Characterization of genomic clones specifying rabbit alpha- and beta-ventricular myosin heavy chains.

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Abstract
Gene sequences were isolated coding for the .alpha.- and .beta.-myosin H chains (HC) of rabbit ventricular muscle. A rabbit genomic library was screened with previously characterized c[complementary]DNA clones specifying part of the light meromyosin and the entire subfragment 2 portion of .alpha.- and .beta.-myosin HC, as well as with a clone containing the 3'' nontranslated sequences of the .alpha.-myosin HC mRNA. Seven strongly hybridizing clones were analyzed in detail. One genomic clone encoded all of the 3'' nontranslated sequences of an .alpha.-cDNA clone and contained the 3'' end of the .alpha.-myosin HC gene. EM heteroduplex analysis and DNA sequence analysis showed that this clone overlapped a 2nd genomic clone providing more than 25 kilobase pairs of the .alpha.-myosin HC gene. The exons within this region corresponded to .apprxeq. 85% of the mRNA and were separated by a least 28 introns. A clone for the .beta.-myosin HC gene was also identified by Southern blot hybridization, by heteroduplex mapping, and by comparing the DNA sequence of a subfragment 2 exon to sequences of the .alpha.- and .beta.-cDNA clones. The introns of the .alpha. and .beta.-myosin HC genes were in the same position but showed marked variation in length. The .alpha.- and .beta.-myosin HC are products of separate genes.