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W E Nance

Publications and source records attributed to W E Nance.

At least 19 recordsLinked to original sources
PubMed2005

A novel locus for autosomal dominant non-syndromic deafness, DFNA53, maps to chromosome 14q11.2-q12.

BACKGROUND: Non-syndromic hearing loss is among the most genetically heterogeneous traits known in humans. To date, at least 50 loci for autosomal dominant non-syndromic sensorineural hearing loss (ADNSSHL) have been identified by linkage analysis. OBJECTIVE: To report the mapping of a novel autosomal dominant deafness locus on the long arm of chromosome 14 at 14q11.2-q12, DFNA53, in a large multigenerational Chinese family with post-lingual, high frequency hearing loss that progresses to involve all frequencies. RESULTS: A maximum multipoint LOD score of 5.4 was obtained for marker D14S1280. The analysis of recombinant haplotypes mapped DFNA53 to a 9.6 cM region interval between markers D14S581 and D14S1021. Four deafness loci (DFNA9, DFNA23, DFNB5, and DFNB35) have previously been mapped to the long arm of chromosome 14. The critical region for DFNA53 contains the gene for DFNA9 but does not overlap with the regions for DFNB5, DFNA23, or DFNB35. Screening of the COCH gene (DFNA9), BOCT, EFS, and HSPC156 within the DFNA53 interval did not identify the cause for deafness in this family. CONCLUSIONS: Identifying the DFNA53 locus is the first step in isolating the gene responsible for hearing loss in this large multigeneration Chinese family.

Adolescent↗
PubMed2003

USH1C: a rare cause of USH1 in a non-Acadian population and a founder effect of the Acadian allele.

Usher syndrome (USH) is characterized by the associated findings of hearing loss and retinitis pigmentosa (RP), leading to progressive loss of vision. Three forms of USH can be distinguished clinically. In the most severe form, USH1, profound congenital deafness is associated with vestibular dysfunction and RP. To determine the frequency of USH1C mutations as a cause for USH1, 128 probands with Usher syndrome type 1 including seven from Acadian and 121 from non-Acadian populations were systematically screened for mutations in USH1C using a combined single-strand conformational polymorphisms (SSCP)/heteroduplex and sequencing method. All seven Acadian USH1 patients were found to be homozygous for both the 216G>A mutation and the 9-repeat VNTR which characterizes the Acadian allele, confirming previous evidence for a founder effect by haplotype analysis. However, USH1C mutations were identified in only two non-Acadian USH1 probands (1.65%) including one from Pakistan who was homozygous for a 238-239insC mutation and one from Canada was also homozygous for the Acadian allele. The low prevalence of USH1C mutations in the present study suggests that the high prevalence of the 238-239insC in Germany may reflect a founder effect. Comparison of the affected haplotypes in the Canadian patient with the Acadian USH1 patients yielded evidence for a founder effect. Our data suggest that USH1C is a relatively rare form of USH1 in non-Acadian populations and that in addition to the 216G>A Acadian mutation, the 238-239insC mutation appears to be common in some populations.

Adaptor Proteins, Signal Transducing↗
PubMed2003

Origins and frequencies of SLC26A4 (PDS) mutations in east and south Asians: global implications for the epidemiology of deafness.

Recessive mutations of SLC26A4 (PDS) are a common cause of Pendred syndrome and non-syndromic deafness in western populations. Although south and east Asia contain nearly one half of the global population, the origins and frequencies of SLC26A4 mutations in these regions are unknown. We PCR amplified and sequenced seven exons of SLC26A4 to detect selected mutations in 274 deaf probands from Korea, China, and Mongolia. A total of nine different mutations of SLC26A4 were detected among 15 (5.5%) of the 274 probands. Five mutations were novel and the other four had seldom, if ever, been identified outside east Asia. To identify mutations in south Asians, 212 Pakistani and 106 Indian families with three or more affected offspring of consanguineous matings were analysed for cosegregation of recessive deafness with short tandem repeat markers linked to SLC26A4. All 21 SLC26A4 exons were PCR amplified and sequenced in families segregating SLC26A4 linked deafness. Eleven mutant alleles of SLC26A4 were identified among 17 (5.4%) of the 318 families, and all 11 alleles were novel. SLC26A4 linked haplotypes on chromosomes with recurrent mutations were consistent with founder effects. Our observation of a diverse allelic series unique to each ethnic group indicates that mutational events at SLC26A4 are common and account for approximately 5% of recessive deafness in south Asians and other populations.

Asia, Southeastern↗
PubMed2002

A novel locus for autosomal dominant non-syndromic deafness (DFNA41) maps to chromosome 12q24-qter.

We have studied 36 subjects in a large multigenerational Chinese family that is segregating for an autosomal dominant adult onset form of progressive non-syndromic hearing loss. All affected subjects had bilateral sensorineural hearing loss involving all frequencies with some significant gender differences in initial presentation. After excluding linkage to known loci for non-syndromic deafness, we used the Center for Inherited Disease Research (CIDR) to test for 351 polymorphic markers distributed at approximately 10 cM intervals throughout the genome. Analysis of the resulting data provided evidence that the locus designated DFNA41 maps to a 15 cM region on chromosome 12q24.32-qter, proximal to the marker D12S1609. A maximum two point lod score of 6.56 at theta=0.0 was obtained for D12S343. This gene is distal to DFNA25, a previously identified locus for dominant adult onset hearing loss that maps to 12q21-24. Positional/functional candidate genes in this region include frizzled 10, epimorphin, RAN, and ZFOC1.

Adolescent↗
PubMed2001

Mutations in GJA1 (connexin 43) are associated with non-syndromic autosomal recessive deafness.

Mutations in four members of the connexin gene family have been shown to underlie distinct genetic forms of deafness, including GJB2 [connexin 26 (Cx26)], GJB3 (Cx31), GJB6 (Cx30) and GJB1 (Cx32). We have found that alterations in a fifth member of this family, GJA1 (Cx43), appear to cause a common form of deafness in African Americans. We identified two different GJA1 mutations in four of 26 African American probands. Three were homozygous for a Leu-->Phe substitution in the absolutely conserved codon 11, whereas the other was homozygous for a Val-->Ala transversion at the highly conserved codon 24. Neither mutation was detected in DNA from 100 control subjects without deafness. Cx43 is expressed in the cochlea, as is demonstrated by PCR amplification from human fetal cochlear cDNA and by RT-PCR of mouse cochlear tissues. Immunohistochemical staining of mouse cochlear preparations showed immunostaining for Cx43 in non-sensory epithelial cells and in fibrocytes of the spiral ligament and the spiral limbus. To our knowledge this is the first alpha connexin gene to be associated with non-syndromic deafness. Cx43 must also play a critical role in the physiology of hearing, presumably by participating in the recycling of potassium to the cochlear endolymph.

Amino Acid Sequence↗
PubMed2001

Connexin 26 (GJB2) mutations in the Turkish population: implications for the origin and high frequency of the 35delG mutation in Caucasians.

Mutations in the Connexin 26 (GJB2/Cx26) gene are responsible for more than half of all cases of prelingual non-syndromic recessive deafness in many Caucasian populations. To determine the importance of Cx26 mutations as a cause of deafness in Turks we screened 11 families with prelingual non-syndromic deafness, seven (64%) of which were found to carry the 35delG mutation. We subsequently screened 674 Turkish subjects with no known hearing loss and found twelve 35delG heterozygotes (1.78%; 95% confidence interval: 0.9%-3%) but no examples of the 167delT mutation. To search for possible founder effects, we typed chromosomes carrying the 35delG mutation for closely linked polymorphic markers in samples from Turkey and United States and compared the allele frequencies with those of hearing subjects. The data showed a modest degree of disequilibrium in both populations. Analyses of two pedigrees from Turkey demonstrated both conserved and different haplotypes, suggesting possible founder effects and multiple origins of the 35delG mutation.

Alleles↗
PubMed2001

W44C mutation in the connexin 26 gene associated with dominant non-syndromic deafness.

Although more than 50% of recessive non-syndromic deafness is attributed to mutations in the connexin 26 (Cx26) gene, only a few reported families have shown dominant transmission of the trait. The W44C mutation was originally reported in two families from the same geographic region of France, which exhibited dominant non-syndromic hearing loss. In this report, we describe a third family with early-onset severe-to-profound non-syndromic hearing loss segregating with the W44C mutation. Our observation places W44C among recurrent mutations in the Cx26 gene and emphasizes the importance of screening for this as well as other Cx26 mutations in autosomal dominant families.

Adolescent↗
PubMed2001

Haplotype analysis of the USH1D locus and genotype-phenotype correlations.

Usher syndrome (USH) is characterised by hearing impairment and progressive pigmentary retinopathy. USH can be divided into three subtypes based on the severity and progression of the major clinical findings. These subtypes are genetically heterogeneous, with at least six loci for USH1, three for USH2 and one for USH3. In the present study, five unrelated consanguineous families with USH1 were analysed for linkage to markers flanking the six USH1 loci. Two of these families, one Pakistani and one Turkish, demonstrated linkage to the USH1D locus. In another family, haplotype segregation was consistent with linkage to USH1C. The remaining families were not linked to any of the six USH1 loci, providing support for the existence of at least one additional USH1 locus. Analysis of these two new USH1D families allowed us to narrow the USH1D candidate region to a 7.3-cM interval with a telomeric flanking marker at D10S1752. Comparison of the affected haplotypes in our Pakistani family with the original Pakistani USH1D family yielded no evidence for a founder effect. The identification of two additional affected families suggests that the USH1D may be a more common form of USH1 than originally suspected. The USH1D (CDH23) gene has recently been cloned. Mutation analysis has shown two different CDH23 mutations in the two Pakistani USH1D families studied, which confirmed our finding that there was no evidence for a founder effect by haplotype analysis. The interesting correlations between genotype and phenotype in CDH23 are also summarised.

Cadherin Related Proteins↗
PubMed2001

Waardenburg syndrome type 3 (Klein-Waardenburg syndrome) segregating with a heterozygous deletion in the paired box domain of PAX3: a simple variant or a true syndrome?

Klein-Waardenburg syndrome or Waardenburg syndrome type 3 (WS-III; MIM 148820) is characterized by the presence of musculoskeletal abnormalities in association with clinical features of Waardenburg syndrome type 1 (WS-I). Since the description of the first patient in 1947 (D. Klein, Arch Klaus Stift Vererb Forsch 1947: 22: 336-342), a few cases have been reported. Only occasional families have demonstrated autosomal-dominant inheritance of WS-III. In a previous report, a missense mutation in the paired domain of the PAX3 gene has been described in a family with dominant segregation of WS-III. In this report, we present a second family (mother and son) with typical clinical findings of WS-III segregating with a heterozygous 13-bp deletion in the paired domain of the PAX3 gene. Although homozygosity or compound heterozygosity has also been documented in patients with severe limb involvement, a consistent genotype-phenotype correlation for limb abnormalities associated with heterozygous PAX3 mutations has not previously been apparent. Heterozygous mutations could either reflect a unique dominant-negative effect or possibly the contribution of other unlinked genetic modifiers in determining the phenotype.

Chromosome Segregation↗
PubMed2001

Epidemiological studies on hearing impairment with reference to genetic factors in Sichuan, China.

Hearing impairment is the most common disorder of sensorineural function and is an economically and socially important cause of human morbidity. A large-scale epidemiological survey of hearing loss was conducted with 126,876 unselected subjects (63,741 male and 63,135 female) from Sichuan, China. The overall prevalence of hearing loss was 3.28% (4,164 of 126,876), and the prevalence increased with age, reaching 12.8% (1,465 of 11,421) at 60 years of age. In 73.03% of all cases (3,041 of 4,164), the hearing loss was sensorineural, and in 20.39% (849 of 4,164), it was conductive; the remaining cases (6%) were mixed hearing loss. Bilateral loss was found in 74.5% of cases (3,103 of 4,164). In 63.79% of cases (2,656 of 4,164), the degree of hearing loss was less than 55 dB hearing level (HL), and in 5.67% of cases (236 of 4,164), it was greater than 90 dB HL. The prevalence of hearing loss in childhood (<15 years of age) was 0.67% (227 of 34,157), of which 57.7% of cases were conductive and 38.8% were sensorineural. The prevalence of genetic hearing loss was 0.28% (349 of 126,876). Persons who lived in the flatlands appeared to have a higher prevalence than those who lived in the hills. Several ethnic groups, including Tibetans, the Yi, and the Lisu, had a higher prevalence of hearing loss. Presbycusis, otitis media, and genetic factors were the most commonly recognized causes of hearing impairment overall, but otitis media and genetic factors were the main causes of hearing loss in children. Causes for the observed differences in prevalence and etiologic factors between China and industrialized countries will be discussed. In China, infections and genetic factors appear to be of major importance as causes of hearing loss.

Adolescent↗
PubMed2000

Usher syndrome 1D and nonsyndromic autosomal recessive deafness DFNB12 are caused by allelic mutations of the novel cadherin-like gene CDH23.

Genes causing nonsyndromic autosomal recessive deafness (DFNB12) and deafness associated with retinitis pigmentosa and vestibular dysfunction (USH1D) were previously mapped to overlapping regions of chromosome 10q21-q22. Seven highly consanguineous families segregating nonsyndromic autosomal recessive deafness were analyzed to refine the DFNB12 locus. In a single family, a critical region was defined between D10S1694 and D10S1737, approximately 0.55 cM apart. Eighteen candidate genes in the region were sequenced. Mutations in a novel cadherin-like gene, CDH23, were found both in families with DFNB12 and in families with USH1D. Six missense mutations were found in five families with DFNB12, and two nonsense and two frameshift mutations were found in four families with USH1D. A northern blot analysis of CDH23 showed a 9.5-kb transcript expressed primarily in the retina. CDH23 is also expressed in the cochlea, as is demonstrated by polymerase chain reaction amplification from cochlear cDNA.

Alleles↗
PubMed2000

Relation between choice of partner and high frequency of connexin-26 deafness.

Recessive mutations at the connexin-26 gene locus are now recognised as the cause of nearly half of all cases of genetic deafness in many populations. We suggest that this high frequency is only seen in populations with a long tradition of intermarriage among deaf people. Available data are consistent with the hypothesis that such marriages might well have contributed to the high frequency of connexin-26 deafness in the USA, and could represent a novel mechanism for maintaining specific genotypes at unexpectedly high frequencies.

Connexin 26↗
PubMed2000

Mutations in connexin31 underlie recessive as well as dominant non-syndromic hearing loss.

Mutations in the GJB3 gene encoding connexin31 (Cx31) can cause a dominant non-syndromic form of hearing loss (DFNA2). To determine whether mutations at this locus can also cause recessive non-syndromic deafness, we screened 25 Chinese families with recessive deafness and identified in two families affected individuals who were compound heterozygotes for Cx31 mutations. The three affected individuals in the two families were born to non-consanguineous parents and had an early onset bilateral sensorineural hearing loss. In both families, differing SSCP patterns were observed in affected and unaffected individuals. Sequence analysis in both families demonstrated an in-frame 3 bp deletion (423-425delATT) in one allele, which leads to the loss of an isoleucine residue at codon 141, and a 423A-->G transversion in the other allele, which creates an Ile-->Val substitution at codon 141 (I141V). Neither of these two mutations was detected in DNA from 100 unrelated control subjects. The altered isoleucine residue lies within the third conserved alpha-helical transmembrane domain (M3), which is critical for the formation of the wall of the gap junction pore. Both the deletion of the isoleucine residue 141 and its substitution to valine in the two families could alter the structure of M3, and impair the function of the gap junction. The present data demonstrate that, like mutations in connexin26, mutations in Cx31 can lead to both recessive and dominant forms of non-syndromic deafness.

Adult↗