Figure 3

Organization of the PmDscam gene. The PmDscam gene consists of 175 exons and/or exon variants: 31 exons are constitutive (black lines), 7 exons (all in the cytoplasmic tail) can be either inserted or skipped (gray lines), and 137 exon variants are subject to mutually exclusive alternative splicing (colored lines). (A) The PmDscam extracellular region is encoded by exon 1 to exon 31. The variable regions are exon 4 (red), exon 6 (blue) and exon 15 (green), which contain 26 variants, 81 variants and 26 variants, respectively. The dashed line represents exon 1, which was not identified from the P. monodon gene. (B) The cytoplasmic tail is encoded by exon 31 to exon 44. The variable regions are exon 32 and exon 44, with each of these two exons derived from two mutually exclusive variants; that is, after RNA splicing, each transcript contains one of the alternative variants for each of these exons. (C) The extracellular region of PmDscam mRNA (upper panel) contains both constitutive exons (white) and exons that are subject to mutually exclusive alternative splicing. Alternatively spliced exons encode the N-terminal half of Ig2 (red), the N-terminal half of Ig3 (blue), and the entirety of Ig7 (green). In the cytoplasmic tail (purple), both the transmembrane domain (exon 32) and exon 44 are subject to mutually exclusive alternative splicing. The PmDscam protein structure (lower panel) is comprised of the extracellular region, which contains 10 immunoglobulin (Ig) domains and six fibronectin type 3 (FNIII) domains, followed by the cytoplasmic tail.