Aims: The BRAFV600E oncogene, reported in 40-60% of papillary thyroid carcinoma (PTC), has an important role in the pathogenesis of PTC. It is associated with the loss of thyroid iodide-metabolizing genes, such as sodium/iodide symporter (NIS) and therefore with radioiodide-refractoriness. Inhibition of MAPK pathway, constitutively activated by BRAFV600E, is not always efficient in resistant tumors suggesting that other compensatory mechanisms contribute to a BRAFV600E adaptive resistance. Recent studies pointed to a key role of TGF-β in BRAFV600E-induced effects. The reactive oxygene species (ROS)-generating NADPH oxidase NOX4, which is increased in PTC, has been identified as a new key effector of TGF-β in cancer, suggestive of a potential role in BRAFV600E-induced thyroid tumors. Results: Here, using two human BRAFV600E mutated thyroid cell lines and a rat thyroid cell line expressing BRAFV600E in a conditional manner we show that NOX4 up-regulation is controlled at the transcriptional level by the oncogene via the TGF-β/Smad3 signaling pathway. Importantly, treatment of cells with NOX4-targeted siRNA downregulates BRAFV600E-induced NIS repression. Innovation and Conclusion: Our results establish a link between BRAFV600E and NOX4, which is confirmed by a comparative analysis of NOX4 expression in human (TCGA) and mouse thyroid cancers. Remarkably, analysis of human and murine BRAFV600E-mutated thyroid tumors highlights that the level of NOX4 expression is inversely correlated to thyroid differentiation suggesting that other genes involved in thyroid differentiation in addition to NIS might be silenced by a mechanism controlled by NOX4-derived ROS. This study opens a new opportunity to optimize thyroid cancer therapy

The genetic causes of congenital hypothyroidism due to thyroid dysgenesis (TD) remain largely unknown. We identified three novel TUBB1 gene mutations that co‐segregated with TD in three distinct families leading to 1.1% of TUBB1 mutations in TD study cohort. TUBB1 (Tubulin, Beta 1 Class VI) encodes for a member of the β‐tubulin protein family. TUBB1 gene is expressed in the developing and adult thyroid in humans and mice. All three TUBB1 mutations lead to non‐functional α/β‐tubulin dimers that cannot be incorporated into microtubules. In mice, Tubb1 knock‐out disrupted microtubule integrity by preventing β1‐tubulin incorporation and impaired thyroid migration and thyroid hormone secretion. In addition, TUBB1 mutations caused the formation of macroplatelets and hyperaggregation of human platelets after stimulation by low doses of agonists. Our data highlight unexpected roles for β1‐tubulin in thyroid development and in platelet physiology. Finally, these findings expand the spectrum of the rare paediatric diseases related to mutations in tubulin‐coding genes and provide new insights into the genetic background and mechanisms involved in congenital hypothyroidism and thyroid dysgenesis. Synopsis Whole‐exome sequencing in a consanguineous family with congenital hypothyroidism (CH) revealed a novel homozygous mutation in TUBB1, encoding for a member of beta‐tubulins, essential for microtubule organisation. Until now, TUBB1 mutations were only known to be involved in platelet disorders. Two more mutations were identified in two distinct families with thyroid dysgenesis (TD) and abnormal platelet physiology, reinforcing the link between TUBB1 mutations and thyroid disease. TUBB1 is expressed in the developing and adult thyroid in humans and mice. Tubb1^−/− mice have large platelets and show hypothyroidism with early thyroid progenitors proliferation defects, altered thyroid migration and failure of thyroid hormone synthesis. Platelet findings concerned basal activation and increased aggregation. These results expand our knowledge on genetic background of CH and TD.

Primary congenital hypothyroidism (CH) is the most common neonatal endocrine disorder, and may be etiologically subdivided into thyroid dysgenesis, referring to abnormal thyroid development, and dyshormonogenesis, where a defective thyroid hormone biosynthesis pathway results in inadequate hormone production despite a structurally intact gland. Delayed treatment of neonatal hypothyroidism may result in irreversible neurodevelopmental impairment; therefore, where available, CH screening programs facilitate prompt diagnosis. However, the molecular basis for CH remains unclear in most of the cases. This review summarizes current understanding of the genetic etiologies underlying primary CH and associated phenotypes. Classical genetic causes are discussed in the context of their role in normal thyroid physiology. Genes recently reported to play a role in the pathogenesis of CH are discussed, and novel genomic mechanisms in CH are described.

Objective: To elucidate the molecular cause in a well-characterized cohort of patients with Congenital Hypothyroidism (CH) and Dyshormonogenesis (DH) by using targeted next-generation sequencing (TNGS).Study design: We studied 19 well-characterized patients diagnosed with CH and DH by targeted NGS including genes involved in thyroid hormone production. The pathogenicity of novel mutations was assessed based on in silico prediction tool results, functional studies when possible, variant location in important protein domains, and a review of the recent literature.Results: TNGS with variant prioritization and detailed assessment identified likely disease-causing mutations in 10 patients (53%). Monogenic defects most often involved TG, followed by DUOXA2, DUOX2, and NIS and were usually homozygous or compound heterozygous. Our review shows the importance of the detailed phenotypic description of patients and accurate analysis of variants to provide a molecular diagnosis.Conclusions: In a clinically well-characterized cohort, TNGS had a diagnostic yield of 53%, in accordance with previous studies using a similar strategy. TG mutations were the most common genetic defect. TNGS identified gene mutations causing DH, thereby providing a rapid and cost-effective genetic diagnosis in patients with CH due to DH.

Background: Congenital central hypothyroidism (CCH) is a rare condition that is often diagnosed in late childhood in countries where neonatal screening programs rely solely on detecting thyrotropin (TSH) elevation. TSHβ gene mutation is one of the causes of CCH. We describe two cases of c.Q49X mutation and three cases of c.C105Vfs114X mutation in exon 3 of the TSH β-subunit gene. Summary: We found two different TSHβ gene mutations in two families. In one family, we identified a missense mutation in exon 3 leading to a premature stop at position 49 (c.Q49X) in the two affected twins. In the other family, the three affected siblings had a 313delT nucleotide deletion leading to a frame shift responsible for premature termination at codon 114 (c.C105Vfs114X); neonatal screening showed very low TSH levels in all three patients. The presence of inappropriately low TSH levels at birth in the three affected members of the second family raises questions about the value of the TSH level for CCH screening. Conclusions: The marked phenotypic variability in patients with the c.Q49X mutation suggests modulation by interacting genes and/or differences in the genetic background. TSHβ gene mutations should be suspected in neonates with inappropriately low TSH levels.