IDENTIFICATION OF A GENOMIC LOCUS CONTAINING 3 SLOW MYOSIN HEAVY-CHAIN GENES IN THE CHICKEN

Two unique cDNA clones containing chicken slow myosin heavy chain (MyH C) inserts have been isolated from an expression library. Immunochemic al analyses of the expressed proteins using different slow MyHC specif ic monoclonal antibodies were consistent with the two clones encoding slow MyHC 1 (SM1) and slow MyHC 2 (SM2) protein sequences. Northern bl ot analyses showed that the clones hybridized with 6-kb mRNAs that are differentially expressed in developing and adult slow muscles, furthe r supporting the conclusion that these two clones represent SMI and SM 2 cDNAs. Sequence analyses show that both clones encode the highly con served fight meromyosin portion of the sarcomeric myosin rad and are 7 8-81% homologous to a mammalian slow/cardiac beta-MyHC cDNA. Hybridiza tion using PCR generated probes specific for SMI and SM2 sequences dem onstrated that the genes encoding these two slow MyHCs colocalized to an XO-kb BssHII genomic fragment, We further show that a probe specifi c to a third slow MyHC gene also hybridized with the same 80-kb genomi c fragment. We conclude that in the chicken genome there is a slow MyH C locus containing at least three distinct slow MyHC genes. (C) 1997 E lsevier Science B.V.