Nucleotide substitution(s) in exon 4 resulted in the amino acid substitution of methionine for threonine at position 158 (T158M). This mutation affects the DNA binding domain. An EGFP was fused in-frame downstream of the coding sequence in exon 4. Cre-mediated recombination removed the floxed neomycin resistance cassette inserted downstream of EGFP. The T158M mutation represents 12% of Rhett Syndrome missense mutations. (J:203745)