Construct: The 5' regulatory region, first exon, first intron and translational start site of Act88F are fused upstream of cDNA/genomic sequences encoding an embryonic form of Mhc lacking the globular head region. The Mhc coding sequences extend from 45 amino acids upstream of the head-rod junction through to the C-terminus. Exon 15b is included and is prespliced at the 3' end such that exon 18 is excluded (this alters the amino acid sequence at the C-terminus so that it matches the embryonic isoform). A 1.5kb fragment from the 3' region of Mhc (which includes polyadenylation signals) is included downstream of the Mhc coding sequences.