Schematic of the normal and mutant products of the Foxp3/JM2 gene, indicating the mutations that lead to XLAAD and Scurfy. Regions of the Foxp3 open reading frame (ORF) found by cDNA sequencing and not predicted by the exon prediction programs of the human genome project (HGP) are shown by hatched red bars. This additional NH₂-terminal sequence is encoded in part by an additional 5′ exon, as noted by Brunkow et al. (2). Chatila et al. (1), following the HGP-annotated sequence, predicted a shorter NH₂-terminal domain. The mutant protein in the XLAAD-100 family and Scurfy mice are truncated at similar positions, whereas the mutant protein in the XLAAD-200 family carries a single amino acid deletion in the Zip domain. Zn, Zinc-finger domain; Zip, Zip motif; FKH, fork head homology domain.