Exon 2 was replaced with one in which nucleotide substitutions result in the amino acid substitution of serine with a STOP codon at position 210 (S210X). The modified exon was followed by a floxed neo cassette that was removed via germ line, cre mediated recombination. The predicted product lacks 74 amino acids of the C terminus. A 75% reduction in full-length expression was confirmed by western blot analysis on E13.5 pancreatic extracts. (J:152582)