Fig. 4.

Caprin-1 is expressed in the inner ear in both supporting cells and hair cells. (A) Levels of Caprin-1 and Pou4f3 mRNA were determined by qPCR in mouse cochlea, utricle and brain. For all qPCR experiments, 18S rRNA was used as an endogenous control and expression levels were calculated relative to this endogenous control. Error bars represent 95% confidence intervals. (B) Schematic showing the arrangement of cells within the organ of Corti. OH, outer hair cells; IH, inner hair cells; D, Deiters' cells; H, Hensen's cells; C, Claudius' cells; P, pillar cells; and Ph, phalangeal cells. (C) Vibratome slices through a P2 rat cochlea show Caprin-1 (green) expression in cells in the sensory epithelium (the organ of Corti), the hair cell marker myosin VIIa (red) and nuclei stained with DAPI (blue). Arrowheads indicate greater Caprin-1 expression in phalangeal processes of the Deiters' cells that intercalate between hair cells. The asterisks indicate expression in Claudius' cells. Scale bar: 10 μm. (D) Samples enriched for particular cell types (supporting-cell-enriched, hair-cell-enriched and a mixed-cell sample of Deiters' and hair cells) were collected and analysed by qPCR. Expression levels of p27^kip1, Myo7a, Pou4f3 and Caprin-1 were calculated relative to the endogenous control. p27^kip1 and Myo7a levels indicate the degree of enrichment for supporting cells and hair cells, respectively. Pou4f3 expression is highest in the hair-cell-enriched pool, whereas Caprin-1 was lowest in the hair-cell-enriched pool. (E) Single-cell qPCR. Caprin-1 levels were measured in individual hair cell samples (X, Y and Z) that expressed Myo7a but not p27^kip1. These cells were collected from the same explant culture, but are representative of results obtained from more than five cultures.