first study showing Nrf2 exerts an important role in regulation of SLC4A11 gene expression.

Molecular diagnosis of SLC26A4-related hereditary hearing loss in a group of patients from two provinces of Iran.

The SLC26A4 gene has been described as the second gene involved in most cases of autosomal recessive non-syndromic hearing loss (ARNSHL), after GJB2. Over 500 different SLC26A4 mutations have been reported, with each ethnic population having its own distinctive mutations. Here, we aimed to determine the frequency and mutation profile of the SLC26A4 gene from two different provinces (center and west) of Iran. This study included 50 nuclear families with two or more siblings segregating presumed ARNSHL. All affected tested negative for mutations in GJB2 at the DFNB1 locus and were therefore screened for autozygosity by descent using short tandem repeat polymorphisms (STRPs) of DFNB4. Sanger sequencing was performed to screen the 20 exons of the SLC26A4 gene for the families linked to this locus. In silico analyses were also performed using available software tools. Four out of 25 (16%) and 3 of 25 (12%) studied families of Isfahan and Hamedan provinces, respectively. were linked to DFNB4. Sanger sequencing led to the identification of six different mutations, one of which (c.919-2A>G) was recurrent and accounted for 31% of all mutant alleles. One out of 7 (14.3%) families with mutations were confirmed to be Pendred syndrome (PS). The SLC26A4 mutations have a high carrying rate in ARNSHL Iranian patients. The identification of a disease causing mutation can be used to establish a genotypic diagnosis and provide important information to the patients and their families.

Clinical heterogeneity of the SLC26A4 gene in UAE patients with hearing loss and bioinformatics investigation of DFNB4/Pendred syndrome missense mutations

BackgroundThe development of next generation sequencing-based techniques showed an important progress in the identification of pathogenic variants related to monogenetic diseases with genetic and phenotypic heterogeneities. Hereditary hearing loss is considered as one of these heterogeneous diseases, given the large number of deafness causing genes, the different modes of inheritance and the phenotypic variabilities associated to the severity, age of onset and/or presence or absence of other clinical manifestations. Material and methodsIn this study, we performed next-generation sequencing (NGS) in 51 UAE patients with hearing loss and no GJB2 mutations. In addition, we reviewed all reported SLC26A4 missense mutations with a confirmed DFNB4/Pendred syndrome phenotype and tried to find a genotype/phenotype correlation using different criteria. ResultsBy analyzing the NGS data, we identified one new SLC26A4 variant c.1150G > C (p.Glu384Gln) and one known SLC26A4 mutation c.716T > A (p.Val239Asp) in two different patients. Direct Sanger sequencing and segregation analyses confirmed the implication of both DNA variants in the deafness phenotype. Moreover, the clinical examination of both patients showed that one patient has syndromic deafness (Pendred syndrome) and the second one has non-syndromic deafness. The analysis of all confirmed missense mutations didn't reveal a complete genotype/phenotype correlation. ConclusionTo the best of our knowledge, this is the first report of mutations associated with DFNB4/Pendred deafness in the GCC region.

Digenic inheritance of mutations in EPHA2 and SLC26A4 in Pendred syndrome

Enlarged vestibular aqueduct (EVA) is one of the most commonly identified inner ear malformations in hearing loss patients including Pendred syndrome. While biallelic mutations of the SLC26A4 gene, encoding pendrin, causes non-syndromic hearing loss with EVA or Pendred syndrome, a considerable number of patients appear to carry mono-allelic mutation. This suggests faulty pendrin regulatory machinery results in hearing loss. Here we identify EPHA2 as another causative gene of Pendred syndrome with SLC26A4. EphA2 forms a protein complex with pendrin controlling pendrin localization, which is disrupted in some pathogenic forms of pendrin. Moreover, point mutations leading to amino acid substitution in the EPHA2 gene are identified from patients bearing mono-allelic mutation of SLC26A4. Ephrin-B2 binds to EphA2 triggering internalization with pendrin inducing EphA2 autophosphorylation weakly. The identified EphA2 mutants attenuate ephrin-B2- but not ephrin-A1-induced EphA2 internalization with pendrin. Our results uncover an unexpected role of the Eph/ephrin system in epithelial function.