Abstract: 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 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.

Abstract: 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 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.

Abstract: The method for producing a pancreatic hormone-producing cell according to the present invention is characterized in that a specific differentiation/induction promoter is added to a culture medium in the process of differentiating/inducing of a pluripotent stem cell or a pancreatic tissue stem/progenitor cell into the pancreatic hormone-producing cell. The differentiation/induction promoter to be used is: a polypeptide which comprises an amino acid sequence encoded by DNA comprising the nucleotide sequence represented by SEQ ID NO: 1 or a variant thereof; or a culture supernatant of a cell into which DNA comprising the nucleotide sequence represented by SEQ ID NO: 1 or DNA capable of hybridizing with DNA comprising a nucleotide sequence complementary to the aforementioned DNA under stringent conditions is integrated as a foreign gene.

Abstract: Disclosed are: an insulin secretion inducer; an insulin secretion-inducing composition; a process for the production of the composition; an accelerator for increasing the number of pancreatic ?-cells; a composition for increasing the number of pancreatic ?-cells; a process for the production of the composition; and a viral vector for gene therapy. The insulin secretion inducer or the accelerator for increasing the number of pancreatic ?-cells comprises a polypeptide having an amino acid sequence encoded by DNA that is known to encode a membrane protein Tm4sf20 (transmembrane 4 L six family member 20) or the like or a fragment of the polypeptide as an active ingredient.

Abstract: Disclosed are: an insulin secretion inducer; an insulin secretion-inducing composition; a process for the production of the composition; an accelerator for increasing the number of pancreatic ?-cells; a composition for increasing the number of pancreatic ?-cells; a process for the production of the composition; and a viral vector for gene therapy. The insulin secretion inducer or the accelerator for increasing the number of pancreatic ?-cells comprises a polypeptide having an amino acid sequence encoded by DNA that is known to encode a membrane protein Tm4sf20 (transmembrane 4 L six family member 20) or the like or a fragment of the polypeptide as an active ingredient.