Fig. 4. Hex is not required for expression of early pancreatic genes in vitro. (A,B) RT-PCR analysis of E9.5 dorsal and ventral midgut tissues and of ventral endoderm explants isolated from E8.25 (2-6S) embryos and cultured for 48 hours. Different cycle steps are shown; albumin and actin PCR was performed in the same PCR reaction (Gualdi et al., 1996). PCR cycle numbers for other markers were normalized by actin levels. Positive controls were embryonic liver for albumin and E13.5 embryonic RNA for the other genes. (C) Representative ventral endoderm cultures used for the RT-PCR shown in B. (D) RT-PCR analysis of ventral endoderm explants isolated from E8.25 (2-6S) embryos and cultured for 48 hours with or without cardiogenic mesoderm; a headfold ectoderm explant served as a negative control.