Figure 3.

Baf-1 deletion (gk324/gk324) homozygous animals have premature and ectopic fusion of the seam cells. (A) An illustration of seam cell fusion during larval development adapted from Shemer and Podbilewicz (2003). The epithelial seam cells divide during each larval molt, yielding epidermal daughter cells (which fuse to the hypodermis) and ectoblastic daughter cells, which stay unfused, forming single, lengthwise rows along the left and right sides (L1). These aligned cells fuse to themselves and form two syncytia that will form specific cuticle structures (L4/A). (B, a–d) Fluorescence micrographs of animals either homozygous or heterozygous for a baf-1 deletion expressing AJM-1–GFP. In gk324/hT2 animals, the ectoblastic seam cells stayed unfused at the late L3/early L4 stage (arrows in a). In gk324/gk324 animals, the seam cells ectopically fused to the epidermis (arrows in b), and, by the late L4/A stage, all of the seam cells fused to the epidermis (arrows in c). Transgenic expression of GFP–BAF-1 in gk324/gk324 animals rescued the cell fusion phenotype, allowing L4 stage seam cells to fuse to themselves and form two parallel syncytia (arrow in d); the GFP–BAF-1 nuclear signal is not in focus. Bars, 10 μm.