Fig. 4. Expression of Mesp2 or mespb is autoregulated. Mesp2/+, mespb/+ or neo-mespb/+ mice were crossed with Mesp2-lacZ/+ mice and the expression pattern of Mesp2 or mespb was visualized. Mesp2 (A), mespb (B-C) and Mesp2-lacZ (D-G) transcripts are shown by whole-mount in situ hybridization. The lack of autoregulation that results in the loss of Mesp2-lacZ restriction to the rostral compartment is revealed by the caudally extended expression pattern of ß-gal activities (I-K), which are different from the striped expression pattern of Mesp2+/L (H; Mesp2 heterozygous embryo).