Northern hybridization with probe specific for the mouse Il4i1_2 splice variant. Blots contained poly A+ RNA from fetal mice 7 dpc (1), 11 dpc (2), 15 dpc (3), 17 dpc (4) and adult mouse tissues (heart (5), brain (6), spleen (7), lung (8), liver (9), skeletal muscle (10), kidney (11), and testis (12). Hybridization was with a probe comprising the joining exons 2 and 3 of the mouse Il4i1_2 variant, which are equivalent to human exons 3 and 4 (red arrowheads in Fig. 1). The blots were reprobed for beta actin mRNA as control for RNA content. The probe cross-hybridized with gamma actin mRNA where expressed.