Δ34 protein shows delayed localization
into discrete bands during early stages of muscle cell organization.
Each column shows embryos from a given strain. Each row depicts a
different developmental stage: 1.5-fold (A–D), twofold (E–H), or
threefold (I–L). The staining pattern in unc-54(e190)
is similar to that in wild-type, despite the lack of MHC B and the
resultant reduction in total myosin. The third column shows full-length
MHC A that is overexpressed from a transgene in myo-3;
stEx80 animals (array chosen for robust rescue; see MATERIALS
AND METHODS). Increased MHC A results in stray filamentous staining
(arrowhead in G) and occasional aberrant expansion of stain within or
near the contractile apparatus (K). However, strong bands of stain are
evident at the 1.5-fold stage (C). Distribution of Δ34 protein in
myo-3; stEx129 animals is distinct, with diffuse stain
outlining the nuclei (D and H). Occasional abnormal round accumulations
that are found within the muscle cell body (L) may be due to
inappropriate levels of MHC accumulation. Animals are stained with MHC
A-specific antibody (5–6), which recognizes endogenous protein in
wild-type and unc-54 mutants, and transgenic protein in
the remaining genotypes. In wild type, four muscle quadrants run
longitudinally along the length of the animal. In most areas,
four longitudinal bands of stain are apparent across the width of a
single muscle quadrant (between the arrowheads in I). The stages refer
to the length of the elongating animal compared with the surrounding
eggshell: at 1.5-fold, the posterior tip (arrowhead in A) has reached
half the length of the egg as it elongates and moves toward the
anterior end (arrow), positioned at the opposite pole of the egg. Bar,
5 μm. Myosin localization during embryogenesis has been described
previously (Epstein et al., 1993; Hresko et
al., 1994; Williams and Waterston, 1994).