Figure 1: Organization of two novel Dscam gene subfamilies in M. martensii.
From: A large family of Dscam genes with tandemly arrayed 5′ cassettes in Chelicerata
(a) Organization of the sDscamα gene. The sDscamα gene is composed of multiple tandemly arrayed regions (indicated by the coloured boxes) and common region exons (indicated by the black boxes). ‘()’ represents the number of tandem cassettes. The arrows indicate the transcription start sites. FNIII, fibronectin III domains; Ig, immunoglobulin domains. The N-terminal small boxes represent the leader peptides. The grey and black boxes represent the transmembrane (TM) and cytoplasmic domains, respectively. These cassettes are composed of two exons (indicated by the coloured boxes). Each variable cassette was transcribed by an alternative promoter followed by alternative splicing. The sDscamα variable cassette encoded the N-terminal Ig1 (blue), which corresponded to the variable Ig7 domain of Drosophila Dscam1. (b) Organization of the sDscamβ genes. This sDscamβ subfamily was composed of six members (sDscamβ1–sDscamβ6), 5′ tandem cassettes of which generally contained four exons. The variable cassette encoded the N-terminal Ig1+2 domains (coloured), which corresponded to the variable Ig7+8 domains of Drosophila Dscam1.
