Meeting Abstract

P1.71  Monday, Jan. 4  Coordination of branchial arch development in neonatal mice SWIDERSKI, D.L.; Univ of Michigan, Ann Arbor dlswider@umich.edu

Changes in branchial arch function and development are among the most revolutionary in vertebrate evolution. During development of the branchial arch skeleton, as in its evolution, elements from different arches become anatomically linked and integrated and elements from the same arch become differentiated and independent; some reintegrating at a later stage. These changing patterns of independence and integration should be reflected in the coordination of growth and remodeling, as well as in the expression of cell signaling pathways. To identify critical intervals for control of differential growth and shape transformation through developmental signaling interactions, I am assessing the rate and localization of skeletal growth during early postnatal ontogeny of mice. During the first postnatal week, the dentary and tympanic (1^st arch membrane bones) exhibit tremendous changes in size and shape whereas the malleus and incus (1^st arch endochondral bones), undergo much smaller and subtler changes in both size and shape. The stapes (2^nd arch endochondral bone) undergoes little change in size, but an intermediate amount of shape change. These bones also differ substantially in degree of ossification. Whereas the dentary changes from a lacy mesh to a much denser, but still very porous framework, the malleus and incus go from cartilages devoid of bone, to bony frameworks at least as dense as the dentary, lacking cartilage except at articulations. The stapes undergoes a similar transformation in ossification. Thus there are profound differences in this week between elements that contribute to feeding (dentary and hyoid) and elements that contribute to hearing (malleus, incus and stapes), as well as between the arches and between endochondral and membrane bones of the same arch. These results predict there also will be gene expression differences both within and between arches.