OBJECTIVESTo review the identified deafness genes related to nonsyndromic hearing loss (NSHL) and summarize their expressions and functions in the cochlea and to introduce the current studies of molecular genetics on NSHL in China.

METHODSThe presented data are based on a review of the literature as well as the author' s experience with NSHL and communications with other researchers in China over the past 3 years.

RESULTSCurrently, 23 deafness genes related to NSHL have been cloned and identified. Some genes are associated with both NSHL and syndromic hearing loss (SHL), in both dominant and recessive deafness. Deafness genes have a highly specific expression pattern in the inner ear. Some functional categories are starting to emerge from a characterization of deafness genes. There are interacting genes in the genetic background that influence the extent of hearing impairment. The GJB3 gene, which is associated with high-frequency hearing impairment, was cloned in a Chinese laboratory. Mutations in some genes, such as GJB2 and mitochondrial 12S rRNA, have been screened in Chinese patients with NSHL. Mapping new deafness gene loci as well as identifying new genes and their functions is an active area of study in China.

CONCLUSIONSIt is challenging for us to continue identifying new deafness genes and analyze gene functions. By identifying genes responsible for monogenic hearing impairment, more insight may be gained into the molecular process of hearing and the pathology of hearing loss.

Chromosome Mapping ; Cloning, Molecular ; Connexin 26 ; Connexin 30 ; Connexins ; genetics ; Deafness ; genetics ; Humans ; Mutation

BACKGROUNDThe DFNB1 locus, which contains the gap junction beta-2 (GJB2) and gap junction beta-6 (GJB6) genes, plays a key role in the nonsyndromic and sporadic hearing impairment. Mutations of DFNB1 result in autosomal recessive nonsyndromic hearing impairment (ARNSHI). Previous researches have identified mutations in GJB2 and GJB6, but single nucleotide polymorphisms (SNPs) of DFNB1 locus have not been studied. So we chose five SNPs to evaluate whether there is difference between deafness people and normal-hearing people in Han Chinese.

METHODSFive SNPs in the DFNB1 region were examined using a case-control association study between cases with sporadic hearing impairment and controls with normal hearing. The HWEsoft and SHEsis softwares were used to analyze the results.

RESULTSSingle-locus association analysis showed a positive association for three SNPs: rs9315400, rs2274084 and 235delC. When we compared the distributions of the haplotypes, we also found significant differences between cases and controls in the haplotype combination of rs2274084 and rs2274083 (chi(2) = 12.978, df = 3, global P = 0.004719).

CONCLUSIONSThe haplotypes composed of rs2274084 and rs2274083 suggested that C-C may be a risk haplotype for the sporadic hearing impairment while T-T may be protective against hearing impairment. From that point of view, we can conclude that the SNPs of DFNB1 locus also plays an important role in sporadic hearing impairment cases.

Adolescent ; Child ; Connexin 26 ; Connexin 30 ; Connexins ; genetics ; Female ; Haplotypes ; Hearing Loss ; genetics ; Humans ; Male ; Polymorphism, Single Nucleotide

OBJECTIVETo investigate the clinical features and molecular mechanism of hidrotic ectodermal dysplasia (HED).

METHODSA clinical and gene study was performed for five generations (91 people) in the family of one proband with HED. GJB6 gene detection was performed for 7 patients and 3 normal people in this family.

RESULTSAmong the 91 people in this family, there were 17 HED patients, who were manifested as having dysplasia of the fingernails and toenails and sparse or absent hair or body hair. The male patients had a greater degree of sparse hair compared with female patients. In the younger generations, damage to the fingernails and toenails was gradually alleviated. There were patients in each generation, the patient's mother or father definitely had this disease. Both males and females developed this disease, and the inheritance pattern was autosomal dominant inheritance. A heterozygous missense mutation, 31G→A, in GJB6 gene was detected in all patients in this family, but this mutation was not detected in family members without the clinical manifestations of HED.

CONCLUSIONSHED is a hereditary disease with autosomal dominant inheritance and has the clinical features of dysplasia of the fingernails and toenails, hyperkeratosis of palms and soles, and sparse or absent hair or body hair. Male patients have a greater degree of sparse hair. In the younger generations, damage to the fingernails and toenails is gradually alleviated. The missense mutation 31G→A in the GJB6 gene may be one of the molecular mechanisms for HED.

Adolescent ; Connexin 30 ; Connexins ; genetics ; Ectodermal Dysplasia ; genetics ; Female ; Humans ; Male ; Mutation

Clouston syndrome (OMIM #129500), also known as hidrotic ectodermal dysplasia type 2, is a rare autosomal dominant skin disorder. To date, four mutations in the GJB6 gene, G11R, V37E, A88V, and D50N, have been confirmed to cause this condition. In previous studies, the focus has been mainly on gene sequencing, and there has been a lack of research on clinical manifestations and pathogenesis. To confirm the diagnosis of this pedigree at the molecular level and summarize and analyse the clinical phenotype of patients and to provide a basis for further study of the pathogenesis of the disease, we performed whole-exome and Sanger sequencing on a large Chinese Clouston syndrome pedigree. Detailed clinical examination included histopathology, hair microscopy, and scanning electron microscopy. We found a novel heterozygous missense variant (c.134G>C:p.G45A) for Clouston syndrome. We identified a new clinical phenotype involving all nail needling pain in all patients and found a special honeycomb hole structure in the patients' hair under scanning electron microscopy. Our data reveal that a novel variant (c.134G>C:p.G45A) plays a likely pathogenic role in this pedigree and highlight that genetic testing is necessary for the diagnosis of Clouston syndrome.
Humans ; Connexin 30/genetics* ; Connexins/genetics* ; East Asian People ; Ectodermal Dysplasia/pathology* ; Phenotype

OBJECTIVE: To investigate the contribution of GJB6 gene (encoding connexin 30) mutation in Chinese population with sporadic non-syndromic hearing impairment. METHOD: Three hundred and seventy-two nonsyndromic hearing impairment patients and 182 normal controls were first tested for GJB6 del(GJB6 > D13S1830) using specific PCR primers. Then PCR was performed with a pair of primer flanking the whole coding sequence of GJB6 gene. Sequencing of GJB6 whole coding sequence PCR products was subsequently applied in all subjects with hearing loss and normal controls. RESULT: None of the patients and normal controls carried GJB6 del (GJB6 > D13S1830). Two single base pair changes were detected , one in the patient group and the other in the control group. The mutation found in the patient group was not detected in the control subjects. CONCLUSION Mutation of GJB6 gene is not frequent in Chinese non-syndromic hearing-loss population. Screening for GJB6 gene can be ranked as unconventional deaf gene test in China temporarily.
Adolescent ; Alleles ; Asian Continental Ancestry Group ; genetics ; Case-Control Studies ; Child ; Connexin 30 ; Connexins ; genetics ; DNA Mutational Analysis ; Deafness ; genetics ; Female ; Humans ; Male ; Mutation

OBJECTIVE: To investigate the genetic causes of nonsyndromic deaf patients in special educational school of Chifeng city. Inner Mongolia by genetic screening testing method. This study focused on analyzing mutations of coding sequence of GJB2, GJB3 and GJB6 gene. METHOD: DNA were extracted out from peripheral blood of 134 nonsyndromic deaf probands of Chifeng special educational school and 100 normal hearing controls in northern China. First, GJB2 gene mutation was analyzed by direct sequencing for its only exon in the open reading frame. Individuals found with heterozygous GJB2 mutation were given further testing for GJB6 del(GJB6-D13S1830) and direct sequencing for its exon. In 91 probands with unknown genetic cause (excluding probands who carried mtDNA A1555G mutation and GJB2 gene bi allele mutation and probands who were diagnosed as enlarged vestibular aqueduct by temporal CT), GJB3 gene mutation was analyzed by direct sequencing for its exon. RESULT: The sequencing results revealed that forty-one cases carried GJB2 mutation. of which twenty-two were homozygous or compound heterozygous and nineteen were heterozygous. Further testing for GJB6 del(GJB6-D13S1830) and analysis of its coding sequence in GJB2 heterozygous cases showed no positive result. Four subjects in control group carried pathogenetic mutation of GJB2 gene. Six types of novel variants of GJB2 gene were detected. Of the 91 deaf probands with unknown etiology. two probands were found carrying heterozygous pathogenetic mutation of GJB3 gene. one of whom also carried GJB2 235delC heterozygous mutation. One subjects in the control group carried pathogenetic mutation of GJB3 gene. Three types of novel variants of GJB3 gene were found. CONCLUSION By screening GJB2.GJB3 and GJB6 gene, we found 32.1% probands carrying GJB2, GJB3, and GJB6 mutations and we are able to determine genetic cause related to these three genes from one family for 16.42 percent of nonsyndromic deaf probands in special educational school of Chifeng city. The discovery of novel variants of GJB2 and GJB3 gene makes the mutational and polymorphic spectrum more plentiful in Chinese population.
Adolescent ; Asian Continental Ancestry Group ; genetics ; Case-Control Studies ; Child ; Child, Preschool ; China ; Connexin 26 ; Connexin 30 ; Connexins ; genetics ; DNA Mutational Analysis ; Education, Special ; Female ; Genetic Testing ; Genotype ; Hearing Loss ; genetics ; Heterozygote ; Humans ; Male ; Mutation ; Polymorphism, Genetic ; Students ; Young Adult

OBJECTIVETo analyze the mutations in Cx30 gene in a Chinese family with hidrotic ectodermal dysplasia (HED) and to make prenatal diagnosis on the embryo which has been pregnant for 5 months.

METHODSA family including 2 affected and 4 unaffected individuals was collected, and their informed consents were obtained. The affected woman had a five-month pregnancy. An 884 bp fragment containing the whole GJB6 coding sequence was amplified by PCR and the products were bi-direction sequenced directly. The mutation was further confirmed with restriction endoenzyme digesting. On the base of successful gene diagnosis, the following detection procedure on the pregnant baby was performed. First the whole coding region of Cx30 was amplified using primers Cx30-F and Cx30-R and the PCR products were digested by Hae II. Then the PCR products were cloned into pUCm-T vector. Blue-white blot screening method and PCR-restriction endoenzyme digesting technique were used to identify the correct clones. The mutant allele clone was sequenced to confirmed the mutation.

RESULTSA heterozygous missense mutation 263C --> T in the Cx30 gene was detected in the affected little girl and her affected mother, which led to an amino acid substitution (A88V) in the second transmembrane domain of GJB6. The mutation was confirmed by Hae II digestion. A88V mutant allele cannot be cut while the wild normal allele can be cut into two fragments, 520 and 278 bp. The result of analyse on the five-month pregnancy show the embryo carried the A88V mutation too. So the embryo will be a patient.

CONCLUSIONAn A88V missense mutation in the Cx30 gene can also cause HED in Chinese Han population. Based on the gene diagnosis, prenatal diagnosis can be played using bi-direction sequencing and confirmed with restriction endoenzyme digesting.

Adult ; Amino Acid Substitution ; Asian Continental Ancestry Group ; genetics ; China ; Connexin 30 ; Connexins ; genetics ; Ectodermal Dysplasia ; ethnology ; genetics ; Female ; Fetal Diseases ; diagnosis ; ethnology ; genetics ; Genetic Testing ; Heterozygote ; Humans ; Mutation, Missense ; Pedigree ; Pregnancy ; Prenatal Diagnosis ; methods ; Sequence Analysis, DNA