Provided are a new peptide, a vector inserting a DNA that codes said peptide, a transformant obtained by transformation with that vector, and applications of said peptide, vector and transformant. The peptide according to the present invention comprises an amino acid sequence set forth in SEQ ID NO: 1, or an amino acid sequence obtained by substituting, deleting or adding one or more amino acids to/from the amino acid sequence set forth in SEQ ID NO: 1. This peptide and the vector inserting a DNA that codes this peptide are suitable for use in an agent for promoting the proliferation of pancreatic hormone-producing cells, or a differentiation induction promoter that induces differentiation to pancreatic hormone-producing cells.
