Fig. 1. Spatial and temporal expression pattern of lin-3. (A) Different extents of 5' noncoding and coding regions of lin-3 were cloned into a gfp reporter construct as described in the Materials and methods. Construct 1 begins near the 3' end of the fourth intron, construct 2 begins from the 3' half of the second lin-3 intron, and constructs 3 and 4 contain the first intron and the first promoter. The two arrows indicate lin-3 promoters; blue and red boxes represent two alternative signal peptides right after translational initiation codons; purple boxes are exons encoding an EGF domain; and yellow box represents a domain that exists only in one form of lin-3 and is created by alternative splicing. The arrow from ACEL (anchor cell-specific enhancer of lin-3) marks the position of an enhancer element that drives the expression of lin-3 in the AC. Cells expressing lin-3::gfp were summarized as –, no expression; and +, expression. (B-M) The expression of lin-3::gfp in pharynx (pha), spermatheca valve (spv), a subset of the primary vulval cells (vulF), male tail (F and U cells), and in the anchor cell (AC) and the pre-anchor (AC)/ventral uterine precursor cells (VU). (B-D,H-J) Nomarski images; (E-G,K-M) corresponding images of lin-3::gfp expression.