Mutation of GATA1 in TMD. (A) SSCP analysis of the second exon of GATA1 revealed the presence of mutated conformational GATA1 alleles in DNA from each of 7 TMD patients. In contrast, GATA1 mutations were not detected in DNAs from 5 healthy individuals. A longer exposure of the SSCP gel revealed a mutant allele in DNA from TMD-2 (arrow, TMD-2* lane). (B) Schematic illustration of the functional domains of GATA-1. AD indicates activation domain; Nf, N terminal zinc finger; Cf, C-terminal zinc finger. The asterisks indicate the positions of the mutations in the 7 individuals with TMD (numbered 1 through 7). Met84 is an alternative translation initiation codon, which leads to the production of GATA-1s.