Human cardiac myosin heavy chain genes. Isolation of a genomic DNA clone and its characterization and of a second unique clone also present in the human genome.

A gene sequence coding for myosin heavy chain (MHC) of human cardiac muscle was isolated by screening a human genomic library with a 32P-labelled 1.1kb SacI restriction fragment from a previously characterized cDNA clone specifying the light meromyosin and 3' untranslated region of mRNA encoding rabbit cardiac alpha-MHC. The DNA of this human genomic clone (lambda HCMHC8) hybridized much more strongly than did other clones isolated under similar, low stringency conditions both to the rabbit cDNA probe and to mRNA isolated from rat cardiac, but not skeletal, muscle tissue. Probe made from a DNA restriction fragment of lambda HCMHC8 hybridized a single 31S band of human ventricular mRNA. This size is identical to that of cardiac MHC mRNA of other species. Heteroduplex analysis showed hybridization of lambda HCMHC8 with exon segments in a rabbit cardiac MHC genomic clone (lambda MHC alpha 12/1). It also showed that lambda HCMHC8 spanned 14 kb of DNA and contained exon segments estimated to code for two-thirds of a MHC including the carboxylic acid terminus. By rescreening the library under more stringent conditions, where only DNA sequences having strong homology to cardiac MHC genes would be expected to hybridize, clones having restriction maps overlapping lambda HCMHC8 were isolated together with a unique clone (lambda HCMHC9). DNA gel blot hybridization of human genomic DNA with lambda HCMHC8 probe at medium stringency gave a pattern of restriction fragments similar to the restriction map of lambda HCMHC8. A weaker set of bands also appeared which corresponded in pattern to the map of lambda HCMHC9.(ABSTRACT TRUNCATED AT 250 WORDS)