Apoptosis Plays a Role in Removal of the First and Second Aortic Arch Arteries, in Remodeling of the Thyroid Rudiment and in Rupture of Closing Plates in Chick Embryos.

Samuel J. Klempner and Sue Ann Miller
Department of Biology, Hamilton College, Clinton, New York


Extensive modification is an important part of avian pharyngenesis. Aortic arch arteries form and are then removed or altered, pharyngeal pouches are remodeled as their closing plates rupture, and the thyroglossal duct is lost after the thyroid evaginates from the pharyngeal floor. Differential cell proliferation is part of pharyngeal remodeling (Miller, et al, 1993), but involvement of apoptosis has not been conclusively demonstrated in chick embryos. We used the TUNEL technique (ApopTag™, Serologicals, Inc.) to determine if apoptosis correlated with these morphogenetic events. Apoptotic cells are present in the mesenchyme around aortic arch arteries 1 and 2 at the time they regress via a capillary plexus (stages HH18-20 and HH23-25 respectively). Extensive apoptosis is apparent in the thyroid rudiment (HH18-20) and later in the thyroglossal duct of HH23-25 embryos. Apoptotic cells were also marked in closing plates of pharyngeal pouches 2 and 3. Our results suggest that programmed cell death acts in conjunction with cell proliferation, cell shape changes and possible cell migration during remodeling of the chick embryo pharynx.

This research was done as part of SJK's year as a Senior Fellow at Hamilton College.
Grant sponsors: Sigma Xi Grant-in-Aid of Research and Hamilton College.

Developmental Biology 259: 588 (2003) Abstract 652

Apoptotic figures appear as small dark spots in this image of developing thyroid in an HH22 embryo that has been counterstained with Fast Green. 1 marks apoptotic bodies in the thyroid and 2 marks clusters of apoptotic bodies in a stran of tissue. The latter suggests that apoptosis is involved in earliest removal of the thyroglossal duct.

Sam presented this research at the 62nd Annual Meeting of the Society for Developmental Biology, in Boston, August 2003.

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