The invention provides a polypeptide and a specific partial peptide thereof, as well as a polynucleotide and a specific partial nucleotide thereof, that can be used as a biomarker specific for the brain/nerves or specific for nerve differentiation; an expression vector for such a polynucleotide and a specific partial peptide thereof; a transformant incorporating such an expression vector; an antisense molecule, RNAi-inducing nucleic acid (e.g., siRNA), aptamer, or antibody for such a biomarker, and a composition comprising the same; a mammalian cell or non-human mammal wherein the expression or a function of such a biomarker is regulated; a measuring means (e.g., primer set, nucleic acid probe, antibody, aptamer) for such a biomarker, and a reagent comprising the same and the like.