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Proc Natl Acad Sci U S A. 1992 Feb 15;89(4):1497-501.

Mutually exclusive exon splicing of the cardiac calcium channel alpha 1 subunit gene generates developmentally regulated isoforms in the rat heart.

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  • 1Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, OH 45267-0575.


Several clones were isolated from a rat genomic library in order to further characterize a region of variability within the third membrane-spanning region of the fourth motif (IVS3) of the L-type voltage-dependent calcium channel. We report here that this diversity arises from alternative splicing of a primary transcript containing a single pair of adjacent exons each encoding a unique sequence for the IVS3 region. Definitive proof of a mutually exclusive splicing mechanism was obtained by genomic mapping of flanking upstream and downstream exons and by extensive sequence analysis of the relevant exon/intron boundaries. S1 nuclease protection experiments revealed that both variant forms of the IVS3 were equally expressed in newborn and fetal rat heart, whereas only a single isoform predominated in adult rat heart. The results demonstrate the existence of an important developmentally regulated switch mediated by alternatively spliced exons in cardiac tissue at a time when major changes in excitation occur.

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