Clin Exp Otorhinolaryngol.  2019 Feb;12(1):50-57. 10.21053/ceo.2018.00213.

Two Compound Heterozygous Were Identified in SLC26A4 Gene in Two Chinese Families With Enlarged Vestibular Aqueduct

• Yu Y
• Yang Y
• Lu J
• Jin Y
• Yang Y
• Hong E
• Shi J
• Chen F
• Han S
• Chu P
• Guo Y
• Ni X

• KMID: 2437491
• DOI: http://doi.org/10.21053/ceo.2018.00213

Abstract

OBJECTIVES
To investigate the genetic causes of hearing loss with enlarged vestibular aqueduct (EVA) in two children from unrelated two Chinese families.
METHODS
Sanger sequencing of all coding exons in SLC26A4 (encoding Pendrin protein) was performed on the two patients, their sibling and parents respectively. To predict and visualize the potential functional outcome of the novel variant, model building, structure analysis, and in silico analysis were further conducted.
RESULTS
The results showed that the proband from family I harbored a compound heterozygote of SLC26A4 c.1174A>T (p.N392Y) mutation and c.1181delTCT (p.F394del) variant in exon 10, potentially altering Pendrin protein structure. In family II, the proband was identified in compound heterozygosity with a known mutation of c.919-2A>G in the splice site of intron 7 and a novel mutation of c.1023insC in exon 9, which results in a frameshift and translational termination, consequently leading to truncated Pendrin protein. Sequence homology analysis indicated that all the mutations localized at high conservation sites, which emphasized the significance of these mutations on Pendrin spatial organization and function.
CONCLUSION
In summary, this study revealed two compound heterozygous mutations (c.1174A>T/c.1181delTCT; c.919- 2A>G/c.1023insC) in Pendrin protein, which might account for the deafness of the two probands clinically diagnosed with EVA. Thus this study contributes to improve understanding of the causes of hearing loss associated with EVA and develop a more scientific screening strategy for deafness.

Keyword

Hearing Loss; Vestibular Aqueduct; SLC26A4 Protein; Frameshift Mutation

MeSH Terms

Asian Continental Ancestry Group*
Child
Clinical Coding
Computer Simulation
Deafness
Exons
Extravehicular Activity
Frameshift Mutation
Hearing Loss
Heterozygote
Humans
Introns
Mass Screening
Parents
Sequence Homology
Siblings
Vestibular Aqueduct*

Figure

• 

  Fig. 1. Clinical phenotype presentations of the two hearing loss children. (A) Bilateral play audiometry detection. The X-axis indicates frequency in hertz (Hz) and the Y-axis indicates hearing level in decibels (dB HL). (B) The temporal bone computed tomography scan of the two probands shows the bilateral enlarged vestibular aqueduct (arrows).

• 

  Fig. 2. Pedigree map and sequence electropherograms in family I. (A) Pedigree map. Squares and circles denote males and females, respectively. (B) Sequence electropherograms showed wild type or abnormal sequence from four members of family I. The red box shows site of the heterozygous mutation of c.1174A>T and c.1181delTCT in the SLC26A4 gene.

• 

  Fig. 3. Protein alignment showed conservation of p.N392 and p.F394 residues across 10 species. These two mutations occurred at evolutionarily conserved amino acids (red arrows). The red helixes mark α-helix regions in protein structure.

• 

  Fig. 4. Illustration of the three-dimensional structure of the wild-type and mutant Pendrin protein. (A) Wide type. (B) p.N392Y. (C) p.F394del.

• 

  Fig. 5. Pedigree map and sequence electropherograms in family II. (A) Pedigree map. Squares and circles denote males and females, respectively. (B) Sequence electropherograms showed wild type or abnormal sequence from four members of family II. The red box shows site of the novel heterozygous mutation of c.919-2A>G, c.1023insC and c.1983C>A in the SLC26A4 gene.

• 

  Fig. 6. Wide type and mutants of Pendrin alignment in family II. (A) Protein alignment showed that the novel mutation of c.1023insC induced a frameshift mutation, caused a stop codon at position of 376 amino acid, resulting in truncated of Pendrin protein. (B) The putative schematic representation of Pendrin protein and mutants in family II. Notes: both c.919-2A>G and p.D661E were known deleterious mutations.

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