Screening of NKX2.5 mutations in patients with congenital hypothyroidism combined with thyroid ectopy

Objective The study focused on NKX2.5 gene mutations of thyroid dysgenesis(TD) with ectopy, in order to enrich the NKX2.5 gene mutation library and provide some evidence for gene diagnosis and prenatal diagnosis. Methods Blood samples were collected from 90 TD patients with ectopy who had been proved to exclude other congenital diseases, especially congenital heart disease.Genomic DNA was extracted from peripheral blood leukocytes.The whole 2 exons of gene NKX2.5 were amplified with 3 pairs of primers using PCR and direct sequencing to find new mutation types of gene NKX2.5.A χ2 test was used to find whether there was an association between the single nucleotide poymorphism(SNP) and the disease. Results Analysis of NKX2.5 in 90 TD patients with ectopy revealed no mutations in the area of both exons and joint area between exons and introns.Nevertheless, a SNP(rs2277923, c.63T>C) which was demonstrated to be a synonymous mutation(Glu→Glu) was found in exon 1, and the allele frequency of this SNP was T=0.416 7.It was demonstrated to have no significant difference with the allele frequency of minor allele frequency(MAF) minor allele count(χ2=3.437 6, P>0.05), suggesting that there might not be any correlation between this rs2277923 and TD. Conclusions It has never been reported to screen the volunteer genes for congenital hypothyroidism(CH) in such a mass of patients with ectopy in China, and the quantity is also at the forefront in the world.The data suggest that NKX2.5 mutations are highly rare in TD patients with ectopy and do not serve as the main cause of congenital hypothyroidism in Shandong province. Key words: Congenital hypothyroidism; Thyroid dysgenesis; Ectopy; NKX2.5; Mutation