Active iodide (I−) transport in both the thyroid and some extrathyroidal tissues is mediated by the N a+/I− symporter (NIS). In the thyroid, NIS-mediated I− uptake plays a pivotal role in thyroid hormone (TH) biosynthesis. THs are key during embryonic and postembryonic development and critical for cell metabolism at all stages of life. The molecular characterization of NIS in 1996 and the use of radioactive I− isotopes have led to significan advances in the diagnosis and treatment of thyroid cancer and provide the molecular basis for studies aimed at extending the use of radioiodide treatment in extrathyroidal malignancies. This review focuses on the most recent finding on I− homeostasis and I− transport deficiency-causin NIS mutations, as well as current knowledge of the structure/function properties of NIS and NIS regulatory mechanisms. We also discuss employing NIS as a reporter gene using viral vectors and stem cells in imaging, diagnostic, and therapeutic procedures.

A novel approach to analyzing binding data from proteins with two binding sites for the same substrate provides information beyond that accessible with traditional Hill equation analysis.

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Background: The thyroid plays a key role in development and homeostasis, but it has been difficult to establish causality with diseases and phenotypic traits because of several potential confounders. Methods: To determine the causal effect of euthyroid function, we conducted a two-sample Mendelian randomization study of euthyroid thyrotropin (TSH) and free thyroxine (FT4) levels with respect to 2419 traits assessed in 337,199 individuals from UK Biobank. Additionally, we investigated the molecular differences between hypothyroidism and hyperthyroidism using genome-wide data. Results: After multiple testing correction, sixteen traits appear to be affected by genetically-determined euthyroid TSH, including multiple thyroid-related traits, e.g., hypothyroidism (p = 2.39 × 10−17), height (p = 2.76 × 10−10), body fat distribution (impedance of whole body, p = 4.43 × 10−8), pulse rate (p = 2.84 × 10−8), female infertility (p = 4.91 × 10−6), and hearing aid use (p = 7.10 × 10−5). Moreover, we found a consistent genetic correlation between hypothyroidism and hyperthyroidism (rg = 0.45, p = 5.45 × 10−6) with several immune pathways shared between these diseases. Two molecular pathways survived multiple testing correction for specificity to hyperthyroidism, JAK/STAT signaling (p = 1.02 × 10−6) and Rac guanyl-nucleotide exchange factor activity (p = 4.39 × 10−6). Conclusion: Our data shed new light on the inter-individual variability of euthyroid function and the molecular mechanisms of the two thyroid disorders investigated.

Background: We propose micro single-photon emission computed tomography/computed tomography imaging of the hNIS (human sodium/iodide symporter) to noninvasively quantify adeno-associated virus 9 (AAV9)-mediated gene expression in a murine model of peripheral artery disease. Methods: AAV9-hNIS (2×10 11 viral genome particles) was injected into nonischemic or ischemic gastrocnemius muscles of C57Bl/6J mice following unilateral hindlimb ischemia ± the α-sialidase NA (neuraminidase). Control nonischemic limbs were injected with phosphate buffered saline or remained noninjected. Twelve mice underwent micro single-photon emission computed tomography/computed tomography imaging after serial injection of pertechnetate ( 99m TcO 4 − ), a NIS substrate, up to 28 days after AAV9-hNIS injection. Twenty four animals were euthanized at selected times over 1 month for ex vivo validation. Forty-two animals were imaged with 99m TcO 4 − ± the selective NIS inhibitor perchlorate on day 10, to ascertain specificity of radiotracer uptake. Tissue was harvested for ex vivo validation. A modified version of the U-Net deep learning algorithm was used for image quantification. Results: As quantitated by standardized uptake value, there was a gradual temporal increase in 99m TcO 4 − uptake in muscles treated with AAV9-hNIS. Hindlimb ischemia, NA, and hindlimb ischemia plus NA increased the magnitude of 99m TcO 4 − uptake by 4- to 5-fold compared with nonischemic muscle treated with only AAV9-hNIS. Perchlorate treatment significantly reduced 99m TcO 4 − uptake in AAV9-hNIS-treated muscles, demonstrating uptake specificity. The imaging results correlated well with ex vivo well counting (r 2 =0.9375; P <0.0001) and immunoblot analysis of NIS protein (r 2 =0.65; P <0.0001). Conclusions: Micro single-photon emission computed tomography/computed tomography imaging of hNIS-mediated 99m TcO 4 − uptake allows for accurate in vivo quantification of AAV9-driven gene expression, which increases under ischemic conditions or neuraminidase desialylation in skeletal muscle.