Figure 9. Location of
sma-1 RNA in C. elegans embryos by whole-mount in situ hybridization. Embryos were hybridized with pAZ4 DIG-labeled antisense probe. In all pictures anterior is to the left. (A) Early morphogenesis; lateral view, mid-focal plane, dorsal is at top of photograph.
sma-1 RNA is present in cells on the posterior dorsal surface of the embryo. (B-D) Early morphogenesis (older than A); dorsal view, multiple focal planes of single embryo. (B) Upper focal plane;
sma-1 RNA is present in the cells of the dorsal epidermis. (C) Mid-focal plane;
sma-1 RNA is seen in the outermost layer of cells, except in the region of the head. Arrowhead, early
sma-1 RNA expression in the intestine. (D) Lower focal plane;
sma-1 RNA is seen in a small group of cells on the left and right side of the ventral surface (arrowheads). The position of these
sma-1 expressing cells corresponds to that of the leading cells' (Williams-Masson et al., 1997), which initiate ventralward migration of the epidermis and are the first epidermal cells to reach the ventral surface. (E-H) Lateral view; mid-focal plane, dorsal is at top of photograph. By lima bean stage (E),
sma-1 RNA is present on the ventral surface of the embryo (arrowhead); by comma stage (F),
sma-1 RNA is present on the anterior surface of the embryo (arrowhead).
sma-1 expression in pharynx and intestine is most apparent in 1.75-fold stage embryos (G); arrow marks location of boundary between pharynx and intestine. At the 2.5-fold stage (H)
sma-1 RNA is not detected in the epidermis, but is still present in the intestine. Additional
sma-1 expression is seen in the excretory cell (white arrowhead) and an unidentified cell near the anus (white arrow). Bar in H is 10 µm.