The Ambiguous Role of NKX2-5 Mutations in Thyroid Dysgenesis

Abstract

NKX2-5 is a homeodomain-containing transcription factor implied in both heart and thyroid development. Numerous mutations in NKX2-5 have been reported in individuals with congenital heart disease (CHD), but recently a select few have been associated with thyroid dysgenesis, among which the p.A119S variation. We sequenced NKX2-5 in 303 sporadic CHD patients and 38 families with at least two individuals with CHD. The p.A119S variation was identified in two unrelated patients: one was found in the proband of a family with four affected individuals with CHD and the other in a sporadic CHD patient. Clinical evaluation of heart and thyroid showed that the mutation did not segregate with CHD in the familial case, nor did any of the seven mutation carriers have thyroid abnormalities. We tested the functional consequences of the p.A119S variation in a cellular context by performing transactivation assays with promoters relevant for both heart and thyroid development in rat heart derived H10 cells and HELA cells. There was no difference between wildtype NKX2-5 and p.A119S NKX2-5 in activation of the investigated promoters in both cell lines. Additionally, we reviewed the current literature on the topic, showing that there is no clear evidence for a major pathogenic role of NKX2-5 mutations in thyroid dysgenesis. In conclusion, our study demonstrates that p.A119S does not cause CHD or TD and that it is a rare variation that behaves equal to wildtype NKX2-5. Furthermore, given the wealth of published evidence, we suggest that NKX2-5 mutations do not play a major pathogenic role in thyroid dysgenesis, and that genetic testing of NKX2-5 in TD is not warranted.

Mutations in the T (brachyury) gene cause a novel syndrome consisting of sacral agenesis, abnormal ossification of the vertebral bodies and a persistent notochordal canal

“…Nuclear localisation in COS7 cells was performed as described previously18 using the primary antibody anti-brachyury (C-19) (Tebu-bio, SC-17745 1:500) and Alexa488-conjugated donkey anti-goat IgG (Invitrogen, 1:500) as the secondary antibody.…”

“…Procedures were as described previously 18. Input was corrected for T expression, and total amount of protein was kept constant at 4.0 µg by addition of empty pSG5 vector.…”

Transcriptional Defect of an Inherited NKX2-5 Haplotype Comprising a SNP, a Nonsynonymous and a Synonymous Mutation, Associated with Human Congenital Heart Disease

“…However, the findings of Engelen et al [13] differ from those reported by Dentice et al [12] who likewise investigated the transcriptional properties of WT and the p.A119S NKX2–5 mutant in HeLa cells. In their study the mutant p.A119S NKX2-5 was able to activate the reporter gene in a dose-dependent manner, but the activity was reduced at all tested concentrations in all assays performed when compared with WT.…”

Hepatitis B Virus Protein X Induces Degradation of Talin-1

“…The amplification product was digested with BamHI and KpnI and ligated after the hEF1α promoter in a lentiviral vector digested with the same enzymes [39]. The TG-Luc construct bearing a luciferase reporter under control of the thyroglobulin promoter was a kind gift of Dr. Aho Ilgun (University of Amsterdam, The Netherlands) [40]. The R9 vector, which contains a 1.2-fold overlength HBV DNA genome (subtype adw) in a pGEM7zf+ backbone, was kindly provided by Dr. Thomas Baumert (University of Strasbourg, France) [41,42].…”