KIMMEL, CHARLES B.*; MCGUIGAN, KATRINA; ULLMANN, BONNIE; CURREY, MARK; CRESKO, WILLIAM A.; University of Oregon; University of Oregon; University of Oregon; University of Oregon; University of Oregon: Dorsoventral Patterning of Facial Bone Morphology

Evolution within the Endothelin1 (Edn1) regulatory pathway might underlie key features of craniofacial evolution. Bone morphology within the opercle-branchiostegal ray series of the hyoid arch varies marvelously in different actinopterygians, and zebrafish edn1-pathway mutants mimic the macroevolutionary changes. Edn1 plays a central role in dorsoventral (DV) facial patterning; expressed ventrally in the embryonic pharyngeal arches it determines how many skeletal elements will develop, their DV positions, sizes, and shapes. Since identifying genes responsible for vertebrate macroevolution currently is impossible, we have examined microevolution of opercular morphology in threespine sticklebacks, where direct genetic studies are straightforward. Evolution from Alaska marine to lake forms is accompanied by correlated size reduction and DV shortening of the opercle, underlain by a major-effect QTL on LG19. The zebrafish studies suggest that both changes can come about simultaneously by up-regulation of Edn1, which motivates the hypothesis that in sticklebacks developmental bias is influencing morphological evolution of the operculum. Current work examines this proposal. (Supported by the NIH and NSF).