Thyroglobulin regulates the expression and localization of the novel iodide transporter solute carrier family 26 member 7 (SLC26A7) in thyrocytes.

Solute carrier family 26 member 7 (SLC26A7), identified as a causative gene for congenital hypothyroidism, was found to be a novel iodide transporter expressed on the apical side of the follicular epithelium of the thyroid. We recently showed that TSH suppressed the expression of SLC26A7 and induces its localization to the plasma membrane, where it functions. We also showed that the ability of TSH to induce thyroid hormone synthesis is completely reversed by an autocrine negative-feedback action of thyroglobulin (Tg) stored in the follicular lumen. In the present study, we investigated the potential effect of follicular Tg on SLC26A7 expression and found that follicular Tg significantly suppressed the promoter activity, mRNA level, and protein level of SLC26A7 in rat thyroid FRTL-5 cells. In addition, follicular Tg inhibited the ability of TSH to induce the membrane localization of SLC26A7. In rat thyroid sections, the expression of SLC26A7 was weaker in follicles with a higher concentration of Tg, as evidenced by immunofluorescence staining. These results indicate that Tg stored in the follicular lumen is a feedback suppressor of the expression and membrane localization of SLC26A7, thereby downregulating the transport of iodide into the follicular lumen.

Circular RNA SLC26A4 regulates the maturation of microRNA-15a in non-small cell lung cancer cells.

To the best of our knowledge, the oncogenic role of circular RNA solute carrier family 26 member 4 (circSLC26A4) has only been reported in cervical cancer, while its role in non-small cell lung cancer (NSCLC) is unknown. The present study explored the involvement of circSLC26A4 in NSCLC. NSCLC tissues and paired adjacent non-tumor tissues were collected from 64 patients with NSCLC. The expression levels of circSLC26A4, mature microRNA-15a (miR-15a) and miR-15a precursor in these tissues were determined by reverse transcription-quantitative PCR (RT-qPCR). NSCLC cells were transfected with pcDNA3.1-circSLC26A4 vector to overexpress circSLC26A4, followed by the measurement of the expression levels of mature miR-15a and miR-15a precursor using RT-qPCR. Cell proliferation was analyzed using a Cell Counting Kit-8 assay. circSLC26A4 expression was upregulated in NSCLC tissues, and its high expression was significantly associated with poor survival of patients with NSCLC. The expression levels of circSLC26A4 were correlated with the expression levels of mature miR-15a, but not the expression levels of miR-15a precursor in NSCLC tissues. In NSCLC cells, overexpression of circSLC26A4 was associated with downregulation of mature miR-15a expression, but not miR-15a precursor expression. A cell proliferation assay revealed that overexpression of circSLC26A4 reduced the inhibitory effects of overexpression of miR-15a on cell proliferation. Therefore, circSLC26A4 may suppress the maturation of miR-15a in NSCLC to inhibit cancer cell proliferation.

A novel genotyping technique for discriminating LVAS-associated high-frequency variants in SLC26A4 gene.

An increasing number of biological and epidemiological evidence suggests that c.919-2A > G and c.2168A > G variants of solute carrier family 26, member 4 (SLC26A4) gene play a critical role in the development of large vestibular aqueduct syndrome (LVAS). In this study, we developed a rapid genotyping method for discriminating LVAS-associated high-frequency variants in SLC26A4 gene. The genotyping technique consists of 3' terminal exonuclease-resistant phosphorothioate-modified allele specific primer extension mediated by exo+ polymerase. In PCR amplification by Pfu polymerase, allelic specific primers perfectly matching wild type allele were extended while no specific products were yielded from primers targeting variant allele. Similarly, allelic specific primers perfectly matching variant allele were extended and no specific products were observed from primers targeting wild type allele. The clinical application of 3' terminal phosphorothioate-modified allele specific primer extension mediated by Pfu polymerase identified both homozygous for SLC26A4 gene c.919-2A > G variant in two patients clinically diagnosed as LVAS by temporal bone CT scan. The genetic results from this method are consistent with that of DNA sequencing. The data suggest that exo+ polymerase-mediated 3' terminal phosphorothioate-modified primer extension is reliable in the identification of SLC26A4 gene high-frequency variant prior to high-resolution CT scan. The method is extremely suitable for quickly molecular etiologic screening and early diagnosis and aggressive prevention therapy of LVAS.

Gene therapy for hereditary hearing loss by SLC26A4 mutations in mice reveals distinct functional roles of pendrin in normal hearing.

Rationale: Mutations of SLC26A4 that abrogate pendrin, expressed in endolymphatic sac, cochlea and vestibule, are known to cause autosomal recessive sensorineural hearing loss with enlargement of the membranous labyrinth. This is the first study to demonstrate the feasibility of gene therapy for pendrin-related hearing loss. Methods: We used a recombinant viral vector to transfect Slc26a4 cDNA into embryonic day 12.5 otocysts of pendrin-deficient knock-out (Slc26a4∆/∆ ) and pendrin-deficient knock-in (Slc26a4tm1Dontuh/tm1Dontuh ) mice. Results: Local gene-delivery resulted in spatially and temporally limited pendrin expression, prevented enlargement, failed to restore vestibular function, but succeeded in the restoration of hearing. Restored hearing phenotypes included normal hearing as well as sudden, fluctuating, and progressive hearing loss. Conclusion: Our study illustrates the feasibility of gene therapy for pendrin-related hearing loss, suggests differences in the requirement of pendrin between the cochlea and the vestibular labyrinth, and documents that insufficient pendrin expression during late embryonal and early postnatal development of the inner ear can cause sudden, fluctuating and progressive hearing loss without obligatory enlargement of the membranous labyrinth.

Estimating the concentration of therapeutic range using disease-specific iPS cells: Low-dose rapamycin therapy for Pendred syndrome.

INTRODUCTION: Pendred syndrome is an autosomal-recessive disease characterized by congenital hearing loss and thyroid goiter. Previously, cell stress susceptibilities were shown to increase in patient-derived cells with intracellular aggregation using an in vitro acute cochlear cell model derived from patient-specific pluripotent stem (iPS) cells. Moreover, we showed that rapamycin can relieve cell death. However, studies regarding long-term cell survival without cell stressors that mimic the natural course of disease or the rational minimum concentration of rapamycin that prevents cell death are missing. METHODS: In this report, we first investigated the rational minimum concentration of rapamycin using patient-specific iPS cells derived-cochlear cells with three different conditions of acute stress. We next confirmed the effects of rapamycin in long-term cell survival and phenotypes by using cochlear cells derived from three different patient-derived iPS cells. RESULTS: We found that inner ear cells derived from Pendred syndrome patients are more vulnerable than those from healthy individuals during long-term culturing; however, this susceptibility was relieved via treatment with low-dose rapamycin. The slow progression of hearing loss in patients may be explained, in part, by the vulnerability observed in patient cells during long-term culturing. We successfully evaluated the rational minimum concentration of rapamycin for treatment of Pendred syndrome. CONCLUSION: Our results suggest that low-dose rapamycin not only decreases acute symptoms but may prevent progression of hearing loss in Pendred syndrome patients.