Perturbation of Hoxb5 signalling in vagal neural crest cells causes defective development of the enteric nervous system

Abstract

Introduction: Vagal neural crest cells (NCCs) colonize the gut in a rostrocaudal manner; differentiate into neurons and glia of the enteric nervous system (ENS). ENS development is dependent on the intrinsic properties of NCCs, and also affected by gut microenvironment. Hoxb5 is expressed in both the migrating NCCs and the gut mesenchyme, and the expression pattern is intimately associated with the migration wave and differentiation of NCCs (Fu, 2003. Dev Dyn 228:1). Methodologies: To circumvent the problem of functional redundancy of Hox proteins and study the role of Hoxb5 in NCCs in ENS, transgenic mice carrying a chimaeric protein engrailed-Hoxb5 (en-b5) is generated, in which the transcription activation domain of Hoxb5 is replaced with a transcription repressor domain of the Drosophila engrailed (en) protein. This en-b5 protein shall bind and repress the expression of Hoxb5 target genes, and perturb Hoxb5 signalling. Using Cre/loxP technology, vagal NCC-expression of en-b5 is induced and phenotypes are studied in mice. Results: Neonate expressing en-b5 displays absence of neurons and glia at the distal midgut and hindgut; develops intestinal obstruction. In embryos, NCCs expressing en-b5 were detected at the E10.5 midgut, indicating that perturbation of Hoxb5 signalling did not prohibit NCCs from migrating to the midgut. However, en-b5 expression resulted in reduced number of NCCs and retarded colonization of E11.5 midgut. Delay NCC colonization could result in absence of neurons and glia at the distal gut in transgenic neonates. Conclusion: We provide the first evidence that defective Hoxb5 signalling of NCCs results in abnormal ENS.