Smn1^{tm4(SMN2)Mrph}

A 2.2 kb segment of mouse genome containing exons 7 and 8 of the mouse Smn1 (survival motor neuron 1) gene was replaced with a 1.3 kb fragment of human genomic DNA containing exons 7 and 8 of the human SMN2 (survival of motor neuron 2, centromeric) gene. A selection cassette located downstream from the human SMN2 polyadenylation signal was removed by FLPe expression in ES cells leaving a FRT site at the downstream junction between human and mouse DNA. Because exon 7 is derived from human SMN2, it is skipped in approximately 90% of the processed mRNA derived from the hybrid allele. (J:135424)