Identification of Two Missense Mutations in DUOX1 (p.R1307Q) and DUOXA1 (p.R56W) That Can Cause Congenital Hypothyroidism Through Impairing H2O2 Generation

Abstract

<b>Context:</b> The DUOX/DUOXA systems play a key role in H₂O₂ generation in thyroid cells, which is required for iodine organification and thyroid hormone synthesis. DUOX2/DUOXA2 defects can cause congenital hypothyroidism (CH), but it is unknown whether <i>DUOX1/DUOXA1</i> mutations can also cause CH. <b>Objective:</b> We aimed to identify <i>DUOX1/DUOXA1</i> mutations and explore their role in the development of CH by investigating their functional impacts on H₂O₂ generation. <b>Patients and Methods:</b> Forty-three children with CH with goiter were enrolled, in whom all exons and flanking intronic regions of <i>DUOX1/DUOXA1</i> were directly sequenced. We characterized the functional effects of identified mutations on the expression of <i>DUOX1</i> and <i>DUOXA1</i> and H₂O₂ generation. <b>Results:</b> We identified a heterozygous <i>DUOX1</i> missense mutation (G > A base substitution at nucleotide 3920 in exon 31) that changed a highly conserved arginine to glutamine at residual 1307 (p.R1307Q) in patient 1. A heterozygous-missense mutation (c.166 C>T; p.R56W) was identified in <i>DUOXA1</i> in patient 2. Functional studies demonstrated that both p.R1307Q mutant or p.R56W mutant decreased the <i>DUOX1</i> expression at mRNA and protein levels, with a corresponding impairment in H₂O₂ generation (<i>P</i> < 0.01). The results also showed that intact DUOXA1 was required for full activity of DUOX1 and H₂O₂ generation. <b>Conclusions:</b> We have identified two heterozygous missense mutations in <i>DUOX1</i> and <i>DUOXA1</i> in two patients that can cause CH through disrupting the coordination of DUOX1 and DUOXA1 in the generation of H₂O₂. This study for the first time demonstrates that the DUOX1/DUOXA1 system, if genetically defective, can cause CH.