Ultrastructure of the inner ear of NKCC1-deficient mice

The transduction of the auditory signal is dependent on the flow of ions wi thin the inner ear. We have generated mice deficient in NKCC1, an ion cotra nsporter that is thought to be involved in the secretion of K+ by the stria l marginal cells. Inner ear histology revealed partial to almost total abse nce of the scala media and collapse of Reissner's membrane. Ultrastructural analysis showed that Reissner's membrane consists of 3-4 cell layers inste ad of the usual two, and a substance of unknown composition is present betw een Reissner's membrane and underlying structures. Within the tunnel of Cor ti, hair cells and supporting cells were difficult to identify. The locatio n of the tectorial membrane was altered, and a precipitate was observed sur rounding it. Severe structural defects were noted in the interdental cells and Boettcher cells, and mild defects were observed in the stria vascularis and in type II and type IV fibrocytes. The finding that major defects occu r predominantly in cells that are not known to express NKCC1 suggests that loss of NKCC1 results in functional defects in cells expressing NKCC1 and a morphological effect on cell populations downstream in the proposed K+ rec ycling pathway. (C) 2001 Elsevier Science B.V. All rights reserved.