title: A new case of congenital goiter with hypothyroidism caused by a homozygous p.R277X mutation in the exon 7 of the thyroglobulin gene: a mutational hot spot could explain the recurrence of this mutation.
abstract: Identification of thyroglobulin (TG) gene mutations may provide insight into the structure-function relationship. In this study, we have performed molecular studies in a patient with congenital goiter, hypothyroidism, and impairment of TG synthesis. Genomic DNA sequencing revealed a homozygous c.886C-->T mutation in exon 7, resulting in a premature stop codon at amino acid 277 (p.R277X). The same nonsense mutation had been reported previously in two Brazilian families with multiple occurrence of congenital hypothyroidism with goiter. We compared the insertion/deletion polymorphism in intron 18, microsatellites (Tgm1, Tgm2, TGrI29, and TGrI30), and exonic single-nucleotide polymorphism haplotypes identified in the patient with a member of the previously reported family, who also carry the mutation as a compound heterozygous mutation. The single-nucleotide polymorphism and microsatellite analysis revealed that the two affected individuals do not share a common TG allele. This suggests that the p.R277X mutation is a mutational hot spot. No difference in either splicing or abundance of the amplified product was detected by RT-PCR, excluding that an alternative splicing mechanism, by skipping of exon 7, would restore the normal reading frame. In conclusion, we report a new case of congenital goiter and hypothyroidism caused by a p.R277X mutation in the TG gene. Moreover, we show that nucleotide 886 is a mutational hot spot that explains the recurrence of this mutation.
authors.affiliation: Laboratorio de Biología Molecular, Cátedra de Genética y Biología Molecular, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Avenida Córdoba 2351, 4 piso-sala 5, 1120 Buenos Aires, Argentina.
authors.forename: Carina M
authors.initials: CM
authors.lastname: Rivolta
authors.forename: Christian M
authors.initials: CM
authors.lastname: Moya
authors.forename: Viviana J
authors.initials: VJ
authors.lastname: Gutnisky
authors.forename: Viviana
authors.initials: V
authors.lastname: Varela
authors.forename: José M
authors.initials: JM
authors.lastname: Miralles-García
authors.forename: Rogelio
authors.initials: R
authors.lastname: González-Sarmiento
authors.forename: Héctor M
authors.initials: HM
authors.lastname: Targovnik
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001483:Base Sequence; D005091:Exons / Q000235:genetics*; D014644:Genetic Variation; D006042:Goiter / Q000151:congenital* / Q000235:genetics*; D006720:Homozygote; D006801:Humans; D007037:Hypothyroidism / Q000235:genetics; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D020641:Polymorphism, Single Nucleotide; D012016:Reference Values; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013954:Thyroglobulin / Q000235:genetics*
chemical_list: D013954:Thyroglobulin