CALCIUM-CHANNEL SUBUNITS IN THE MOUSE COCHLEA

Messages for subunits of voltage-gated calcium channels were examined in the cochlea of the CBA(J) mouse by PCR analysis. Total RNA was extr acted from the auditory organs of 16-18-day-old animals. After reverse transcription, resulting cDNA was amplified by PCR with primers targe ted to nucleotide sequences corresponding to 12 different calcium chan nel subunits. PCR products representing subunit gene expression were s trongly and consistently amplified for alpha(1c), alpha(1D), alpha(1E) , alpha(2) delta, beta(1), beta(3), and beta(4) but not for alpha(1A), alpha(1B), alpha(1S), beta(2), or gamma. The chosen primers amplified cochlear cDNA to yield an overall pattern of bands different from tha t of any tissue studied thus far, in particular with respect to the al pha(2) delta and beta(1) subunits; the alpha(2) delta product was foun d to be significantly shorter than the corresponding brain and skeleta l muscle isoforms. Nucleotide sequencing confirmed the identity of mou se cochlear subunit cDNAs. The results suggest that L-type and presump tive R-type calcium channels are expressed in the mammalian cochlea an d that the alpha(2) delta subunits may be coded by a characteristic sp lice-variant mRNA.