The levels of Smn1, Crabp1, Crabp2, Isl1, Nkx2.2, Pla2g1b and Vim transcripts were measured in severe SMA mice at embryonic day 13.5 (e13.5) relative to age-matched control littermates. This evidence concerns the gene NKX2-2 and proximal spinal muscular atrophy.