Fig. 2. spon-1 encodes a member of the F-spondin family. (A) Genetic map position, gene organization, and minimal spon-1 rescuing DNA fragment (pCZ695). The nc30 mutation affects the last base pair of exon 3 (CAGgtaa to CAAgtaaa; codon 104), which is likely to force the use of an alternative cryptic splice site, resulting in a frameshift and a premature stop in the reelin domain. (B) Domain organization of SPON-1, and percentage identity to Drosophila fat-spondin and rat F-spondin. (C) Phylogenetic tree of spondin domains of C. elegans SPON-1, Drosophila fat-spondin (CG6953), CG17739, CG30203 and CG30046, rat (Rn) F-spondin, zebrafish (Br) spondin 1a and 1b (F-spondin 1 and 2), Xenopus (Xl) spon-1A and Amphioxus Amphi-F-spondin (Bf, Branchiostoma floridae), made with ClustalW and displayed using njplot (Perrière and Gouy, 1996). (D) Alignment of the thrombospondin type I repeats from SPON-1; missense alterations are shown in red.