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THREE FAMILIES WITH HYPOTHYROIDISM AND MONOALLELIC THYROGLOBULIN MUTATION ANALYZED BY NEXT GENERATION SEQUENCING (NGS).
SOFIA SIFFO; MAURICIO GOMES PIO; EZEQUIELA ADROVER
Congreso; LXIII REUNIÓN ANUAL DE LA SOCIEDAD ARGENTINA DE INVESTIGACIÓN CLÍNICA; 2018
Thyroid dyshormonogenesis due to thyroglobulin (TG) gene mutations have an estimated incidence of approximately 1 in 100,000 newborns. Up to now, one hundred and thirty-seven mutations in the human TG gene have been identified and characterized associated to thyroid diseases.In three families, with two siblings affected each, only one mutated allele was detected even after sequencing by Sanger all exonic coding sequence, the promoter región and the exon/intron boundaries of the TG gene. This can be considered as straightforward cases of haploid insufficiency in a context of recessive inheritance. In all three families the monoallelic mutation was a nonsense mutation, in one case it was the p.R296* (family A), in another case it was p.R787* (family B) and in the remaining one it was p.E1854* (family C). The objective of the present work is to analyze by next generation sequencing (NGS) in order to identify possible oligogenicity in our monoallelic cases harboring additional mutations in other thyroid genes that could contribute to the CH phenotype. A custom panel targeting 8 genes associated with dishormonogenesis (TPO, IYD, SLC26A4, TG, DUOX2, DOUXA2, TSHR, SLC5A5) was used for NGS. All exons and exon?intron boundaries of these genes were amplified by multiplex PCR. Deep sequencing of these amplicon libraries was carried out by using the Miseq Ilumina platform. The NGS confirmed the monoallelic TG mutations in the three families and showed no potentially pathogenic mutations asociates in the other 7 genes analized. Interesting discrepancies in the number of allele variants of some polymorphism were observed between sequencing by NGS and by Sanger and consequently the nucleotide variants in the primers of both sequence methods were analyzed. In conclusión, It is likely that the apparent absence of a second mutation could be explained by technical limitations of the sequencing analysis, that would indicate the possible amplification of only one allele.