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Antisense modulation of the coding or regulatory sequence of the folate receptor (folate binding protein-1) in mouse embryos leads to neural tube defects.

BACKGROUND
Although folic acid decreases the incidence of neural tube defects (NTDs) in humans, the mechanism for this protection is unknown. We have employed antisense technology to alter expression of the gene for the folate receptor (folate binding protein-1 [Folbp1]) in mouse embryos cultured in vitro.


METHODS
Embryos were explanted on day 8 of gestation and cultured for 44 hr. Several oligodeoxyribonucleotides designed to modulate the coding region or a regulatory sequence in the 5'-untranslated region of Folbp1 were microinjected into the amniotic sac of embryos at the beginning of the culture period.


RESULTS
Two different antisense sequences to the 5' and 3' coding region in Folbp1 produced concentration-dependent increases in the number of embryos with NTDs. Coinjection of 5-methyltetrahydrofolate with these sequences decreased the frequency of abnormal embryos. A semi-quantitative RT-PCR technique used to measure the amount of Folbp1 mRNA in treated and control embryos confirmed that the mRNA level was decreased by treatment with the antisense sequences. An antisense oligodeoxyribonucleotide to a 17 base cis regulatory element also generated a concentration-dependent increase in the frequency of embryos with NTDs, and a decrease in the level of Folbp1 mRNA.


CONCLUSIONS
These results demonstrate that alterations in expression of Folbp1 by perturbing either the coding sequence or a critical regulatory cis-element can play a role in NTDs.