study a possible involvement of inwardly rectifying K+ 4.1 (K-ir 4.1) chann
els in neural cell development, RT-PCR, immunocytochemistry and whole-cell
patch-clamp techniques were used to assess expression of K-ir 4.1 channels
in proliferating and differentiated NG108-15 cells. RT-PCR revealed co-expr
ession of K-ir 4.1 and rat ether-a-go-go-related gene (R-ERG) mRNAs in both
proliferating and differentiated cells. The relative K-ir 4.1 mRNA concent
ration increased markedly as cells progressed from undifferentiated to diff
erentiated cells, K-ir 4.1-immunoreactivity was barely detectable in undiff
erentiated cells, but clearly detected in differentiated cells, indicating
that K-ir 4.1 gene and protein expressions are developmentally regulated. H
owever, corresponding K-ir 4.1 current could not be detected in differentia
ted cells using whole-cell patch-clamp recording. The 'silent' channel/rece
ptor, often found in tumor cells, may carry genetic defects, which prevent
functional expression of the channel. NG108-15 may serve as unique model fo
r studying the relationship between the expression of an ion channel gene a
nd the electrophysiological phenotype it encodes. (C) 1999 Published by Els
evier Science B.V. All rights reserved.