| Abstract: | While the existence of post-hatch and adult myosin heavy chain isoforms in the large, avian type IIB pectoralis major muscle
has been clearly established, the number and nature of fast myosin heavy chains during in ovo development and the peri-hatch
period have not been resolved. In the present study, developmental fast heavy chain proteins purified by high resolution anion-exchange
have been characterized by sequence analysis of a unique CNBr peptide and by complementary mRNA analysis. The four proteins
present at 15/16 days in ovo are shown to differ uniquely in primary structure. They correlate with heavy chains II, IV, VI
and VII, characterized recently as major or minor species in adult fast muscles using similar methods. These four heavy chains
are expressed in a time-dependent fashion from 8 to 16 days in ovo. At the mRNA level, heavy chain VI predominates until 12
days in ovo. Heavy chain IV mRNA is upregulated dramatically at 16 days in ovo preparatory to its protein's predominance in
the peri-hatch period. Heavy chains II, IV and V (the post-hatch isoform which replaces heavy chain IV) have major roles in
adult fast muscles.
This revised version was published online in August 2006 with corrections to the Cover Date. |
