Erschienen in:
01.11.2015 | Original Article
Segregation of S292F TPO gene mutation in three large Tunisian families with thyroid dyshormonogenesis: evidence of a founder effect
verfasst von:
Noura Bougacha-Elleuch, Nadia Charfi, Nabil Miled, Houda Bouhajja, Neila Belguith, Mouna Mnif, Paula Jaurge, Nessrine Chikhrouhou, Hammadi Ayadi, Mongia Hachicha, Mohamed Abid
Erschienen in:
European Journal of Pediatrics
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Ausgabe 11/2015
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Abstract
We aimed to identify causal mutation(s) in 13 patients with thyroid dyshormonogenesis (TD) from three consanguineous Tunisian families. A 12-year clinical follow-up showed phenotypic variability ranging from the presence to the absence of goiter, sensorineural deafness, and mental retardation. Genetic analysis using microsatellite markers within two candidate genes (TPO and PDS) gave evidence of linkage with the TPO gene. Sequencing of its 17 exons and their flanking intron-exon junctions revealed the previously described c.875C>T (p.S292F) mutation in homozygous state. No additional mutations were found in either a 900 bp of the TPO gene promoter or PDS gene. In silico analysis showed that p.S292F mutation might reduce the catalytic cavity of the TPO which would restrict access of a potential substrate to the catalytic pocket. Using 4SNPs and one microsatellite marker in the TPO gene, an associated haplotype: G-C-G-G-214 was found, giving evidence of a founder mutation.
Conclusion: This is the first description of a TD causing mutation in Tunisia and thus may help to develop a genetic screening protocol for congenital hypothyroidism in the studied region. Although structural modeling suggested a pathogenic effect of this mutation, functional studies are needed. Additional causing and/or modifier genes, together with late diagnosis could explain the clinical variability observed in our patients.
What is known:
• TPO mutations are the most frequent in congenital hypothyroidism (CH) with the most severe being in the catalytic domain.
• The TPO c.875 C>T(S292F) mutation described in CH leads to hearing and intellectual impairment.
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What is new:
• This is the first clinical and genetic study of CH in Tunisia with a founder c.875 C>T mutation.
• Structural modeling suggests pathogenic effects of S292F and A257S on TPO activity.
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