Expression pattern of iodotyrosine dehalogenase 1 (DEHAL1) during chick ontogeny.

The iodotyrosine dehalogenase1 (DEHAL1) enzyme is a transmembrane protein that belongs to the nitroreductase family and shows a highly conserved N-terminal domain. DEHAL1 is present in the liver, kidney and thyroid of mammals. DEHAL1 is known to act on diiodotyrosine (DIT) and monoiodotyrosine (MIT), and is involved in iodine recycling in relation to thyroglobulin. Here, we show the distribution of DEHAL1 during gastrulation to neurulation in developing chick. Immunocytochemistry using an anti-serum directed against the N-terminal domain (met(27)-trp(180) fragment) of human DEHAL1 revealed labelled cells in the embryonic ectoderm, embryonic endoderm, neural plate and in the yolk platelets of the chick embryo at gastrulation stage. Distinct DEHAL1 positive cells were located in the presumptive head ectoderm, presumptive neural crest, head mesenchymal cells and in the dorsal, lateral and ventral parts of neural tube during neurulation. Some cells located at the margin of the developing notochord and somites were also DEHAL1-positive. While the functional significance of this observation is not known, it is likely that DEHAL1 might serve as an agent that regulates cell specific deiodination of MIT and DIT before the onset of thyroidal secretion. The presence of DEHAL1 in different components of the chick embryo suggests its involvement in iodine turnover prior to the formation of functional thyroid.