Mutation Screening and Functional Study of SLC26A4 in Chinese Patients with Congenital Hypothyroidism

Objective Defects in the human solute carrier family 26 member 4 (SLC26A4) gene are reported to be one of the causes of congenital hypothyroidism (CH). We aimed to identify SLC26A4 mutations in Chinese patients with CH and analyze the function of the mutations. Methods 273 patients with primary CH were screened for 21 CH candidate genes mutations by targeted next-generation sequencing. All the exons and exon-intron boundaries of SLC26A4 were found and analyzed. The function of 6 missense mutation in SLC26A4 were further investigated in vitro. Results Among 273 patients with CH, 7 distinct SLC26A4 heterozygous mutations (p.S49R, p.I363L, p.R409H, p.T485M, p.D661E, p.H723R, c.919-2A>G) were identified in 10 patients (3.66%, 10/273). In vitro experiments showed that mutation p.I363L, p.R409H,p.H723R affect the membrane location and ion transport of SLC26A4, ,while p.S49R did not.Mutation p.T485M and p.D661E only affect the ion transport, but has no effect on the membrane location. Conclusion Our study indicated that the prevalence of SLC26A4 mutations was 3.66% in the Chinese patients with CH. Five mutations (p.I363L, p.R409H, p.T485M, p.D661E and p.H723R) impaired the membrane location or ion transport function of SLC26A4，which revealed important role of the Ile363,Arg409, Thr485, Asp661, His723 residues in function of SLC26A4. Because these mutations are heterozygous mutations, the pathogenesis of these patients cannot be explained, and the pathogenesis of these patients needs further study.