The time-effect relationship between positional transferred novel gene(HCY-2) and neural tube teratogenesis, and their possible mechanisms were studied. An eukaryotic expressing vector which containing whole-length HCY-2 cDNA was microinjected into chick embryos in culture at days 0, 1 and 2 (approximately Hamburger-Hamilton stages 1, 6 and 12) mediated by lipofect AMINE reagent. The techniques of RT-PCR, immunohistochemical staining, scanning electron microscope(SEM) and transmission electron microscope (TEM) were used to investigate the expression and distribution of HCY-2 mRNA with its coding product and dysmorphogenesis of the neural tube at 96 h (approximately stage 22). Neural tube defects (NTDs) were discovered in every transferred gene group, only the day 1 embryos which positional site injected was the area pellucida of head, however, the rate of NTDs was the highest (35.3%). There was an obvious time-effect relationship. The phenotypes of NTD were encephalocele, anencephaly, spina bifida and microcephaly. The embryos with transferred gene could express HCY-2 mRNA and its coding product, and the HCY-2 protein mainly distributed in embryonic brain cells as compared to controls. It was found that HCY-2 gene could result in abnormal ultrastructure at the surface and inside of cells under SEM and TEM. It has been observed apoptosis at the sites with NTDs. It is concluded that HCY-2 gene may be a new genotoxic factor, which plays an important role in the mechanisms of neural tube teratogenesis during the early developing stage of embryos.