The 5′ UTR is essential for high expression of ProtB and Mst77F. (A, C, E, G) Adult testes of reporter lines were stained for β-Galactosidase activity in parallel for 0.5 h. pc-protB2ΔInt (A) and pc-77F3 (E) include the 5′ UTR, whereas pc-protB2ΔInt1ΔEx1 (C) and pc-77F3Δ5′UTR (G) lack most of the 5′ UTR (see Fig. 2A, D). (B, D, F, H) Adult testes from these reporter lines were analyzed by in-situ hybridization with an antisense probe to lacZ RNA.