TUBB 1 mutations cause thyroid dysgenesis associated with abnormal platelet physiology

The genetic causes of congenital hypothyroidism due to thyroid dysgenesis ( TD ) remain largely unknown. We identified three novel TUBB 1 gene mutations that co‐segregated with TD in three distinct families leading to 1.1% of TUBB 1 mutations in TD study cohort. TUBB 1 (Tubulin, Beta 1 Class VI ) encodes for a member of the β‐tubulin protein family. TUBB 1 gene is expressed in the developing and adult thyroid in humans and mice. All three TUBB 1 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, TUBB 1 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.