Maternal methionine supplementation promotes the remediation of axial defects in Axd mouse neural tube mutants

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Abstract
The Axd (axial defects) mouse model system (Essien et al., Teratology 42:183-194, '90) is characterized by a dominant mutation which causes posterior open neural tube defects (NTD) and a variety of tail anomalies (curly tails, or CT). Repeated backcrosses to BALB/cByJ mice have resulted in a 50% increase in Axd penetrance among neonates of heterozygous matings and loss of a correlation with maternal tail phenotype. Analysis of D12-D18 embryos from Axd/ + × Axd/ + matings indicates that soft tissues can superficially heal over some lesions from open NTD and that some curly tails can straighten (macroscopically) as gestation proceeds. Similarly, in embryos of Axd/ + × BALB crosses, there is remediation of approximately 33% of the tail flexion defects by birth. Numerous studies show that maternal nutritional status can affect the development of the neural tube and related axial structures. One nutrient of special interest is methionine, which is required for neurulation in cultured rat embryos (Coelho et al., J. Nutr. 119:1716, '89). Thus, the major question addressed by this study was whether supplemental methionine administered to Axd/ + dams crossed to Axd/ + males would alter the prenatal expression of the gene. When given IP (70 mg/kg) on D8 and D9, methionine resulted in a 41% reduction (from 29% to 17%) in the incidence of NTD in D 14 embryos (P <0.01).