The mutation was caused by the spontaneous insertion of a 245-nucleotide B2 short interspersed nuclear element (SINE) within exon 3. This results in a truncated transcript lacking exon 3, which is predicted to cause a frameshift and result in a premature stop codon in exon 4. Western blot analysis confirmed the absence of protein expression in the brain, heart, liver and skeletal muscle. (J:186512)