Microarray-based mutation detection of pediatric sporadic nonsyndromic hearing loss in China

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 (χ² = 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.

Genetic screening involving 101 hot spots for neonates not passing newborn hearing screening and those random recruited in Dongguan

In order to investigate essential molecular causes for hearing loss and mutation frequency of deafness-related genes, 1315 newborns who did not pass the Newborn Hearing Screening (NHS) (audio-no-pass) and 1000 random-selected infants were subjected to detection for 101 hotspot mutations in 18 common deafness-related genes. Totally, 23 alleles of 7 deafness genes were detected out. Significant difference (χ² = 25.320, p = 0.000) existed in causative mutation frequency between audio-no-pass group (81/1315, 6.160%) and random-selected cohort (18/1000, 1.80%). Of the genes detected out, GJB2 gene mutation was with significant difference (χ² = 75.132, p = 0.000) between audio-no-pass group (417/1315, 31.711%) and random-selected cohort (159/1000, 15.900%); c.109G > A was the most common allele, as well as the only one with significantly different allele frequency (χ² = 79.327, p = 0.000) between audio-no-pass group (392/1315, 16.84%) and random-selected cohort (140/1000, 7.55%), which suggested c.109G > A mutation was critical for newborns' hearing loss. This study performed detection for such a large scale of deafness-associated genes and for the first time compared mutations between audio-no-pass and random-recruited neonates, which not only provided more reliable DNA diagnosis result for medical practioners and enhanced clinical care for the newborns, but gave more accurate estimation for mutation frequency.

A Mutational Analysis of GJB2, SLC26A4, MT-RNA1, and GJB3 in Children with Nonsyndromic Hearing Loss in the Henan Province of China

BACKGROUND

Hearing impairment is one of the most common neurosensory disorders afflicting humans. Approximately half of all cases have a genetic etiology. The distribution and frequency of genetic mutations that cause deafness differ significantly by ethnic group and geographic region.

METHODS

130 sporadic nonsyndromic hearing loss (NSHL) children from the Henan province were subjected to microarray-based mutation detection. Nine pathogenic mutations were detected in four of the most common deafness-related genes (GJB2, GJB3, SLC26A4, and MT-RNA1).

RESULTS

Fifty percent of the analyzed patients (65/130) were shown to have genetic defects known to be related to deafness. Slightly >30% (41/130) had biallelic pathogenic mutations. One patient had pathogenic mutations in their mitochondrial genes (MT-RNA1); no mutations were detected in the GJB3 gene. Twenty-three (17.69%) patients were carriers of a single mutation in a recessive gene; these findings alone, however, cannot be interpreted as a cause of hearing loss. Utilizing this molecular strategy, we were able to arrive at a conclusive diagnosis for 42 of the NSHL children.

CONCLUSION

Genetic factors play a major role in sporadic NSHL patients from the Henan province, but it is clear that our screen needs to be expanded to include additional genes and alleles. Screening of potential pathogenic genes is important for patient risk assessment.

Prevalence of mutations in the GJB2, SLC26A4, GJB3, and MT-RNR1 genes in 103 children with sensorineural hearing loss in Shaoxing, China

Mutations in the GJB2, SLC26A4, GJB3, and MT-RNR1 genes are known to be a common cause of hearing loss. However, the frequency of hot-spot mutations and genotype-phenotype correlations in patients with sensorineural hearing loss (SNHL) has been less frequently reported. We conducted a study of 103 children-56 boys and 47 girls, aged 5 months to 9 years (mean: 4.1 yr)-with SNHL who underwent genetic screening for 20 hot-spot mutations of the GJB2, SLC26A4, GJB3, and MT-RNR1 genes. Mutations were detected by multiple-PCR-based MALDI-TOF MS assay. At least one mutated allele was detected in 48 patients (46.6%), and 30 patients (29.1%) carried pathogenic mutations. Among all the detected mutations, the most common were GJB2 c.235delC and SLC26A4 c.919-2A>G, with allele frequencies of 23.8 and 6.8%, respectively. At least one mutant allele of SLC26A4 was detected in the 13 patients who had an enlarged vestibular aqueduct (EVA). Almost half of the children with SNHL carried a common deafness-related mutation, and nearly one-third carried a pathogenic mutation. The mutations in SLC26A4 were prevalent and correlated strongly with EVA.

Analysis of mutation spectrum of common deafness-causing genes in Hakka newborns in southern China by semiconductor sequencing

Hearing loss is a common neurosensory disorder, approximately half of the cases are caused by genetic factors, and approximately 70% of hereditary hearing impairments are nonsyndromic hearing loss (NSHL). The mutations of GJB2 (gap junction beta-2 protein), GJB3 (gap junction beta-3 protein), SLC26A4 (solute carrier family 26 member 4), and MT-RNR1 (mitochondrially encoded 12S RNA) are the most common inherited causes of NSHL. Because of different genetic backgrounds, the mutation spectrum of these common deafness-causing genes varies among different regions in China. Because no data are known on these mutations among the Hakka population of Southern China, we aim to investigate the mutation spectrum to add these to neonatal screening and genetic counseling. A total of 1252 blood samples from newborns have been detected by semiconductor sequencing for 100 mutations loci of 18 deafness-causing genes. Of the participants, 95 subjects carried deafness-causing genes mutations with the carrier rate of 7.59%. The mutation frequencies of GJB2, SLC26A4, GJB3, and mitochondrial genes were 3.04%, 3.51%, 0.16%, and 0.88%, respectively. We followed up subjects with single-gene homozygous or compound heterozygous mutations. Our study firstly analyzed deafness-causing genes mutation spectrum in Hakka population, providing evidence for future neonatal screening and genetic counseling in this area.

Newborn Screening of Genetic Mutations in Common Deafness Genes With Bloodspot-Based Gene Chip Array

PURPOSE

This study screens for deafness gene mutations in newborns in the Northwest China population.

METHOD

The 9 sites of 4 common deafness genes (GJB2, GJB3, SLC26A4, and mt 12S rRNA) were detected by bloodspot-based gene chip array in 2,500 newborns.

RESULTS

We detected mutations of the 4 genes in 101 (4.04%) newborns; particularly, 0.20% detected the double mutations. In the Hui population, 4.58% of the newborns tested positive for mutations, whereas 4.01% of Han newborns tested positive for mutations. The detective rates are as follows: 1.44% for GJB2 235delC, 1.08% for SLC26A4 IVS7-2A>G, 0.48% for GJB2 299_300delAT, 0.28% for SLC26A4 2168A>G, 0.2% for mt 12S rRNA 1555A>G, and 0.16% for GJB3 538C>T. The 31.25% (5/16) of infants with GJB2 235delC, 50% (3/6) with GJB2 299_300delAT, and 25% (3/12) with SLC26A4 IVS7-2A>G showed abnormal hearing when tested; only 1 double mutation case received the hearing test, and this infant showed abnormality in both ears on the hearing test.

CONCLUSIONS

High mutation rates in the common deafness genes were detected in newborns in Northwest China. Our study is helpful in understanding the deafness genomic epidemiology and also provides evidence for prenatal and postnatal care as well as policy making on population health in the region.

Genetic frequencies related to severe or profound sensorineural hearing loss in Inner Mongolia Autonomous Region

The aim was to study the frequencies of common deafness-related mutations and their contribution to hearing loss in different regions of Inner Mongolia. A total of 738 deaf children were recruited from five different ethnic groups of Inner Mongolia, including Han Chinese (n=486), Mongolian (n=216), Manchurian (n=24), Hui (n=6) and Daur (n=6). Nine common mutations in four genes (GJB2, SLC26A4, GJB3 and mitochondrial MT-RNR1 gene) were detected by allele-specific PCR and universal array. At least one mutated allele was detected in 282 patients. Pathogenic mutations were detected in 168 patients: 114 were homozygotes and 54 were compound heterozygotes. The 114 patients were carriers of only one mutated allele. The frequency of GJB2 variants in Han Chinese (21.0%) was higher than that in Mongolians (16.7%), but not significantly different. On the other hand, the frequency of SLC26A4 variants in Han Chinese (14.8%) was lower than that in Mongolians (19.4%), but also not significantly different. The frequency of patients with pathogenic mutations was different in Ulanqab (21.4%), Xilingol (40.0%), Chifeng (40.0%), Hulunbeier (30.0%), Hohhot (26.3%), and in Baotou (0%). In conclusion, the frequency of mutated alleles in deafness-related genes did not differ between Han Chinese and Mongolians. However, differences in the distribution of common deafness-related mutations were found among the investigated areas of Inner Mongolia.

Application of a New Genetic Deafness Microarray for Detecting Mutations in the Deaf in China

Objective

The aim of this study was to evaluate the GoldenGate microarray as a diagnostic tool and to elucidate the contribution of the genes on this array to the development of both nonsyndromic and syndromic sensorineural hearing loss in China.

Methods

We developed a microarray to detect 240 mutations underlying syndromic and nonsyndromic sensorineural hearing loss. The microarray was then used for analysis of 382 patients with nonsyndromic sensorineural hearing loss (including 15 patients with enlarged vestibular aqueduct syndrome), 21 patients with Waardenburg syndrome, and 60 unrelated controls. Subsequently, we analyzed the sensitivity, specificity, and reproducibility of this new approach after Sanger sequencing-based verification, and also determined the contribution of the genes on this array to the development of distinct hearing disorders.

Results

The sensitivity and specificity of the microarray chip were 98.73% and 98.34%, respectively. Genetic defects were identified in 61.26% of the patients with nonsyndromic sensorineural hearing loss, and 9 causative genes were identified. The molecular etiology was confirmed in 19.05% and 46.67% of the patients with Waardenburg syndrome and enlarged vestibular aqueduct syndrome, respectively.

Conclusion

Our new mutation-based microarray comprises an accurate and comprehensive genetic tool for the detection of sensorineural hearing loss. This microarray-based detection method could serve as a first-pass screening (before next-generation-sequencing screening) for deafness-causing mutations in China.

Prevalence of mutations in GJB2, SLC26A4, and mtDNA in children with severe or profound sensorineural hearing loss in southwestern China

AIM

To study the distribution characteristics of common mutations in the GJB2, SLC26A4, and mtDNA genes in children with severe or profound sensorineural hearing loss (SNHL) in southwestern China.

MATERIALS AND METHODS

A total of 1,164 individuals were recruited to screen for the common GJB2, SLC26A4, and mtDNA mutations by microarrays. Subsequencing for the coding region of the GJB2 gene in the samples without the GJB2 hotspot mutations as well as subsequencing for the exon 1 of the TRMU gene in those samples with the mtDNA hotspot mutations was performed by Sanger sequencing. All mutations were analyzed in association with medical imaging.

RESULTS

In this study, 28.43% of all subjects carried mutations. The mutation frequencies in the GJB2, SLC26A4, and mtDNA genes were 17.27%, 7.04%, and 4.12%, respectively. No TRMU mutation was found in the study. The frequency of the mtDNA mutations in the multiethnic minorities was six times that in the Han (11.23% vs. 1.91%; p approaches 0.000) and in the urban group was one-third of that in the suburban group(1.49% vs. 4.47%; p=0.047). The frequency of the GJB2 mutations in urban and suburban groups was 23.38% and 15.99%, respectively (p=0.012). The enlarged vestibular aqueduct (EVA) was the most common inner ear malformation and ∼79.10% of EVA cases were associated with the SLC26A4 mutations.

CONCLUSIONS

More than one-fourth of children with severe or profound SNHL carried the common deafness mutations. The proportions of ethnic minorities and urban subjects could impact the frequency of the GJB2 and mtDNA mutations. The SLC26A4 hotspot mutations are prevalent and correlate strongly with EVA.

Mono-allelic mutations of SLC26A4 is over-presented in deaf patients with non-syndromic enlarged vestibular aqueduct

OBJECTIVES

Recessive mutations of SLC26A4 are the major cause of hearing impairment associated with enlarged vestibular aqueduct (EVA). In a significant percentage of non-syndromic EVA patients, however, only mono-allelic mutations of SLC26A4 can be identified. In this study, we aimed to evaluate whether presence of mono-allelic mutations of SLC26A4 in those patients was coincidental or etiologically associated with the disorder.

METHODS

The exons and flanking splicing sites of SLC26A4 were sequenced in 150 Chinese Han deaf probands with non-syndromic EVA. c.919-2A >G and p.H723R, two frequent mutations of SLC26A4 in Chinese Hans, were screened by an allele-specific PCR-based array in 3056 ethnically-matched normal hearing controls. The frequency of mono-allelic c.919-2A >G and p.H723R mutations was determined in each group. The statistical significance of the difference was analyzed by Fisher's exact test.

RESULTS

Bi-allelic, mono-allelic and no mutation of SLC26A4 were detected in 98 (65.3%), 18 (12%) and 34 (22.67%) deaf probands with non-syndromic EVA, respectively. The frequency of mono-allelic c.919-2A >G and p.H723R mutations were significantly higher in the 150 deaf probands with non-syndromic EVA (8.67%) than in the 3056 normal hearing controls (1.4%, P=1.8×10(-6)).

CONCLUSION

Presence of mono-allelic mutations of SLC26A4 in non-syndromic EVA patients is etiologically associated with this disorder. Additional genetic or environmental causes may be present in those patients and demand further investigation and consideration during the genetic diagnosis and counseling.

NADf chip, a two-color microarray for simultaneous screening of multigene mutations associated with hearing impairment in North African Mediterranean countries

Hearing impairment (HI) is the most frequent sensory defect. Genetic causes are involved in two thirds of prelingual cases. Moreover, the autosomal recessive HI frequency is increased in countries where there is a high rate of consanguinity, such as in North African Mediterranean countries. This population shares several features, including history and social behavior, that promote the spread of founder mutations. HI is characterized by tremendous heterogeneity in both the genetic and clinical aspects. The identification of the causal mutation is important for early diagnosis, clinical follow-up, and genetic counseling. Addressing the extreme genetic heterogeneity of HI using classic molecular methods would be expensive and time-consuming. We designed a cost-effective North African Deafness chip for rapid and simultaneous analysis of 58 mutations using multiplex PCR coupled with dual-color arrayed primer extension. These mutations are found in North African HI patients and are distributed over 31 exons and five introns in 21 distinct genes. Assay specificity was initially optimized using 103 archived DNA samples of known genotypes. Blind validation of HI-unrelated patients revealed mutant alleles in 13 samples, and these mutations were confirmed by Sanger sequencing. The North African Deafness chip allows for simultaneous genotyping of eight different samples, at a minimal cost and in a single day, and is therefore amenable to large-scale molecular screening of HI in North Africa.

GJB2 mutations are rare in probands with hearing loss in Chinese assortative mating families

OBJECTIVE

GJB2 mutation is recognized as the prevalent causes of non-syndromic hearing loss (NSHL) worldwide. However, the mutation profiles of GJB2 are rarely reported in deafness probands of the assortative mating family. Therefore, this study aimed to characterize the frequencies of GJB2 mutations in probands with hearing loss in the assortative mating family in Hubei province, Central China.

METHODS

Genomic DNA was extracted from blood samples of 29 probands with hearing loss. The target fragments were amplified by polymerase chain reaction (PCR) and subjected to sequencing to identify sequence variations.

RESULTS

None of 29 probands harbored homozygous mutation in GJB2, while GJB2 heterozygous mutations c.134G>A, c.139G>T, and a deletion c.235delC were identified in three probands, respectively.

CONCLUSION

GJB2 mutations are rare in Chinese probands of assortative mating families. Screening for responsible genes other than GJB2 is necessary for NSHL in these probands.

A Novel mutation in the SLC26A4 gene in a Chinese family with Pendred syndrome

OBJECTIVE

To investigate the mutations in the SLC26A4 gene in a Chinese patient with Pendred syndrome.

METHODS

The diagnosis of Pendred syndrome was confirmed by the family history, pure tone audiogram, perchlorate discharge test (PDT), and computed tomography (CT) of the temporal bone. DNA extraction, PCR and DNA sequencing were performed according to standard procedures. Mutations in the SLC26A4 gene were compared with 100 unrelated subjects to exclude common polymorphism. Splice-site mutation was further confirmed by restriction enzyme length polymorphism (RFLP) with the specifically designed primers.

RESULTS

The proband presented with typical features of bilateral sensorineural deafness since childhood and goiter development in the early adulthood. Thyroid studies disclosed euthyroidism with elevated thyroglobulin, but negative for PDT. Marked enlargement of bilateral vestibular aqueduct (>1.5 mm) was found by CT of the temporal bone. A novel SLC26A4 splice-site mutation c.1263+1G>A (IVS10+1G>A) was identified in compound heterozygosity with the missense mutation c.1079C>T (p.A360V) in the proband. Both mutations were not found in the 100 unrelated Chinese.

CONCLUSIONS

Our results support previous findings that Pendred syndrome can be caused by compound heterozygous mutation in the SLC26A4 gene, in which IVS10+1G>A is a novel pathogenic mutation.