PCR-BASED ASSIGNMENT OF 2 MYOSIN HEAVY-CHAIN CDNA CLONES TO BIOCHEMICALLY AND HISTOCHEMICALLY DEFINED SINGLE TYPE-IIB AND TYPE-IID FIBERS OF RABBIT MUSCLE

The present study assigns two as yet unidentified fast myosin cDNA clo nes to specific myosin heavy chain (MHC) isoforms and their mRNAs in d ifferent fiber types of rabbit skeletal muscle. Specific oligonucleoti de primers were used for reverse transcription and polymerase chain re action (PCR) to yield products of defined lengths. The method was sens itive enough to detect specific mRNA sequences in total RNA extracts f rom microdissected, freeze-dried, single-fiber fragments down to 16 ng dry weight. The fibers were typed histochemically and biochemically b y their electrophoretically assessed MHC complement. The following res ults were obtained: clone pMHC20-40 was assigned to type IIB fibers an d clone pMHC24-79 to type IID fibers.