Expression and distribution of Nob1 in the developing rat cochleae.

BACKGROUND: Mammalian inner ear cells are produced during embryonic development. NIN1/RPN12 binding protein 1 homolog (Nob1), a ribosome assembly factor, is believed to be involved in transcriptional regulation and may play an important role in mediating certain physiological and pathological functions.

METHODS: We investigated the expression levels and distribution patterns of Nob1 in rat cochlea at different developmental stages using reverse transcription-polymerase chain reaction (RT-PCR), Western blot analysis, and immunofluorescence microscopy (P0, P3, P7, P14, and P30, n = 11 per age group).

RESULTS: The expression of Nob1 was gradually upregulated from Postnatal day (P) 0 to P14 and stabilized at P30. Our results analyzing Nob1 expression at P0 and P3 in the rat cochleae revealed expression in the greater epithelial ridge cells, lesser epithelial ridge cells, and spiral ganglion neurons (SGNs), whereas low levels of Nob1 expression were observed in the stria vascularis cells. During the development of the cochlea, the organ of Corti undergoes dramatic architectural remodeling. Nob1 expression was stably detected in supporting cells and hair cells from P7 to P30, and its expression gradually increased in the SGNs.

CONCLUSIONS: Thus, the present study revealed that upregulation of Nob1 might explain the maturation of the cytoarchitecture in the cochlea during the postnatal period, and a complete understanding of its function in the mammalian inner ear may help to develop strategies to resolve auditory hair cell loss.