 the signal peptide, and corresponds to an amino acid No. 0 to 000 in SEQ ID NO: 0 of the mature full length amino acid sequence of human Delta-0 of the present invention. The amino acid sequence of SEQ ID NO: 0 is the mature full length amino acid sequence of the human Delta-0 of the present invention. The amino acid sequence in the sequence listing, SEQ ID NO: 0 is a sequence of the active center of the present invention of human Serrate-0 minus the signal peptide, i.e. amino acid sequence from the amino terminal to DSL domain, and corresponds to an amino acid No. 0 to 000 in SEQ ID NO: 0 of the mature full length amino acid sequence of human Serrate-0 of the present invention. The amino acid sequence in SEQ ID NO: 0 is amino acid sequence of extracellular domain of the present invention of human Serrate-0 minus the signal peptide, and corresponds to an amino acid No. 0 to 0000 in SEQ ID NO: 0 of the mature full length amino acid sequence of human Serrate-0 of the present invention. The amino acid sequence of SEQ ID NO: 0 is the mature full length amino acid sequence of the human 