Fig. 1. Generation of Fmr1 mutant flies. (A) A P-element inserted in the first intron of the Fmr1 gene can be overexpressed because of the Gal4-binding sites in the P-element. (B) Western blot analysis indicated that Fmr1, an 80 kDa protein with multiple isoforms, is not expressed in mutant lines Fmr1¹, Fmr1² and Fmr1⁴. (C) Fmr1 contains several highly conserved domains, including the FMR1/FXR-interacting domain, KH domains and the ribosomal-association domain. EMS-induced mutations have been identified. For example, a point mutation in the Fmr1⁴ allele changes amino acid 289 to a stop codon, and a small deletion in the Fmr1¹ allele causes a frame-shift in the N terminus after the amino acid 126.