Fig. 4. Tissue-enriched and compartmentalized expression of TF mRNAs. (A) Partial results from comparative expression of 66 TF mRNAs in multiple fetal mouse tissues at E13 (left) and E17 (right), determined by RT-PCR. Twelve factors are considerably enriched in the developing stomach and/or intestine, with persistent expression of some TFs in the adult GI tract. GAPDH provides a mRNA loading control, and three examples of TFs with broad tissue distribution are included. (B) Illustrative examples of two TFs, an uncharacterized ZnB protein (left) and Isx (right) revealed by in situ hybridization to be expressed in the E13 mesentery (left) and E15 mucosa (right, arrows), respectively. (C) Pie-chart representation of mRNA localization of the 66 tested TFs, which either increase during intestine development or differ notably between stomach and intestine.