Hearing impairment is considered as the most prevalent impairment worldwide. Almost 600 million people in the world suffer from mild or moderate hearing impairment, an estimated 10% of the human population. Genetic fa...Hearing impairment is considered as the most prevalent impairment worldwide. Almost 600 million people in the world suffer from mild or moderate hearing impairment, an estimated 10% of the human population. Genetic factors play an important role in the pathogenesis of this disorder. Hereditary hearing loss is divided into syndromic hearing loss （associated with other anomalies） and non-syndromic hearing loss （not associated with other anomalies）. Approximately 80% of genetic deafness is non-syndromic. On the basis of the frequency of hearing loss, hereditary non-syndromic hearing loss can be divided into high-, mid-, low-, and total-frequency hearing loss. An audiometric finding of mid-frequency sensorineural hearing loss, or a ＂bowl-shaped＂ audiogram, is uncommon. Up to now, merely 7 loci have been linked to mid-frequency hearing loss. Only four genetic mid- frequency deafness genes, namely, DFNA10 （EYA4）, DFNA8/12 （TECTA）, DFNA13 （COLIIA2）, DFNA44 （CCDC50）, have been reported to date. This review summarizes the research progress of the four genes to draw attention to mid-frequency deafness genes.展开更多
Polydactyly is a malformation during the development of the human limb,which is characterized by the presence of more than the normal number of fingers or toes.It is considered to be one of the most common inherited h...Polydactyly is a malformation during the development of the human limb,which is characterized by the presence of more than the normal number of fingers or toes.It is considered to be one of the most common inherited hand disorders.It can be divided into two major groups:Non-syndromic polydactyly or syndromic polydactyly.According to the anatomical location of the duplicated digits,polydactyly can be generally subdivided into pre-,post-axial,and mesoaxial forms.Non-syndromic polydactyly is often inherited with an autosomal dominant trait and defects during the procedure of anterior-posterior patterning of limb development are incriminated for the final phenotype of the malformation.There are several forms of polydactyly,including hand and foot extra digit manifestations.The deformity affects upper limbs with a higher frequency than the lower,and the left foot is more often involved than the right.The treatment is always surgical.Since the clinical presentation is highly diverse,the treatment combines single or multiple surgical operations,depending on the type of polydactyly.The research attention that congenital limb deformities have recently attracted has resulted in broadening the list of isolated gene mutations associated with the disorders.Next generation sequencing technologies have contributed to the correlation of phenotype and genetic profile of the multiple polydactyly manifestations and have helped in early diagnosis and screening of most nonsyndromic and syndromic disorders.展开更多
γ -actin （ACTG1） gene is a cytoplasmic nonmuscle actin gene, which encodes a major cytoskeletal protein in the sensory hair cells of the cochlea. Mutations in ACTG1 were found to cause autosomal dominant, progressi...γ -actin （ACTG1） gene is a cytoplasmic nonmuscle actin gene, which encodes a major cytoskeletal protein in the sensory hair cells of the cochlea. Mutations in ACTG1 were found to cause autosomal dominant, progressive, sensorineural hearing loss linked to the DFNA 20/26 locus on chromosome 17q25.3 in European and American families, respectively. In this study, a novel missense mutation （c.364A〉G; p.I122V） co-segregated with the affected individuals in the family and did not exist in the unaffected family members and 150 unrelated normal controls. The alteration of residue Ile122 was predicted to damage its interaction with actin-binding proteins, which may cause disruption of hair cell organization and function. These findings strongly suggested that the I122V mutation in ACTG1 caused autosomal dominant non-syndromic hearing impairment in a Chinese family and expanded the spectrum of ACTG1 mutations causing hearing loss.展开更多
BACKGROUND Variants in the MYO7A gene commonly result in Usher syndrome,and in rare cases lead to autosomal dominant non-syndromic deafness(DFNA11).Currently,only nine variants have been reported to be responsible for...BACKGROUND Variants in the MYO7A gene commonly result in Usher syndrome,and in rare cases lead to autosomal dominant non-syndromic deafness(DFNA11).Currently,only nine variants have been reported to be responsible for DFNA11 and their clinical phenotypes are not identical.Here we present a novel variant causing DFNA11 identified in a three-generation Chinese family.CASE SUMMARY The proband was a 53-year-old Han male who presented with post-lingual bilateral symmetrical moderate sensorineural hearing loss.We learned from the patient’s medical history collection that multiple family members also had similar hearing loss,generally occurring around the age of 40.Subsequent investigation by high-throughput sequencing identified a novel MYO7A variant.To provide evidence supporting that this variant is responsible for the hearing loss in the studied family,we performed Sanger sequencing on 11 family members and found that the variant co-segregated with the deafness phenotype.In addition,the clinical manifestation of the 11 affected family members was found to be lateonset bilateral slowly progressive hearing loss,inherited in this family in an autosomal dominant manner.None of the affected family members had visual impairment or vestibular symptoms;therefore,we believe that this novel MYO7A variant is responsible for the rare DFNA11 in this family.CONCLUSION We report a novel variant leading to DFNA11 which further enriches the collection of MYO7A variants,and our review of the nine previous variants that have been identified to cause DFNA11 provides a reference for clinical genetic counseling.展开更多
Hearing loss is one of the most common birth defects,with inherited genetic defects play an important role,contributing to about 60%of deafness occurring in infants.However,hearing impairment is genetically heterogene...Hearing loss is one of the most common birth defects,with inherited genetic defects play an important role,contributing to about 60%of deafness occurring in infants.However,hearing impairment is genetically heterogeneous,with both common and rare forms occurring due to mutations in estimated 500 genes.Due to the large number and presumably low mutation frequencies of those genes,it would be highly expensive and time-consuming to address this issue by conventional gene-by-gene Sanger sequencing.Next-generation sequencing is a revolutionary technology that allows the simultaneous screening of mutations in a large number of genes.It is cost effective compared to classical strategies of linkage analysis and direct sequencing when the number or size of genes is large,and thus has become a highly efficient strategy for identifying novel causative genes and mutations involved in heritable disease.In this review, we describe major NGS methodologies currently used for genetic disorders and highlight applications of these technologies in studies of molecular diagnosis and the discovery of genes implicated in non-syndromic hearing loss.展开更多
Cleft lip and/or palate(CLP)are the most common craniofacial malformations in humans.Speech problems often persist even after cleft repair,such that follow-up articulation training is usually required.However,the neur...Cleft lip and/or palate(CLP)are the most common craniofacial malformations in humans.Speech problems often persist even after cleft repair,such that follow-up articulation training is usually required.However,the neural mechanism behind effective articulation training remains largely unknown.We used fMRI to investigate the differences in brain activation,functional connectivity,and effective connectivity across CLP patients with and without articulation training and matched normal participants.We found that training promoted task-related brain activation among the articulation-related brain networks,as well as the global attributes and nodal efficiency in the functional-connectivity-based graph of the network.Our results reveal the neural correlates of effective articulation training in CLP patients,and this could contribute to the future improvement of the post-repair articulation training program.展开更多
Hearing loss (HL) is the most common sensory disorder, affecting all age groups, ethnicities, and gen-ders. According to World Health Organization (WHO) estimates in 2005, 278 million people worldwide have moderate to...Hearing loss (HL) is the most common sensory disorder, affecting all age groups, ethnicities, and gen-ders. According to World Health Organization (WHO) estimates in 2005, 278 million people worldwide have moderate to profound HL in both ears. Results of the 2002 National Health Interview Survey indicate that nearly 31 million of all non-institutionalized adults (aged 18 and over) in the United States have trouble hearing. Epidemiological studies have estimated that approximately 50%of profound HL can be attributed to genetic causes. With over 60 genes implicated in nonsyndromic hearing loss, it is also an extremely het-erogeneous trait. Recent progress in identifying genes responsible for hearing loss enables otolaryngologists and other clinicians to apply molecular diagnosis by genetic testing. The advent of the $1000 genome has the potential to revolutionize the identification of genes and their mutations underlying genetic disorders. This is especially true for extremely heterogeneous Mendelian conditions such as deafness, where the muta-tion, and indeed the gene, may be private. The recent technological advances in target-enrichment methods and next generation sequencing offer a unique opportunity to break through the barriers of limitations im-posed by gene arrays. These approaches now allow for the complete analysis of all known deafness-causing genes and will result in a new wave of discoveries of the remaining genes for Mendelian disorders. This re-view focuses on describing genotype-phenotype correlations of the most frequent genes including GJB2, which is responsible for more than half of cases, followed by other common genes and on discussing the im-pact of genomic advances for comprehensive genetic testing and gene discovery in hereditary hearing loss.展开更多
Non-syndromic hearing loss(NSHL)is a common defect in humans.Variants of MARVELD2 at the DFNB49 locus have been shown to cause bilateral,moderate to profound NSHL.However,the role of MARVELD2 in NSHL susceptibility in...Non-syndromic hearing loss(NSHL)is a common defect in humans.Variants of MARVELD2 at the DFNB49 locus have been shown to cause bilateral,moderate to profound NSHL.However,the role of MARVELD2 in NSHL susceptibility in the Chinese population has not been studied.Here we conducted a case-control study in an eastern Chinese population to profile the spectrum and frequency of MARVELD2 variants,as well as the association of MARVELD2 gene variants with NSHL.Our results showed that variants identified in the Chinese population are significantly different from those reported in Slovak,Hungarian,and Czech Roma,as well as Pakistani families.We identified 11 variants in a cohort of 283 NSHL cases.展开更多
Objective To investigate the effects of YOD1 overexpression on the proliferation and migration of human oral keratinocytes（HOKs）, and to clarify whether the mechanisms involve transforming growth factor-β（TGF-β）...Objective To investigate the effects of YOD1 overexpression on the proliferation and migration of human oral keratinocytes（HOKs）, and to clarify whether the mechanisms involve transforming growth factor-β（TGF-β） signaling. Methods HOKs were transfected with the plasmid p EGFP-N3-YOD1 containing YOD1. The mR NA levels of YOD1 and TGF-β were determined by q PCR. The protein expressions of YOD1, TGF-β, Smad2/3, Smad4, and phospho-Smad2/3 were determined by western blotting. Cell proliferation and migration were evaluated by Cell Counting Kit-8 assay and wound healing assay, respectively. Results The m RNA and protein levels of YOD1 were higher in HOKs transfected with YOD1. YOD1 overexpression significantly enhanced the migration of HOKs. The mR NA and protein levels of TGF-β3 were increased by YOD1 overexpression. HOKs transfected with YOD1 exhibited increased phospho-Smad2/3 levels. Conclusion YOD1 overexpression enhances cell migration by promoting TGF-β3 signaling which may play an important role in lip and palate formation. YOD1 mutation may contribute to aberrant TGF-β3 signaling associated with decreased cell migration resulting in NSCLP.展开更多
Introduction: Non-Syndromic Clefts Lip-Palates (NSCLP/CP) are most common congenital malformation in the world, with very important psychic and social impact. Formation of NSCLP/CP arises from the interaction of envir...Introduction: Non-Syndromic Clefts Lip-Palates (NSCLP/CP) are most common congenital malformation in the world, with very important psychic and social impact. Formation of NSCLP/CP arises from the interaction of environmental and genetic factors. This paper provides a review of recent progress in defining the genetic causes of NSCLP. Methods: A literature review was conducted on the Medline data by searching for the following keywords: genes, non-syndromic cleft lip-palate, and genetics of clefts lip-palates, until January 2018. Results: Various genes are identified in different population and country, with the study using case parent’s trio. The aim of this study contributes to review relative gene which has been identify in non-syndromic cleft lip and palate, and to help to have a better understanding of the inheritance pattern of this pathology and the prevention of genetic disease. Conclusion: Although three major genes have been confirmed, the genetic research is necessary to provide an understanding of the pathophysiology of the clefts lip-palates.展开更多
Mutations in the GJB2 gene are the most frequently found mutations in patients with nonsyndromic hearing impairment. However, the mutation spectrum and prevalence of mutations vary among different ethnic groups. Every...Mutations in the GJB2 gene are the most frequently found mutations in patients with nonsyndromic hearing impairment. However, the mutation spectrum and prevalence of mutations vary among different ethnic groups. Every year, 30, 000 babies are born with congenital hearing impairment in China. In order to provide appropriate genetic testing and counseling to the family, we investigated the molecular etiology of nonsyndromic deafness in 135 unrelated school children attending Chifeng Municipal Special Education School in Inner Mongolia, China. The coding exon of the GJB2 gene was PCR amplified and sequenced. In addition, the 12S rRNA gene and tRNAser(UCN) of mitochondrial genome were screened for mutations responsible for hearing impairment. Sixty four GJB2 mutant alleles, including 60 confirmed pathogenic alleles and 4 unclassified variants, were identified in 31.1% (42/135) of the subjects. Twenty two subjects carried two pathogenic mutations and 20 subjects carried one mutant allele, including one subject with one autosomal dominant mutation. The 235delC was the most common mutation accounting for 65.6%(42/64) GJB2 mutant alleles. When compared to other Asian populations, our subject cohort had higher frequency of 235delC mutation than the Japanese population. The GJB2 mutant alleles account for 23.7% (64/270) of all chromosomes responsible for nonsyndromic hearing impairment. Testing of the 4 most prevalent deleterious frame shift mutations(235delC, 29900delAT, 17691del16, and 56005ins46) in this cohort detected 90% of all GJB2 mutant alleles. These results demonstrate that effective genetic testing of the GJB2 gene for patients and families with nonsyndromic hearing impairment is possible in the Chinese population. Since the most common 309kb GJB6 deletion is not detected and only one 1555 A>G mutation in mitochondrial DNA is detected in our patients, investigation of mutations in other nuclear genes and/or environmental factors responsible for nonsyndromic hearing impairment in the Chinese population is necess展开更多
文摘Hearing impairment is considered as the most prevalent impairment worldwide. Almost 600 million people in the world suffer from mild or moderate hearing impairment, an estimated 10% of the human population. Genetic factors play an important role in the pathogenesis of this disorder. Hereditary hearing loss is divided into syndromic hearing loss （associated with other anomalies） and non-syndromic hearing loss （not associated with other anomalies）. Approximately 80% of genetic deafness is non-syndromic. On the basis of the frequency of hearing loss, hereditary non-syndromic hearing loss can be divided into high-, mid-, low-, and total-frequency hearing loss. An audiometric finding of mid-frequency sensorineural hearing loss, or a ＂bowl-shaped＂ audiogram, is uncommon. Up to now, merely 7 loci have been linked to mid-frequency hearing loss. Only four genetic mid- frequency deafness genes, namely, DFNA10 （EYA4）, DFNA8/12 （TECTA）, DFNA13 （COLIIA2）, DFNA44 （CCDC50）, have been reported to date. This review summarizes the research progress of the four genes to draw attention to mid-frequency deafness genes.
文摘Polydactyly is a malformation during the development of the human limb,which is characterized by the presence of more than the normal number of fingers or toes.It is considered to be one of the most common inherited hand disorders.It can be divided into two major groups:Non-syndromic polydactyly or syndromic polydactyly.According to the anatomical location of the duplicated digits,polydactyly can be generally subdivided into pre-,post-axial,and mesoaxial forms.Non-syndromic polydactyly is often inherited with an autosomal dominant trait and defects during the procedure of anterior-posterior patterning of limb development are incriminated for the final phenotype of the malformation.There are several forms of polydactyly,including hand and foot extra digit manifestations.The deformity affects upper limbs with a higher frequency than the lower,and the left foot is more often involved than the right.The treatment is always surgical.Since the clinical presentation is highly diverse,the treatment combines single or multiple surgical operations,depending on the type of polydactyly.The research attention that congenital limb deformities have recently attracted has resulted in broadening the list of isolated gene mutations associated with the disorders.Next generation sequencing technologies have contributed to the correlation of phenotype and genetic profile of the multiple polydactyly manifestations and have helped in early diagnosis and screening of most nonsyndromic and syndromic disorders.
基金the National Natural Science Foundation of China (No. 30670736 and 30500168)the Department of Science and Technology of Jiangsu Province (No. BS2006533).
文摘γ -actin （ACTG1） gene is a cytoplasmic nonmuscle actin gene, which encodes a major cytoskeletal protein in the sensory hair cells of the cochlea. Mutations in ACTG1 were found to cause autosomal dominant, progressive, sensorineural hearing loss linked to the DFNA 20/26 locus on chromosome 17q25.3 in European and American families, respectively. In this study, a novel missense mutation （c.364A〉G; p.I122V） co-segregated with the affected individuals in the family and did not exist in the unaffected family members and 150 unrelated normal controls. The alteration of residue Ile122 was predicted to damage its interaction with actin-binding proteins, which may cause disruption of hair cell organization and function. These findings strongly suggested that the I122V mutation in ACTG1 caused autosomal dominant non-syndromic hearing impairment in a Chinese family and expanded the spectrum of ACTG1 mutations causing hearing loss.
文摘BACKGROUND Variants in the MYO7A gene commonly result in Usher syndrome,and in rare cases lead to autosomal dominant non-syndromic deafness(DFNA11).Currently,only nine variants have been reported to be responsible for DFNA11 and their clinical phenotypes are not identical.Here we present a novel variant causing DFNA11 identified in a three-generation Chinese family.CASE SUMMARY The proband was a 53-year-old Han male who presented with post-lingual bilateral symmetrical moderate sensorineural hearing loss.We learned from the patient’s medical history collection that multiple family members also had similar hearing loss,generally occurring around the age of 40.Subsequent investigation by high-throughput sequencing identified a novel MYO7A variant.To provide evidence supporting that this variant is responsible for the hearing loss in the studied family,we performed Sanger sequencing on 11 family members and found that the variant co-segregated with the deafness phenotype.In addition,the clinical manifestation of the 11 affected family members was found to be lateonset bilateral slowly progressive hearing loss,inherited in this family in an autosomal dominant manner.None of the affected family members had visual impairment or vestibular symptoms;therefore,we believe that this novel MYO7A variant is responsible for the rare DFNA11 in this family.CONCLUSION We report a novel variant leading to DFNA11 which further enriches the collection of MYO7A variants,and our review of the nine previous variants that have been identified to cause DFNA11 provides a reference for clinical genetic counseling.
基金supported by grants from the Project of the National Natural Science Foundation of China(Grant Nos.30801285,81230020,81200751,81070792,81000415, 81360159)grants from China Postdoctoral Science Foundation(No.2012M,2013T52187860947)a grant from Minister of Science and Technology of China(2012BAI09B02)
文摘Hearing loss is one of the most common birth defects,with inherited genetic defects play an important role,contributing to about 60%of deafness occurring in infants.However,hearing impairment is genetically heterogeneous,with both common and rare forms occurring due to mutations in estimated 500 genes.Due to the large number and presumably low mutation frequencies of those genes,it would be highly expensive and time-consuming to address this issue by conventional gene-by-gene Sanger sequencing.Next-generation sequencing is a revolutionary technology that allows the simultaneous screening of mutations in a large number of genes.It is cost effective compared to classical strategies of linkage analysis and direct sequencing when the number or size of genes is large,and thus has become a highly efficient strategy for identifying novel causative genes and mutations involved in heritable disease.In this review, we describe major NGS methodologies currently used for genetic disorders and highlight applications of these technologies in studies of molecular diagnosis and the discovery of genes implicated in non-syndromic hearing loss.
基金We are grateful to all the patients and healthy controls for their generous participation in this study.This work was supported by grants from the National Natural Science Foundation of China(81771909,61701323,and 62171300)the Discipline Construction Foundation of Beijing Stomatological Hospital(19-09-24)+1 种基金the Capital Medical University Research and Development Fund(PYZ19081)Beijing Municipal Administration of Hospitals Clinical Medicine Development of Special Funding Support(XML201714).
文摘Cleft lip and/or palate(CLP)are the most common craniofacial malformations in humans.Speech problems often persist even after cleft repair,such that follow-up articulation training is usually required.However,the neural mechanism behind effective articulation training remains largely unknown.We used fMRI to investigate the differences in brain activation,functional connectivity,and effective connectivity across CLP patients with and without articulation training and matched normal participants.We found that training promoted task-related brain activation among the articulation-related brain networks,as well as the global attributes and nodal efficiency in the functional-connectivity-based graph of the network.Our results reveal the neural correlates of effective articulation training in CLP patients,and this could contribute to the future improvement of the post-repair articulation training program.
文摘Hearing loss (HL) is the most common sensory disorder, affecting all age groups, ethnicities, and gen-ders. According to World Health Organization (WHO) estimates in 2005, 278 million people worldwide have moderate to profound HL in both ears. Results of the 2002 National Health Interview Survey indicate that nearly 31 million of all non-institutionalized adults (aged 18 and over) in the United States have trouble hearing. Epidemiological studies have estimated that approximately 50%of profound HL can be attributed to genetic causes. With over 60 genes implicated in nonsyndromic hearing loss, it is also an extremely het-erogeneous trait. Recent progress in identifying genes responsible for hearing loss enables otolaryngologists and other clinicians to apply molecular diagnosis by genetic testing. The advent of the $1000 genome has the potential to revolutionize the identification of genes and their mutations underlying genetic disorders. This is especially true for extremely heterogeneous Mendelian conditions such as deafness, where the muta-tion, and indeed the gene, may be private. The recent technological advances in target-enrichment methods and next generation sequencing offer a unique opportunity to break through the barriers of limitations im-posed by gene arrays. These approaches now allow for the complete analysis of all known deafness-causing genes and will result in a new wave of discoveries of the remaining genes for Mendelian disorders. This re-view focuses on describing genotype-phenotype correlations of the most frequent genes including GJB2, which is responsible for more than half of cases, followed by other common genes and on discussing the im-pact of genomic advances for comprehensive genetic testing and gene discovery in hereditary hearing loss.
基金Project supported by the National Basic Research Priorities Program of China(Nos.2014CB541702 and 2014CB541704)the National Natural Science Foundation of China(Nos.8147068 5?yand 81600817)the Zhejiang Provincial Public Welfare Technology Applied Research Project(No.2016C33148),China
文摘Non-syndromic hearing loss(NSHL)is a common defect in humans.Variants of MARVELD2 at the DFNB49 locus have been shown to cause bilateral,moderate to profound NSHL.However,the role of MARVELD2 in NSHL susceptibility in the Chinese population has not been studied.Here we conducted a case-control study in an eastern Chinese population to profile the spectrum and frequency of MARVELD2 variants,as well as the association of MARVELD2 gene variants with NSHL.Our results showed that variants identified in the Chinese population are significantly different from those reported in Slovak,Hungarian,and Czech Roma,as well as Pakistani families.We identified 11 variants in a cohort of 283 NSHL cases.
基金supported by National Natural Science Foundations of China[No.81273103]the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘Objective To investigate the effects of YOD1 overexpression on the proliferation and migration of human oral keratinocytes（HOKs）, and to clarify whether the mechanisms involve transforming growth factor-β（TGF-β） signaling. Methods HOKs were transfected with the plasmid p EGFP-N3-YOD1 containing YOD1. The mR NA levels of YOD1 and TGF-β were determined by q PCR. The protein expressions of YOD1, TGF-β, Smad2/3, Smad4, and phospho-Smad2/3 were determined by western blotting. Cell proliferation and migration were evaluated by Cell Counting Kit-8 assay and wound healing assay, respectively. Results The m RNA and protein levels of YOD1 were higher in HOKs transfected with YOD1. YOD1 overexpression significantly enhanced the migration of HOKs. The mR NA and protein levels of TGF-β3 were increased by YOD1 overexpression. HOKs transfected with YOD1 exhibited increased phospho-Smad2/3 levels. Conclusion YOD1 overexpression enhances cell migration by promoting TGF-β3 signaling which may play an important role in lip and palate formation. YOD1 mutation may contribute to aberrant TGF-β3 signaling associated with decreased cell migration resulting in NSCLP.
文摘Introduction: Non-Syndromic Clefts Lip-Palates (NSCLP/CP) are most common congenital malformation in the world, with very important psychic and social impact. Formation of NSCLP/CP arises from the interaction of environmental and genetic factors. This paper provides a review of recent progress in defining the genetic causes of NSCLP. Methods: A literature review was conducted on the Medline data by searching for the following keywords: genes, non-syndromic cleft lip-palate, and genetics of clefts lip-palates, until January 2018. Results: Various genes are identified in different population and country, with the study using case parent’s trio. The aim of this study contributes to review relative gene which has been identify in non-syndromic cleft lip and palate, and to help to have a better understanding of the inheritance pattern of this pathology and the prevention of genetic disease. Conclusion: Although three major genes have been confirmed, the genetic research is necessary to provide an understanding of the pathophysiology of the clefts lip-palates.
文摘Mutations in the GJB2 gene are the most frequently found mutations in patients with nonsyndromic hearing impairment. However, the mutation spectrum and prevalence of mutations vary among different ethnic groups. Every year, 30, 000 babies are born with congenital hearing impairment in China. In order to provide appropriate genetic testing and counseling to the family, we investigated the molecular etiology of nonsyndromic deafness in 135 unrelated school children attending Chifeng Municipal Special Education School in Inner Mongolia, China. The coding exon of the GJB2 gene was PCR amplified and sequenced. In addition, the 12S rRNA gene and tRNAser(UCN) of mitochondrial genome were screened for mutations responsible for hearing impairment. Sixty four GJB2 mutant alleles, including 60 confirmed pathogenic alleles and 4 unclassified variants, were identified in 31.1% (42/135) of the subjects. Twenty two subjects carried two pathogenic mutations and 20 subjects carried one mutant allele, including one subject with one autosomal dominant mutation. The 235delC was the most common mutation accounting for 65.6%(42/64) GJB2 mutant alleles. When compared to other Asian populations, our subject cohort had higher frequency of 235delC mutation than the Japanese population. The GJB2 mutant alleles account for 23.7% (64/270) of all chromosomes responsible for nonsyndromic hearing impairment. Testing of the 4 most prevalent deleterious frame shift mutations(235delC, 29900delAT, 17691del16, and 56005ins46) in this cohort detected 90% of all GJB2 mutant alleles. These results demonstrate that effective genetic testing of the GJB2 gene for patients and families with nonsyndromic hearing impairment is possible in the Chinese population. Since the most common 309kb GJB6 deletion is not detected and only one 1555 A>G mutation in mitochondrial DNA is detected in our patients, investigation of mutations in other nuclear genes and/or environmental factors responsible for nonsyndromic hearing impairment in the Chinese population is necess
