Developmental expression and localization of KCNJI0 K+ channels in the guinea pig inner ear

The inward rectifier Kir4.1, composed of KCNJ10 K+ channel subunits, plays an essential role in inner ear K+ homeostasis. We have investigated the developmental expression and localization of KCNJ10 (Kir4.1) in the guinea pig inner ear using semi-quantitative reverse transcription polymerase chain reaction and immunohistochemistry. Kcnj10 was expressed at low levels from embryonic day 30 (E30), increased from E45, and persisted from E50 to adulthood. KCNJ10 channel protein was detected in spiral ganglion satellite cells of the basal turn at E40, and at E45 its expression proceeded with a base-to-apex gradient along the cochlear spiral. KCNJ10 protein was enriched in the myelin sheath around the cochlear nerve between E40 and E45 and disappeared gradually with age. In the strial intermediate cells, KCNJ10 channel expression was first observed at E50, and lagged behind that of the spiral ganglion. In addition, KCNj10 channel protein was expressed and localized in vestibular transitional cells. Differential expression of KCNJ10 channel protein suggests roles for KCNJ10 channels in inner ear development and onset of auditory function. NeuroReport 17:475-479 (c) 2006 Lippincott Williams & Wilkins.