To replicate t(2;13), a chromosomal transloction associated with the pediatric disease alveolar rhabdomyosarcoma, a sequence fragment from a PAX3-FOXO1A fusion cDNA was inserted at the endogenous locus via homologous recombination. The last 50 bp of the endogenous exon 7 were replaced with related PAX3 sequence and a 3' portion of FOXO1A. Various analyses indicated low levels of expression of the knock-in allele. (J:79365)