Hes1 gene represses the expression of proneural basic helix-loop-helix (bHLH) factor Mash1, which is essential for the differentiation of the sympathetic ganglia and carotid body glomus cells. The sympathetic ganglia, carotid body, and common carotid artery in Wnt1-Cre/R26R double transgenic mice were intensely labeled by X-gal staining, i.e., the neural crest origin. The deficiency of Hes1 caused severe hypoplasia of the superior cervical ganglion (SCG). At embryonic day (E) 17.5-E18.5, the volume of the SCG in Hes1 null mutants was reduced to 26.4% of the value in wild-type mice. In 4 of 30 cases (13.3%), the common carotid artery derived from the third arch artery was absent in the null mutants, and the carotid body was not formed. When the common carotid artery was retained, the organ grew in the wall of the third arch artery and glomus cell precursors were provided from the SCG in the null mutants as well as in wild-types. However, the volume of carotid body in the null mutants was only 52.5% of the value in wild-types at E17.5-E18.5. These results suggest that Hes1 plays a critical role in regulating the development of neural crest derivatives in the mouse cervical region. Developmental Dynamics 241:1289-1300, 2012. V C 2012 Wiley Periodicals, Inc.Key words: Hes1 knockout mice; Wnt1-Cre/R26R transgenic mice; superior cervical ganglion of sympathetic trunk; carotid body; common carotid artery; neural crest cells; tyrosine hydroxylase
Key findings:Hes1 gene plays a role in maintaining the undifferentiated cells during development. Hes1 null mutant embryos displayed a severe hypoplasia of the superior cervical ganglion (SCG) of sympathetic trunk. Hes1 null mutants failed to form the common carotid artery as a partially penetrated phenotype (13.3%), resulting in the absence of the carotid body. When the carotid artery was retained, the carotid body of the null mutants was smaller in size than that of wild types. Neural crest derivatives, including the SCG, carotid body, and common carotid artery, were affected by the lack of Hes1.