Table 2 Thyroid developmental markers containing ARE-sequences and phenotypes studied on double knock-out mice, modified from [85].

Pax8 -/-

Regression of thyroid primordium at E11.5

Thyroid precursor cells disappear at E12

No follicles, no Tg, no TPO;

thyroids exclusively consist of C-cells (Ttif1-positive)

Pax9 -/-

Lack of ultimobranchial body formation

Ttif1/Nkx2.1 -/-

Thyroid precursor cells disappear at E10.5-11.5;

Mice lack C-cells and thyroid follicular cells

Hhex -/-

Thyroid anlage present at E9;

Absence of thyroid primordium at E10

Eya1 -/-

lack of fusion between ultimobranchial bodies and thyroid lobes; thyroid hypoplasia; severe reduction in number of C-cells and follicular cells;

Hoxa3 -/-

Thyroid hypoplasia; persistent ultimobranchial bodies with C-cells

Hoxa5 -/-

Disorganized follicle formation; decreased TPO; Nkx2.1, Titf2, Pax8 gene expression altered, but normal serum T4 level