Crooked tail (Cd) models human folate-responsive neural tube defects.

Genetic correlation of human neural tube defects (NTDs) with NTD genes identified in mouse may unravel predisposing complex traits for assessment of individual risk and treatment in clinical settings. Folic acid (FA) can reduce the recurrence of NTDs in human populations by as much as 50-70%, though the mechanism of this rescue is unknown. We examined whether Crooked tail ( Cd ), a mouse strain prone to exencephaly, could provide a genetic animal model for folate-responsive NTDs. The Cd locus was localized to a 0.2 cM interval of the Mouse Genome Database genetic map, identifying tightly linked markers for genotyping prior to phenotypic expression. In a controlled diet study, Cd was found to mimic closely the clinical response to FA. FA supplementation reduced the recurrence risk of Cd exencephaly by as much as 55%. This rescue was dose dependent and did not require subjects to be inherently folate deficient. Like the female predominance of NTDs in humans, female Cd embryos were most likely to display exencephaly and were more responsive than males to the FA rescue. Importantly, FA supplementation shifted the severity of Cd phenotypic expression from early embryonic lethality to longer survival, and reduced the incidence of NTDs. The Cd locus is distinct from the known genes associated with neurulation defects, and isolation of this gene will assist identification of biochemical, genetic and gender-dependent factors contributing to folate-responsive NTDs.