Wingless-type MMTV integration site familywas obtained from the transcriptome database) and its entire cDNA sequence was acquired by SMART-RACE was 1239 bp in length and encoded 355 amino acids. The WNT4 amino acids sequences were specific to the WNT family. Homologous analysis of the amino acids showed that Platynereis dumeriliiemi-quantative RT-PCR results showed no expressiontestes, gill and mantle tissues results indicated that resting stage and the lowest expression at the growing stage. The expression levels of were characteristically testis-predominant during the entire reproductive cycle. The multiple tissue expression characteristics imply that WNT4 plays various biological roles in . We can infer from the expression pattern in the gonads that WNT4 also contributes to the process of gonadal development and germ cell maturation.