Abstract: Abstract: To determine molecular mechanism in hyperglycemia induced congenital neural tube defects, yolk sac cells were harvested at gestational day 12 from streptozotocin (STZ) -induced diabetic rats with congenital neural tube defects in offspring, STZ-induced diabetic rats without neural tube defects and normal control group. We analyzed gene expression profiles in yolk sac cells using a DNA microarray technique. Changes in apoptotic and MAP Kinase signaling pathways were detected by Western blotting analyses. Comparison of genes in yolk sac cells with a total of 1 200 genes in the control cells, 79 genes differently expressed between the two groups were detected. Forty-two of them were up-regulated and 37 were down-regulated. There was strong characteristic apoptotic DNA ladder in yolk sac cells in embryopathic offspring from experimentally-induced diabetic rats. The activity of ERK1/2 was dramatically decreased and the activity of JNK1/2 was significantly increased. Differentially expressed genes, MAP Kinase, and apoptotic signal pathways play very impor-tant roles in hyperglycemia induced neural tube defects. We hope that these could provide useful hallmark to rapid identifi-cation of early diabetic embryopathy.