The beta 1 subunit mRNA of the rat brain Na+ channel is expressed in glial cells.
Although the molecular characteristics of glial Na+ channels are not well understood, recent studies have shown the presence of mRNA for rat brain Na+ channel alpha subunits in astrocytes and Schwann cells. In this study, we asked whether the mRNA for the rat brain Na+ channel beta 1 subunit is expressed in glial cells. We performed in situ hybridization using a complementary RNA probe for the coding regions of the rat brain Na+ channel beta 1 subunit mRNA and detected beta 1 subunit mRNA in cultured rat optic nerve astrocytes and sciatic nerve Schwann cells. The beta 1 subunit was amplified by reverse transcription-polymerase chain reaction in rat optic and sciatic nerves, which lack neuronal somata but contain astrocytes and Schwann cells, respectively. Doublet bands of the beta 1 subunit mRNA were amplified from both optic and sciatic nerves. Through the cloning and sequencing of these bands, we confirmed the amplification of a mRNA highly homologous to the previously cloned rat brain Na+ channel beta 1 subunit (beta 1.1) and a novel form of the beta 1 subunit mRNA (beta 1.2), which is closely homologous to beta 1.1 but contains an additional 86-nucleotide insert in 3' noncoding regions. Two beta 1 subunit mRNAs were also amplified from rat brain and skeletal muscle, but not from rat liver or kidney. These results indicate that rat brain Na+ channel beta 1 subunit mRNAs are expressed in glial cells as well as in neurons.
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Department of Neurology, Yale University School of Medicine, New Haven, CT 06510.
Waxman
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D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D001483:Base Sequence; D015152:Blotting, Northern; D001921:Brain / Q000378:metabolism*; D002478:Cells, Cultured; D003001:Cloning, Molecular; D003062:Codon; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D015870:Gene Expression; D017403:In Situ Hybridization; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D009900:Optic Nerve / Q000378:metabolism*; D016133:Polymerase Chain Reaction / Q000379:methods; D015221:Potassium Channels / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D012583:Schwann Cells / Q000378:metabolism*; D012584:Sciatic Nerve / Q000378:metabolism*
D003062:Codon; D046911:Macromolecular Substances; D015221:Potassium Channels; D012333:RNA, Messenger; D004247:DNA