Biallelic Stop Codon Mutations (p.F353Pfs*36/p.Y425X) in DUOX2 Gene Associated with Transient Congenital Hypothyroidism: Report of a Family and Literature Review

Abstract

Purpose: DUOX2 deficiency is a transient or permanent disorder that results in thyroid dyshormonogenesis. The purpose of this study was to identify and characterize new mutations in the DUOX2 gene in an attempt to increase the understanding of genotype-phenotype correlation for this disorder. The current study summarizes also the spectrum of DUOX2 variations reported to date in the literature. Methods: Two siblings from an nonconsanguineous family with clinical and biochemical criteria suggestive of transient CH were studied. Single-Strand Conformation Polymorphism (SSCP) analysis and sequencing of DNA of TPO and DUOX2 genes were performed. Results: Sequencing analysis of DUOX2 gene revealed two inactivating mutations, a novel c.1057_1058delTT mutation (p.F353Pfs*36, father’s mutation) and a possible previously reported c.1275T>G mutation (p.Y425X, mother’s mutation). Consequently, the two siblings carry a compound heterozygous for p.F353Pfs*36/ p.Y425X mutations, whereas the healthy brother is heterozygous for the c.1275T>G mutation and does not carry the c.1057_1058delTT mutation. Up to date, hundred twenty pathogenic variations and functional single nucleotide polymorphisms in the human DUOX2 gene have been reported associated with transient or permanent CH: 78 missense mutations, 11 nonsense mutations, 26 deletions and insertions, and 6 splice site mutations. The transient or persistent variability of the CH phenotype is not directly related to the number of mutant DUOX2 alleles. Pathogenic DUOX2 mutations were identified together with likely pathogenic variants in the TSHR, DUOXA2, Thyroid peroxidase, Thyroglobulin and SLC26A4 genes. Conclusion: In the present study, we have identified a novel p.F353Pfs*36 mutation in peroxidase like domain of DUOX2 and we have confirmed that total loss of DUOX2 activity by biallelic premature termination codon causes transient CH phenotype.