Expression of nestin-associated genes in the inner ear of newborn rats following injury and hypoxia

Abstract

We used organotypic cultures of the stria vascularis (SV), the organ of Corti (OC) and the modiolus (MOD) of newborn rats to analyze the differential expression levels and responses of cytoskeletal, myelin-and neural growth factor-associated genes following preparatory injury and hypoxia. The transcript mRNA levels of the neurofilaments Nefl, Nefm, the microtubule-associated proteins Mapt, Map1a, Map2, and of the myelin basic protein Mbp decrease during 24 h in a coordinated way across the MOD and OC regions. The increased cell death rate in the MOD region is associated with an increased expression of Nes, the transcript encoding the intermediate filament nestin, and of the neural growth factor receptor Ngfr, the growth-associated protein 43 Gap43 and the Purkinje cell protein Pcp4. The correlation analysis revealed close associations between Nes expression and genes involved in apoptotic and necrotic cell death (caspase Casp3, calpains Capn1, Capn2, Capns1), the glutamate pathway (glutamate receptor NMDA associated protein 1 Grina, glial high affinity glutamate transporter Slc1a3), cytoskeletal genes (Nefm, Map2, Map1a, Mbp), transcription factors (hypoxia inducible factor Hif-1a, jun proto-oncogene Jun, brain expressed myelocytomatosis B-myc, HES family bHLH transcription factor 1 Hes-1, forkhead-box D3 Foxd3) and neural growth factors (Ngfr, Gap43 and Pcp4). The unique response and the composition of the Nes cluster made us conclude that the expression of cell-death-associated genes and the regeneration-associated genes takes place in a coordinated way, and differs between the MOD and the OC/SV regions.