An emerging role of pendrin in health and disease

The pendrin gene ( SLC26A4 ) was initially identified through the positional cloning in patients with Pendred syndrome, a heritable recessive genetic disorder (MIM #274600) characterized by deafness and goiter (Everett et al. 1997). Pendrin encodes for a transmembrane electroneutral exchanger for monovalent anions (e.g. I−, formate, HCO3−, and Cl−). As predicted from the linkage between pendrin gene and characteristics of Pendred's syndrome, pendrin is highly expressed in the inner ear and thyroid gland, where it controls the volume and pH of the endolymphatic fluid, and the transport of iodide required for organification of thyroid hormones, respectively. Pendrin is also highly expressed in the kidney where it controls the final excretion of bicarbonate (Royaux et al. 2001) and NaCl reabsorption and overall blood pressure (Eladari et al. 2014).Although physiological roles of pendrin have been most extensively investigated in the three organs discussed above, pendrin is also expressed in airway epithelia, mammary gland and liver (Wangemann 2013). In these different organs, the function of pendrin is still unknown. However, there is an emerging interest in the relevance of pendrin in airway surface epithelia, because several studies show a possible association of pendrin with asthma. For example, Nakao et al. (Nakao et al. 2008) demonstrated that forced expression …