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[Sequencing of SLC26A4 exons 7 and 8 and hot spot mutation analysis in 1552 moderate to profound sensorineural hearing loss patients in China].

OBJECTIVE
To investigate the hot spot mutation of SLC26A4 gene and its incidence among patients with moderate to profound sensorineural hearing loss (SNHL) and to analyze the epidemiology of enlarged vestibular aqueduct syndrome in China.


METHODS
Peripheral blood samples were collected from 1,552 students of deaf and dumb school in 21 cities throughout China. The nationality distribution of the 1,552 students included Han (n = 1290), Uigur (n = 69), Hui (n = 37), Mongolian (n = 31), and Southwest minorities including Yi, Zhuang, Bai, Miao and other 14 nationalities (n = 125). The hot spot mutation IVS7-2A > G and other mutations in the SLC26A4 exons 7 and 8 with intron 7 were analyzed by direct sequencing.


RESULTS
Mutation in the SLC26A4 exons 7 and 8 or intron 7 were found in 199 students, of whom 83 carried IVS7-2A > G homozygous mutation, 114 carried IVS7-2A > G heterozygous mutation, and the other two carried two other kinds of mutation. Of the 1,552 cases, the percentage of cases carrying IVS7-2A > G mutation was 12.7% (197/1,552), and this percentage reached up to 14.3% in 1,290 cases of Han nationality, while in the 69 cases of Uigur nationality this ratio was 0. The prevalence rates of IVS7-2A > G mutation in Zhuozhou and Gaobeidian, Hebei province, and Anyang, Henan province, were 24.7% and 28.3% respectively, both significantly higher than the percentages of the whole China and other regions (all P < 0.05).


CONCLUSION
Hereditary SNHL caused by SLC26A4 mutations accounts for a high percentage in China. It is of great importance to screen SLC26A4 gene for making etiological diagnosis for deafness. Screening of the hot spot mutation of IVS7-2A > G is of advantage for large scale screening among patients with deafness.