S. Ennion et al., CHARACTERIZATION OF HUMAN SKELETAL-MUSCLE FIBERS ACCORDING TO THE MYOSIN HEAVY-CHAINS THEY EXPRESS, Journal of muscle research and cell motility, 16(1), 1995, pp. 35-43
Using a method of single muscle fibre analysis, we investigated the pr
esence of RNA transcripts for various isoforms of the myosin heavy cha
in (MyoHC) gene in histochemically, immunohistochemically and electrop
horetically characterized individual muscle fibres (n = 65) from adult
human vastus lateralis muscle. A cDNA clone isolated in this study wa
s shown to contain the 3' end of a previously uncharacterized human My
oHC gene which is expressed specifically in human fast IIA muscle fibr
es and we conclude that this clone contains part of the human fast IIA
MyoHC gene. In all the fibres histochemically, immunohistochemically
and electrophoretically characterized as containing the previously cla
ssified IIB MyoHC (n = 23), it was shown that the human equivalent to
the rat type IIX MyoHC gene is expressed. This observation was taken t
o suggest that the previously classified IIB muscle fibres in human mu
scle express a MyoHC isoform equivalent to the rat IIX, not the IIB, a
nd would therefore be more accurately classified as IIX fibres.