Figure 2. Hemicentin Is Required for BM-BM Adherence(A) A ventral perspective of the BM shows GFP::hemicentin (green, top; white, bottom) in punctate accumulations in the BM (laminin::mCherry, magenta) specifically under the AC (dashed circle) beginning at the P6.p one-cell stage (left). Hemicentin punctae are pushed aside as the AC invades through the BM, forming a ring at the edge of the BM gap (right). (B) Nascent hemicentin accumulations (green, top; white, bottom) are marked with a new color at 10 min intervals to highlight their stability. This animal corresponds to Movie S1. (C) Worms in which the gonadal and ventral BMs could be resolved reveal that the BMs are not adherent in hemicentin mutant (
him-4(
rh319)) animals prior to (mid P6.p two-cell stage) or during invasion (P6.p four-cell stage; n = 10 animals). Insets are 2-fold magnifications and arrowheads delineate the BMs under the AC. The BMs in hemicentin mutants fuse following invasion (right, arrowheads, inset; n = 10 animals). (D) Graph shows the average distance between the gonadal and ventral BM in wild-type worms and
him-4(
rh319) worms underneath the AC and adjacent to the AC (n R 10 animals analyzed for each group, **p < 0.005, Student's t test, error bars represent SEM). (E) A small region of the BMs (laminin::GFP, white)under the AC of
him-4(
rh319) animals at the mid two-cell stage was photobleached (brackets, left). Following tissue shift, the photobleached regions of the gonadal BM (highlighted in dark green) and the ventral BM (highlighted in light green) were no longer aligned (n = 3/4, right). (F) Transmission electron micrographs of
him4(rh319) animals with the AC highlighted in magenta reveal an absence of structures (boxed area at higher magnification, right) spanning the gonadal and ventral BMs (arrows, n = 4/4). Scale bars, 5 um.