DUOX2 Mutations Are Associated With Congenital Hypothyroidism With Ectopic Thyroid Gland

Abstract Context Thyroid dysgenesis (TD) is the leading cause of congenital hypothyroidism (CH). The etiology of TD remains unknown in ∼90% of cases, the most common form being thyroid ectopia (TE) (48% to 61%). Objective To search for candidate genes in hypothyroid children with TE. Design, Setting, and Participants We followed a cohort of 268 children with TD and performed whole-exome sequencing (WES) in three children with CH with TE (CHTE) and compared them with 18 thyroid-healthy controls. We then screened an additional 41 children with CHTE by Sanger sequencing and correlated the WES and Sanger molecular findings with in vitro functional analysis. Main Outcome Measures Genotyping, mutation prediction analysis, and in vitro functional analysis. Results We identified seven variants in the DUOX2 gene, namely G201E, L264CfsX57, P609S, M650T, E810X, M822V, and E1017G, and eight known variations. All children carrying DUOX2 variations had high thyroid-stimulating hormone levels at neonatal diagnosis. All mutations were localized in the N-terminal segment, and three of them led to effects on cell surface targeting and reactive oxygen species generation. The DUOX2 mutants also altered the interaction with the maturation factor DUOXA2 and the formation of a stable DUOX2/DUOXA2 complex at the cell surface, thereby impairing functional enzymatic activity. We observed no mutations in the classic genes related to TD or in the DUOX1 gene. Conclusion Our findings suggest that, in addition to thyroid hormonogenesis, the DUOX2 N-terminal domain may play a role in thyroid development. Exome analysis unexpectedly revealed DUOX2 mutations in patients with ectopic thyroid, suggesting that DUOX2 could also be involved in thyroid ontogenesis.