The paired box transcription factor Pax8 is essential for function and survival of adult thyroid cells

• We examine the phenotype of mice with a conditional inactivation of the Pax8 gene
• We demonstrate that inactivation of Pax8 occurs late in development.
• Thyroid deprived of Pax8 are small and deprived of proteins essential for thyroid function.
• Pax8 controls both survival and differentiation of thyreocytes.

The transcription factor Pax8 is already known to be essential at very early stages of mouse thyroid gland development, before the onset of thyroid hormone production. In this paper we show, using a conditional inactivation strategy, that the removal of the Pax8 protein late in gland development results in severe hypothyroidism, consequent to a reduced gland size and a deranged differentiation. These results demonstrate that Pax8 is also an essential player in controlling survival and differentiation of adult thyroid follicular cells.