Studying the role of Sox10 in enteric neural crest cell migration with Sox10NGFP mouse mutant

Abstract

Sox10 is an HMG domain containing transcription factor required for maintaining the multipotent neural crest stem cells during the development of the enteric nervous system. Mutation of SOX10 in human leads to Waardenburg-Shah syndrome which is characterized by colonic aganglionosis, pigmentation defects and deafness. In addition to maintenance of the enteric neural crest progenitors, other factors including interactions of the neural crest cells with the gut microenvironment will also affect the colonization of these cells in the gut. In this study, I hypothesize that Sox10 is involved in maintaining enteric neural crest cell migration behaviors, possibly through regulating cell-cell or cell-extracellular matrix interactions. The aim of this study is to characterize the abnormal migration behavior of Sox10 mutant enteric neural crest cells, and to identify signaling pathway that may be involved in enteric neural crest cell migration.

To investigate the migration behavior of Sox10 mutant enteric neural crest cells, gut explants from heterozygous 〖Sox10〗^NGFP mutant mice, which expressed GFP protein in the enteric neural crest cells, were cultured on fibronectin coated dish. Movements of cells from the explants were recorded for 24 hours by confocal time-lapse live-cell imaging. The speed, displacement and persistence of the enteric neural crest cells in the gut explant culture were analyzed. While 〖Sox10〗^(NGFP/+) cells moved 32% faster than control cells, their persistence was 43% lower than control cells, giving a significant 26% reduction in final displacement. Furthermore, by western blot analysis using protein extracts of mutant and normal midguts, I found that the level of phospho-FAK397, the activated form of focal adhesion kinase required for cell motility, was reduced in 〖Sox10〗^(NGFP/NGFP ) and 〖Sox10〗^(NGFP/+) mutants. These results indicate that Sox10 is required for normal enteric neural crest cell migration.

It has been shown that PDGFRα is a downstream target of Sox10 in oligodendrocyte precursor cells and is essential for their migration. However, the role PDGFRα in the developing enteric nervous system was unclear. By immunohistochemical staining of E10.5, E12.5 and E14.5 〖Sox10〗^(NGFP/+) and wildtype gut samples, PDGFRα was detected in the differentiated neuroblasts, but not in undifferentiated neural crest cells during these stages. Interestingly, treatment of gut explant cultures by PDGFR inhibitor disrupted the emigration and spreading of enteric neural crest cells from both Sox10NGFP/+ and wildtype explants, and this effect was more prominent in 〖Sox10〗^(NGFP/+). Therefore, PDGF signaling is important for enteric neural crest cell movements. However, how PDGF signaling may control enteric neural crest cell migration requires further investigations.

In summary, Sox10 is involved in enteric neural crest cell migration by maintaining normal cell migration behavior through modulating cell motility pathway. PDGFRα is a novel gene found to be expressed in the developing enteric nervous system. PDGF signaling is required for normal enteric neural crest cell migration in vitro, suggesting a potential novel pathway essential for gut colonization.