Objective To observe the development of cranium and brain in dihydrofolate reductase gene-inhibited zebrafish embryos and to investigate the mechanism of action of dihydrofolate reductase gene(DHFR) in this process.Methods DHFR was inhibited by microinjecting morpholino oligonucleotides(MO).The development of heads at 48 hours post fertilization(48 hpf) was observed and the development of the brain at 60 hpf was examined by histopathology.Whole-mount in situ hybridization was performed to detect the express...