Figure 4.

α spectrin is required for embryonic elongation. Nomarski images of representative wild-type (A and B) and spc-1(ra409) (C) embryos. (A) A wild-type embryo that has completed embryonic elongation (arrows indicate fully elongated pharynx). (B) A 1.5-fold wild-type embryo that has partially completed elongation (arrows indicate developing pharynx). (C) A spc-1 mutant embryo at the same stage as the wild-type embryo shown in A. spc-1 mutant embryos undergo elongation at a slower rate than wild-type animals and fail to complete elongation. Arrows indicate the abnormal morphology of the pharynx. Bar, 10 μM. (D) Lengths of N2 (n = 7), spc-1 (n = 5), egl-19 (n = 4), sma-1 (n = 6), let-502 (n = 5), and mlc-4 (n = 4) embryos measured every 15 min from first cleavage at 24°C. All the embryos initiated elongation at the same time. N2 and egl-19 continue at the same rate until twofold in length where egl-19 ceases elongation. spc-1, sma-1, let-502, and mlc-4 undergo elongation at a slower rate. Additionally, body wall muscle contraction commenced at the same time (∼400 min) in all the embryos except egl-19, which failed to display muscle contraction. Data is shown as the mean ± SD.