Over-expression of mutant SOX10 in the vagal neural crest causes hypoganglionic colon development in transgenic mice

Abstract

The neural and glial cells of the intrinsic ganglia of the enteric nervous system (ENS) are derived from the hindbrain neural crest at the vagal level (VNC), but the sacral neural crest (SNC) also has some contribution. The coordination of neural crest migration and the molecular control of their differentiation into specific cell types are not clearly known. Several genes have been found to be involved in ENS development, including Sox10 which when mutated caused megacolon in mice as observed in the Dom mutant. We have identified a VNC specific enhancer element from the mouse Hoxb3 gene, b3-IIIa, which could direct lacZ reporter gene expression in the ENS of transgenic mice. When crossed with the Dom mutant, the hybrid mutant displayed an absence of lacZ marked cells in the hindgut, further con- firming the specificity of this enhancer in the ENS. In order to understand the role of Sox10 during the development of vagal neural crest to the ENS, we have taken a transgenic approach making use of the VNC specific enhancer. We have generated a gain-of-function mutant in which mutant Sox10 with a Dom mutation was ectopically expressed in the vagal neural crest of transgenic mice. The mutants did not have a megacolon phenotype, but immunohistochemical analysis of 14.5 and 16.5 dpc transgenic mutant embryos using anti-neurofilament antibody showed that the ENS development was affected. The distal colons of the mutants were hypoganglionic, with deficient number and complexity of ganglionic plexuses. It is possible that in the transgenic mice, the mutant Sox10 proteins expressed in the VNC may compete with wildtype proteins in a dominant negative manner and as a consequence affect the proliferation and/or differentiation of the enteric ganglia.