Phenotypic analyses and mutation screening of the SLC26A4 and FOXI1 genes in 101 Taiwanese families with bilateral nonsyndromic enlarged vestibular aqueduct (DFNB4) or Pendred syndrome.

[pendred syndrome]

Recessive mutations in the SLC 26 A 4 gene are responsible for nonsyndromic enlarged vestibular aqueduct (EVA ) and Pendred syndrome . However , in some affected families , only 1 or 0 mutated allele can be identified , as well as no clear correlation between SLC 26 A 4 genotypes and clinical phenotypes , hampering the accuracy of genetic counseling . To elucidate the genetic composition of nonsyndromic EVA and Pendred syndrome , we screened related genomic fragments , including the SLC 26 A 4 coding regions , the SLC 26 A 4 promoter and the FOXI 1 transcription factor gene , in 101 Taiwanese families , and analyzed their phenotypic and genotypic results . Mutation screening in the SLC 26 A 4 coding regions by direct sequencing and quantitative polymerase chain reaction detected 2 mutations in 63 (62 %) families , 1 mutation in 24 (24 %) families and no mutation in 14 (14 %) families . The radiological findings , the presence of goiters and the audiological results were not different among probands (i .e . index cases of the families ) with different SLC 26 A 4 genotypes . Specifically , probands heterozygous for SLC 26 A 4 mutations demonstrated clinical features indistinguishable from those of probands with 2 mutated alleles , implicating that there might be undetected mutations . However , except for a variant (c .-2554 G >A of SLC 26 A 4 ) with possible pathological consequences , no definite mutation was detected after extensive screening in the SLC 26 A 4 promoter and FOXI 1 . In other words , in most Taiwanese families nonsyndromic EVA or Pendred syndrome might not result from aberrance in the transcriptional control of SLC 26 A 4 by FOXI 1 . Meanwhile , exploration of undetected mutations in the SLC 26 A 4 noncoding regions revealed 9 divergent haplotypes among the 21 no -mutation -detected SLC 26 A 4 alleles of the c .919 -2 A >G heterozygotes , indicating that there might be no common and predominant mutations in the SLC 26 A 4 introns .

Diseases
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Diseases presenting "that there might be no common" symptom

pendred syndrome

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