ARSENIC-INDUCED NEURAL-TUBE DEFECTS IN MICE - ALTERATIONS IN CELL-CYCLE GENE-EXPRESSION

The potential of arsenic to cause neural tube defects (NTD) in the hum an population remains a topic of controversy. While clearly toxic, the lack of well-defined human epidemiologic studies on this subject has made it difficult to fully understand the effects arsenic may have on the developing human neural tube. In the absence of good clinical data , we have tried to develop a murine model where hypotheses about the r eproductive toxicity of arsenate can be tested. For these studies a mu rine strain (LM/Bc) that has proven to be susceptible to arsenic-induc ed NTD was use. Because cellular proliferation is vital for normal neu ral tube closure (NTC) to occur, in the present study we investigated whether an acute arsenate treatment could alter the expression of seve ral cell cycle genes during murine neurulation. Pregnant LM/Bc dams we re injected intraperitoneally on gestation day (GD) 7:12 (day:hour) an d 8:12 with 40 mg/kg of arsenate, a treatment that causes exencephaly in 90 to 100% of the exposed fetuses. Neural tubes were then isolated from both control and arsenic treated embryos at GD 9:00, 9:12, 10:00, and 10:12, which encompasses all the stages of neurulation for this m urine strain. Using the molecular techniques of in situ transcription and antisense RNA amplification (RT/aRNA) the expression pattern for b cl-2, p53, wee-1, and wnt-1 was analyzed at each of these time points. In the neural tubes isolated from control embryos, the expression of all four genes was significantly altered as neurulation progressed, de monstrating their developmental regulation. Following arsenate treatme nt, however, there was a significant upregulation in the expression of bcl-2 and p53 at gestational day 9:0, compared to their control value s. The heightened expression of both of these genes suggests that arse nic inhibits cell proliferation, rather than inducing apoptosis, which delayed NTC and ultimately led to the neural tube defects observed in exposed embryos. (C) 1996 Elsevier Science Inc.