EXPRESSION OF PLASMA-MEMBRANE CALCIUM-PUMPING ATPASE MESSENGER-RNAS IN DEVELOPING RAT-BRAIN AND ADULT BRAIN SUBREGIONS - EVIDENCE FOR STAGE-SPECIFIC EXPRESSION

The plasma membrane calcium-pumping ATPases (Ca2+-ATPases) maintain resting free cytosolic calcium concentrations in cells at the submicromolar level. These Ca2+-ATPases are encoded by four genes that can be alternately spliced to produce nine different mRNAs, each of which has a unique tissue-specific distribution. Examination of the expression of these mRNAs in rat brain during development revealed that transcripts from three of the four known genes are expressed by the end of gestation. However, the stage of transcription induction varies among the isoforms. The mRNA encoding plasma membrane Ca2+-ATPase (PMCA) 1b, the isoform thought to maintain a housekeeping function, was present from embryonic day 10. The other alternately spliced PMCA1 mRNAs, PMCA1a and c, which are preferentially expressed in the brain, did not appear until embryonic day 14. PMCA2a mRNA and the alternatively spliced PMCA2b and c transcripts were coordinately induced on embryonic day 18. The PMCA3a transcript first appeared on embryonic day 18 but did not reach steady-state levels until postnatal day 3, whereas production of PMCA3b mRNA first occurred on embryonic day 10 and reached steady-state expression by embryonic day 18. Several PMCA mRNAs tested varied in expression in specific regions of the brain that were examined at three postnatal time points.