FRS2 alpha 2F/2F mice lack carotid body and exhibit abnormalities of the superior cervical sympathetic ganglion and carotid sinus nerve

The docking protein FRS2α is an important mediator of fibroblast growth factor (FGF)-induced signal transduction, and functions by linking FGF receptors (FGFRs) to a variety of intracellular signaling pathways. We show that the carotid body is absent in FRS2α^2F/2F mice, in which the Shp2-binding sites of FRS2α are disrupted. We also show that the carotid body rudiment is not formed in the wall of the third arch artery in mutant embryos. In wild-type mice, the superior cervical ganglion of the sympathetic trunk connects to the carotid body in the carotid bifurcation region, and extends thick nerve bundles into the carotid body. In FRS2α^2F/2F mice, the superior cervical ganglion was present in the lower cervical region as an elongated feature, but failed to undergo cranio-ventral migration. In addition, few neuronal processes extended from the ganglion into the carotid bifurcation region. The number of carotid sinus nerve fibers that reached the carotid bifurcation region was markedly decreased, and baroreceptor fibers belonging to the glossopharyngeal nerve were absent from the basal part of the internal carotid artery in FRS2α^2F/2F mutant mice. In some of the mutant mice (5 out of 14), baroreceptors and some glomus cells were distributed in the wall of the common carotid artery, onto which the sympathetic ganglion abutted. We propose that the sympathetic ganglion provides glomus cell precursors into the third arch artery derivative in the presence of sensory fibers of the glossopharyngeal nerve.