Expression Of Neurogenin2and Math6in The Embryonal And Postnatal Mouse Inner Ear

Objective To reveal the precise spatial and temporal pattern of neurogenin2and math6expression in the embryonic and postnatal spiral ganglion, and toexplode the effect on the developmental spiral ganglion.Methods HE stain was applied to identify its sub-structures in different periodof cochlear sections(E13.5、E14.5、P1and Adult). Immunohistochemistrymethod was also adopted for above–mentioned sections to detect expression ofngn2and math6. Meanwhile, the quantity of ngn2and math6expression inmRNA was examined by real-time qPCR at seven time points (E12.5、E13.5、E14.5、E17.5、P1、P7and Adult).Results At E13.5, the cochlear duct has completed approximately three-quarters ofone turn, the SAG is differentiated to SG and VG, meanwhile the SG has not extend nervefiber that will form contacts with developing sensory epithelia; At E14.5, the SG begins toextend nerve fiber, and the cylindrical epithelium starts differentiation. At P1, the cochlear duct reaches its mature length of approximately one and three-quarter turns, and the neuronshave formed contacts with hair cells in the developing sensory epithelia, meanwhile, thetectorial membrane begins to form at basal turn. At adult, the sub-structures of cochleacan be identified clearly and correctly, inner and outer hair cells, tectorialmembrane and so on.The results of immunohistochemistry showed that ngn2and math6wereexpressed in the spiral ganglion at E13.5、E14.5and P1, and the protein of math6was less expressed in adult spiral ganglion than embryonic. There is statisticallysignificant difference in the protein expression of ngn2and math6at variantpoints (P<0.05).The expression level of ngn2mRNA reached a peak at E12.5，thengradually decreased from E13.5to Adult. In addition, the expression level ofmath6mRNA increased at E12.5and P1, then decreased till Adult.Conclusion The highest expression of ngn2in spiral ganglion is at E12.5. Itsuggests that ngn2plays very import role in dividing neural progenitors; whilethe high expression of math6is from E12.5to P1, it indicates that math6may berelated to regulation of dividing neural progenitors and being differentiated intopostmitotic neurons. The identity and difference of spatial and temporal patternof ngn2and math6expression suggest that there may be some gene regulatingboth of them in signaling pathways.